Higher Chemistry PPA Questions Unit 1 PPA1 Effect of Concentration Changes On Reaction Rate Unit 1 PPA2 Effect of Temperature On Reaction Rate

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Shawn Shields
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1 Higher Chemistry PPA Questions Unit 1 PPA1 Effect of Concentration Changes On Reaction Rate Describe how the concentration of potassium iodide was varied during the reaction. State two factors which had to be kept constant during the reaction. How was the reaction rate determined? What was the purpose in keeping the total volume of reaction mixture the same in each experiment Why was the procedure adopted to determine the reaction time effective and accurate? Unit 1 PPA2 Effect of Temperature On Reaction Rate State two factors which had to be kept constant during the reaction. How was the reaction rate determined? Why did the beaker used in each experiment have to be dry? Why might it be difficult to get an accurate reaction time if the experiment was carried out at room temperature? Unit 1 PPA 3 Enthalpy of Combustion Draw a labelled diagram of the apparatus used to determine enthalpy of combustion. List five measurements that are made during the experiment. The theoretical value for enthalpy of combustion is always much higher than the experimental values. Suggest 2 reasons for this. Why does enthalpy of combustion always have a negative sign? 0.25 g of ethanol was burned and the energy released increased the temperature of water from 20 o C to 32.5 o C. Calculate the enthalpy of combustion of ethanol.

2 Unit 2 PPA1 Oxidation Which are able to be oxidised aldehydes or ketones? Name three oxidising agents that can be used to distinguish between aldehydes and ketones. For each oxidising agent describe the change that indicates a positive test. Explain why a water bath is used in this experiment and the reaction mixtures are not heated directly. Unit 2 PPA2 Making Esters Draw a labelled diagram of the apparatus used to prepare an ester. How can the reaction rate be increased during the experiment? What is the function of the wet paper towel? What is the purpose of the concentrated sulphuric acid? What is the purpose of the sodium hydrogen carbonate? State two pieces of evidence which suggest that an ester has been formed. Write an equation using full structural formulae to show the formation of ethyl propanoate from ethanol and propanoic acid.

3 Unit 2 PPA 3 Factors Affecting Enzyme Activity State two factors which may affect enzyme activity. Draw a labelled diagram for the apparatus used to investigate the effect of catalase on the decomposition of hydrogen peroxide. How was the activity of the enzyme measured? What is meant by optimum activity? Why was the potato left in the buffer for 3 minutes before adding the hydrogen peroxide?

4 Unit 3 PPA1 Hess s Law Describe the two routes by which solid sodium hydroxide was converted into sodium chloride solution. Write a chemical equation, including state symbols, to represent the formation of a solution of sodium chloride from solid sodium chloride. What is Hess s Law Route g of sodium hydroxide was added to 25 cm 3 of hydrochloric acid and the temperature of the reaction mixture increased by 24 o C. Route 2 Part A 0.85g of sodium hydroxide was added to 25cm 3 of water and the temperature increased by 10 o C. Part B When 25 cm 3 of hydrochloric acid was added to this solution of sodium hydroxide (25cm 3 ), the temperature increased by 5 o C. Calculate the enthalpy change for each route. If Hess s Law is correct the enthalpy change for route 1 should equal route 2. Unit 3 PPA2 Quantitative Electrolysis Draw a labelled diagram of the circuit used in quantitative electrolysis. List all of the measurements which have to be made during the experiment What is the purpose of the variable resistor?

5 Unit 3 PPA 3 A Redox titration Write the ion-electron half equation for the reduction of iodine Write the ion-electron equation for the oxidation of vitamin C (C 6 H 8 O 6 ) converted to C 6 H 6 O 6. Write a balanced equation for the redox reaction between vitamin C and iodine. Describe the experimental procedure carried out to find the mass of vitamin C in one tablet. A vitamin C tablet was added to a beaker, dissolved and the solution added to a 250cm3 standard flask cm 3 of iodine, concentration mol l -1, was required to react with a 25cm 3 sample of the vitamin C solution. Calculate the mass of the vitamin C tablet.

A student adds the following volumes of aqueous sodium thiosulfate, dilute hydrochloric acid and distilled water to the conical flask.

A student adds the following volumes of aqueous sodium thiosulfate, dilute hydrochloric acid and distilled water to the conical flask. 1 When aqueous sodium thiosulfate and dilute hydrochloric acid are mixed, a precipitate of insoluble sulfur is produced. This makes the mixture difficult to see through. Na 2 S 2 O 3 (aq) + 2HCl (aq) S(s)