The empirical formula of an organic compound containing carbon and hydrogen is CH₂. The mass of one litre of this organic gas at STP  is exactly equal to that of one litre of N₂ at STP. Therefore, the molecular formula of the organic gas is:

1. C₂H₄

2. C₃H₆

3. C₆H₁₂

4. C₄H₈

A sample of pure compound is found to have Na = 0.0887 mole, O = 0.132 mole, C = 2.65 × 10²² atoms.

The empirical formula of the compound is :

1. Na₂CO₃

2. Na₃O₂C₅

3. ${\mathrm{Na}}_{0.0887}{0}_{0.132}{\mathrm{C}}_{2.65\times {10}^{22}}$

4. NaCO

An organic compound containing C, H, and N gave the following on analysis: C = 40%, H = 13.3% and N = 46.67%. Its empirical formula would be:

1. CHN
2. C₂H₂N
3. CH₄N
4. C₂H₇N

An organic compound has the following composition by mass: C = 40.687%, H = 5.085%, O = 54.228%. Given vapour density = 59, find its molecular formula.

1. C₄H₆O₄

2. C₄H₆O₂

3. C₄H₄O₂

4. None of the above

When 4.77 g of NaCl is mixed with 5.77 g of AgNO₃, AgCl precipitates according to the reaction:

NaCl + AgNO₃ → AgCl↓ + NaNO₃

What is the mass of AgCl precipitated?

1.  11.70 gm.

2.  9.70 gm.

3.  4.86 gm.

4.  2.86 gm.

At standard temperature and pressure (STP), the volume of oxygen required to completely combust 30 ml of acetylene under similar conditions is:

1. 100 ml

2. 75 ml

3. 50 ml

4. 25 ml

What is the volume (in litres) of oxygen at STP required for complete combustion of 32 g of CH₄

(1) 44.8

(2) 89.6

(3) 22.4

(4) 179.2

A mixture of gases contains H₂ and O₂ gases in the ratio of 1:4 (w/w). What is the molar

ratio of the two gases in the mixture?

1. 1:4             

2. 4:1             

3. 16:1               

4. 2:1

Which of the following quantities would change if Avogadro’s number were changed from 6.022 × 10²³ mol⁻¹ to 6.022 × 10²⁰ mol⁻¹?

1. The definition of mass in units of grams.

2. The mass of one mole of carbon.

3. The ratio of chemical species to each other in a balanced equation.

4. The ratio of elements to each other in a compound.

20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide

and 8.0 g magnesium oxide. What will be the percentage purity of magnesium carbonate

in the sample? (Atomic weight of Mg = 24)

1. 75

2. 96

3. 60

4. 84