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Edexcel A-Level Chemistry Algebra Skills

Practise Edexcel A-Level Chemistry algebra skills through equation rearrangement, rate constants, electrode-potential relationships and multi-step mole calculations.

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

Exam points

  • rearrange rate equations or gradient relationships to calculate k or enthalpy change
  • solve electrode-potential equations for concentration using E, E° and constants
  • combine density, percentage volume and molar mass steps to calculate amount of substance

Covered syllabus points

B.2.1—Mathematical symbolsB.2.2—Changing the subject of an equationB.2.3—Substitution into algebraic equationsB.2.4—Solving algebraic equations

B.2 Algebra question 1

[Maximum number: 1]

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.

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}

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.]

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