Question

a) (i) Define equivalent mass. (2m) (ii) Which contains the greatest number of moles of oxygen atoms? (3m) (i) 1 mol of ethanol. (ii) 1 mol of formic acid (iii) 1 mol of H2O​

Answer 1

(1) Define equivalent mass.

answer : equivalent mass is the mass of a substance that will combine with or displace a fixed quantity of another substance.

for example, Al combines with O and forms Al₂O₃

so, equivalent mass of aluminium = atomic mass of Al/valency = 27/3 = 9g

and equivalent mass of oxygen = atomic mass of O/valency = 16/2 = 8g

therefore 9g of aluminium combines with 8g of oxygen.

(2)  which contains the greatest number of moles of oxygen atoms.

(1) 1 mol of ethanol (2) 1 mol of formic acid (3) 1 mol of water.

answer : (ii) 1 mol of formic acid

explanation : (1) 1 mol of ethanol

chemical formula of ethanol is C₂H₅OH.

here you see only one oxygen atom is present in one molecule of ethanol.

so, no of moles of O atoms = 1 × 1 mol = 1 mol

(2) 1 mol of formic acid

chemical formula of formic acid is HCOOH

no of O atoms = 2 × no of formic acid molecules.

so, no of moles of O atoms = 2 × 1 mol = 2 mol

(3) 1 mol of H₂O

no of moles of O atoms = 1 × 1 mol = 1 mol

hence, it is clear that number of moles of oxygen atoms is maximum in option (ii) 1 mol of formic acid.