1) C + HNO3 = CO2 + NO2 + H2O, баланс:
C + 2H2O -4e- = CO2 + 4H+ | 4 | 4 | 1 |
(NO3)- + 2H+ +e- = NO2 + H2O | 1 | | 4 |
C + 4(NO3)- + 4H+ = CO2 + 4NO2 + 2H2O;
C + 4HNO3 = CO2 + 4NO2 + 2H2O;
2) KMnO4 + KI + H2O = MnO2 + I2 + KOH, баланс:
(MnO4)- + 2H2O +3e- = MnO2 + 4(OH)- | 3 | 6 | 2 |
2I- -2e- = I2 | 2 | | 3 |
2(MnO4)- + 4H2O + 6I- = 2MnO2 + 3I2 + 8(OH)-;
2KMnO4 + 6KI + 4H2O = 2MnO2 + 3I2 + 8KOH.
2Cu + O2 = 2CuO M(Mg)=24g/mol , M(CuO)=63.5+16=79.5g/mol
63.5 22.4 2*79.5
n(Cu)=136/63.5=2.14 mol
n(O2)=33.6/22.4=1.5mol
n(Cu)>n(O2)
33.6 / 22.4 = X/159 X=238.5g
n(CuO)=m/M=238.5 / 79.5=3 mol
ответ 238.5 г. 3 моль