Answer to Question #68923 in Molecular Physics | Thermodynamics for DEEPENDRA SINGH
a pure gass which contains 14.3% hydrogen and 85.7% carbon of total mass.its density is 2.5 gram per leter at 0 degree centigrate and 1 atm.what is it molecular formula?
From the equation of state for perfect gas PV=m/M RT We obtain the expression for the density of gas ρ=m/V=PM/RT. Therefore the molar mass of gas is M=ρRT/P=(2.5×8.3×273)/(1.01×〖10〗^5 )=56 g/mol. Because M(H)=1 g/mol,M(C)=12 g/mol. We obtain 14.3/85.7×12=2. So the number of hydrogen atoms is twice of carbon. Because the molar mass of gas is 56, we obtain equation for the number of carbon atoms x 2×1×x+12×x=56 ⇒ x=4. So the molecular formula of the gas is C_4 H_8 Answers: C_4 H_8