Class X Chemistry Quizzes -

BCSE Chemistry 2021

This contains the MCQ and True/False questions from the BCSE Board exam paper 2021

1 / 22

For an endothermic reaction taking place at constant temperature and volume, E will have a negative value

True

False

False. For an endothermic reaction taking place at constant temperature and volume, ΔE\Delta EΔE will have a positive value, as energy is absorbed from the surroundings

2 / 22

An organic compound characterized by one or more hydroxyl groups attached to a carbon atom of hydrocarbon chain is

alcohol

ester.

aldehyde.

ketone

C) alcohol.

An alcohol is an organic compound that contains one or more hydroxyl groups (-OH) attached to a carbon atom of a hydrocarbon chain. The general formula for alcohols is R-OH, where R represents a hydrocarbon group

C) alcohol.

3 / 22

The boiling point of alcohol increases with an increase in molecular weight.

False

True

In transition elements, the partially filled d-orbital electron(s) can be excited and moved between energy levels, allowing for variable oxidation states and complex formation.

4 / 22

Titanium is often used to replace fractured bones in our body because it is

A light. B heavy. C cheap. D corrosive.

light.

corrosive

cheap

heavy

Titanium is used to replace fractured bones because it is lightweight, strong, non-corrosive, and biocompatible, meaning it is not rejected by the body. Additionally, titanium does not react easily with bodily fluids, making it ideal for medical implants

5 / 22

A fire extinguisher cylinder contains 792 grams of carbon dioxide gas. The moles of carbon dioxide gas in a cylinder is

To calculate the number of moles of carbon dioxide (CO₂) in the fire extinguisher, follow these steps:

Step 1: Determine the molar mass of CO₂.

The molecular formula of CO₂ is made up of:

Carbon (C): 12.01 g/mol
Oxygen (O): 16.00 g/mol (there are 2 oxygen atoms)

Molar mass of CO₂=12.01+2×16.00=44.01 g/mol\text{Molar mass of CO₂} = 12.01 + 2 \times 16.00 = 44.01 \, \text{g/mol}Molar mass of CO₂=12.01+2×16.00=44.01g/mol

Step 2: Calculate the number of moles.

The formula to calculate the number of moles is:

Moles of CO₂=Mass of CO₂Molar mass of CO₂\text{Moles of CO₂} = \frac{\text{Mass of CO₂}}{\text{Molar mass of CO₂}}Moles of CO₂=Molar mass of CO₂Mass of CO₂

Given:

Mass of CO₂ = 792 grams
Molar mass of CO₂ = 44.01 g/mol

Moles of CO₂=79244.01≈18 moles\text{Moles of CO₂} = \frac{792}{44.01} \approx 18 \, \text{moles}Moles of CO₂=44.01792≈18moles

Final Answer:

The number of moles of CO₂ is approximately 18 moles.

Thus, the correct answer is: B) 18.

To calculate the number of moles of carbon dioxide (CO₂) in the fire extinguisher, follow these steps:

Step 1: Determine the molar mass of CO₂.

The molecular formula of CO₂ is made up of:

Carbon (C): 12.01 g/mol
Oxygen (O): 16.00 g/mol (there are 2 oxygen atoms)

Molar mass of CO₂=12.01+2×16.00=44.01 g/mol\text{Molar mass of CO₂} = 12.01 + 2 \times 16.00 = 44.01 \, \text{g/mol}Molar mass of CO₂=12.01+2×16.00=44.01g/mol

Step 2: Calculate the number of moles.

The formula to calculate the number of moles is:

Moles of CO₂=Mass of CO₂Molar mass of CO₂\text{Moles of CO₂} = \frac{\text{Mass of CO₂}}{\text{Molar mass of CO₂}}Moles of CO₂=Molar mass of CO₂Mass of CO₂

Given:

Mass of CO₂ = 792 grams
Molar mass of CO₂ = 44.01 g/mol

Moles of CO₂=79244.01≈18 moles\text{Moles of CO₂} = \frac{792}{44.01} \approx 18 \, \text{moles}Moles of CO₂=44.01792≈18moles

Final Answer:

The number of moles of CO₂ is approximately 18 moles.

Thus, the correct answer is: B) 18.

6 / 22

Table salt (NaCl) is one of the basic ingredients that adds flavor to the food. However, consuming excess salt leads to high blood pressure, heart disease and stroke. If a doctor recommends you to take 3 grams daily, how much salt molecules would you be consuming in a day?

3.088 x 10^22

6.023 x 10^21

1.809 x 10^23

5.420 x 10^24

To find out how many salt (NaCl) molecules are consumed when taking 3 grams daily, we can follow these steps:

Step 1: Calculate the Molar Mass of NaCl

The molar mass of sodium chloride (NaCl) can be calculated by adding the atomic masses of sodium (Na) and chlorine (Cl):

Sodium (Na): approximately 22.99 g/mol
Chlorine (Cl): approximately 35.45 g/mol

Molar mass of NaCl=22.99+35.45=58.44 g/mol\text{Molar mass of NaCl} = 22.99 + 35.45 = 58.44 \, \text{g/mol}Molar mass of NaCl=22.99+35.45=58.44g/mol

Step 2: Convert Grams to Moles

Next, convert the mass of NaCl consumed (3 grams) into moles using the molar mass:

Moles of NaCl=Mass of NaClMolar mass of NaCl=3 g58.44 g/mol≈0.0513 moles\text{Moles of NaCl} = \frac{\text{Mass of NaCl}}{\text{Molar mass of NaCl}} = \frac{3 \, \text{g}}{58.44 \, \text{g/mol}} \approx 0.0513 \, \text{moles}Moles of NaCl=Molar mass of NaClMass of NaCl=58.44g/mol3g≈0.0513moles

Step 3: Calculate the Number of Molecules

To find the number of molecules, multiply the number of moles by Avogadro's number (approximately 6.022×10236.022 \times 10^{23}6.022×1023 molecules/mol):

Number of molecules=Moles of NaCl×Avogadro’s number\text{Number of molecules} = \text{Moles of NaCl} \times \text{Avogadro's number}Number of molecules=Moles of NaCl×Avogadro’s number =0.0513 moles×6.022×1023 molecules/mol≈3.09×1022 molecules= 0.0513 \, \text{moles} \times 6.022 \times 10^{23} \, \text{molecules/mol} \approx 3.09 \times 10^{22} \, \text{molecules}=0.0513moles×6.022×1023molecules/mol≈3.09×1022molecules

Final Answer

Therefore, the amount of salt molecules consumed in a day when taking 3 grams of NaCl is approximately:

≈3.088×1022 molecules\approx 3.088 \times 10^{22} \, \text{molecules}≈3.088×1022molecules

So, the correct choice is B) 3.088 x 10²².

To find out how many salt (NaCl) molecules are consumed when taking 3 grams daily, we can follow these steps:

Step 1: Calculate the Molar Mass of NaCl

The molar mass of sodium chloride (NaCl) can be calculated by adding the atomic masses of sodium (Na) and chlorine (Cl):

Sodium (Na): approximately 22.99 g/mol
Chlorine (Cl): approximately 35.45 g/mol

Molar mass of NaCl=22.99+35.45=58.44 g/mol\text{Molar mass of NaCl} = 22.99 + 35.45 = 58.44 \, \text{g/mol}Molar mass of NaCl=22.99+35.45=58.44g/mol

Step 2: Convert Grams to Moles

Next, convert the mass of NaCl consumed (3 grams) into moles using the molar mass:

Step 3: Calculate the Number of Molecules

To find the number of molecules, multiply the number of moles by Avogadro's number (approximately 6.022×10236.022 \times 10^{23}6.022×1023 molecules/mol):

Final Answer

Therefore, the amount of salt molecules consumed in a day when taking 3 grams of NaCl is approximately:

≈3.088×1022 molecules\approx 3.088 \times 10^{22} \, \text{molecules}≈3.088×1022molecules

So, the correct choice is B) 3.088 x 10²².

7 / 22

In the periodic table, the location of transition elements is in between

lanthanides and actinides.

d- and f-block elements

s- and p-block elements

chalcogens and halogens

The correct answer is:

B) s- and p-block elements.

In the periodic table, transition elements are located in the d-block, which is positioned between the s-block (groups 1 and 2) and the p-block (groups 13 to 18). These transition elements are metals and typically have partially filled d-orbitals.

Yes The correct answer is:

B) s- and p-block elements.

8 / 22

The number of hydrogen atoms present in ethyl alcohol is

The molecular formula of ethyl alcohol (ethanol) is C₂H₅OH.

In this formula:

There are 5 hydrogen atoms attached to the carbon atoms in the ethyl group (C₂H₅).
Additionally, there is 1 hydrogen atom attached to the oxygen in the hydroxyl group (-OH).

Therefore, the total number of hydrogen atoms is:

C) 6.

The molecular formula of ethyl alcohol (ethanol) is C₂H₅OH.

In this formula:

There are 5 hydrogen atoms attached to the carbon atoms in the ethyl group (C₂H₅).
Additionally, there is 1 hydrogen atom attached to the oxygen in the hydroxyl group (-OH).

Therefore, the total number of hydrogen atoms is:

C) 6.

9 / 22

The unbalanced chemical equation violates the law of conservation of mass.

True

False

True. The unbalanced chemical equation violates the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction.

10 / 22

Glucose (C6H12O6) is one of the main sources of energy. The percentage of hydrogen present in a glucose molecule is

53.3%.

8.3%

6.6%

40.0%

To calculate the percentage of hydrogen in a glucose molecule (C₆H₁₂O₆), you can follow these steps:

Step-by-Step Calculation

Determine the molar mass of glucose:
- The molecular formula for glucose is C₆H₁₂O₆, which contains:
  - 6 carbon (C) atoms
  - 12 hydrogen (H) atoms
  - 6 oxygen (O) atoms
Find the molar masses of each element:
- Carbon (C): approximately 12.01 g/mol
- Hydrogen (H): approximately 1.008 g/mol
- Oxygen (O): approximately 16.00 g/mol
Calculate the total molar mass of glucose:
Molar mass of glucose=(6×12.01)+(12×1.008)+(6×16.00)\text{Molar mass of glucose} = (6 \times 12.01) + (12 \times 1.008) + (6 \times 16.00)Molar mass of glucose=(6×12.01)+(12×1.008)+(6×16.00) =72.06+12.096+96.00=180.156 g/mol= 72.06 + 12.096 + 96.00 = 180.156 \, \text{g/mol}=72.06+12.096+96.00=180.156g/mol
Calculate the total mass of hydrogen in glucose:
Mass of hydrogen=12×1.008=12.096 g\text{Mass of hydrogen} = 12 \times 1.008 = 12.096 \, \text{g}Mass of hydrogen=12×1.008=12.096g
Calculate the percentage of hydrogen:
Percentage of hydrogen=(Mass of hydrogenMolar mass of glucose)×100\text{Percentage of hydrogen} = \left( \frac{\text{Mass of hydrogen}}{\text{Molar mass of glucose}} \right) \times 100Percentage of hydrogen=(Molar mass of glucoseMass of hydrogen)×100 =(12.096180.156)×100≈6.7%= \left( \frac{12.096}{180.156} \right) \times 100 \approx 6.7\%=(180.15612.096)×100≈6.7%

Thus, the percentage of hydrogen in a glucose molecule is approximately 6.7%, which corresponds to the closest answer of 6.6%.

To calculate the percentage of hydrogen in a glucose molecule (C₆H₁₂O₆), you can follow these steps:

Step-by-Step Calculation

Determine the molar mass of glucose:
- The molecular formula for glucose is C₆H₁₂O₆, which contains:
  - 6 carbon (C) atoms
  - 12 hydrogen (H) atoms
  - 6 oxygen (O) atoms
Find the molar masses of each element:
- Carbon (C): approximately 12.01 g/mol
- Hydrogen (H): approximately 1.008 g/mol
- Oxygen (O): approximately 16.00 g/mol
Calculate the total molar mass of glucose:
Molar mass of glucose=(6×12.01)+(12×1.008)+(6×16.00)\text{Molar mass of glucose} = (6 \times 12.01) + (12 \times 1.008) + (6 \times 16.00)Molar mass of glucose=(6×12.01)+(12×1.008)+(6×16.00) =72.06+12.096+96.00=180.156 g/mol= 72.06 + 12.096 + 96.00 = 180.156 \, \text{g/mol}=72.06+12.096+96.00=180.156g/mol
Calculate the total mass of hydrogen in glucose:
Mass of hydrogen=12×1.008=12.096 g\text{Mass of hydrogen} = 12 \times 1.008 = 12.096 \, \text{g}Mass of hydrogen=12×1.008=12.096g
Calculate the percentage of hydrogen:
Percentage of hydrogen=(Mass of hydrogenMolar mass of glucose)×100\text{Percentage of hydrogen} = \left( \frac{\text{Mass of hydrogen}}{\text{Molar mass of glucose}} \right) \times 100Percentage of hydrogen=(Molar mass of glucoseMass of hydrogen)×100 =(12.096180.156)×100≈6.7%= \left( \frac{12.096}{180.156} \right) \times 100 \approx 6.7\%=(180.15612.096)×100≈6.7%

Thus, the percentage of hydrogen in a glucose molecule is approximately 6.7%, which corresponds to the closest answer of 6.6%.

11 / 22

Tashi checked his body temperature with a thermal scanner before entering the school campus. If his body temperature reads 35°C, the reading on the Kelvin scale would be

100 K

273 K

238 K

308 K

12 / 22

In transition elements, the partially filled d-orbital electron(s) can be excited and moved between energy levels.

False

True

In transition elements, the partially filled d-orbital electron(s) can be excited and moved between energy levels, allowing for variable oxidation states and complex formation.

13 / 22

The correct electronic configuration of an element having atomic number 17 is

1s2 2s2 2p5 3s3 3p5.

1s2 2s2 2p5 3s2 3p6

1s2 2s2 2p6 3s2 3p5.

1s2 2s2 2p6 3s1 3p6.

The correct electronic configuration of an element with atomic number 17 (chlorine) is:

C) 1s² 2s² 2p⁶ 3s² 3p⁵.

This configuration shows that chlorine has 17 electrons, with the first two shells fully filled and 7 electrons in the third shell (2 in the 3s orbital and 5 in the 3p orbital), which corresponds to its position in Group 17 of the periodic table

The correct electronic configuration of an element with atomic number 17 (chlorine) is:

C) 1s² 2s² 2p⁶ 3s² 3p⁵.

14 / 22

In the chemical reaction, Fe(s) + 2HCl(aq) FeCl2 (aq) + gas, the gas evolved is

oxygen

hydrogen

chlorine

helium

The correct answer is:

D) hydrogen.

In the reaction:

Fe(s)+2HCl(aq)→FeCl2(aq)+H2(g)\text{Fe(s)} + 2\text{HCl(aq)} \rightarrow \text{FeCl}_2\text{(aq)} + \text{H}_2\text{(g)}Fe(s)+2HCl(aq)→FeCl2(aq)+H2(g)

Iron (Fe) reacts with hydrochloric acid (HCl) to produce iron(II) chloride (FeCl₂) and hydrogen gas (H₂). Therefore, the gas evolved in this reaction is hydrogen.

The correct answer is:

D) hydrogen.

In the reaction:

Fe(s)+2HCl(aq)→FeCl2(aq)+H2(g)\text{Fe(s)} + 2\text{HCl(aq)} \rightarrow \text{FeCl}_2\text{(aq)} + \text{H}_2\text{(g)}Fe(s)+2HCl(aq)→FeCl2(aq)+H2(g)

Iron (Fe) reacts with hydrochloric acid (HCl) to produce iron(II) chloride (FeCl₂) and hydrogen gas (H₂). Therefore, the gas evolved in this reaction is hydrogen.

15 / 22

If you take an inflated football from a hot place to a cold place, its volume will increase

False

True

If you take an inflated football from a hot place to a cold place, its volume will decrease due to the gas inside contracting as it cools (according to Charles's Law).

16 / 22

Arrange the following gases in increasing order of their masses.

1.0 mole of O3
1.0 mole of N2
1.0 mole of O2
1.0 mole of CO2

I < II < III < IV

IV < II < III < I

II < III < I < IV

II < III < IV < I

To arrange the gases in increasing order of their masses, we need to find the molar mass of each gas. Here’s how to do that step by step:

Step 1: Calculate the Molar Masses

Ozone (O₃):
- Molar mass = 3×atomic mass of O3 \times \text{atomic mass of O}3×atomic mass of O
- Atomic mass of O = 16.00 g/mol
- Molar mass of O₃ = 3×16.00=48.00 g/mol3 \times 16.00 = 48.00 \, \text{g/mol}3×16.00=48.00g/mol
Nitrogen (N₂):
- Molar mass = 2×atomic mass of N2 \times \text{atomic mass of N}2×atomic mass of N
- Atomic mass of N = 14.01 g/mol
- Molar mass of N₂ = 2×14.01=28.02 g/mol2 \times 14.01 = 28.02 \, \text{g/mol}2×14.01=28.02g/mol
Oxygen (O₂):
- Molar mass = 2×atomic mass of O2 \times \text{atomic mass of O}2×atomic mass of O
- Molar mass of O₂ = 2×16.00=32.00 g/mol2 \times 16.00 = 32.00 \, \text{g/mol}2×16.00=32.00g/mol
Carbon Dioxide (CO₂):
- Molar mass = atomic mass of C+2×atomic mass of O\text{atomic mass of C} + 2 \times \text{atomic mass of O}atomic mass of C+2×atomic mass of O
- Atomic mass of C = 12.01 g/mol
- Molar mass of CO₂ = 12.01+2×16.00=12.01+32.00=44.01 g/mol12.01 + 2 \times 16.00 = 12.01 + 32.00 = 44.01 \, \text{g/mol}12.01+2×16.00=12.01+32.00=44.01g/mol

Step 2: List the Molar Masses

N₂: 28.02 g/mol
O₂: 32.00 g/mol
CO₂: 44.01 g/mol
O₃: 48.00 g/mol

Step 3: Arrange in Increasing Order

Now, we can arrange these gases based on their molar masses from lowest to highest:

N₂: 28.02 g/mol
O₂: 32.00 g/mol
CO₂: 44.01 g/mol
O₃: 48.00 g/mol

Final Answer

Thus, the increasing order of their masses is:

II < III < IV < I, which corresponds to:

A) II < III < IV < I.

To arrange the gases in increasing order of their masses, we need to find the molar mass of each gas. Here’s how to do that step by step:

Step 1: Calculate the Molar Masses

Ozone (O₃):
- Molar mass = 3×atomic mass of O3 \times \text{atomic mass of O}3×atomic mass of O
- Atomic mass of O = 16.00 g/mol
- Molar mass of O₃ = 3×16.00=48.00 g/mol3 \times 16.00 = 48.00 \, \text{g/mol}3×16.00=48.00g/mol
Nitrogen (N₂):
- Molar mass = 2×atomic mass of N2 \times \text{atomic mass of N}2×atomic mass of N
- Atomic mass of N = 14.01 g/mol
- Molar mass of N₂ = 2×14.01=28.02 g/mol2 \times 14.01 = 28.02 \, \text{g/mol}2×14.01=28.02g/mol
Oxygen (O₂):
- Molar mass = 2×atomic mass of O2 \times \text{atomic mass of O}2×atomic mass of O
- Molar mass of O₂ = 2×16.00=32.00 g/mol2 \times 16.00 = 32.00 \, \text{g/mol}2×16.00=32.00g/mol
Carbon Dioxide (CO₂):
- Molar mass = atomic mass of C+2×atomic mass of O\text{atomic mass of C} + 2 \times \text{atomic mass of O}atomic mass of C+2×atomic mass of O
- Atomic mass of C = 12.01 g/mol
- Molar mass of CO₂ = 12.01+2×16.00=12.01+32.00=44.01 g/mol12.01 + 2 \times 16.00 = 12.01 + 32.00 = 44.01 \, \text{g/mol}12.01+2×16.00=12.01+32.00=44.01g/mol

Step 2: List the Molar Masses

N₂: 28.02 g/mol
O₂: 32.00 g/mol
CO₂: 44.01 g/mol
O₃: 48.00 g/mol

Step 3: Arrange in Increasing Order

Now, we can arrange these gases based on their molar masses from lowest to highest:

N₂: 28.02 g/mol
O₂: 32.00 g/mol
CO₂: 44.01 g/mol
O₃: 48.00 g/mol

Final Answer

Thus, the increasing order of their masses is:

II < III < IV < I, which corresponds to:

A) II < III < IV < I.

17 / 22

The effective nuclear charge is the net positive charge experienced by valence electrons. If the shielding electron increases, the effective nuclear charge would

be in negative value

remains same

increase.

decrease

If the shielding (or screening) effect increases, it means that inner electrons are blocking more of the positive charge of the nucleus from reaching the valence electrons. This reduces the effective nuclear charge experienced by the valence electrons, causing the overall attraction between the nucleus and the outer electrons to decrease

Yes The correct answer is:

B) decrease.

18 / 22

Generally people use alcohol based hand sanitizers in the absence of soap and water to reduce the risk of spreading corona virus. This is because alcohol has

reducing property

antimicrobial property

oxidising property

antibiotic property

The correct answer is:

D) antimicrobial property.

Alcohol-based hand sanitizers are effective because alcohol has antimicrobial properties, meaning it can kill or inactivate many types of microbes, including viruses like the coronavirus, by disrupting their cell membranes or protein structures

The correct answer is:

D) antimicrobial property.

19 / 22

The amount of heat transferred to convert unit mass of solid to vapour or vice versa is known as the heat of

evaporation

neutralization

sublimation

formation

Sublimation refers to the process where a solid directly converts into a vapor without passing through the liquid phase. The amount of heat transferred during this conversion is known as the heat of sublimation.

20 / 22

Metallic cans are often used for packing beverages because of its advantages. However, some of the metals are toxic and harmful. One such toxic metal is

lead

chromium

copper

tin

The correct answer is:

B) lead.

Lead is a toxic metal that can be harmful if ingested or absorbed into the body. It was historically used in some cans but has been largely phased out due to its harmful effects. Modern beverage cans are typically made from materials like aluminum or tin-coated steel, which are safer.

The correct answer is:

B) lead.

21 / 22

Lead nitrate (PbNO3) is used in the manufacture of matches and explosives. When it reacts with potassium iodide (KI) in an aqueous solution, the reaction it undergoes is

displacement

decomposition

neutralization

double displacement

The correct answer is:

D) double displacement.

When lead nitrate (Pb(NO₃)₂) reacts with potassium iodide (KI), a double displacement reaction occurs, resulting in the formation of lead iodide (PbI₂), which precipitates out of the solution, and potassium nitrate (KNO₃). The reaction can be represented as:

Pb(NO3)2(aq)+2KI(aq)→PbI2(s)+2KNO3(aq)\text{Pb(NO}_3\text{)}_2 (aq) + 2 \text{KI} (aq) \rightarrow \text{PbI}_2 (s) + 2 \text{KNO}_3 (aq)Pb(NO3)2(aq)+2KI(aq)→PbI2(s)+2KNO3(aq)

In this reaction, the cations and anions exchange partners, characteristic of a double displacement reaction.

yes

The correct answer is:

D) double displacement.

Pb(NO3)2(aq)+2KI(aq)→PbI2(s)+2KNO3(aq)\text{Pb(NO}_3\text{)}_2 (aq) + 2 \text{KI} (aq) \rightarrow \text{PbI}_2 (s) + 2 \text{KNO}_3 (aq)Pb(NO3)2(aq)+2KI(aq)→PbI2(s)+2KNO3(aq)

In this reaction, the cations and anions exchange partners, characteristic of a double displacement reaction.

22 / 22

Silver, platinum and gold are used for making ornaments. These metals are found in their native state in nature because they are

least reactive

highly reactive

rare

expensive

The correct answer is:

C) least reactive.

Silver, platinum, and gold are least reactive, which means they do not easily react with air, water, or other chemicals in the environment. This property allows them to be found in their native (uncombined) state in nature, making them ideal for use in making ornaments.

The correct answer is:

C) least reactive.

Your score is

The average score is 13%

BCSE Chemistry 2020

This quiz contains MCQ from BCSE 2020 Board Exam Paper

1 / 26

What is the number of electron(s) required by a halogen to form a halide ion?

A halogen requires 1 electron to complete its outer shell and achieve a stable electron configuration (similar to that of a noble gas). This is because halogens have 7 electrons in their outermost shell, and gaining 1 electron gives them a full octet.

Therefore, the correct answer is:

D: 1.

Great going!

Therefore, the correct answer is:

D: 1.

2 / 26

Fluorine is the most electronegative element because it

has variable oxidation state

has negative oxidation state

exhibits positive oxidation state

has low nuclear charge

Fluorine is the most electronegative element because it has a strong tendency to attract electrons due to its small atomic size and high effective nuclear charge. It always exhibits a negative oxidation state (−1) in its compounds, as it is highly electronegative and does not give up electrons easily.

The correct answer is:

C: has negative oxidation state.

The correct answer is:

C: has negative oxidation state.

WOW! correct

3 / 26

The percentage composition of oxygen in CaSO4 is

11.76%

47.05%.

18.18%

16%

To find the percentage composition of oxygen in CaSO₄ (calcium sulfate), we need to first determine its molar mass and then calculate the proportion of oxygen.

Molar masses of elements:
- Calcium (Ca) = 40.08 g/mol
- Sulfur (S) = 32.06 g/mol
- Oxygen (O) = 16.00 g/mol
Molar mass of CaSO₄:
MCaSO₄=(1×40.08)+(1×32.06)+(4×16.00)=40.08+32.06+64.00=136.14 g/molM_{\text{CaSO₄}} = (1 \times 40.08) + (1 \times 32.06) + (4 \times 16.00) = 40.08 + 32.06 + 64.00 = 136.14 \, \text{g/mol}MCaSO₄=(1×40.08)+(1×32.06)+(4×16.00)=40.08+32.06+64.00=136.14g/mol
Mass of oxygen in CaSO₄:
4×16.00=64.00 g/mol4 \times 16.00 = 64.00 \, \text{g/mol}4×16.00=64.00g/mol
Percentage composition of oxygen:
Percentage of oxygen=(64.00136.14)×100=47.02%\text{Percentage of oxygen} = \left( \frac{64.00}{136.14} \right) \times 100 = 47.02\%Percentage of oxygen=(136.1464.00)×100=47.02%

So, the percentage composition of oxygen in CaSO₄ is approximately 47.05%, which matches option A.

To find the percentage composition of oxygen in CaSO₄ (calcium sulfate), we need to first determine its molar mass and then calculate the proportion of oxygen.

Molar masses of elements:
- Calcium (Ca) = 40.08 g/mol
- Sulfur (S) = 32.06 g/mol
- Oxygen (O) = 16.00 g/mol
Molar mass of CaSO₄:
MCaSO₄=(1×40.08)+(1×32.06)+(4×16.00)=40.08+32.06+64.00=136.14 g/molM_{\text{CaSO₄}} = (1 \times 40.08) + (1 \times 32.06) + (4 \times 16.00) = 40.08 + 32.06 + 64.00 = 136.14 \, \text{g/mol}MCaSO₄=(1×40.08)+(1×32.06)+(4×16.00)=40.08+32.06+64.00=136.14g/mol
Mass of oxygen in CaSO₄:
4×16.00=64.00 g/mol4 \times 16.00 = 64.00 \, \text{g/mol}4×16.00=64.00g/mol
Percentage composition of oxygen:
Percentage of oxygen=(64.00136.14)×100=47.02%\text{Percentage of oxygen} = \left( \frac{64.00}{136.14} \right) \times 100 = 47.02\%Percentage of oxygen=(136.1464.00)×100=47.02%

So, the percentage composition of oxygen in CaSO₄ is approximately 47.05%, which matches option A.

4 / 26

The complete equipment used to carry out electrolysis is known as an electrolytic

cell

circuit

process

current

5 / 26

Which one of the following is an example of a non-electrolyte?

copper sulphate

urea

sodium hydroxide

table salt

A non-electrolyte is a substance that, when dissolved in water, does not conduct electricity because it does not dissociate into ions.

Among the options:

Sodium hydroxide (NaOH) is a strong electrolyte.
Copper sulfate (CuSO₄) is a strong electrolyte.
Table salt (NaCl) is a strong electrolyte.

Urea, however, is a covalent compound and does not dissociate into ions in solution, so it does not conduct electricity.

The correct answer is:

D: urea.

Awesome !

A non-electrolyte is a substance that, when dissolved in water, does not conduct electricity because it does not dissociate into ions.

Among the options:

Sodium hydroxide (NaOH) is a strong electrolyte.
Copper sulfate (CuSO₄) is a strong electrolyte.
Table salt (NaCl) is a strong electrolyte.

Urea, however, is a covalent compound and does not dissociate into ions in solution, so it does not conduct electricity.

The correct answer is:

D: urea.

6 / 26

The branch of chemistry that deals with changes in heat energy during chemical reactions is called

green chemistry

thermochemistry

chemical energetics

analytical chemistry

The branch of chemistry that deals with changes in heat energy during chemical reactions is called thermochemistry. It specifically focuses on the study of heat absorbed or released during chemical reactions.

The correct answer is:

B: thermochemistry.

As pretty as you ! Correct!

The correct answer is:

B: thermochemistry.

7 / 26

Tshering has a balloon which contains 5.22 moles of helium. How many grams of helium are present in the balloon?

10g

20g

21g

Given that the molar mass of helium (He) is approximately 4.00 g/mol, and Tshering's balloon contains 5.22 moles of helium, we can calculate the mass of helium as follows:

Mass of helium=number of moles×molar mass\text{Mass of helium} = \text{number of moles} \times \text{molar mass}Mass of helium=number of moles×molar mass Mass of helium=5.22 moles×4.00 g/mol=20.88 g\text{Mass of helium} = 5.22 \, \text{moles} \times 4.00 \, \text{g/mol} = 20.88 \, \text{g}Mass of helium=5.22moles×4.00g/mol=20.88g

Since 20.88 g is closest to 21 g, the correct answer is:

C: 21 g.

Given that the molar mass of helium (He) is approximately 4.00 g/mol, and Tshering's balloon contains 5.22 moles of helium, we can calculate the mass of helium as follows:

Since 20.88 g is closest to 21 g, the correct answer is:

C: 21 g.

8 / 26

Which of the following is an example of an endothermic reaction?

burning of wood

fermentation

photosynthesis

respiration

Photosynthesis is an example of an endothermic reaction. In this process, plants absorb energy from sunlight to convert carbon dioxide and water into glucose and oxygen. The absorption of sunlight makes it endothermic.

The other processes listed are exothermic, as they release energy.

Thus, the correct answer is:

A: photosynthesis.

Well Done !

The other processes listed are exothermic, as they release energy.

Thus, the correct answer is:

A: photosynthesis.

9 / 26

Some halogen compounds have a negative impact on the environment. The compound that depletes the ozone layer is

chlorofluorocarbon

polytetrafluoroethylene

hydrogen fluoride

sodium fluoride

The compound that depletes the ozone layer is chlorofluorocarbon (CFC). CFCs are known to release chlorine atoms in the stratosphere, which can catalyze the breakdown of ozone (O₃) molecules.

The correct answer is:

B: chlorofluorocarbon.

Absolutely !

The compound that depletes the ozone layer is chlorofluorocarbon (CFC). CFCs are known to release chlorine atoms in the stratosphere, which can catalyze the breakdown of ozone (O₃) molecules.

The correct answer is:

B: chlorofluorocarbon.

10 / 26

Hydrochloric acid dissolves in water with the absorption of heat.

True

False

Hydrochloric acid dissolves in water with the absorption of heat.

11 / 26

The smaller the size of a halogen atom, the stronger is its oxidising power

False

True

True: The smaller the size of a halogen atom, the stronger its oxidizing power.

12 / 26

The molar volume of an ideal gas at STP is

2300 cm cube

2100 cm cube

2200 cm cube

22400

The molar volume of an ideal gas at Standard Temperature and Pressure (STP) is 22.4 liters.

This means that one mole of any ideal gas occupies 22.4 L at STP, where:

Standard Temperature = 273 K (0°C)

Standard Pressure = 1 atmosphere (atm)

Yes!

The molar volume of an ideal gas at Standard Temperature and Pressure (STP) is 22.4 liters.

This means that one mole of any ideal gas occupies 22.4 L at STP, where:

Standard Temperature = 273 K (0°C)

Standard Pressure = 1 atmosphere (atm)

13 / 26

Standard Temperature and Pressure (STP) values are most often used for gases as their characteristics change dramatically with temperature and pressure. Which of the following set has the correct values of STP?

273 Kelvin and 0 atmosphere

0 Kelvin and 1 atmosphere

273 Kelvin and 1 atmosphere

273 Kelvin and 760 atmospheres

The correct set of values for Standard Temperature and Pressure (STP) is:

D: 273 Kelvin and 1 atmosphere

At STP, the standard temperature is 273 K (or 0°C), and the standard pressure is 1 atmosphere (atm) or 760 mmHg (torr).

Yes ! The correct set of values for Standard Temperature and Pressure (STP) is:

D: 273 Kelvin and 1 atmosphere

At STP, the standard temperature is 273 K (or 0°C), and the standard pressure is 1 atmosphere (atm) or 760 mmHg (torr).

14 / 26

The number of ligands and oxidation number present in the compound [Fe(H₂O)₆]³⁺ is

6 and 3

3 ad 2

3 and 6

2 and 3

The coordination compound [Fe(H₂O)₆]³⁺ consists of:

Number of ligands: The compound has 6 water molecules (H₂O) acting as ligands.

Oxidation number of Fe: The overall charge on the complex is +3, and since water (H₂O) is a neutral ligand, the oxidation state of iron (Fe) is +3.

Thus, the correct answer is:

A: 6 and 3.

BINGO ! You got it right!

The coordination compound [Fe(H₂O)₆]³⁺ consists of:

Number of ligands: The compound has 6 water molecules (H₂O) acting as ligands.

Oxidation number of Fe: The overall charge on the complex is +3, and since water (H₂O) is a neutral ligand, the oxidation state of iron (Fe) is +3.

Thus, the correct answer is:

A: 6 and 3.

15 / 26

Which of the following hydrocarbon family has the highest boiling point?

ether

alcohol

alkane

halo-alkane

Among the given options, alcohols generally have the highest boiling point due to the presence of hydrogen bonding between molecules. Hydrogen bonding because of OH is a strong intermolecular force, which significantly increases the boiling point compared to other hydrocarbon families like alkanes, halo-alkanes, or ethers.

Therefore, the correct answer is:

D: alcohol.

Therefore, the correct answer is:

D: alcohol.

16 / 26

A compound has an empirical formula of C2H4Owith a molar mass of 132g. What is the molecular formula of the compound?

CH₁₂O₃

C4H12O8

C2H4O4

C₆H₁₂O₃

To determine the molecular formula of a compound, we need to follow these steps:

Step 1: Calculate the molar mass of the empirical formula.

The empirical formula is C₂H₄O.

The molar masses of the elements are:

Carbon (C) = 12.01 g/mol
Hydrogen (H) = 1.01 g/mol
Oxygen (O) = 16.00 g/mol

The molar mass of C₂H₄O is calculated as follows:

(2×12.01)+(4×1.01)+(1×16.00)=24.02+4.04+16.00=44.06 g/mol(2 \times 12.01) + (4 \times 1.01) + (1 \times 16.00) = 24.02 + 4.04 + 16.00 = 44.06 \, \text{g/mol}(2×12.01)+(4×1.01)+(1×16.00)=24.02+4.04+16.00=44.06g/mol

Step 2: Determine the ratio of the molecular mass to the empirical formula mass.

The molecular mass given is 132 g/mol, and the empirical formula mass is 44.06 g/mol.

Now, calculate the ratio:

Ratio=Molecular massEmpirical formula mass=13244.06≈3\text{Ratio} = \frac{\text{Molecular mass}}{\text{Empirical formula mass}} = \frac{132}{44.06} \approx 3Ratio=Empirical formula massMolecular mass=44.06132≈3

Step 3: Multiply the empirical formula by the ratio.

Since the ratio is approximately 3, the molecular formula is 3 times the empirical formula C₂H₄O.

Molecular formula=(C2H4O)×3=C6H12O3\text{Molecular formula} = (C₂H₄O) \times 3 = C₆H₁₂O₃Molecular formula=(C2H4O)×3=C6H12O3

Final Answer:

The molecular formula of the compound is C₆H₁₂O₃.

Yes!

To determine the molecular formula of a compound, we need to follow these steps:

Step 1: Calculate the molar mass of the empirical formula.

The empirical formula is C₂H₄O.

The molar masses of the elements are:

Carbon (C) = 12.01 g/mol
Hydrogen (H) = 1.01 g/mol
Oxygen (O) = 16.00 g/mol

The molar mass of C₂H₄O is calculated as follows:

Step 2: Determine the ratio of the molecular mass to the empirical formula mass.

The molecular mass given is 132 g/mol, and the empirical formula mass is 44.06 g/mol.

Now, calculate the ratio:

Step 3: Multiply the empirical formula by the ratio.

Since the ratio is approximately 3, the molecular formula is 3 times the empirical formula C₂H₄O.

Molecular formula=(C2H4O)×3=C6H12O3\text{Molecular formula} = (C₂H₄O) \times 3 = C₆H₁₂O₃Molecular formula=(C2H4O)×3=C6H12O3

Final Answer:

The molecular formula of the compound is C₆H₁₂O₃.

17 / 26

The gram molecular mass of Ca (OH)2 is 58g.

False

True

The gram molecular mass of Ca (OH)2 is 58g.

18 / 26

Chlorine reacts with hydrogen to form hydrogen chloride. As chlorine is more electronegative, it attracts shared paired of electrons towards itself. What type of compound is HCl?

ionic compound

non-polar covalent compound

metallic compound

polar covalent compound

In the case of hydrogen chloride (HCl), chlorine is more electronegative than hydrogen, which leads to an unequal sharing of electrons between the two atoms. This results in a dipole moment, with a partial negative charge on the chlorine atom and a partial positive charge on the hydrogen atom.

Thus, HCl is classified as a polar covalent compound.

The correct answer is:

B: polar covalent compound.

Roger That ! you are right!

Thus, HCl is classified as a polar covalent compound.

The correct answer is:

B: polar covalent compound.

19 / 26

Chlorine water bleaches coloured materials due to presence of

hydrochloric acid

chloride ion

hypochlorous acid

hydrogen Ion

Chlorine water bleaches colored materials due to the presence of hypochlorous acid (HOCl). When chlorine dissolves in water, it reacts to form hypochlorous acid, which is a powerful oxidizing agent and responsible for the bleaching action.

The correct answer is:

A: hypochlorous acid.

Jigdra !

The correct answer is:

A: hypochlorous acid.

20 / 26

1.809 x 10^23

3.088 x 10^22

6.023 x 10^21

5.420 x 10^24

To find out how many salt (NaCl) molecules are consumed when taking 3 grams daily, we can follow these steps:

Step 1: Calculate the Molar Mass of NaCl

The molar mass of sodium chloride (NaCl) can be calculated by adding the atomic masses of sodium (Na) and chlorine (Cl):

Sodium (Na): approximately 22.99 g/mol
Chlorine (Cl): approximately 35.45 g/mol

Molar mass of NaCl=22.99+35.45=58.44 g/mol\text{Molar mass of NaCl} = 22.99 + 35.45 = 58.44 \, \text{g/mol}Molar mass of NaCl=22.99+35.45=58.44g/mol

Step 2: Convert Grams to Moles

Next, convert the mass of NaCl consumed (3 grams) into moles using the molar mass:

Step 3: Calculate the Number of Molecules

To find the number of molecules, multiply the number of moles by Avogadro's number (approximately 6.022×10236.022 \times 10^{23}6.022×1023 molecules/mol):

Final Answer

Therefore, the amount of salt molecules consumed in a day when taking 3 grams of NaCl is approximately:

≈3.088×1022 molecules\approx 3.088 \times 10^{22} \, \text{molecules}≈3.088×1022molecules

So, the correct choice is B) 3.088 x 10²².

To find out how many salt (NaCl) molecules are consumed when taking 3 grams daily, we can follow these steps:

Step 1: Calculate the Molar Mass of NaCl

The molar mass of sodium chloride (NaCl) can be calculated by adding the atomic masses of sodium (Na) and chlorine (Cl):

Sodium (Na): approximately 22.99 g/mol
Chlorine (Cl): approximately 35.45 g/mol

Molar mass of NaCl=22.99+35.45=58.44 g/mol\text{Molar mass of NaCl} = 22.99 + 35.45 = 58.44 \, \text{g/mol}Molar mass of NaCl=22.99+35.45=58.44g/mol

Step 2: Convert Grams to Moles

Next, convert the mass of NaCl consumed (3 grams) into moles using the molar mass:

Step 3: Calculate the Number of Molecules

To find the number of molecules, multiply the number of moles by Avogadro's number (approximately 6.022×10236.022 \times 10^{23}6.022×1023 molecules/mol):

Final Answer

Therefore, the amount of salt molecules consumed in a day when taking 3 grams of NaCl is approximately:

≈3.088×1022 molecules\approx 3.088 \times 10^{22} \, \text{molecules}≈3.088×1022molecules

So, the correct choice is B) 3.088 x 10²².

21 / 26

The correct sequence of filling up orbitals is

1s 2s 2p 3p 3s 4s 3d

1s 2s 3s 2p 3p 4s 3d

1s 2s 2p 3s 3p 4s 3d

1s 2s 2p 3s 3p 3d 4s

The Aufbau principle governs the sequence in which electrons fill atomic orbitals. According to this rule, electrons fill orbitals starting from the lowest energy level to the highest. The energy levels of orbitals are not strictly in numerical order due to electron-electron interactions and shielding effects.

Correct Filling Sequence:

1s: The lowest energy orbital, so it fills first.

2s: Next in energy, so it fills after 1s.

2p: Higher energy than 2s, so it fills next.

3s: Higher than 2p, so it fills after 2p.

3p: Fills after 3s.

4s: Even though it's in the 4th shell, it has lower energy than 3d, so it fills before 3d.

3d: Fills after 4s due to its higher energy.

Thus, the correct sequence of filling is:

1s 2s 2p 3s 3p 4s 3d\text{1s} \, 2s \, 2p \, 3s \, 3p \, 4s \, 3d1s2s2p3s3p4s3d

This is why option B: 1s 2s 2p 3s 3p 4s 3d is the correct answer.

BOOM ! Correct !

Correct Filling Sequence:

1s: The lowest energy orbital, so it fills first.

2s: Next in energy, so it fills after 1s.

2p: Higher energy than 2s, so it fills next.

3s: Higher than 2p, so it fills after 2p.

3p: Fills after 3s.

4s: Even though it's in the 4th shell, it has lower energy than 3d, so it fills before 3d.

3d: Fills after 4s due to its higher energy.

Thus, the correct sequence of filling is:

1s 2s 2p 3s 3p 4s 3d\text{1s} \, 2s \, 2p \, 3s \, 3p \, 4s \, 3d1s2s2p3s3p4s3d

This is why option B: 1s 2s 2p 3s 3p 4s 3d is the correct answer.

22 / 26

The reaction of carboxylic acids with alcohols in the presence of conc. as a catalyst is

combustion

neutralization

oxidation

esterification

The reaction of carboxylic acids with alcohols in the presence of a concentrated acid catalyst is known as esterification. This process forms an ester and water.

Therefore, the correct answer is:

B: esterification.

The reaction of carboxylic acids with alcohols in the presence of a concentrated acid catalyst is known as esterification. This process forms an ester and water.

Therefore, the correct answer is:

B: esterification.

23 / 26

In an atom, the ‘p’ orbital can accommodate a maximum of six electrons

False

True

True: In an atom, the 'p' orbital can accommodate a maximum of six electrons.

24 / 26

The high solubility of ethyl alcohol in water is due to the formation of high intramolecular hydrogen bonding.

False

True

False: The high solubility of ethyl alcohol in water is due to the formation of intermolecular hydrogen bonding.

25 / 26

When an aqueous solution of NaCl is electrolysed, the gas evolved at cathode is

oxygen

hydrogen peroxide

hydrogen

chlorine

When an aqueous solution of NaCl (sodium chloride) is electrolyzed, water is reduced at the cathode, producing hydrogen gas.

The reaction at the cathode is:

2H2O+2e−→H2+2OH−2H_2O + 2e^- \rightarrow H_2 + 2OH^-2H2O+2e−→H2+2OH−

Thus, the gas evolved at the cathode is hydrogen.

The correct answer is:

A: hydrogen.

When an aqueous solution of NaCl (sodium chloride) is electrolyzed, water is reduced at the cathode, producing hydrogen gas.

The reaction at the cathode is:

2H2O+2e−→H2+2OH−2H_2O + 2e^- \rightarrow H_2 + 2OH^-2H2O+2e−→H2+2OH−

Thus, the gas evolved at the cathode is hydrogen.

The correct answer is:

A: hydrogen.

26 / 26

Which of the following sequence is correct for the oxidation of alcohol?

ethanolà ethanoic acidà ethanal

ethanolà ethanol à ethanoic acid

ethanalà ethanoic acidà ethanol

ethanalà ethanolà ethanoic acid

The correct sequence for the oxidation of alcohol is:

Ethanol (an alcohol) can be oxidized to ethanal (an aldehyde) and then further oxidized to ethanoic acid (acetic acid).

So the correct sequence is:

A: ethanol → ethanal → ethanoic acid.

True , The correct sequence for the oxidation of alcohol is:

Ethanol (an alcohol) can be oxidized to ethanal (an aldehyde) and then further oxidized to ethanoic acid (acetic acid).

So the correct sequence is:

A: ethanol → ethanal → ethanoic acid.

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