As a result of the reaction of 109.5 grams of a solution of hydrochloric acid with an excess of zinc, a gas with a volume of 3.36 litres Was released. Calculate the mass fraction of hydrochloric acid in the original solution

Explanation:

Volume of gas produced = 3.36 L

as molar volume of gas at STP is 22.4 L

so

no of moles of H2 = 3.36 ÷ 22.4 = 0.15 mole

from balanced reaction equation

Zn + 2HCl = ZnCl2 + H2

Ratio of no of moles between H2 : HCl is 1:2

as H2 moles = 0.15 mole

so

HCl moles reacted = 0.15 × 2 = 0.3 mole

as HCl molar mass = 1 + 35.5 = 36.5 g/mole

so Mass of 0.3 mole of HCl = 0.3 × 36.5 = 10.85 gram

fraction of HCl in Solution

= 10.85 ÷ 109.5 = 0.1

0.1 ×100 so HCl is 10% of solution mass

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"