0620/61 · May/June 2023
Download PDFEthanol can be made by fermentation of sugars found in plants. A by-product of fermentation is carbon dioxide gas. A student made some ethanol using the following method. step 1 Cut up some sugar cane and crush it. step 2 Add hot water to the sugar cane and stir to dissolve the sugar in the sugar cane. step 3 Remove the solids from the mixture to obtain sugar solution. step 4 Let the sugar solution cool and then add yeast. step 5 Place the mixture obtained in the apparatus shown in Fig. 1.1. step 6 Leave the apparatus until fermentation is complete.
Name the item of apparatus labelled A in Fig. 1.1.
Explain why hot water rather than cold water is used in step 2.
Name the method used to remove the solids from the mixture in step 3 and draw a diagram to show how this is done. name of process ........................................................................................................................ diagram
State why the sugar solution is allowed to cool before the yeast is added in step 4.
Describe how the appearance of the limewater changes as fermentation takes place.
Describe how the student could tell that fermentation is complete.
Name the process used to separate ethanol from the mixture obtained by fermentation.
A student investigates the reaction between aqueous ammonia and two different aqueous solutions of copper(II) sulfate labelled A and B. Solutions A and B have different concentrations. The student does two experiments. Experiment 1 ● Fill a burette with solution A. ● Run some of solution A out of the burette so that the level of solution A is on the burette scale and record the initial burette reading. ● Use a measuring cylinder to pour of aqueous ammonia into a conical flask. ● Stand the conical flask on a white tile. ● Slowly add solution A from the burette to the conical flask, while swirling the flask, until the mixture in the conical flask just starts to become cloudy. ● Record the final burette reading. Experiment 2 ● Empty the conical flask and rinse it with distilled water. ● Empty the burette and rinse it with distilled water. ● Rinse the burette with solution B. ● Repeat Experiment 1 using solution B instead of solution A.
Use the burette diagrams in Fig. 2.1 and Fig. 2.2 to complete Table 2.1.
Explain why a white tile is used during the titration.
State why both the burette and the conical flask are rinsed with water.
Explain why the burette is then rinsed with solution B.
Describe how the result of Experiment 2 would be different if the conical flask is rinsed with aqueous ammonia after rinsing with water. Explain your answer.
Deduce which solution of copper(II) sulfate, A or B, is more concentrated. Explain your answer.
Deduce how many times more concentrated this solution of copper(II) sulfate is than the other solution of copper(II) sulfate.
Describe how the reliability of the results obtained can be checked.
Deduce the volume of solution A required when Experiment 1 is carried out with of aqueous ammonia.
In Experiments 1 and 2, the volume of aqueous ammonia is measured using a measuring cylinder. Give an advantage and a disadvantage of using a volumetric pipette instead of a measuring cylinder to measure the volume of aqueous ammonia. advantage .................................................................................................................................. disadvantage .............................................................................................................................
A student tests two solids: solid E and solid F. Tests on solid E Table 3.1 shows the tests and the student’s observations.
State what conclusion can be made about solid E from the observations in test 1.
Identify the gas produced in test 3.
State what conclusion can be made about solid E from the observations in test 4.
Identify the three ions in solid E.
Tests on solid F Solid F is zinc sulfite. Complete the expected observations. The student dissolves solid F in water to form solution F. The student divides solution F into three portions. To the first portion of solution F, the student adds aqueous ammonia dropwise until it is in excess. observations adding dropwise ................................................................................................... observations in excess ..............................................................................................................
To the second portion of solution F, the student adds a few drops of acidified aqueous potassium manganate(VII). observations ..............................................................................................................................
To the third portion of solution F, the student adds depth of dilute nitric acid followed by a few drops of aqueous barium nitrate. observations ..............................................................................................................................
Solid cobalt(II) oxide is a base which is insoluble in water. It reacts very slowly with cold dilute sulfuric acid to form a solution of cobalt(II) sulfate. Describe how to make pure, dry crystals of hydrated cobalt(II) sulfate. You are provided with cobalt(II) oxide, dilute sulfuric acid and common laboratory apparatus.