(a)(i) What is the general… | Chemistry

Question 1 Report

(a)(i) What is the general formula for alkanoic acids?

(ii) State two chemical properties of ethanoic acid.

(b) Which of propene, butane and pentane

(i) will decolorize acidified KMnO\(_4\) solution?

(ii) can be easily polymerized?

(iii) is an isomer of methylpropane?

(iv) can be obtained from an alkanol by dehydration?

Answer

Answer Details

(a)(i) The general formula for alkanoic acids is \(C_nH_{2n+1}COOH\) (equivalently \(C_nH_{2n}O_2\)).

(ii) Two chemical properties of ethanoic acid, \(CH_3COOH\):

It reacts with reactive metals to liberate hydrogen, e.g. \(2CH_3COOH + Mg \rightarrow (CH_3COO)_2Mg + H_2\).
It reacts with alkanols in the presence of concentrated \(H_2SO_4\) to form an ester (esterification). (It also reacts with bases and trioxocarbonate(IV) salts, turning blue litmus red as a weak acid.)

(b) Of propene, butane and pentane:

(i) The one that decolorizes acidified \(KMnO_4\) solution is propene (it is unsaturated, containing a C=C double bond).
(ii) The one that can be easily polymerized is propene (alkenes polymerize; propene gives polypropene).
(iii) The isomer of methylpropane is butane (both have the molecular formula \(C_4H_{10}\)).
(iv) The one that can be obtained from an alkanol by dehydration is propene (dehydration of propanol gives propene).

(a)(i) What is the general formula for alkanoic acids? (ii) State two chemical properties of ethanoic acid. (b) Which of propene, butane and pentane (i) wil...