CH3CHO+Ag2O=2Ag+CH3COOH
1------------------------2
n(Ag)=2.7:108=0.025
n(CH3CHO)=0.025:2=0.0125
m(CH3CHO)=0.0125*44=0.55
M(CH3CHO)=44
Na2S+Pb(NO3)2 → 2NaNO3 + PbS↓
2Na + S + Pb +2NO3 → 2Na + 2NO3 + PBS↓
Pb + S → PbS↓
Mr(H₂) = 1·2 = 2
Mr(PH₃) = 31 + 1·3 = 34
34\2 = 17 водород легче фосфина в 17 раз