Question

Question 5.7 What will be the pressure exerted by a mixture of 3.2 g of methane and 4.4 g of carbon dioxide contained in a 9 dm^3 flask at 27 °C ?

Class XI States of Matter Page 153

Answer 1

mass of methane = 3.2g
molar mass of methane ( CH4) = 16g/mol
hence, mole of methane = mass of methane/molar mass of methane
= 3.2/16 = 0.2 mol

similarly , mass of CO2 = 4.4g
molar mass of CO2 = 44g
hence, mole of CO2 = 4.4/44 = 0.1 mol

so, total mole of mixture = mole of CH4 + mole of CO2 = 0.2 + 0.1 = 0.3 mol

now, use gaseous formula,
PV = nRT
so, P = nRT/V
here, n = 0.3 mol , R = 0.0821 dm³atm/K/mol
T = 27°C or 300K , V = 9 dm³
now, P = 0.3 × 0.0821 × 300/9 =0.821 atm

hence, pressure exerted by mixture = 0.821 atm