The reaction between an acid and an alkali is exothermic. You will carry out a neutralisation experiment to determine the enthalpy change involved. You will mix different volumes of an acid with a fixed volume of an alkali and measure the temperature rises that occur. FB 4 is aqueous sodium hydroxide, NaOH . FB 5 is $$$2.00 \mathrm{~mol} \mathrm{dm}^{-3}$$$ hydrochloric acid, HCl . - Use the thermometer to measure the initial temperature of FB 4. Record this initial temperature in the space for results. - Support the cup in the $$$250 \mathrm{~cm}^{3}$$$ beaker. - Fill one burette with FB 5. Label the burette FB 5. - Fill the other burette with distilled water. Experiment 1 - Use the $$$10 \mathrm{~cm}^{3}$$$ pipette to transfer $$$10.0 \mathrm{~cm}^{3}$$$ of FB 4 into the cup. - Add $$$9.00 \mathrm{~cm}^{3}$$$ of distilled water from the burette to the same cup. - Add $$$1.00 \mathrm{~cm}^{3}$$$ of FB 5 from the other burette to the same cup. - Stir the mixture and use the thermometer to measure the maximum temperature. If necessary, tilt the cup so that the solution covers the bulb of the thermometer. - Record the maximum temperature in Table 2.1. - Empty, rinse and dry the cup ready for use in further experiments. Further experiments Repeat this method for Experiments $$$2-5$$$, using $$$10.0 \mathrm{~cm}^{3}$$$ of FB 4 and the volumes of water and FB 5 shown in Table 2.1. In each case, measure and record the maximum temperature. Carry out two further experiments, Experiments 6 and 7, which will enable you to determine more precisely the volume of FB 5 that gives the largest maximum temperature. Record your measurements in Table 2.1.

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_s25_qp_38 Year：2025 Question No：2(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

7.2.1 state the names and formulae of the common acids, limited to hydrochloric acid, HC/, sulfuric acid, ethanoic acid,

7.2.10 select suitable indicators for acid-alkali titrations, given appropriate data

7.2.2 state the names and formulae of the common alkalis, limited to sodium hydroxide, NaOH, potassium hydroxide, KOH, ammonia,

7.2.3 describe the Brønsted–Lowry theory of acids and bases

7.2.4 describe strong acids and strong bases as fully dissociated in aqueous solution and weak acids and weak bases as partially dissociated in aqueous solution

7.2.5 appreciate that water has pH of 7, acid solutions pH of below 7 and alkaline solutions pH of above 7

7.2.6 explain qualitatively the differences in behaviour between strong and weak acids including the reaction with a reactive metal and difference in pH values by use of a pH meter, universal indicator or conductivity

7.2.7 understand that neutralisation reactions occur when

7.2.8 understand that salts are formed in neutralisation reactions

7.2.9 sketch the pH titration curves of titrations using combinations of strong and weak acids with strong and weak alkalis

Answer:

Knowledge points:

Solution:

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