дано
m техн(Al) = 90 g
W(пр.) = 15%
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V(H2)-?
m чист (Al) = 90 - (90* 15% / 100%) = 76.5 g
6HF+2Al-->2AlF3+3H2
M(AL) = 27 g/mol
n(Al) = m/M = 76.5 / 27 = 2.83 mol
2n(AL) = 3n(H2)
n(H2) = 3*2.83 / 2 = 4.245 mol
V(H2) = Vm*n = 22.4 * 4.245 = 95 L
ответ 95 л