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Edexcel A-Level Chemistry AS B 0 2 Ratios Fractions and Percentages Questions

Practise Edexcel IAL Chemistry 7.1.3 by calculating percentage composition, scaling yield and volume data, and reporting weighted means or percentage errors accurately.

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

Exam points

  • Calculate percentage by mass from formulae or repeat units, checking every carbonyl, chlorine or OH contribution.
  • Use percentage yield or composition to scale masses, volumes and land area with unit conversions.
  • Calculate weighted mean energy density and percentage error with appropriate significant figures.

Edexcel A-Level Chemistry AS B 0 2 Ratios Fractions and Percentages Questions question 1

[Maximum number: 2]

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

Give your answer to an appropriate number of significant figures.

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