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An aqueous solution is 1.00 molal in KI. Which change will cause the vapour pressure of the solution to increase? ( neet pyq )

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Question:
An aqueous solution is 1.00 molal in KI. Which change will cause the vapour pressure of the solution to increase?

1. Addition of NaCl
2. Addition of Na2SO4
3. Addition of 1.00 molal KI
4. Addition of water



Answer:
 An aqueous solution is molal in . So, the addition of water will cause the vapour pressure to increase. This is according to Raoult's Law.

In the other three options, electrolyte undergo ionization, which leads to lowering of vapour pressure.

Hence, the correct option is D

Or 

According to raoults law
Ps = PoXa (Xa = mole fraction of solvent)
and on addition of water the mole fraction of water in the solution increases therefore vapour pressure increases.








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