Chemistry 9701 · AS & A Level
Hydrocarbons
100 practice questions on Hydrocarbons, with worked solutions and instant marking.
But-2-ene-1,4-diol is changed in two stages via an intermediate X to give oxobutanedioic acid. HOCH$_2$CH=CHCH$_2$OH $\xrightarrow{\text{step 1}}$ X $\xrightarrow[\text{hot, acidified KMnO}_4]{\text{step 2}}$ HO$_2$CCOCH$_2$CO$_2$H What reagent could be used for step 1, and what is the intermediate X?
Feb/March 2016
Hydrogen bromide may be added to T to form compound U. Compound U may then be hydrolysed to produce compound V. Four students, W, X, Y and Z, made these statements. W: Every atom in a molecule of compound T is in one plane. X: Compound V has only one chiral centre. Y: Step 1 is an electrophilic addition reaction. Z: Step 2 is a nucleophilic substitution reaction. Which two students are correct?
Feb/March 2016
Structural isomerism and stereoisomerism need to be taken into account when answering this question. Compound J is treated with KOH dissolved in ethanol. Three isomeric alkenes with molecular formula C$_4$H$_8$ are produced. What is J?
Feb/March 2016
Propene can take part in several different reactions. Which row is correct?
Feb/March 2017
Which compounds can be produced from but-2-ene in one reaction?
Feb/March 2017
What kinds of stereoisomerism are displayed by 2,4-dimethylhex-2-ene?
Feb/March 2018
Carbon and silicon are both elements in Group 14.
Feb/March 2018
Compound L has molecular formula $\text{C}_{10}\text{H}_{16}$. A sample of L was then reacted with an excess of hot, concentrated, acidified potassium manganate(VII), and compound M was formed. What might the structure of compound L be?
Feb/March 2019
A number of reactions occur in a car engine and in its catalytic converter. Which pair of substances are formed by reactions in both a car engine and a catalytic converter?
Feb/March 2019
When working through this question, you should take account of structural isomerism and stereoisomerism. 2-bromopentane is heated with an excess of ethanolic sodium hydroxide. How many different hydrocarbons are formed?
Feb/March 2019
When answering this question, take into account structural isomerism and stereoisomerism. How many isomers are non-cyclic with the molecular formula $\text{C}_5\text{H}_{10}$?
Feb/March 2020
Dibromopentanes are able to undergo ‘double elimination’ reactions, forming hydrocarbons. $\text{2NaOH} + \text{C}_5\text{H}_{10}\text{Br}_2 \rightarrow \text{C}_5\text{H}_8 + \text{2NaBr} + \text{2H}_2\text{O}$ Which isomer gives just one hydrocarbon product?
Feb/March 2021
For this question, you should take alkenes and cyclic alkanes into account. How many structural isomers of $\text{C}_4\text{H}_8$ are there?
Feb/March 2022
Which compound is able to decolourise $\text{Br}_2\text{(aq)}$?
Feb/March 2022
Cyclohexa-1,4-diene is reacted with bromine dissolved in tetrachloromethane, with no light present. Which product is produced?
Feb/March 2023
2-methylbut-2-ene is treated with hot, concentrated, acidified potassium manganate(VII) solution. Which products are formed in this reaction?
Feb/March 2023
When But-2-ene is treated with cold, dilute, acidified $\text{KMnO}_4$, product X is formed. When But-2-ene is treated with hot, concentrated, acidified $\text{KMnO}_4$, product Y is formed. Which statement about product X and product Y is correct?
Feb/March 2024
Which compound could be made from an alkene with formula $\text{C}_4\text{H}_8$ by an addition reaction?
Feb/March 2025
Which structural formulae correspond to 2,2-dimethylpentane?
May/June 2010
On heating with chlorine, the hydrocarbon 2,2-dimethylbutane reacts by free radical substitution. In a propagation step, the free radical X• is generated: $\text{(structure)} + \text{Cl}• \rightarrow X• + \text{HCl}$ How many distinct forms of X• can be produced?
May/June 2010
Which alkenes, when treated with steam at $600\,\text{K}$ and $6 \times 10^6\,\text{Pa}$ pressure in the presence of a phosphoric acid catalyst, may form an alcohol that contains a chiral carbon atom?
May/June 2011
How many isomers having the formula $\text{C}_5\text{H}_{10}$ possess structures that contain $\pi$ bonding?
May/June 2011
To answer this, consider how $\text{KMnO}_4$ reacts with different functional groups under the conditions given. The diagram depicts the structure of the naturally found molecule cholesterol. Cholesterol is then treated separately with cold, dilute acidified $\text{KMnO}_4$, and with hot, concentrated acidified $\text{KMnO}_4$. What change occurs in the number of chiral carbon atoms in the molecule in each reaction?
May/June 2011
Which compounds are formed from ethene in one reaction?
May/June 2011
In the reaction route shown below, an alkane is changed into a carboxylic acid over a number of steps. $\text{C}_{10}\text{H}_{22} \xrightarrow{\text{stage 1}} \text{C}_2\text{H}_4 \xrightarrow[\text{catalytic hydration}]{\text{stage 2}} \text{C}_2\text{H}_5\text{OH} \xrightarrow{\text{stage 3}} \text{CH}_3\text{CO}_2\text{H}$ What processes take place at stage 1 and at stage 3?
May/June 2011
Which of the following alkenes could, by reaction with steam at $600\ \text{K}$ and $6 \times 10^6\ \text{Pa}$ in the presence of a phosphoric acid catalyst, give an alcohol with a chiral carbon atom?
May/June 2011
Some intercontinental jet airliners run on kerosene. Its formula may be assumed to be $\text{C}_{14}\text{H}_{30}$.
May/June 2011
Crude oil is made up of a blend of hydrocarbons, together with other organic compounds whose molecules may include nitrogen, oxygen or sulfur. In an oil refinery, once crude oil has been separated by fractional distillation, several further processes can be applied, such as ‘cracking’, ‘isomerisation’, and ‘reforming’.
May/June 2011
Ethyne gas, $\mathrm{C_2H_2}$, better known as acetylene, is produced for making organic compounds by synthesis. It is also burned with oxygen in oxy-acetylene torches for cutting and welding metals. On an industrial scale, ethyne is prepared from calcium carbide, $\mathrm{CaC_2}$, or by cracking liquid hydrocarbons.
May/June 2011
Which substance does not give off a poisonous gas when it is burnt in a limited supply of air?
May/June 2012
Isomers X and Y each react with HBr. A blend of X and Y is then treated with HBr. Which three structures are the three different possible products formed in this reaction?
May/June 2012
Which compounds can be produced from propene in a single reaction?
May/June 2012
The two conversions shown here are as follows. $\text{NH}_4^{+} \rightarrow \text{NH}_3$ $\text{C}_2\text{H}_4 \rightarrow \text{C}_2\text{H}_6$ What common characteristic is shared by these two conversions?
May/June 2012
Ethene can be made in a school or college laboratory from ethanol by using the apparatus shown below.
May/June 2012
But-2-ene, $\text{CH}_3\text{CH}=\text{CHCH}_3$, is a useful compound produced when hydrocarbons in crude oil are cracked.
May/June 2012
Bromine reacts with ethene to produce $1,2$-dibromoethane. Which option gives the correct description of the organic intermediate in this reaction?
May/June 2013
The compound hex-3-en-1-ol, P, has a strong 'leafy' scent like freshly cut grass and is used in perfumery. $\text{CH}_3\text{CH}_2\text{CH}=\text{CHCH}_2\text{CH}_2\text{OH}$. What is formed when P is treated with excess hot concentrated acidified $\text{KMnO}_4$?
May/June 2013
Ethene undergoes reaction with steam in the presence of sulfuric acid. $\text{C}_2\text{H}_4 + \text{H}_2\text{O} \rightarrow \text{CH}_3\text{CH}_2\text{OH}$ What kind of reaction is shown here?
May/June 2013
What is the total number of isomers, covering structural isomers and stereoisomers, that have the formula $\text{C}_4\text{H}_8$ and contain structures with $\pi$ bonding?
May/June 2013
The hydrocarbon $\text{C}_{17}\text{H}_{36}$ can be cracked. Which compound is least likely to form in this reaction?
May/June 2014
When ethene reacts with aqueous bromine, it produces two compounds, $\text{CH}_2\text{BrCH}_2\text{Br}$ and $\text{CH}_2\text{BrCH}_2\text{OH}$. Which of the following statements about these products is correct?
May/June 2014
Which molecule cannot be produced by cracking one molecule of nonane, $\text{CH}_3(\text{CH}_2)_7\text{CH}_3$?
May/June 2014
The free radical substitution reaction between methane and chlorine passes through initiation, propagation and termination stages. Which row is correct?
May/June 2014
Bromine reacts with both alkanes and alkenes.
May/June 2014
Crude oil is refined to yield a broad range of hydrocarbons.
May/June 2014
A hydrocarbon $P$, with the formula $\text{C}_6\text{H}_{12}$, quickly decolourises bromine. When it is treated with hot, concentrated, acidified potassium manganate(VII) solution, one organic product, $Q$, is formed. $Q$ gives an orange precipitate with 2,4-dinitrophenylhydrazine, 2,4-DNPH reagent, but shows no reaction with Tollens’ reagent.
May/June 2014
Define what is meant by mole.
May/June 2014
Students W, X, Y and Z each made the statements below about alkanes and alkenes. W: 'Bromine reacts with alkanes by electrophilic substitution.' X: 'Bromine reacts with alkenes by a free-radical addition mechanism.' Y: 'Alkenes can be oxidised by acidified manganate(VII) ions.' Z: 'Alkenes are formed from alkanes by cracking.' Which two students are correct?
May/June 2015
Which reaction would not produce propene?
May/June 2015
Alkane X has the molecular formula $\text{C}_4\text{H}_{10}$. In sunlight, X reacts with $\text{Cl}_2(g)$ to form only two distinct monochloroalkanes, $\text{C}_4\text{H}_9\text{Cl}$. When each of these monochloroalkanes is heated with ethanolic KOH, the same alkene Y is obtained, and no other organic products are formed. What is formed when Y is treated with hot concentrated acidified $\text{KMnO}_4$?
May/June 2015
Ethane undergoes reaction with chlorine to produce chloroethane. $\text{C}_2\text{H}_6(g) + \text{Cl}_2(g) \rightarrow \text{C}_2\text{H}_5\text{Cl}(g) + \text{HCl}(g)$
May/June 2015
The displayed structure for H is shown.
May/June 2015
The initial propagation stage in the reaction between methane and chlorine is shown below. $\text{CH}_4 + \text{Cl}\cdot \rightarrow \text{CH}_3\cdot + \text{HCl}$ How many distinct first propagation stages are possible in the reaction between pentane and chlorine?
May/June 2016
Geranyl ethanoate occurs in ginger and cocoa, and is used as a perfume in shampoos and soaps. When it reacts with an excess of bromine in an organic solvent, $X$, a bromo-derivative, is formed. Including geranyl ethanoate, how many cis-trans isomers does geranyl ethanoate have, and how many chiral centres does $X$ contain?
May/June 2016
The diagram illustrates the structure of cyclohexene. Which structures might be produced by addition reactions when cyclohexene is the only reactant?
May/June 2016
Oct-1-ene, $\text{CH}_3(\text{CH}_2)_5\text{CH}=\text{CH}_2$, may undergo thermal cracking. Which set of compounds W, X, Y and Z could be formed by thermally cracking oct-1-ene? W: $\text{CH}_2=\text{CH}_2$ X: $\text{CH}_3\text{CH}=\text{CH}_2$ Y: $\text{CH}_3\text{CH}_2\text{CH}_3$ Z: $\text{CH}_2=\text{CHCH}=\text{CH}_2$
May/June 2016
A cycloalkene having molecular formula $\text{C}_7\text{H}_{12}$ was oxidised using hot concentrated acidified $\text{MnO}_4^-$. The sole organic product formed was 2-methylhexane-1,6-dioic acid. What is the identity of this cycloalkene?
May/June 2016
On heating with chlorine, the hydrocarbon 2,2-dimethylbutane reacts by free radical substitution. During a propagation step, a free radical X$\bullet$ is produced. $\text{CH}_3\text{CH}_2{-}\text{C}(\text{CH}_3)_2{-}\text{CH}_3 + \text{Cl}\bullet \rightarrow X\bullet + \text{HCl}$ How many different structures of X$\bullet$ can there be?
May/June 2016
This question concerns molecules whose molecular formula is $\text{C}_4\text{H}_8$.
May/June 2016
Crude oil is a blend of hydrocarbons and, after processing, it supplies many useful chemicals. Two of the stages used in crude oil processing are fractional distillation and cracking.
May/June 2016
An alkene is treated with acidified manganate(VII) ions, $\text{MnO}_4^-$. The required organic product has a relative molecular mass that is $34$ higher than that of the alkene. What conditions should be used?
May/June 2017
In the dark, bromine reacts with ethene. Which statement correctly describes the organic intermediate formed in this reaction?
May/June 2017
P, Q and R each possess the molecular formula $\text{C}_3\text{H}_6\text{O}$. All three are structural isomers of one another. In both P and Q, an oxygen atom is attached directly to a carbon atom that is $sp^2$ hybridised. In R, the oxygen atom is attached directly to a carbon atom that is $sp^3$ hybridised.
May/June 2017
The hydrocarbons A, $\text{C}_4\text{H}_{10}$, and B, $\text{C}_4\text{H}_8$, are both unbranched. A does not decolourise bromine, whereas B decolourises bromine and also shows geometrical isomerism.
May/June 2017
Combustion data may be used to work out the empirical formula, molecular formula and relative molecular mass of many organic compounds. However, combustion data cannot tell different structural isomers apart.
May/June 2017
A, B and C each have the formula $\text{C}_4\text{H}_8$. Each one decolourises bromine, and they are structural isomers of one another.
May/June 2017
Limonene is present in lemons. Limonene is heated with concentrated acidified potassium manganate(VII). Which compounds are formed?
May/June 2018
Which equation shows a correct propagation step in the chlorination of ethane?
May/June 2018
Maleic acid has applications in the food industry and also in drug stabilisation. It is the cis-isomer of butenedioic acid, and its structural formula is $\text{HO}_2\text{CCH}=\text{CHCO}_2\text{H}$. What product is produced when maleic acid reacts with cold, dilute, acidified manganate(VII) ions?
May/June 2018
Sibirene, $\text{C}_{15}\text{H}_{24}$, is allowed to react with an excess of $\text{HBr}(g)$. The main product formed is X. What is the skeletal formula for X?
May/June 2018
Crude oil consists of a complex blend of hydrocarbon molecules. Fractional distillation is used to separate the hydrocarbons in crude oil because the different hydrocarbon molecules have different boiling points.
May/June 2018
Most fuels used in vehicles consist of hydrocarbons that come from crude oil.
May/June 2018
What is the structural formula of the main product formed when hydrogen bromide reacts with $2$-methylbut-$2$-ene?
May/June 2019
When answering this question, consider both structural isomerism and stereoisomerism. 3-methylhexan-3-ol is heated with concentrated sulfuric acid to produce a number of isomeric compounds having the molecular formula $\text{C}_7\text{H}_{14}$. How many isomeric compounds can be formed in this reaction?
May/June 2019
3-methylbut-1-ene is capable of taking part in several kinds of reaction. Which row correctly gives the reaction types?
May/June 2019
Propene, bromine and hydrogen bromide are combined in the absence of light. Several products are produced, with some present only in very small amounts. Which substance will be absent from the product mixture?
May/June 2019
Butane, $(\text{CH}_3)(\text{CH}_2)_2\text{CH}_3$, has an isomer called methylpropane, $(\text{CH}_3)_2\text{CHCH}_3$.
May/June 2019
A wide range of aliphatic and aromatic hydrocarbons exists.
May/June 2019
Describe the observation when aqueous bromine is added to alkene $X$.
May/June 2019
Cars are fitted with catalytic converters that eliminate pollutants from the exhaust gases. Some of the reactions involved need oxygen, and this oxygen is taken from the air. Which exhaust pollutants will react with oxygen on the catalyst surface of the catalytic converter?
May/June 2020
When reacted with hot concentrated acidified potassium manganate(VII), which substance produces propanoic acid as one of the products?
May/June 2020
Structural and stereoisomerism need to be taken into account for this question. When HBr reacts with trans-pent-2-ene, how many distinct products are possible?
May/June 2020
2-methylbut-2-ene reacts with $\text{HBr(g)}$ to give two isomeric products. In this reaction, two positively charged intermediates may be formed. Which diagram represents the more stable of the two positively charged intermediates?
May/June 2020
Under the stated conditions, 2-methylbut-1-ene reacts with acidified manganate(VII) ions to give two organic products, X and Y. X then reacts straight away with the acidified manganate(VII) ions, producing carbon dioxide and water. Y has structural formula $\text{CH}_3\text{CH}_2\text{COCH}_3$.
May/June 2020
Hexane, $\text{C}_6\text{H}_{14}$, is a colourless liquid. There are equal quantities of hexane in two test-tubes. $1\ \text{cm}^3$ of bromine, $\text{Br}_2\text{(aq)}$, is added to each test-tube. One tube is left in the dark, while the other is placed in sunlight. The table shows what each test-tube looks like after one hour.
May/June 2020
Which compound would form two different carboxylic acids on treatment with hot, concentrated, acidified manganate(VII) ions?
May/June 2021
The table shows four reactions involving propene. Which row is correct?
May/June 2021
Compound P is reacted with excess hydrogen gas in the presence of a nickel catalyst. The resulting product Q is completely saturated. What number of chiral carbon atoms are present in product Q?
May/June 2021
Compound X is an unbranched hydrocarbon with an $M_r$ of $84$. What can be inferred about X?
May/June 2021
Two carbon-containing products are formed when alkene Z reacts with a hot, concentrated, acidified solution of potassium manganate(VII). One of the products gives an orange precipitate with 2,4-dinitrophenylhydrazine reagent. The other product is a gas that produces a white precipitate with aqueous calcium hydroxide. Which alkene could be alkene Z?
May/June 2021
Naphtha is a mixture made up only of hydrocarbon molecules.
May/June 2021
Propene, $\text{C}_3\text{H}_6$, undergoes reaction with $\text{H}_2\text{O}$ in the presence of an acid catalyst to produce an alcohol whose molecular formula is $\text{C}_3\text{H}_8\text{O$.
May/June 2021
The table presents the structural formulae of four compounds, A, B, C and D, with molecular formula $\text{C}_4\text{H}_8$.
May/June 2021
When answering this question, allow for structural isomerism and stereoisomerism. How many isomeric alkenes with formula $\text{C}_5\text{H}_8$ are found in the mixture formed when $1,4$-dibromopentane reacts with NaOH in ethanol?
May/June 2022
The alkene displayed reacts with an excess of HBr by electrophilic addition. Which is the major product that is produced?
May/June 2022
Limonene occurs in lemon and orange oils. What is the principal product formed when limonene reacts with an excess of dry hydrogen chloride?
May/June 2022
When bromoethane is reacted with hot ethanolic sodium hydroxide, a colourless gas is produced. This gas causes aqueous bromine to lose its colour. What is the colourless gas?
May/June 2023
Alkynes are hydrocarbons containing a single triple $\text{C} \equiv \text{C}$ bond. As with alkenes, alkynes undergo addition reactions, and this can produce a saturated compound. For instance, ethyne, $\text{H}-\text{C} \equiv \text{C}-\text{H}$, reacts with excess hydrogen to give ethane. Propyne, $\text{C}_3\text{H}_4$, reacts with excess hydrogen bromide by addition in two steps. Markovnikov’s rule is used for the addition of HBr in each step. Which is the main product formed when propyne reacts with excess hydrogen bromide?
May/June 2023
During electrophilic addition of bromine to alkenes, a cation appears as the intermediate species. Which combination would lead to the most stable intermediate cation?
May/June 2023
On reaction of 1-methylcyclohexene with $\text{Br}_2$, the product formed is $X$. On reaction of 1-methylcyclohexene with HBr, the major product formed is $Y$. Which statement is correct?
May/June 2023