m(Ca з дом.) = 10 g

W(дом.) = 20%

V(H2) - ?
m(Ca) = 10 g - 10*0.2 g = 8 g

n(Ca) = 8 g / 40 g / mol = 0.2 mol

Ca + 2CH3COOH = (CH3COO)2Ca + H2

за УХР: n(Ca) = n(H2) = 0.2 mol ;
V(H2) = 0.2 mol * 22.4 l / mol = 4.48 l

Ответ: 4.48 l .