a cylinder was filled with gaseous mixture containing CO N₂ (equal masses).The ratio of their partial pressure in cylinder are???

The total pressure of a mixture of gases is equal to the sum of the pressures that each would exert if it were present alone.
P_t = P_I + P₂ + P₃ + _{• •} 
This equation implies that each gas in the mixture behaves independently of the other.
 If each of the gases obeys the ideal-gas equation, we can write: 
$P_{CO}=n_{CO}\left(\frac{RT}{V}\right), P_{N_2}=n_{N_2}\left(\frac{RT}{V}\right)$
$\frac{P_{CO}}{P_{N_2}}=\frac{n_{CO}}{n_{N_2}}=\frac{{\displaystyle \frac{Mass of CO}{Molecular mass of CO}}}{{\displaystyle \frac{Mass of N_2}{Molecular mass of N_2}}}=\frac{Molecular mass of N_2}{Molecular mass of CO}=\frac{28}{28}=1$
Hence the ratio of partial pressure of CO:N₂​ is equal to 1 :1.