Chemistry Class 12 NCERT Solutions: Chapter 2 Solutions Part 12

Q: 23. Suggest the most important type of intermolecular attractive interaction in the following pairs.

(i) n-hexane and n-octane

(ii) Equation

(iii) Equation and water

(iv) Methanol and acetone

(v) Acetonitrile Equation and acetone Equation .


(i) Van der Wall's forces of attraction

(ii) Van der Wall's forces of attraction

(iii) Ion-dipole interaction

(iv) Hydrogen bonding

(v) Dipole-dipole interaction

Q: 24. Based on solute-solvent interactions, arrange the following in order of increasing solubility in n-octane and explain. Cyclohexane, Equation .

Answer :

n-octane is a non-polar solvent. Therefore, the solubility of a non-polar solute is more than that of a polar solute in the n-octane.

The order of increasing polarity is:

Cyclohexane Equation

Therefore, the order of increasing solubility is:


Q: 25. Amongst the following compounds, identify which are insoluble, partially soluble and highly soluble in water?

(i) phenol (ii) toluene (iii) formic acid

(iv) ethylene glycol (v) chloroform (vi) pentanol.


(i) Phenol Equation has the polar group Equation and non-polar group Equation . Thus, phenol is partially soluble in water.

(ii) Toluene Equation has no polar groups. Thus, toluene is insoluble in water.

(iii) Formic acid Equation has the polar group Equation and can form H-bond with water. Thus, formic acid is highly soluble in water

(iv) Ethylene glycol

Q 25 Image of Ethylene glycol

Q 25 Image of Ethylene Glycol

Q 25 Image of Ethylene glycol

has polar Equation group and can form Equation bond. Thus, it is highly soluble in water.

(v) Chloroform is insoluble in water.

(vi) Pentanol Equation has polar -OH group, but it also contains a very bulky non-polar - Equation group. Thus, pentanol is partially soluble in water.

Q: 26. If the density of some lake water is Equation and contains Equation of Equation ions per kg of water, calculate the molality of Equation ions in the lake.


Number of moles present in Equation of Equation ions = Equation = 4 mol

Therefore, molality of Na+ ions in the lake Equation


Q: 27. If the solubility product of Equation is Equation , calculate the maximum molarity of CuS in aqueous solution.

Answer :

Solubility product of Equation

Let s be the solubility of Equation in mol Equation


Now, Equation



Then, we have, Equation



Hence, the maximum molarity of Equation in an aqueous solution is Equation

Q: 28. Calculate the mass percentage of aspirin Equation in acetonitrile Equation when Equation of Equation is dissolved in Equation .


6.5 g of Equation is dissolved in = 450 g of Equation

Total mass of the solution = (6.5 + 450) g

= 456.5 g

Therefore, mass percentage of Equation Equation


Q: 29. Nalorphine Equation , similar to morphine, is used to combat withdrawal symptoms in narcotic users. Dose of nalorphine generally given is 1.5 mg. Calculate the mass of Equation aqueous solution required for the above dose.

Equation of water contains Equation mol Equation

Therefore, total mass of the solution Equation


This implies that the mass of the solution containing Equation of nalorphine is Equation .

Therefore, mass of the solution containing Equation of nalorphine is:



Hence, the mass of aqueous solution required is Equation .

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