0620/62 · Oct/Nov 2025
Download PDFEggshells are made from a mixture of calcium carbonate and other insoluble substances. Calcium carbonate reacts with dilute hydrochloric acid. The equation for the reaction is shown. The other substances in eggshells do not react with dilute hydrochloric acid. A student finds the percentage by mass of calcium carbonate in an eggshell. Fig. 1.1 shows the first three steps of the method the student uses.
Describe what is seen when the calcium carbonate in the eggshell reacts with dilute hydrochloric acid.
Describe what the student should do to make sure the acid is in excess and all of the calcium carbonate has reacted.
After step 3, the student filters the mixture to obtain the unreacted solid left from the eggshell. Draw a labelled diagram of the apparatus the student should use to filter the mixture.
After the filtration, the student washes the residue. Identify the two substances removed from the residue by washing. substance 1 ....................................................................................................................... substance 2 .......................................................................................................................
After washing the residue, the student dries the residue in an oven. The student then measures the mass of the dry residue. The masses the student records are shown in Table 1.1. Table 1.1
Use the data in Table 1.1 to calculate the percentage by mass of calcium carbonate in the eggshell. percentage of calcium carbonate = .........................................................
A student investigates the reaction between acidic solution B and two different solutions of aqueous sodium hydroxide, solution C and solution D, using two different indicators. The student does two experiments. Experiment 1 • Rinse a burette with distilled water and then with solution C. • Fill the burette with solution C. Run some of solution C out of the burette so that the level of the solution is on the burette scale. • Record the initial burette reading. • Use a measuring cylinder to pour of solution B into a conical flask. • Add five drops of methyl orange indicator and five drops of thymolphthalein indicator to the conical flask. • Stand the conical flask on a white tile. • Slowly add solution C from the burette to the conical flask, while swirling the flask, until the solution changes colour from red to orange. This is the first end-point. • Record the burette reading at the first end-point. • Continue to add solution C from the burette to the conical flask while swirling the flask. The solution changes colour from orange to yellow. • Continue to add solution C, while swirling the flask, until the solution changes colour from yellow to green. This is the second end-point. • Record the burette reading at the second end-point. Experiment 2 • Empty the conical flask and rinse it with distilled water. • Repeat Experiment 1 using solution D instead of solution C.
Use the burette diagrams in Fig. 2.1 and Fig. 2.2 to record the readings for Experiment 1 and Experiment 2 in Table 2.1. Complete Table 2.1.
Explain why the conical flask is rinsed with distilled water at the start of Experiment 2.
At the start of Experiment 1, the burette is rinsed with distilled water and then with solution C. Explain how the volume added from the burette to reach the first end-point would be different if the burette was not rinsed with solution C.
Explain why the conical flask is placed on a white tile during the titration.
Compare the concentration of solution C used in Experiment 1 with the concentration of solution D used in Experiment 2. Explain your answer.
Deduce the volume of solution C required to reach the first end-point if Experiment 1 is repeated using of solution B instead of . volume of solution C = ..............................
State why using of solution B would cause a problem when finding the volume of solution C needed to reach the second end-point in Experiment 1.
A student repeats Experiment 2. The student warms solution B in the conical flask before carrying out the titration. State the effect, if any, on the volume of solution D required to reach the second end-point in Experiment 2. Explain your answer. effect on volume of solution D .................................................................................................. explanation ...............................................................................................................................
State one change to the apparatus that will improve the accuracy of the results.
A student tests two solids: solid E and solid F. Tests on solid E Solid E is ammonium sulfate. Record the expected observations. The student dissolves solid E in distilled water to form solution E. The student divides solution E into three approximately equal portions.
To the first portion of solution E, the student adds about of aqueous sodium hydroxide. The student warms the mixture gently and tests any gas produced. observations ......................................................................................................................
Identify the gas given off in (a)(i).
To the second portion of solution E, the student adds about of dilute nitric acid followed by a few drops of aqueous barium nitrate. observations .............................................................................................................................
To the third portion of solution E, the student adds a few drops of acidified aqueous potassium manganate(VII). observations .............................................................................................................................
Tests on solid F Table 3.1 shows the tests and the student’s observations for solid F. Table 3.1
| Carry out a flame test on solid F. | yellow flame |
| Dissolve the remaining solid F in distilled water | |
| to form solution F. Divide solution F into three | |
| portions. | |
| yellow precipitate forms | |
| of dilute nitric acid followed by a few drops of | |
| aqueous silver nitrate. | |
| To the second portion of solution F, add aqueous | white precipitate forms |
| sodium hydroxide dropwise until in excess. | the precipitate dissolves in excess |
| aqueous sodium hydroxide to form a | |
| colourless solution | |
| To the third portion of solution F, add aqueous | white precipitate forms |
| ammonia dropwise until in excess. | the precipitate dissolves in excess |
| aqueous ammonia to form a colourless solution |
Identify the three ions in solid F.
Liquid alcohols can be burned as fuels in spirit burners. The energy given out can be used to heat water in a boiling tube as shown in Fig. 4.1. Describe how to investigate which of three liquid alcohols, ethanol, propanol and butanol, heats the water in the boiling tube the fastest. You are provided with three spirit burners, samples of the three alcohols, water and common laboratory apparatus.
