The Total solution for NCERT class 6-12
Calculate the mass of anon-volatile solute (molar mass 40 g mol−1) which should bedissolved in 114 g octane to reduce its vapour pressure to 80%.
Let the vapour pressure of pure octane be
Molar mass of solute, M2 =40 g mol−1
Mass of octane, w1 =114 g
Molar mass of octane, (C8H18), M1 =8 × 12 + 18 × 1
= 114 g mol−1
Hence, the required mass of thesolute is 8 g.