Mixtures and separation techniques

A student investigates the reaction of magnesium carbonate and dilute sulfuric acid.

The student wants to measure the pH of the dilute sulfuric acid.

Suggest the pH of dilute sulfuric acid.

Name an indicator that the student could use to measure the pH of dilute sulfuric acid.

State the colour of the indicator after it has been added to the dilute sulfuric acid.

Name of indicator........

Name a piece of equipment the student could use to measure the pH more accurately.

When magnesium carbonate reacts with dilute sulfuric acid, it forms a salt, water and carbon dioxide.

What is the name of the salt?

The student adds an excess of magnesium carbonate to dilute sulfuric acid until no more of it reacts.

magnesium carbonate(s) + sulfuric acid(aq) salt(aq) + water(l) + carbon dioxide(g)

Magnesium carbonate is a white powder that is insoluble in water.

A colourless solution of the salt is formed.

Describe two observations the student would see as the reaction is happening.

The student separates the salt from the solution formed at the end of the reaction.

Step 1: They remove the excess magnesium carbonate.

Step 2: They remove the water from the salt solution.

State the names of the separation techniques used in Step 1 and Step 2.

The student measures the mass of the salt obtained when different masses of magnesium carbonate are added to the same volume of dilute sulfuric acid.

The table shows their results.

Describe the relationship between the mass of magnesium carbonate and the mass of the salt.

A student thinks that when 6.0 g of magnesium carbonate has been added it is in excess.

Explain why the student is correct.

A student investigates the reaction of magnesium carbonate and dilute sulfuric acid.

The student wants to measure the pH of the dilute sulfuric acid.

Suggest the pH of dilute sulfuric acid.

Name an indicator that the student could use to measure the pH of dilute sulfuric acid.

State the colour of the indicator after it has been added to the dilute sulfuric acid.

Name of indicator........

Name a piece of equipment the student could use to measure the pH more accurately.

When magnesium carbonate reacts with dilute sulfuric acid, it forms a salt, water and carbon dioxide.

What is the name of the salt?

The student adds an excess of magnesium carbonate to dilute sulfuric acid until no more of it reacts.

magnesium carbonate(s) + sulfuric acid(aq) salt(aq) + water(l) + carbon dioxide(g)

Magnesium carbonate is a white powder that is insoluble in water.

A colourless solution of the salt is formed.

Describe two observations the student would see as the reaction is happening.

The student separates the salt from the solution formed at the end of the reaction.

Step 1: They remove the excess magnesium carbonate.

Step 2: They remove the water from the salt solution.

State the names of the separation techniques used in Step 1 and Step 2.

The student measures the mass of the salt obtained when different masses of magnesium carbonate are added to the same volume of dilute sulfuric acid.

The table shows their results.

Describe the relationship between the mass of magnesium carbonate and the mass of the salt.

A student thinks that when 6.0 g of magnesium carbonate has been added it is in excess.

Explain why the student is correct.

A student investigates mixtures of salt and water.

The student has a solution of salt dissolved in water. The diagram shows how they separate pure water from the solution.

What name is given to this method of separation? Tick (✓) one box.

The particle diagrams represent changes of state.

Which diagram represents what happens in the boiling tube?

Tick (✓) one box.

After several minutes the glass tube becomes hot, and no more water is collected in the test tube.

Give one reason why the glass tube becomes hot.

The student wants the experiment to work for longer.

What other piece of equipment can they use instead of the glass tube?

The student also investigates how adding salt to ice changes the melting point of the ice.

The table shows their results.

The student draws a bar chart of the results.

Draw a bar on the bar chart for the results when 4 g of salt are added to the ice.

Describe how changing the mass of salt changes the melting point.

The student thinks the results show that pure ice will have a melting point of 0 C.

Explain why the student is correct.

A student does some experiments to separate water from muddy water.

Fig. 11.1 shows the equipment the student uses in their first experiment.

Fig. 11.1

What is the name of this separation technique?

The water produced in the experiment is a very light brown colour.

Why is the student not sure that the water produced is potable ?

Tick (✓) two boxes.

Fig. 11.2 shows the equipment the student uses in their second experiment.

Fig. 11.2

The student leaves the equipment in a sunny place.

The statements describe how the experiment produces water.

The statements are not in the correct order.

A The water drips into the beaker.

B The sun heats up the muddy water.

C The water evaporates.

D The water vapour cools and condenses.

E The water vapour rises upwards.

F The water vapour touches the cold piece of glass.

Write the remaining letters in the boxes to show the correct order of the statements.

A student does an experiment to separate water from muddy water.

The diagram shows the equipment they use.

The student leaves the equipment in a sunny place.

Explain how the student’s equipment separates water from muddy water.

13* A student has a mixture of sand and a salt solution.

They do a two stage experiment to obtain a sample of pure salt from the mixture.

Describe the two stages of the student’s experiment. Include labelled diagrams of how the equipment is set up in each stage.

Which diagram shows the correct equipment diagram for simple distillation?

A student investigates how to make a sample of a pure salt.

His method is shown in Fig. 14.1.

React an excess of copper oxide with 50 cm³ dilute hydrochloric acid. Stage 1

Stage 2 Heat the solution from Stage 1.

Copper oxide is an insoluble compound that neutralises dilute hydrochloric acid.

Name the type of insoluble compound that neutralises an acid to form a salt and water.

Dilute hydrochloric acid is a hazardous chemical.

Describe one safety precaution the student should take when using dilute hydrochloric acid.

Stage 1 uses an excess of copper oxide.

Give a reason why.

Calculate the number of moles of copper oxide, CuO, in 0.500 g.

Give your answer to 3 significant figures.

Use your answer to (d)(i) and the balanced symbol equation to explain why the copper oxide is in excess.

Another student thinks that the method in Fig. 14.1 will not make pure copper chloride.

Explain why this student is correct.

A student does an experiment to identify an unknown metal M.

The student weighs metal M. Then the student adds metal M to a solution of copper sulfate, CuSO₄(aq).

A reaction takes place forming copper metal, Cu:

The student separates the copper and then weighs the copper.

These are the student’s results: Mass of metal M = 8.10 g Mass of copper = 21.2 g

How could the student separate the copper from the solution?

Use your answer from (b)(i) and the Periodic Table to identify the metal M.

Which separation technique in the laboratory requires a condenser?

A Chromatography

B Crystallisation

C Filtration

D Distillation