0620/63 · May/June 2024
Download PDFA sample of rock salt contains sodium chloride, sand and mud. Sodium chloride is soluble in water. Sand and mud are insoluble in water. A student obtains dry crystals of pure sodium chloride from a lump of rock salt. Fig. 1.1 shows some of the steps the student uses. step 1 Grind the rock salt into smaller pieces. step 2 Add the rock salt to water and heat while stirring with a glass rod. step 3 Filter the mixture.
Explain why the rock salt is made into smaller pieces in step 1.
Name an item of apparatus that can be used to heat the water in step 2.
Name the apparatus labelled A in step 3.
Describe what the student must do after step 3 to obtain dry crystals of pure sodium chloride.
A student investigates the rate at which hydrogen gas is made when magnesium ribbon reacts with dilute ethanoic acid at two different temperatures. Instructions The student does two experiments using the apparatus shown in Fig. 2.1. Experiment 1 ● Use a measuring cylinder to pour of dilute ethanoic acid into a conical flask. ● Use a thermometer to measure the initial temperature of the dilute ethanoic acid and record the initial temperature. ● Set the apparatus up as shown in Fig. 2.1, ensuring the inverted measuring cylinder is full of water. ● Remove the bung from the conical flask, ensuring the delivery tube remains in the measuring cylinder. ● Add a coil of magnesium ribbon to the conical flask, immediately put the bung back into the conical flask and start the timer. If the magnesium sticks to the side of the flask, gently shake the flask so that it is washed off the side. ● Measure the volume of gas collected in the inverted measuring cylinder every 15 seconds for 150 seconds. Record the volume of gas collected. ● Use the thermometer to measure the final temperature of the mixture in the conical flask and record the final temperature. ● Rinse out the conical flask with distilled water. Experiment 2 ● Repeat Experiment 1 but warm the acid by about after it has been poured into the conical flask and before the initial temperature is measured and recorded.
Use the thermometer diagrams to complete Table 2.1. Table 2.1
Use the diagrams of the inverted measuring cylinders to complete Table 2.2. Table 2.2
Complete a suitable scale on the y-axis and plot the results for Experiments 1 and 2 on Fig. 2.2. Draw two lines of best fit. Both lines must start at (0,0). Label your lines.
Deduce the volume of gas collected between 20 seconds and 40 seconds in Experiment 1. Show clearly on Fig. 2.2 how you worked out your answer. volume of gas collected between 20 seconds and 40 seconds ..............................
Use Fig. 2.2 to explain which experiment had the faster rate of reaction. experiment with faster rate ........................................................................................................ explanation ................................................................................................................................ ....................................................................................................................................................
During Experiment 1, the temperature of the mixture in the conical flask changed. State how this change in temperature affects the rate of the reaction.
Describe how the apparatus could be altered to minimise the change in temperature.
Some gas escapes in the short time between adding the magnesium ribbon to the conical flask and putting the bung back into the conical flask. Explain how the apparatus could be altered so that no gas escapes and the results of the experiment are more accurate. You may draw a diagram to help explain your answer.
Describe one other way in which the results of Experiments 1 and 2 could be made more accurate.
Sketch on Fig. 2.2 the graph you would expect when Experiment 2 is repeated using ethanoic acid with a higher concentration. Label your line X.
A student tests two substances: solid K and solution L. Tests on solid K Solid K is copper(II) carbonate. Complete the expected observations.
The student adds about of dilute hydrochloric acid to solid K. observations .............................................................................................................................. ..............................................................................................................................................
The solution made in (a) is solution M. The student divides solution M into two portions. To the first portion of solution M, the student adds aqueous ammonia dropwise until it is in excess. observations .............................................................................................................................. .................................................................................................................................................... ..............................................................................................................................................
The student carries out a flame test on the second portion of solution M. State the colour the Bunsen burner flame becomes during the flame test.
Describe how the student should carry out the flame test.
Tests on solution L Table 3.1 shows the tests and the student’s observations for solution L. Solution L was divided into two portions. Table 3.1 tests | observations test 1: To the first portion of solution L, add aqueous sodium hydroxide dropwise until in excess. | a white precipitate forms which is insoluble in excess test 2: To the second portion of solution L, add of dilute nitric acid followed by a few drops of aqueous silver nitrate. | a cream precipitate forms Identify solution L.
Iron rusts slowly when exposed to water and air. There is an increase in mass when iron rusts as the insoluble solid hydrated iron(III) oxide forms. Cast iron, mild steel and stainless steel are all alloys that contain iron. Plan an experiment to find which of these three alloys rusts most quickly when exposed to water and air. Include in your answer how the results of the experiment will show which alloy rusts most quickly. You are provided with powdered cast iron, powdered mild steel, powdered stainless steel and common laboratory apparatus.