More practice questions

5. Q5. Arrange CH₂Cl₂, CCl₄, CH₃Cl and CHCl₃ in order of increasing boiling point.

   Show answerHide answer

   CH₃Cl < CH₂Cl₂ < CHCl₃ < CCl₄: each extra chlorine makes the molecule bigger and heavier, with more electrons, so the van der Waals forces grow (reasoned from NCERT page 168).

6. Q6. What is the mass of 50.0 mL of 1-iodopropane? (Use NCERT Table 6.3.)

   Show answerHide answer

   50.0 mL × 1.747 g/mL = 87.35 g, about 87.4 g (NCERT page 169).

7. Q7. By how many kelvin does 2-bromo-2-methylpropane boil below 2-bromobutane, and which is more branched?

   Show answerHide answer

   364 − 346 = 18 K. 2-Bromo-2-methylpropane is more branched: its central carbon carries three methyl groups, so the molecule is more compact (NCERT page 168; reasoned).

8. Q8. Iodoalkanes and bromoalkanes develop colour on standing in light, but chloroalkanes do not. Suggest a reason.

   Show answerHide answer

   NCERT notes that bromides and iodides develop colour when exposed to light (page 167). The C–I and C–Br bonds are the weakest of the C–X bonds (NCERT Table 6.2, page 164), so light can break them, releasing coloured iodine or bromine (reasoned).