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. $$\[ \mathrm{H}_{2} \mathrm{O}_{2}(\mathrm{aq}) \rightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \quad \Delta H=-98.2 \mathrm{~kJ} \mathrm{~mol}^{-1} \]$$ FA 1 is aqueous hydrogen peroxide, $$\(\mathrm{H}_{2} \mathrm{O}_{2}\)$$. FA 5 is manganese(IV) oxide, $$\(\mathrm{MnO}_{2}\)$$. The concentration of hydrogen peroxide in FA 1 calculated using the method given for Question 1 is more accurate than that using the method given for Question 2. (i) Heat loss is a large source of error when carrying out the method for Question 2. Describe and explain the effect of heat loss on the value of the concentration of hydrogen peroxide calculated. . . (ii) A student suggests that calculating the concentration of hydrogen peroxide using the method in Question 2 would be less accurate when the concentration is lower. Suggest whether the student is correct. Explain your answer. . 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．If a solid is heated，a hard－glass test－tube must be used． Rinse and reuse test－tubes and boiling tubes where possible． No additional tests should be attempted．

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