a)
\(CH_4+2O_2\xrightarrow[]{}CO_2+H_2O\\ n_{CH4}=\frac{V}{22,4}=\frac{5,6}{22,4}=0,25\left(mol\right)\\ V_{O2}=0,5.22,4=11,2l\)
b)
\(V_{kk}=11,2.5=56l\)
c)
\(CO_2+Ca\left(OH\right)_2\xrightarrow[]{}CaCO_3+H_2O\\ n_{CaCO3}=n_{CO2}=n_{CH4}=0,25\left(mol\right)\\ m_{CaCO3}=n.M=0,25.100=25g\)