Equal weights of methane and hydrogen are mixed in an empty container at 25°C. The fraction of total pressure exerted by hydrogen is:

Explanation

According to Dalton's law of partial pressure, the total pressure of a mixture of gases is the sum of the partial pressure of the gases in the mixture. We can calculate the partial pressure by the following formula: Partial pressure H₂/ Partial pressure CH4 =Moles of H2/ Moles of CH4 pH2/ pCH4 = nH2/nCH4 We assume that x is the mass of hydrogen and methane each. The molecular mass of H2=2 The molecular mass of CH4=16 Mole = mass/Mr Moles of H2= x/2 Moles of CH4= x/16 Total moles= x/2 + x/16 = 9x/16 The partial pressure of H2= moles of H2/total moles =(x/2)÷(9x/16) =(x/2) x (16/9x) =8/9 so option B is the right answer.