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

Find the mass of precipitate formed when 50 mL of 16.9% (w/v) AgNO₃ solution is mixed with 50 mL of 5.8% (w/v) NaCl solution.

(Ag = 107.8, N = 14, O = 16, Na= 23,Cl=35.5)

The number of water molecules is maximum in -

1. 18 molecules of water

2. 1.8 g of water

3. 18 g of water

4. 18 moles of water

How many atoms are present in 0.1 mole of a triatomic gas?

Given: Avogadro constant, Nₐ = 6.02 × 10²³ mol⁻¹

A stoichiometric reaction is initiated by filling a sealed steel vessel with 10 g of hydrogen gas and 64 g of oxygen gas, followed by an ignition to trigger an explosion. Determine the total number of moles of water (\(\text{H}_2\text{O}\)) produced by this combustion reaction once the limiting reactant is completely consumed:

1. 2 moles

2. 3 moles

3. 4 moles

4. 1 mole

Volume occupied by one molecule of water (density = 1g cm^-3) is:

1. 9.0 x 10^-23 cm³

2. 6.023 x 10^-23 cm³

3. 3.0 x10^-23 cm³

4. 5.5 x10^-23 cm³

An organic compound contains carbon, hydrogen, and oxygen.
Its elemental analysis gave C, 38.7%, and H, 9.67%.
The empirical formula of the compound would be:

1. CH₃O                                   

2. CH₂O

3. CHO                                     

4. CH₄O

How many moles of lead (II) chloride will be formed from a reaction between 6.5g of PbO and 3.2g of HCl?

(1) 0.044                           

(2) 0.333

(3) 0.011                           

(4) 0.029

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.

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