дано

m(Na2CO3) = 300 g

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V(CO2)-?

Na2CO3+H2SO4-->Na2SO4+H2O+CO2

M(Na2CO3) = 106 g/mol

n(Na2CO3) = m/M = 300 / 106 = 2.83 mol

n(Na2CO3) = n(CO2) = 2.83 mol

V(CO2) = n(CO2) * Vm = 2.83 * 22.4 = 63.4 L

ответ 63.4 л