Test00999

1. Calculate the molar mass of the following:

(i) H2O (ii) CO2 (iii) CH4

Solution:
Correct Option: H_{2}*O = 18g / m * ol C*O_{2} = 44g / m * ol and C*H_{4} = 16g / m * ol
Use atomic masses: H = 1 , C = 12 , O = 16 .
H_{2}*O = (2 * 1) + 16 = 18g / m * ol
- C*O_{2} = 12 + (2 * 16) = 44g / m * ol
- C*H_{4} = 12 + (4 * 1) = 16g / m * ol .
2. Calculate the mass per cent of different elements present in sodium sulphate (Na2SO4).
Solution:
BeWise Classes
Correct Option: Descriptive calculation
Molar mass of Na2SO4 = (2×23) +32+ (4 × 16) = 142 g/mol.
Mass per cent of sodium = 46/142 * 100 = 32.39%
Mass per cent of sulphur = 32/142 * 100 = 22.54%
Mass per cent of oxygen = 64/142 * 100 = 45.07%
DeWe Classes
Therefore, the elements present are sodium 32.39%, sulphur 22.54%, and oxygen 45.07%.