Chemistry Class 12 NCERT Solutions: Chapter 2 Solutions Part 2

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Q: 5. Calculate

(A) Molality

(B) Molarity and

(C) Mole fraction

Of KI if the density of 20% (mass/mass) aqueous KI is .


(A) Molar mass of

(mass/mass) aqueous solution of means is present in 100 g of solution. That is,

20 g of KI is present in of water of water

Therefore, molality of the solution


(B) It is given that the density of the solution

Therefore, molarity of the solution


Moles of water

Therefore, mole fraction of

Q: 6. , a toxic gas with rotten egg like smell, is used for the qualitative analysis. If the solubility of in water at P is m, calculate Henry's law constant.


It is given that the solubility of in water at STP is i.e., of is dissolved in of water. Moles of water

Mole fraction of

At STP, pressure

According to Henry’s law