дано
m(ppa HCL) = 300 g
W(HCL) = 10%
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V(H2)-?
m(HCL) = 300*10% / 100% = 30 g
2HCL+Mg-->MgCL2+H2↑
M(HCL) =36.5 g/mol
n(HCL) = m/M = 30 / 36.5 = 0.82 mol
2n(HCL) = n(H2)
n(H2) = 0.82 / 2 = 0.41 mol
V(H2) = n(H2) * Vm = 0.41 * 22.4 = 9.184 L
ответ 9.184 л