4CH1/2C — June 2021 (Edexcel IGCSE Chemistry): Past Paper

Use the Periodic Table to help you answer this question.

Name the element with atomic number 14

Name the element with a relative atomic mass of 11

Name the element in Group 2 and Period 3

Determine the number of neutrons in a phosphorus atom with mass number 31

State the electronic configuration of an aluminium atom.

State why neon is unreactive.

A student investigates the rusting of iron.

She places an iron nail in a test tube of water and leaves it for several days. water

Predict the appearance of the iron nail after several days.

Name the main compound in rust.

The student then sets up two more test tubes containing iron nails. drying agent oil boiled air water tube 1 tube 2 Explain why the iron nail in tube 1 and the iron nail in tube 2 do not rust. tube 1 tube 2

The diagram shows the industrial equipment used to separate crude oil into fractions

Give the name of the industrial equipment.

Give one use of the fuel oil fraction.

Give the names of fraction A and fraction F. fraction A fraction F

One compound in the gasoline fraction is the alkane octane (C₈H₁₈) and one compound in the kerosene fraction is the alkane dodecane (C₁₂H₂₆) These two alkanes are covalently bonded and have simple molecular structures.

Give the general formula for the alkanes.

Explain, in terms of their structures, why C₁₂H₂₆ has a higher boiling point than C₈H₁₈

Catalytic cracking can be used to convert the alkane C₁₂H₂₆ into more useful products.

Give the name of the catalyst used for catalytic cracking.

Complete the equation for this cracking reaction. C₁₂H₂₆ → C₉H₂₀ +

A student investigates the solubility of potassium nitrate in water. She measures the masses of potassium nitrate that dissolve in 25 cm3 of water at different temperatures. The table shows the student's results. One of the results is anomalous.

Plot the results on the grid.

Draw a circle around the anomalous result.

Ignoring the anomalous result, draw a curve of best fit. Mass of potassium nitrate in g 10 20 30 40 50 60 70 80 Temperature in oC

Suggest two possible mistakes that could have caused the anomalous result. 1 2

Use your graph to find the maximum mass of potassium nitrate that dissolves in 25 cm³ of water at 75 oC. Show on your graph how you obtained your answer. mass = g

Use your graph to calculate the solubility of potassium nitrate in g per 100 g of water at 25 oC. [1.0 cm³ of water has a mass of 1.0 g] solubility = g per 100 g of water

Ethanol, C₂H₅OH, is a member of the homologous series of alcohols.

Give two characteristics of a homologous series. 1 2

When ethanol is heated with potassium dichromate(VI) and one other reagent, the ethanol is oxidised to ethanoic acid, CH₃COOH

Give the formula of the other reagent.

State the colour change that occurs during this oxidation reaction. from to

Draw the displayed formulae for ethanol and ethanoic acid in the boxes. ethanol ethanoic acid

Ethanol can be manufactured by two different methods. The table gives some information about the two methods. Hydration of ethene Fermentation of glucose raw material crude oil sugar cane rate of reaction fast slow purity of ethanol pure impure operating temperature 300 oC 30 oC operating pressure 60 – 70 atmospheres 1 atmosphere catalyst phosphoric acid enzymes in yeast

Discuss the advantages and disadvantages of these two methods, using information from the table.

The word equation for the fermentation process is glucose → ethanol + carbon dioxide Complete the chemical equation for this reaction. C₆H₁₂O₆ → +

The diagram shows how hydrogen gas and chlorine gas can be prepared in the laboratory by electrolysis of a concentrated solution of sodium chloride

Give a test for hydrogen gas.

Give a test for chlorine gas.

The ionic half-equation for the formation of chlorine at the positive electrode is 2Cl⁻ → Cl₂ + 2e−

State why this reaction is an oxidation reaction.

Give the ionic half-equation for the formation of hydrogen at the negative electrode.

State why it is safer to do this electrolysis in a fume cupboard.

Suggest why the volume of chlorine collected during this electrolysis is less than the volume of hydrogen collected.

In the chemical industry, chlorine can be produced by the electrolysis of molten sodium chloride. The overall equation for this reaction is 2NaCl(l) → 2Na(l) + Cl₂(g)

Explain why sodium chloride needs to be molten rather than solid for electrolysis to occur.

Calculate the maximum volume, in dm³, of chlorine gas at rtp that can be obtained from 23.4 tonnes of molten sodium chloride. [1 tonne = 106 g] [Mr of NaCl = 58.5] [molar volume of chlorine at rtp = 24 dm³] Give your answer in standard form. volume = dm³

A student does a titration to find the concentration of a solution of phosphoric acid. He uses these pieces of apparatus X, Y and Z in his titration. cm³ cm³ X Y Z Diagrams are not to scale.

Give the names of X, Y and Z. X Y Z

What is the colour of phenolphthalein in phosphoric acid?

The student titrates 25.0 cm³ of phosphoric acid with a solution of sodium hydroxide (NaOH). Table 1 shows the student’s results. titration number 1 2 3 4 volume of NaOH added in cm³ 30.35 30.25 30.00 30.30 concordant results Table 1 Concordant results are those within 0.20 cm³ of each other.

Add ticks (✓) to table 1 to show the concordant results.

Use your ticked results to calculate the mean (average) volume of NaOH added. mean volume = cm³

Table 2 shows the titration results of another student. volume of phosphoric acid used in cm³ 25.0 concentration of sodium hydroxide solution in mol/dm³ 0.525 mean volume of sodium hydroxide added in cm³ 30.40 Table 2 The equation for the reaction is 3NaOH + H₃PO₄ → Na₃PO₄ + 3H₂O

Calculate the amount, in moles, of NaOH in 30.40 cm³ of sodium hydroxide solution. amount = mol

Calculate the amount, in moles, of H₃PO₄ in 25.0 cm³ of phosphoric acid. amount = mol

Calculate the concentration, in mol/dm³, of the phosphoric acid. concentration = mol/dm³