5070/42 · May/June 2023
Download PDFA student investigates the rusting of iron. Fig. 1.1 shows the apparatus the student uses.
Name apparatus X.
State why a stopper is used in Experiment B.
State why the water in Experiment C is boiled before use.
State why a layer of oil is used in Experiment C.
The experiments are left for one week. Predict in which of the experiments the nail will have rusted. Explain your prediction.
Aqueous ammonia is a solution of ammonia gas. A student titrates two samples of aqueous ammonia, A and B, with hydrochloric acid. The student does four titrations, two with A and two with B. The student: Step 1. rinses and fills a burette with hydrochloric acid Step 2. uses a volumetric pipette to add of A to a conical flask Step 3. adds five drops of methyl orange indicator to the conical flask Step 4. places the conical flask on a white tile Step 5. adds hydrochloric acid from the burette while swirling the contents of the flask, adding drop by drop near the end-point, until the solution just changes colour Step 6. empties the conical flask and rinses it with distilled water Step 7. repeats steps 2 to 6 Step 8. repeats steps 2 to 7 using aqueous ammonia B instead of aqueous ammonia A.
Fig. 2.1 shows the burette readings for the two titrations with A. Record the burette readings in Table 2.1. Complete Table 2.1 with the volume used in each titration. Table 2.1
Fig. 2.2 shows the burette readings for one of the titrations with B. Record the burette readings for Titration 4 in Table 2.2. Complete Table 2.2 with the volume used in each titration. Table 2.2
Explain why the student uses a white tile in these titrations.
Calculate the mean volume of hydrochloric acid needed to neutralise of A and of B. mean volume of acid needed for solution A ........................................................ mean volume of acid needed for solution B ........................................................
The equation for the reaction between hydrochloric acid and aqueous ammonia is shown. Use the mean volume of acid needed to neutralise of A in (d) to calculate the concentration of ammonia in A. Give your answer to an appropriate number of significant figures. concentration ..........................................
Calculate the volume of ammonia gas measured at room temperature and pressure, r.t.p., dissolved in of A. The volume of one mole of any gas at r.t.p. is . volume ..................................................
Use your answers to (d) and (f) to calculate the volume of ammonia gas measured at r.t.p. dissolved in of B. volume ..................................................
The student rinses the burette with hydrochloric acid immediately before it is filled. Explain why the student should not rinse the burette with distilled water immediately before it is filled with hydrochloric acid.
Suggest why universal indicator is not suitable for use in these titrations.
A student investigates solution W and solid X.
Solution W is green in colour and contains ions. Describe how W can be shown to contain ions.
Excess W is added to acidified aqueous potassium manganate(VII). Describe the colour change seen. from ........................................................... to ...........................................................
Describe the observations made when a few drops of aqueous ammonia and then an excess of aqueous ammonia are added to the mixture from (ii). a few drops ........................................................................................................................ an excess ..........................................................................................................................
Solid X is a shiny grey metal. The tests the student does on X are shown in Table 3.1. Some of the observations for these tests are also shown. Table 3.1 Predict the identity of the gas produced in test 1. Describe how the student tests the gas to confirm its identity. gas .................................................................................................................... test .................................................................................................................... observation to confirm gas ................................................................................................
The observations for test 1 are incomplete. State one other observation that the student makes for test 1.
State the conclusion you can make from test 2.
State the conclusion you can make from test 3.
Identify the acid used in test 1.
Suggest the identity of metal X.
Baking soda is used to make bread rise. When baking soda is heated, it decomposes and carbon dioxide gas is released. Baking soda also decomposes gradually when it is stored. The longer the baking soda is stored, the less carbon dioxide it releases when it is heated. Plan an investigation to show which of two different samples of baking soda has been stored for longer. Your plan should include the use of common laboratory apparatus and the two samples of baking soda. No other chemicals should be used. Your plan should include: • the apparatus needed • the method to use • the measurements to take • the variables to control • how to use the results to determine which sample has been stored for longer. You may draw a diagram to help you answer the question.