Question

The aqueous solution that has the highest value
of relative lowering of vapour pressure at a given
temperature is
(a) 0,1 molal sodium phosphate
(b) 01 molal barium chloride
d) 0.1 molal sodium chloride
(d) 01 molal glucose​

Answer 1

Answer:

a,0.1 molal sodium phosphate

Explanation:

Because relative lowering of vapour phase is directly proportional to van hoff's factor

Answer 2

The aqueous solution that has the highest valueof relative lowering of vapour pressure at a given value of temperature is (a) 0,1 molal sodium phosphate.

• Relative lowering of vapour pressure is directly proportional to the mole fraction of solute and vant's Hoff factor.
• Concentration is the same in all. so, vant's Hoff factor will affect the relative lowering in vapour pressure.
• The value of vant's Hoff factor is highest for sodium phosphate and is equal to 4. because sodium phosphate dissociates as Na3(PO4) ------> 3Na + PO4. so, the total number of molecules after dissociation is 4.
• Similarly, vant's Hoff factors for BaCl2, NaCl and glucose are 3, 2 and 1 respectively.
• Glucose does not dissociate.

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