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Edexcel A-Level Chemistry Assessed Mathematical Skills

Practise Edexcel A-Level Chemistry AS and A2 mathematical skills by using titres, graphs, percentages, units and measurement conventions.

Syllabus
Pearson Edexcel International Advanced Subsidiary/Advanced Level
Course
Chemistry XCH11/YCH11
Level
AS

Covered syllabus points

B.0 Arithmetic and numerical computationB.1 Handling dataB.2 AlgebraB.3 GraphsB.4 Geometry and trigonometry

Assessed mathematical skills and measurement conventions question 1

[Maximum number: 4]

Many cars use fuels containing ethanol as well as hydrocarbons. The E numbers of these fuels show the percentage by volume of ethanol in the fuel. For example, an E5 fuel contains 5\% ethanol and 95\% hydrocarbons by volume.

Question (a)

(a)

A brand of E10 fuel contains 92.2% hydrocarbons and 7.80% ethanol by mass.

The energy density is the amount of energy released per kg of a fuel burned. The energy densities of the two components of this brand of fuel are shown.

 energy density of hydrocarbons =46.5MJ kg−1 energy density of ethanol =29.7MJ kg−1\begin{array}{ll} \text { energy density of hydrocarbons } & =46.5 \mathrm{MJ} \mathrm{~kg}^{-1} \\ \text { energy density of ethanol } & =29.7 \mathrm{MJ} \mathrm{~kg}^{-1} \end{array}
[ 4 ]

Question (i)

(i)

Calculate the mean energy density of this E10 fuel in MJ kg −1{ }^{-1}.

Give your answer to an appropriate number of significant figures.

[ 2 ]

Question (ii)

(ii)

The density of the E 10 fuel is 0.729 g cm−30.729 \mathrm{~g} \mathrm{~cm}^{-3}.

Calculate the mass of 1500 cm31500 \mathrm{~cm}^{3} of the fuel.

[ 1 ]

Question (iii)

(iii)

Calculate the energy released when 1500 cm31500 \mathrm{~cm}^{3} of the E10 fuel is burned in excess oxygen, using your answers from (a)(i) and (a)(ii).
[If you did not calculate a value for the mean energy density of the E10 fuel in (a)(i), use a value of 38.1MJkg−138.1 \mathrm{MJ} \mathrm{kg}^{-1}. This is not the correct value.]

[ 1 ]

Assessed mathematical skills and measurement conventions question 2

[Maximum number: 3]

Question (a)

(a)

Question (i)

Question (b)

(b)

Question (i)

Assessed mathematical skills and measurement conventions question 3

[Maximum number: 4]
Table for Question Assessed mathematical skills and measurement conventions question 3 — Edexcel A-Level Chemistry AS

Question (a)

(a)
Figure for Question (a) — Edexcel A-Level Chemistry AS
[ 2 ]

Question (b)

Assessed mathematical skills and measurement conventions question 4

[Maximum number: 1]

Washing soda is hydrated sodium carbonate ( Na2CO3⋅nH2O\mathrm{Na}_{2} \mathrm{CO}_{3} \cdot \mathrm{nH}_{2} \mathrm{O} ). The value of n can be determined by titration.

A titration method was carried out using the following procedure.
Step 14.29 g of Na2CO3⋅nH2O\mathrm{Na}_{2} \mathrm{CO}_{3} \cdot \mathrm{nH}_{2} \mathrm{O} was weighed into a beaker.
Step 2 The Na2CO3⋅nH2O\mathrm{Na}_{2} \mathrm{CO}_{3} \cdot \mathrm{nH}_{2} \mathrm{O} was dissolved in 50 cm350 \mathrm{~cm}^{3} of deionised water.
Step 3 All of the solution was transferred to a 250 cm3250 \mathrm{~cm}^{3} volumetric flask. The beaker was rinsed with deionised water and these washings were added to the volumetric flask.

Step 4 The volumetric flask was made up to the mark with deionised water. The flask was stoppered and inverted several times.

Step 5 A burette, pipette and conical flask were all rinsed with deionised water.
Step 6 The burette was rinsed and then filled with 0.125 moldm−30.125 \mathrm{~mol} \mathrm{dm}^{-3} hydrochloric acid solution. The pipette was rinsed with the sodium carbonate solution and then used to transfer 25.0 cm325.0 \mathrm{~cm}^{3} of the solution to the conical flask.

Step 7 A few drops of methyl orange were added to the conical flask. The sodium carbonate solution was titrated with the hydrochloric acid. This step was repeated until concordant titres were obtained.

The following results were obtained in the titration.

Table for Question Assessed mathematical skills and measurement conventions question 4 — Edexcel A-Level Chemistry AS

Complete the table and calculate the mean titre, using all concordant values.

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