1. Ответ 3).
Ba + 2HCl = BaCl2 + H2
2Ba + O2 = 2BaO
2. Ответ 4).
H2N-CH2-COOH+C2H5OH----(H2SO4)--->H2O + H2N-CH2-COOC2H5
H2N-CH2-COOH+CH3OH----(H2SO4)--->H2O + H2N-CH2COOCH3
HCOH+Ag2O-HCOOH+2Ag
M(HCOH)=2+12+16=30
M(Ag)=2*108=216
72/30=x/216
x=518,4
m(Ag)=518,4