Дано
m(ppa CH3CH2CH2COOH)= 120 g
W = 25%
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V(H2)-?
2CH3CH2CH2COOH+Mg-->(CH3CH2CH2COO)2Mg+H2
m(CH3(CH2)2COOH) = 120*25% / 100% = 30 g
M(CH3CH2CH2COOH)= 88 g/mol
n(CH3CH2CH2COOH) = m/M = 30/88 = 0.34 mol
n(CH3CH2CH2COOH) = n(H2)= 0.34 mol
V(H2) = n*Vm = 0.34*22.4 = 7.62 l
ответ 7.62 л