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Edexcel IAL Chemistry Ratios and Percentages

Practise Edexcel IAL Chemistry ratios, fractions and percentages through percentage composition, yield, error, volume fractions and mole-ratio calculations.

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.
  • Derive mole ratios from percentage composition and relative atomic masses, then simplify to an empirical ratio.

B.0.2—Ratios, fractions and percentages 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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