Chemistry 9701 · AS & A Level
Analytical techniques
75 practice questions on Analytical techniques, with worked solutions and instant marking.
Spathose is an iron ore containing iron(II) carbonate, $\text{FeCO}_3$. The proportion of iron(II) carbonate in spathose may be found by titration with acidified potassium dichromate(VI) solution, using a suitable indicator. The ionic equation is: $\text{Cr}_2\text{O}_7^{2-}(aq) + 14\text{H}^+(aq) + 6\text{Fe}^{2+}(aq) \rightarrow 2\text{Cr}^{3+}(aq) + 6\text{Fe}^{3+}(aq) + 7\text{H}_2\text{O}(l)$. A $5.00\,\text{g}$ portion of spathose was treated with an excess of concentrated hydrochloric acid and then filtered. The filtrate was then diluted to $250\,\text{cm}^3$ in a volumetric flask with distilled water. A $25.0\,\text{cm}^3$ portion of this solution needed $27.30\,\text{cm}^3$ of $0.0200\,\text{mol dm}^{-3}$ dichromate(VI) solution for the reaction to go to completion.
Feb/March 2016
An infrared spectrum for a compound is displayed. Which functional group might be present in the compound?
Feb/March 2024
Compound L is made up of carbon atoms. It is examined in a mass spectrometer. The table gives the relative abundance of the only two peaks detected with $m/e$ greater than 127. The peak at $m/e = 128$ has a relative abundance of 50. The peak at $m/e = 129$ has a relative abundance of 5.5. How many carbon atoms are present in one molecule of compound L?
Feb/March 2025
The diagram illustrates some laboratory apparatus. Which preparations can be carried out using this apparatus?
May/June 2010
The diagram shows some laboratory apparatus. For which preparations could this apparatus be used?
May/June 2010
Oxygen-containing organic compounds can include several different functional groups, such as alcohol, aldehyde, carboxylic acid, ester or ketone groups. These groups can be recognised from how they react with particular reagents.
May/June 2012
Washing soda is hydrated sodium carbonate, $\text{Na}_2\text{CO}_3 \cdot x\text{H}_2\text{O}$. A student set out to find the value of $x$ by titration, and obtained these results: $5.13\,\text{g}$ of washing soda crystals were dissolved in water and the solution was made up to $250\,\text{cm}^3$ in a standard volumetric flask. Then $25.0\,\text{cm}^3$ of this solution reacted exactly with $35.8\,\text{cm}^3$ of $0.100\,\text{mol dm}^{-3}$ hydrochloric acid, with carbon dioxide being produced.
May/June 2012
The most frequently encountered form of iron(II) sulfate is the heptahydrate, $FeSO_4\cdot7H_2O$. When heated to $90^\circ\text{C}$, it loses part of its water of crystallisation and changes into a different hydrated form of iron(II) sulfate, $FeSO_4\cdot xH_2O$. A $3.40\,\text{g}$ sample of $FeSO_4\cdot xH_2O$ was dissolved in water to make $250\,\text{cm}^3$ of solution. A $25.0\,\text{cm}^3$ portion of this solution was acidified and titrated with $0.0200\,\text{mol dm}^{-3}$ potassium manganate(VII). During the titration, $20.0\,\text{cm}^3$ of the potassium manganate(VII) solution was needed to react completely with the $Fe^{2+}$ ions in the sample.
May/June 2014
A $6.30\,\text{g}$ portion of hydrated ethanedioic acid, $\text{H}_2\text{C}_2\text{O}_4\cdot x\text{H}_2\text{O}$, was dissolved in water and the resulting solution was made up to $250\,\text{cm}^3$. A $25.0\,\text{cm}^3$ aliquot of this solution was acidified and titrated with $0.100\,\text{mol dm}^{-3}$ potassium manganate(VII) solution. $20.0\,\text{cm}^3$ of this potassium manganate(VII) solution was needed to react completely with the ethanedioate ions, $\text{C}_2\text{O}_4^{2-}$, in the sample.
May/June 2014
Which reagent would produce a different observation when used with compounds $W$ and $X$?
May/June 2015
Chemists know that atoms contain three kinds of particle. Complete the table below by giving their names and properties. The table has columns for the particle name, relative mass, and relative charge.
May/June 2015
A solid, $T$, was added to an excess amount of the liquid $U$. A colourless gas was evolved and a white precipitate formed. The precipitate was not $T$. What might $T$ and $U$ be?
May/June 2016
Acidified potassium dichromate(VI) is able to oxidise ethanedioic acid, $\text{H}_2\text{C}_2\text{O}_4$. The two relevant half-equations are given below: $\text{Cr}_2\text{O}_7^{2-} + 14\text{H}^+ + 6e^- \rightarrow 2\text{Cr}^{3+} + 7\text{H}_2\text{O}$ $\text{H}_2\text{C}_2\text{O}_4 \rightarrow 2\text{CO}_2 + 2\text{H}^+ + 2e^-$
May/June 2016
A study was performed to find the percentage of iron in an iron-wire sample. A $3.35\,\text{g}$ length of wire was treated with dilute sulfuric acid, with air excluded, so that every iron atom became iron(II) ions. The solution obtained was then made up to $250\,\text{cm}^3$.
May/June 2016
Acetoin, $\text{CH}_3\text{COCH(OH)CH}_3$, and diacetyl, $\text{CH}_3\text{COCOCH}_3$, are two compounds responsible for butter’s distinctive flavour. Their skeletal formulae are shown.
May/June 2016
Which compound produces a positive result with alkaline aqueous iodine and does not exhibit optical isomerism?
May/June 2017
Which pairs of compounds can be told apart by carrying out a test with alkaline aqueous iodine?
May/June 2018
Compound $S$ may be obtained from natural compounds. When $S$ is treated with hot, concentrated $\text{KMnO}_4$, the organic product $T$ is formed. Several absorptions in the infra-red spectra of $S$ and $T$ are given. $S$ shows no strong absorption between $1670$ and $1740\,\text{cm}^{-1}$. $T$ shows a strong absorption at $1720\,\text{cm}^{-1}$, but it does not show any strong, broad absorption between $2500$ and $3000\,\text{cm}^{-1}$. On the basis of this information, what might the formulae of $S$ and $T$ be?
May/June 2018
A solution in water of a calcium compound is first treated with a mixture of dilute aqueous nitric acid and aqueous silver nitrate. The white precipitate that forms then dissolves after dilute aqueous ammonia is added. What is the relative molecular mass, $M_r$, of the calcium compound?
May/June 2019
A mass spectrum for an alloy made of copper and gold is displayed. Which expression can be used to find the relative atomic mass, $A_r$, of the copper in this sample?
May/June 2019
A white solid consists of a mixture of sodium chloride and sodium iodide. It is dissolved in water in a test-tube. Excess aqueous silver nitrate is then added to the test-tube. A precipitate, X, is formed. Next, excess concentrated ammonia is added to the test-tube that contains X. Once the test-tube has been shaken, a precipitate, Y, is formed. Which statement about X or Y is correct?
May/June 2020
The infra-red spectrum of compound X is shown below. What might compound X be?
May/June 2020
Hydrogen cyanide adds to propanal. Which absorptions would be seen in the infra-red spectrum of the product? 1. a weak peak in the range $2200-2250\ \text{cm}^{-1}$ 2. a strong peak in the range $3200-3600\ \text{cm}^{-1}$ 3. a strong peak in the range $1040-1300\ \text{cm}^{-1}$
May/June 2020
Which of the following statements is correct?
May/June 2021
A solid, X, was added to an excess of the liquid Y. A colourless gas was evolved and a white precipitate formed. The precipitate was not X. What might X and Y be?
May/June 2021
The infra-red spectrum for molecule Z is displayed. What might Z be?
May/June 2021
A scientist selects either infrared spectroscopy or mass spectrometry in order to obtain a specific item of information. In which row has the most suitable choice been made?
May/June 2022
Which reaction has a product that forms a yellow precipitate when it is treated with alkaline $\text{I}_2(aq)$?
May/June 2022
The following three organic compounds are given. 1. ethanal 2. propan-1-ol 3. propan-2-ol Which of these compounds would produce a mass spectrum with a fragment peak at $m/e = 43$?
May/June 2022
Z is a molecule made up only of carbon, hydrogen and oxygen. Z has only alkene and carboxyl functional groups.
May/June 2022
Which compound shows the largest percentage decrease in mass when heated strongly?
May/June 2023
Bromine has two isotopes that occur naturally. One isotope contains 44 neutrons, and the other contains 46 neutrons. If fragments are ignored, how many peaks would be observed in the mass spectrum of tribromomethane, $^{12}\text{C}^1\text{HBr}_3$?
May/June 2023
The mass spectrum for compound X shows M, M+1 and M+2 peaks, and there are other peaks as well. Peak M is the molecular ion peak, $\text{M}^+$. The relative abundance of peak M is fifteen times that of peak M+1. Peaks M and M+2 have the same height. Which compound could X be?
May/June 2023
$V$ exhibits stereoisomerism.
May/June 2024
Compound W has the molecular formula C$_4$H$_{10}$O, and it contains just one functional group.
May/June 2024
M reacts to form R through the addition of one reagent, as shown in Fig. 5.1. Identify the reagent and conditions for this reaction.
May/June 2024
In the mass spectrum of $\text{CH}_3\text{Cl}$, a molecular ion peak, $\text{M}^+$, appears at $m/e = 50$ with a relative abundance of $18.0\%$. There are also other peaks in the spectrum. What peak is observed at $m/e = 52$?
May/June 2025
When aqueous silver nitrate is mixed with aqueous sodium chloride, a precipitate is formed. Which reagent, when added to this mixture, results in a colourless solution?
May/June 2025
An organic compound gives a mass spectrum with the following characteristics. • The molecular ion peak appears at $m/e = 60$. Its relative intensity = 100. • A peak is present at $m/e = 61$, and its relative intensity = 2.2. • No fragment peak is seen at $m/e = 17$. • A fragment peak is observed at $m/e = 31$. What may be the identity of the organic compound?
May/June 2025
The mass spectrum for element Z is shown. Which element is Z?
May/June 2025
Fig. 4.1 shows the structure of vitamin C.
May/June 2025
Fig. 5.1 shows the structure of vitamin C.
May/June 2025
W is a colourless liquid, and its structure is shown in Fig. 5.1.
May/June 2025
$\text{H}_2(g)$ and $\text{I}_2(g)$ undergo a reversible reaction to produce $\text{HI}(g)$, as shown in equation 1: $\text{H}_2(g) + \text{I}_2(g) \rightleftharpoons 2\text{HI}(g)$.
May/June 2025
The diagram illustrates a compound found in smoke produced by burning garden waste. Which reagents would show a colour change when they react with this compound?
Oct/Nov 2010
Y and Z are two selective weed killers that are used very commonly. Which reagent can be used to tell Y apart from Z?
Oct/Nov 2011
Y and Z are two selective weed killers that are used very widely. Which reagent can be used to tell Y apart from Z?
Oct/Nov 2011
Compound A is an organic substance containing carbon, hydrogen and oxygen. When $0.240\,\text{g}$ of its vapour is passed slowly over a large quantity of heated copper(II) oxide, $\text{CuO}$, compound A is completely oxidised to carbon dioxide and water. Copper is the only other product formed. The products are collected and it is found that $0.352\,\text{g}$ of $\text{CO}_2$ and $0.144\,\text{g}$ of $\text{H}_2\text{O}$ are obtained.
Oct/Nov 2011
Compound A is an organic compound containing carbon, hydrogen and oxygen. When $0.240\text{ g}$ of vapour of A is passed slowly over a large excess of heated copper(II) oxide, CuO, compound A is completely oxidised to carbon dioxide and water. Copper is the only further product of the reaction. The products are collected and it is found that $0.352\text{ g}$ of $\text{CO}_2$ and $0.144\text{ g}$ of $\text{H}_2\text{O}$ are produced.
Oct/Nov 2011
Compound X is represented by the molecular formula $\text{C}_4\text{H}_8\text{O}_2$.
Oct/Nov 2012
A set of tests was performed on the compound displayed below. Which pairs of reagents would each give a positive result with this compound?
Oct/Nov 2013
Compound $R$ is a weak diprotic (dibasic) acid that dissolves very readily in water.
Oct/Nov 2013
Compound $R$ is a weak diprotic (dibasic) acid that dissolves very readily in water.
Oct/Nov 2013
For which combinations of reagents are the colour changes stated accurately?
Oct/Nov 2014
Which of these reagent mixtures have the colour changes given accurately?
Oct/Nov 2014
A student looks at two semi-precious stones; one is agate, $\text{SiO}_2$, while the other is calcite, $\text{CaCO}_3$. How might they be told apart?
Oct/Nov 2014
The compound illustrated is formed when sugar burns. Which reagents would produce a positive test with this compound?
Oct/Nov 2016
A $0.17\,\text{g}$ portion of a Group 14 chloride, $\text{XCl}_4$, was treated with water, giving an oxide, $\text{XO}_2$, and $\text{HCl}$. Equation 1: $\text{XCl}_4(s) + 2\text{H}_2\text{O}(l) \rightarrow \text{XO}_2(s) + 4\text{HCl}(aq)$. The $\text{HCl}$ formed was collected in $100\,\text{cm}^3$ of $0.10\,\text{mol dm}^{-3}$ sodium hydroxide solution (present in excess). A titration then showed that the remaining sodium hydroxide solution needed $30.0\,\text{cm}^3$ of $0.20\,\text{mol dm}^{-3}$ hydrochloric acid for full neutralisation.
Oct/Nov 2016
A $0.50\,\text{g}$ portion of a Group 2 metal, $M$, was placed into $40.0\,\text{cm}^3$ of $1.00\,\text{mol dm}^{-3}$ hydrochloric acid, which was in excess. Equation 1: $M(s) + 2\text{HCl}(aq) \rightarrow M\text{Cl}_2(aq) + \text{H}_2(g)$
Oct/Nov 2016
A $0.17\,\text{g}$ portion of a Group 14 chloride, $\text{XCl}_4$, was hydrolysed by water to give an oxide, $\text{XO}_2$, and hydrochloric acid. Equation 1: $\text{XCl}_4(s) + 2\text{H}_2\text{O}(l) \rightarrow \text{XO}_2(s) + 4\text{HCl}(aq)$ The $\text{HCl}$ formed was absorbed into $100\,\text{cm}^3$ of $0.10\,\text{mol dm}^{-3}$ sodium hydroxide solution, which was in excess. During a titration, the sodium hydroxide left over needed $30.0\,\text{cm}^3$ of $0.20\,\text{mol dm}^{-3}$ hydrochloric acid for complete neutralisation.
Oct/Nov 2016
Compound $Q$ is a white crystalline substance that is readily soluble in water. On adding concentrated sulfuric acid to a dry sample of $Q$, steamy white fumes are produced which, when bubbled through aqueous silver nitrate solution, give a white precipitate. The precipitate dissolves in dilute ammonia solution. What is the most likely identity of compound $Q$?
Oct/Nov 2017
The compounds shown below are used in perfume manufacture. Which compounds would give a yellow precipitate when treated with alkaline aqueous iodine?
Oct/Nov 2017
The infra-red spectrum of compound L is displayed. What might the structure of L be?
Oct/Nov 2018
Sodium azide, $\text{NaN}_3$, is dissolved in water. Acidified silver nitrate is then added to the solution, producing a white precipitate. After that, aqueous ammonia is added to the white precipitate. The azide ion, $\text{N}_3^-$, shows chemical behaviour similar to the $\text{Cl}^-$ ion. Which row in the table could be predicted from this information?
Oct/Nov 2019
The infra-red spectrum of compound P is displayed. Which compound could P be?
Oct/Nov 2019
For compound Z, the mass spectrum shows the M and M+1 peaks with relative abundances in the ratio $13:1$. Which compound is Z?
Oct/Nov 2022
Three colourless liquids with the formulae shown here are placed in separate unlabelled bottles: $\text{CH}_3\text{CH}_2\text{CO}_2\text{H}$, $\text{CH}_3\text{CH(OH)CO}_2\text{H}$, $\text{CH}_3\text{COCO}_2\text{H}$. Which two tests, when done on separate samples of each liquid, would allow each liquid to be identified successfully?
Oct/Nov 2022
For a compound, Z, the mass spectrum shows that the relative abundances of the M and M+1 peaks are 13 : 1. What is compound Z?
Oct/Nov 2022
Organic compounds may be told apart by means of chemical tests and analytical techniques.
Oct/Nov 2022
The infrared spectrum for compound L is presented. What is the structure of L?
Oct/Nov 2023
For compound J, the mass spectrum shows that the peak-height ratio of the M + 1 ion to the M + ion is $4:91$. When compound J is heated with acidified $\text{K}_2\text{Cr}_2\text{O}_7$, it produces a carboxylic acid. What is compound J?
Oct/Nov 2023
The element oxygen exists as three stable isotopes, $^{16}\text{O}$, $^{17}\text{O}$ and $^{18}\text{O}$. A mass spectrometer was used to examine a sample of oxygen gas, $\text{O}_2$, and each of these isotopes is found in the sample. How many peaks would be expected to be linked with the $\text{O}_2^+$ ion?
Oct/Nov 2023
In the mass spectrum of compound J, the ratio of the height of the $\text{M}+1$ ion peak to the height of the $\text{M}^+$ ion peak is $4:91$. On heating with acidified $\text{K}_2\text{Cr}_2\text{O}_7$, compound J is changed into a carboxylic acid. Identify compound J.
Oct/Nov 2023
The structure of vitamin C is shown below. In the mass spectrum of vitamin C, the molecular ion peak has an $m/\!e$ value of $176$ and a relative abundance of $7.0\%$. Determine the abundance of the $\text{M}+1$ peak.
Oct/Nov 2024
The diagram presents the mass spectrum of a chlorine sample. The peaks are labelled V, W, X, Y and Z. Which of the following statements about this spectrum are correct?
Oct/Nov 2024