In this experiment you will determine the enthalpy change, $$$\Delta H$$$, for the reaction between aqueous copper(II) sulfate and magnesium. $$\[ \mathrm{CuSO}_{4}(\mathrm{aq})+\mathrm{Mg}(\mathrm{s}) \rightarrow \mathrm{Cu}(\mathrm{s})+\mathrm{MgSO}_{4}(\mathrm{aq}) \]$$ FA 3 is $$$1.0 \mathrm{~mol} \mathrm{dm}^{-3}$$$ copper(II) sulfate, $$$\mathrm{CuSO}_{4}$$$. FA 4 is magnesium powder, Mg. A student suggests that the slow rate of the reaction using the method described in (a) means that heat energy is lost from the solution so the temperature change is inaccurate. Describe how you would change the method and processing of the results to improve the accuracy of the enthalpy change for this reaction. You should not change the quantities of FA 3 or FA 4 used. You may wish to illustrate your answer with a sketch graph. ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . Qualitative analysis For each test you should record all your observations in the spaces provided. Examples of observations include: - colour changes seen - the formation of any precipitate and its solubility (where appropriate) in an excess of the reagent added - the formation of any gas and its identification (where appropriate) by a suitable test. You should record clearly at what stage in a test an observation is made. Where no change is observed, you should write 'no change'. Where reagents are selected for use in a test, the name or correct formula of the element or compound must be given. If any solution is warmed, a boiling tube must be used. Rinse and reuse test-tubes and boiling tubes where possible. No additional tests should be attempted.

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_m24_qp_33 Year：2024 Question No：(c)

Answer:

Knowledge points:

5.1.1 understand that chemical reactions are accompanied by enthalpy changes and these changes can be exothermic (ΔH is negative) or endothermic (ΔH is positive)

5.1.2 construct and interpret a reaction pathway diagram, in terms of the enthalpy change of the reaction and of the activation energy

5.1.3.1 standard conditions (this syllabus assumes that these are 298 K and 101 kPa) shown by

5.1.3.2 enthalpy change with particular reference to: reaction, , combustion, , neutralisation,

5.1.4 understand that energy transfers occur during chemical reactions because of the breaking and making of chemical bonds

5.1.5 use bond energies (ΔH positive, i.e. bond breaking) to calculate enthalpy change of reaction

5.1.6 understand that some bond energies are exact and some bond energies are averages

5.1.7 calculate enthalpy changes from appropriate experimental results, including the use of the relationships q = mcΔT and ΔH = –mcΔT/n

Answer:

Knowledge points:

Solution:

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