Chemistry 9701 · AS & A Level · Carboxylic acids and derivatives

Carboxylic acids and derivatives — practice question

V is a liquid compound. By mass, it contains $77.2\%$ carbon, $11.4\%$ hydrogen and $11.4\%$ oxygen. Its relative molecular mass is $280$.
(a)[3]

Calculate the molecular formula for V. Show your working.

(b(i))[2]

Describe a chemical test and observation that confirms the presence of a carboxyl functional group.

(b(ii))[1]

A $3.196\,$g sample of $\text{Br}_2$ reacts completely with $2.800\,$g of V. Calculate how many alkene functional groups are present in one molecule of V. Show your working.

(c(i))[1]

$W$, $X$ and $Y$ have the same molecular formula, $\text{C}_5\text{H}_{10}\text{O}$.\n\n$W$, $X$ and $Y$ are each added separately to different reagents. The observations from these reactions are given in Table 4.1.\n\n$W$, $X$ and $Y$ each have a functional group in common.\n\nName the functional group that is found in all three compounds.

(c(ii))[1]

State the formula of the yellow precipitate produced when $X$ is added to alkaline $\text{I}_2\text{(aq)}$.

(c(iii))[3]

$W$ could be one of four structural isomers.\n\nDraw the skeletal formulae for two possible structural isomers of $W$.\n\nDescribe the type of structural isomerism shown.

(d)[3]

Fig. 5.1 shows the mass spectrum of ketone $Z$, $\text{C}_5\text{H}_{10}\text{O}$.\n\nUse the data in Fig. 5.1 to suggest the formulae of the fragments giving the $m/e$ peaks at 29 and 57. Deduce the identity of $Z$.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: Calculate % or $A_r$ values for C, H and O

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