List of top Chemistry Questions on Percentage Composition

Calculate the mass per cent of different elements present in sodium sulphate \((\text{Na}_2\text{SO}_4)\).

A welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives 3.38 g carbon dioxide, 0.690 g of water and no other products. A volume of 10.0 L (measured at STP) of this welding gas is found to weigh 11.6 g. Calculate:

1. empirical formula, 
2. molar mass of the gas, and 
3. molecular formula

How are 0.50 mol Na₂CO₃ and 0.50 M Na₂CO₃ different?

Convert the following into basic units:

1. 28.7 pm
2. 15.15 pm
3. 25365 mg

Calculate the concentration of nitric acid in moles per litre in a sample which has a density, 1.41 g mL^–1 and the mass per cent of nitric acid in it being 69%.

The following data are obtained when dinitrogen and dioxygen react together to form different compounds: 
          Mass of dinitrogen                Mass of dioxygen 
(i)              14 g                                            16 g 
(ii)             14 g                                             32 g 
(iii)            28 g                                             32 g 
(iv)            28 g                                             80 g 

1. Which law of chemical combination is obeyed by the above experimental data? Give its statement.
2. Fill in the blanks in the following conversions: 
   (i)1 km = ...................... mm = ...................... pm 
   (ii) 1 mg = ...................... kg = ...................... ng 
   (iii) 1 mL = ...................... L = ...................... dm³