Question

if 5 gram and dissolve in 50 gram of water to reduce the pressure having vapour pressure of pure water is 630 mm find relative lowering of vapour pressure​

Answer 1

Answer:

weight of NaOH = 5g

molecular weight of NaOH = 40g/mol

so, number of mole of NaOH , n = 5/40 = 0.125

weight of water = 50g

molecular weight of water = 18g/mol

so, number of mole of water, N = 50/18 = 2.77

now using formula,

relative lowering of vapor pressure = mole fraction of solute

= n/(n + N)

= 0.125/(0.125 + 2.77)

= 0.125/2.895

= 0.0431

and lowering of vapor pressure = vapor pressure of pure water × relative lowering of vapor pressure

= 630 mm Hg × 0.0431

= 27.153 mm Hg

Explanation: