Edexcel IGCSE Chemistry Chemistry Paper 2 June 2019 question paper 4CH1/2CR

This question is about gases in the atmosphere.

The box gives the names of some gases in the atmosphere.

Use gases from the box to answer the questions.

Each gas may be used once, more than once or not at all.

Identify the two noble gases.

Identify the gas that is a compound.

Identify the most abundant gas in the atmosphere.

Identify the greenhouse gas.

Describe the test for oxygen.

The diagram represents an atom of boron.

Use information from the diagram to complete the table.

The first row has been done for you.

Boron has two isotopes, boron‑10 and boron‑11.

A sample of boron contains 18.7% of boron‑10 and 81.3% of boron‑11.

Calculate the relative atomic mass of this sample of boron.

Crude oil is an important source of organic compounds.

The diagram shows crude oil being separated into different fractions.

Name the process used to separate crude oil into different fractions.

State what happens to the crude oil at X.

Describe the differences between fraction B and fraction E.

In your answer, refer to

● size of the molecules

● boiling point

● colour

● viscosity

Crude oil often contains sulfur as an impurity.

Explain why this is a problem when using crude oil fractions as fuels.

This question is about the halogens and their compounds.

The table gives the colour and physical state at room temperature of the halogens.

Complete the table by predicting the colour of astatine and the physical state of fluorine at room temperature.

Chlorine gas is bubbled into a colourless solution of potassium bromide.

Explain why the solution turns orange.

Potassium bromide is an ionic compound.

Draw diagrams to show the outer electrons in a potassium ion and in a bromide ion.

Include the charges on the ions.

A student sets up a circuit to test the electrical conductivity of water, solid sodium chloride and aqueous sodium chloride.

The table shows the student’s results.

Explain these results, with reference to the structure and bonding of the substances.

A concentrated aqueous solution of sodium chloride is electrolysed using graphite electrodes.

Chlorine is formed at the positive electrode (anode).

Give an ionic half‑equation for the formation of chlorine at the positive electrode.

State why this ionic half‑equation represents an oxidation reaction.

Which substance is formed at the negative electrode (cathode)?

This question is about the reactions of carboxylic acids.

Carboxylic acids react with solutions of metal carbonates.

Complete the chemical equation for the reaction of ethanoic acid, CH₃COOH, with potassium carbonate solution.

2CH₃COOH + K₂CO_{3 ........} +_........ +_........

State what you would see in this reaction.

The ester, ethyl ethanoate, can be prepared by reacting ethanol with ethanoic acid.

This is the method for the preparation.

● mix equal amounts of ethanoic acid and ethanol in a boiling tube

● add a few drops of concentrated sulfuric acid

● place the boiling tube in a hot water bath for several minutes

State the role of concentrated sulfuric acid in this reaction.

Suggest why the mixture is heated in a water bath rather than directly with a Bunsen burner flame.

State how you would know that ethyl ethanoate has formed.

Another ester, methyl propanoate, can be prepared by reacting methanol with propanoic acid.

Draw the displayed formulae of methanol, propanoic acid and the ester, methyl propanoate.

Give the name of the other product of this reaction.

Give one use of esters.

When a bottle of wine is left open for several days, some of the ethanol in the wine turns to ethanoic acid, CH₃COOH

A scientist uses a titration method to investigate how much ethanoic acid is formed if a bottle of white wine is left open for one week.

She uses this method.

● fill a burette with the white wine and record the reading

● add 25.0 cm³ of sodium hydroxide solution to a conical flask

● add a few drops of phenolphthalein indicator to the flask

● swirl the flask continuously while adding wine from the burette

● add the wine drop by drop near the end point

● record the reading at the end point

Name the piece of apparatus that would be most suitable for measuring the 25.0 cm³ of sodium hydroxide solution.

Suggest why red wine would not be suitable to use for this investigation.

State why she swirls the flask continuously.

State why she adds the wine drop by drop near the end point.

The diagram shows the burette readings at the start and end of one of the titrations.

Use the readings to complete the table.

Give your values to the nearest 0.05 cm³.

The scientist repeats the titration four more times.

The table shows her results for these four titrations.

Concordant results are those within 0.20 cm³ of each other.

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

Use your ticked results to calculate the mean (average) volume of wine added.

Another scientist repeats the titration with a different bottle of white wine that has been left open for a week.

The equation for the reaction that occurs in this titration is

CH₃COOH + NaOH CH₃COONa + H₂O

The mean volume of wine added is 19.50 cm³.

The concentration of the sodium hydroxide solution is 0.0500 mol/dm³.

Calculate the amount, in moles, of NaOH in 25.0 cm³ of sodium hydroxide solution.

Deduce the amount, in moles, of CH₃COOH in 19.50 cm³ of the wine.

Calculate the concentration, in mol/dm³, of CH₃COOH in the wine.

concentration of CH₃COOH =_........ mol/dm³

Hydrogen gas can be produced by reacting a mixture of methane and steam in the presence of a nickel catalyst.

The reaction conditions are a temperature of 700C and a pressure of 5 atmospheres.

The equation for the reaction is

What does the symbol represent?

The mixture of methane and steam is heated to a temperature greater than 700 °C but the pressure is kept at 5 atmospheres.

Predict the effect of this change on the yield of hydrogen at equilibrium, giving a reason for your answer.

The mixture of methane and steam is kept at the same temperature of 700 °C but the pressure is increased to more than 5 atmospheres.

Predict the effect of this change on the yield of hydrogen at equilibrium, giving a reason for your answer.

Calculate the volume, in dm³, of hydrogen gas at rtp that is produced when 10 tonnes of methane gas completely react with steam.

[molar volume of hydrogen at rtp is 24 dm³]

Give your answer in standard form.