All Questions: AS & A Level Chemistry - 9701 Paper 3 2018 Summer Zone 1
Theory
MCQ
01.
Theory 13 Marks
CH1 - ATOMS, MOLECULES & STOICHIOMETRY

In this experiment you will use a solution of sodium carbonate, $Na_2CO_3$, to determine the concentration of a solution of hydrochloric acid, $HCl$, by carrying out a titration.

$Na_2CO_3(aq) + 2HCl(aq) \rightarrow 2NaCl(aq) + CO_2(g) + H_2O(l)$

$FA 1$ is a solution of sodium carbonate containing $1.30 \text{g } Na_2CO_3$ in each $250 \text{cm}^3$.
$FA 2$ is hydrochloric acid, $HCl$. methyl orange indicator

(a) Method

  • Fill a burette with $FA 2$.
  • Use the pipette to transfer $25.0\text{cm}^3$ of $FA 1$ into a conical flask.
  • Add a few drops of methyl orange indicator.
  • Perform a rough titration and record your burette readings in the space below.
The rough titre is ......................... cm$^3$.
  • Carry out as many accurate titrations as you think necessary to obtain consistent results.
  • Make certain any recorded results show the precision of your practical work.
  • Record in a suitable form below all of your burette readings and the volume of $FA 2$ added in each accurate titration.


(b) From your accurate titration results, obtain a suitable value for the volume of $FA 2$ to be used in your calculations. Show clearly how you obtained this value.

$25.0\text{cm}^3$ of $FA 1$ required ......................... cm$^3$ of $FA 2$. [1]

(c) Calculations
  1. Give your answer to (ii), (iii) and (iv) to an appropriate number of significant figures. [1]
  2. Calculate the number of moles of sodium carbonate present in $25.0\text{cm}^3$ of $FA 1$.
    moles of $Na_2CO_3 = ............................$ mol [1]
  3. Calculate the number of moles of hydrochloric acid that reacted with the number of moles of sodium carbonate you calculated in (ii).
    moles of $HCl = ............................$ mol [1]
  4. Use your answers to (b) and (c)(iii) to calculate the concentration of hydrochloric acid in $FA 2$.
    concentration of $HCl$ in $FA 2 = ............................$ mol$\text{dm}^{-3}$ [1]


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02.
Theory 13 Marks
CH16 - HALOGEN DERIVATIVES

In this question you will determine the identity of the halogen in compound W. Compound W is the halogenethanoic acid CH2XCO2H, where X is a halogen.
4 g of W were heated with 250 cm3 of 0.400 mol dm-3 aqueous sodium hydroxide. Some of the sodium hydroxide reacted with compound W. The solution that remained after this reaction is FA 3.
By titrating FA 3 with hydrochloric acid, you will determine how much of the sodium hydroxide remained after reaction with W. You will then calculate how much sodium hydroxide had reacted and use this to determine the identity of X in CH2XCO2H.

FA 3 is aqueous sodium hydroxide after reaction with W.
FA 4 is 0.100 mol dm-3 hydrochloric acid, HCl.
bromophenol blue indicator

(a) Method

  • Fill the second burette with FA 4.
  • Rinse the pipette with distilled water followed by a little FA 3.
  • Use the pipette to transfer 25.0 cm3 of FA 3 into a conical flask.
  • Add a few drops of bromophenol blue indicator.
  • Perform a rough titration and record your burette readings in the space below.

The rough titre is ............................ cm3.
  • Carry out as many accurate titrations as you think necessary to obtain consistent results.
  • Make certain any recorded results show the precision of your practical work.
  • Record in a suitable form below all of your burette readings and the volume of FA 4 added in each accurate titration.

[Table_1]
From your accurate titration results, obtain a suitable value for the volume of FA 4 to be used in your calculations. Show clearly how you obtained this value.

25.0 cm3 of FA 3 required ............................ cm3 of FA 4.

(b) Calculations
A halogenethanoic acid reacts with aqueous sodium hydroxide in two reactions.
The alkali neutralises the carboxylic acid.
$$ \text{NaOH + CH}_2\text{XCO}_2\text{H} \rightarrow \text{CH}_2\text{XCO}_2\text{Na} + \text{H}_2\text{O} $$
The halogenoalkyl group then undergoes a substitution reaction.
$$ \text{NaOH + CH}_2\text{XCO}_2\text{Na} \rightarrow \text{CH}_2\text{(OH)CO}_2\text{Na} + \text{NaX} $$
(i) Calculate the number of moles of hydrochloric acid, FA 4, present in the volume calculated in (a).

moles of HCl = ............................ mol
Hence deduce the number of moles of sodium hydroxide present in 25.0 cm3 of FA 3.

moles of NaOH in 25.0 cm3 FA 3 = ............................ mol
(ii) Calculate the number of moles of sodium hydroxide added to the 4 g of W.

moles of NaOH added to 4 g W = ............................ mol
Calculate the number of moles of sodium hydroxide that remain after the reaction with compound W.

moles of NaOH remaining after reaction with W = ............................ mol
(iii) Calculate the number of moles of sodium hydroxide that reacted with W.

moles of NaOH that reacted with W = ............................ mol
Hence calculate the number of moles of W that reacted with this number of moles of sodium hydroxide.

moles of W that reacted = ............................ mol
(iv) Use your answer to (iii), and the mass of W used to make FA 3, to calculate the $M_r$ of W.

$M_r$ of W = ............................
(v) W is a halogenethanoic acid, CH2XCO2H. Use your answer to (iv) to determine the identity of X. Explain how you reached your conclusion.
..............................................................................................................
..............................................................................................................
..............................................................................................................

(c) Apart from any inaccuracies in reading the volumes of solutions, suggest a significant source of error in this practical exercise. Explain how you could minimise this error.
..............................................................................................................
..............................................................................................................
..............................................................................................................

(d) State at what $M_r$ value of W, closest to the one calculated in (b)(iv), you would have concluded that X was a different halogen.

$M_r$ value = ............................

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03.
Theory 17 Marks
CH12 - AN INTRODUCTION TO THE CHEMISTRY OF TRANSITION ELEMENTS

(a) Half fill the 250 cm^3 beaker with water. Heat to approximately 70 °C, then turn off the Bunsen burner. This will be used as a water bath.
(i) FA 5 is an aqueous solution of an organic compound. Carry out the following tests on FA 5 and record your observations in the table.

testobservations
To a 1 cm depth of FA 5 in a test-tube add a small spatula measure of sodium carbonate.
To a 1 cm depth of FA 5 in a test-tube add two drops of acidified potassium manganate(VII). Leave to stand in the water bath.
To a 1 cm depth of FA 5 in a test-tube add a few drops of aqueous silver nitrate.
To a 1 cm depth of aqueous silver nitrate in a test-tube add a few drops of aqueous sodium hydroxide and then add aqueous ammonia slowly until the grey precipitate that forms just dissolves. This is Tollens' reagent. To this solution add a 1 cm depth of FA 5 and leave to stand in the water bath. Care: rinse the tube as soon as you have completed this test.


(ii) Suggest two functional groups that could be present in FA 5.
......................................................... and ............................................................

(b) FA 6 is a mixture that contains two cations and two anions from the Qualitative Analysis Notes. Distilled water was added to FA 6, the mixture was stirred and then filtered. You are provided with the dried residue, FA 7, and the filtrate, FA 8, from this process.
(i) Tests on the residue, FA 7
Carry out the following tests and record your observations in the table.
testobservations
Place a spatula measure of FA 7 in a boiling tube. Add dilute hydrochloric acid until no further reaction occurs, then
transfer a 1 cm depth of the solution into a test-tube. To this add aqueous sodium hydroxide.


(ii) Tests on the filtrate, FA 8
Carry out the following tests and record your observations in the table.
testobservations
To a 1 cm depth of FA 8 in a boiling tube add a 1 cm depth of aqueous sodium hydroxide, then
warm gently.
To a 1 cm depth of FA 8 in a boiling tube add a piece of aluminium foil and a 1 cm depth of aqueous sodium hydroxide. Warm gently.


(iii) Conclusions about cations
State one cation that is definitely present in FA 6.
.................................

State two possible identities for the other cation present in FA 6.
.............................................................. or ................................................................
Suggest how you could determine which of these two possible cations is present. Do not carry out this test.
.............................................................................................................................
........................................................................................................................................................................
........................................................................................................................................................................

(iv) Conclusions about anions
State one anion that is definitely present in FA 6.
.................................

State two possible identities for the other anion present in FA 6.
.............................................................. or ................................................................

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