Chemistry Class 12 NCERT Solutions: Chapter 2 Solutions Part 12

Download PDF of This Page (Size: 154K)

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

(i) n-hexane and n-octane

(ii)

(iii) and water

(iv) Methanol and acetone

(v) Acetonitrile and acetone .

Answer:

(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, .

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

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.

Answer:

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

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

(iii) Formic acid has the polar group 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

(v) Chloroform is insoluble in water.

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

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

Answer:

Number of moles present in of ions = = 4 mol

Therefore, molality of Na+ ions in the lake

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

Answer :

Solubility product of

Let s be the solubility of in mol

Now,

Then, we have,

Hence, the maximum molarity of in an aqueous solution is

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

Answer:

6.5 g of is dissolved in = 450 g of

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

= 456.5 g

Therefore, mass percentage of

Q: 29. Nalorphine , 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 aqueous solution required for the above dose.

of water contains mol

Therefore, total mass of the solution

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

Therefore, mass of the solution containing of nalorphine is:

Hence, the mass of aqueous solution required is .