You will now determine the concentration of a solution of hydrogen peroxide by a different method. Hydrogen peroxide decomposes slowly into water and oxygen at room temperature. This reaction is exothermic. When a catalyst is added, the decomposition is fast and there is a measurable temperature rise. $$\[ \mathrm{H}_{2} \mathrm{O}_{2}(\mathrm{aq}) \rightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \quad \Delta H=-98.2 \mathrm{~kJ} \mathrm{~mol}^{-1} \]$$ FA 1 is aqueous hydrogen peroxide, $$$\mathrm{H}_{2} \mathrm{O}_{2}$$$. FA 5 is manganese(IV) oxide, $$$\mathrm{MnO}_{2}$$$. Calculations (i) Calculate the energy change, in J , in Experiment 2. energy change = J (ii) Use the information given and your answer to (b)(i) to calculate the concentration, in $$$\mathrm{mol} \mathrm{dm}^{-3}$$$, of hydrogen peroxide in FA 1. concentration of $$$\mathrm{H}_{2} \mathrm{O}_{2}$$$ in FA $$$1=$$$ $$$\mathrm{mol} \mathrm{dm}^{-3}$$$

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_s25_qp_37 Year：2025 Question No：2(b)

Answer:

Knowledge points:

2.2.1 define and use the term mole in terms of the Avogadro constant

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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