a) Ta có: (n_T)/(n_S)=(P_T)/(P_S)

->(0,25)/(n_S)= $$\dfrac{P}{1,4P}=$$(5)/(7)->n_S=(0,25.7)/(5)=0,35(mol) 

n_{CO_2}=a(mol), n_{CO}=b(mol)

->a+b=0,35(1)

Bảo toàn O: 2.0,25=2a+b(2)

(1),(2)->a=0,15, b=0,2

Bảo toàn C: n_C=n_{CO_2}+n_{CO}=0,15+0,2=0,35(mol)

->m_C=0,35.12=4,2(g)

b) 

%V_{CO_2}=(0,15)/(0,35).100%=42,86%

->%V_{CO}=100%-42,86%=57,14%