You will carry out an experiment to determine the enthalpy change, $$$\Delta H$$$, when one mole of ammonium chloride dissolves in water. FA 5 is ammonium chloride, $$$\mathrm{NH}_{4} \mathrm{Cl}$$$. Method - Weigh the container with FA 5. Record the mass in the space for results. - Support the cup in the $$$250 \mathrm{~cm}^{3}$$$ beaker. - Use the measuring cylinder to transfer $$$25.0 \mathrm{~cm}^{3}$$$ of distilled water into the cup. - Place the thermometer in the water and tilt the cup, if necessary, so that the bulb of the thermometer is fully covered. Record the temperature of the water at time $$$t=0$$$. - Start the stop-clock and leave it running for the whole experiment. - Measure and record the temperature of the water in the cup every half minute for 2 minutes. - At $$$t=2 \frac{1}{2}$$$ minutes, tip all the FA 5 into the cup. Stir the contents of the cup. - Measure and record the temperature of the contents of the cup at $$$t=3$$$ minutes and then every half minute up to and including $$$t=8$$$ minutes. - Weigh the container with any residual FA 5. Record the mass. - Calculate and record the mass of FA 5 added. Results

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_s24_qp_35 Year：2024 Question No：(a)

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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