Дано
V(H2S)=5.6 L
m(ppa KOH)=280 g
W(KOH)=20%
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m(K2S)-?
n(K2S)-?
m(KOH)=280*20%/100%=56 g
n(H2S)=V(H2S) / Vm , Vm=22.4 L/mol
n(H2S)=5.6 / 22.4=0.25 mol
M(KOH)=56 g/mol
n(KOH) = m/M = 56/56 = 1 mol
n(H2S) n(H2S)=n(K2S) = 0.25 mol
2KOH+H2S-->K2S+2H2O
ответ сульфид калия, 0.25 моль