1) 50% 2)33% 3)примерно 71,5% 4)60%
СО2 + 2 NaOH = Na2CO3 + H2O
n NaOH = 40*0.1/40 = 0.1 моль
n CO2 = n Na2CO3 = 0.04 моль
m Na2CO3 = 0.04*(23*2+12+48) = 4.24 г