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Edexcel IGCSE Chemistry A Energetics Questions

Practise energetics through temperature-change practicals, energy level diagrams, bond energy calculations and explanations of heat transfer.

Syllabus
First assessment 2019
Course
Chemistry 4CH1

Exam points

  • calculate Q from mass, specific heat capacity and temperature change, then convert to ΔH in kJ/mol
  • complete energy level diagrams using reactant and product formulae at the correct relative levels
  • explain exothermic reactions by comparing energy taken in to break bonds and released forming bonds

Covered syllabus points

3.1 Exothermic and endothermic changes3.2 Temperature change practical3.3 Energy level diagrams3.4 Bond energy calculations3.5C And explain energy level diagrams to represent3.6C Bond-breaking is an endothermic process and3.7C Bond energies to calculate the enthalpy change3.8 Calorimetry practical

Question 1

[Maximum number: 1]

The teacher demonstrates the reaction between aluminium and iron(III) oxide.

Figure for Question 1 — Edexcel IGCSE Chemistry

The teacher ignites the magnesium fuse. A very exothermic reaction then occurs between aluminium powder and iron(III) oxide.

The products of the reaction are iron and aluminium oxide.

State what is meant by the term exothermic.

Question 2

[Maximum number: 9]

A student investigates the reaction between zinc and copper(II) sulfate solution.
This is the equation for the reaction.

Zn( s)+CuSO4(aq)→ZnSO4(aq)+Cu( s)\mathrm{Zn}(\mathrm{~s})+\mathrm{CuSO}_{4}(\mathrm{aq}) \rightarrow \mathrm{ZnSO}_{4}(\mathrm{aq})+\mathrm{Cu}(\mathrm{~s})

This is the student's method.
Step 1 add 25.0 cm325.0 \mathrm{~cm}^{3} of copper(II) sulfate solution to a glass beaker
Step 2 record the temperature of the solution
Step 3 add between 5 g and 6 g of zinc powder (an excess) and stir the mixture
Step 4 record the highest temperature reached

Question (a)

(a)

Explain an improvement to step 1 to produce a more accurate temperature rise.

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Question (b)

(b)

The table shows the student's results.

Table for Question (b) — Edexcel IGCSE Chemistry

Calculate the heat energy change ( Q ) in joules (J).
[for the solution, c=4.2 J/g/∘C\mathrm{c}=4.2 \mathrm{~J} / \mathrm{g} /{ }^{\circ} \mathrm{C} ]
[mass of 1.0 cm31.0 \mathrm{~cm}^{3} of solution =1.0 g=1.0 \mathrm{~g} ]

Q=……………………………………………………….……………………………………………………………..Q=\ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots . \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots . .
[ 3 ]

Question (c)

(c)

The student repeats the experiment and calculates Q as 3800 J.

The solution used contains 6.38 g of copper(II) sulfate.
Calculate the molar enthalpy change, ΔH\Delta H, in kJ / mol.
Include a sign in your answer.
[for CuSO4,Mr=159.5\mathrm{CuSO}_{4}, M_{\mathrm{r}}=159.5 ]

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