Percentage yield

This question is about mixtures.

Draw one line from each type of mixture to the representation of that mixture.

A student had a mixture of salt and sand.

Salt is soluble in water.

Sand is insoluble in water.

Plan a method to obtain pure dry samples of salt and of sand from the mixture.

Figure 11 shows the chemicals and equipment that can be used.

A mixture of salt and sand contained 16.0 g of salt.

The student obtained 13.6 g of salt after separation from the mixture.

Calculate the percentage yield of the salt.

Use the equation

Zinc reacts with iodine to produce the salt zinc iodide.

The reaction is done in a solution using ethanol as the solvent.

Ethanol is a flammable liquid with a boiling point of 78 °C.

Table 5 shows the solubility of zinc, iodine and zinc iodide in ethanol.

Plan a method to obtain crystals of zinc iodide from zinc and iodine.

A student used 6.35 g of iodine in the reaction.

6.29 g of zinc iodide was produced.

The equation for the reaction is:

Calculate the percentage yield of zinc iodide.

Give your answer to 3 significant figures.

Relative formula masses (M_r): I₂ = 254 ZnI₂ = 319

A student produced a salt by reacting copper carbonate with sulfuric acid.

This is the method used.

1. Measure 50 cm³ of sulfuric acid into a beaker.

2. Add copper carbonate powder.

3. Stir the mixture.

4. Repeat steps 2 and 3 until copper carbonate is in excess.

5. Filter the mixture.

6. Warm the filtrate gently until crystals start to appear.

7. Leave the solution to cool and crystallise.

Complete the word equation for the reaction.

copper + sulfuric → + + carbon

Give one observation the student could make during Step 4 which shows that the copper carbonate is in excess.

Give one reason for filtering the mixture in Step 5.

Name the equipment that can be used to warm the filtrate gently in Step 6.

The maximum theoretical mass of the salt that could be produced using 50 cm³ of the sulfuric acid is 12.5 g.

The percentage yield of the salt is 92.8%.

Calculate the mass of salt actually produced.

Use the equation:

Some salts can be produced by reacting sulfuric acid with a metal.

Neither copper nor sodium is used to produce a salt with sulfuric acid.

Give one reason why each metal is not used.

A student produced a salt by reacting copper carbonate with sulfuric acid.

This is the method used.

1. Measure 50 cm³ of sulfuric acid into a beaker.

2. Add copper carbonate powder.

3. Stir the mixture.

4. Repeat steps 2 and 3 until copper carbonate is in excess.

5. Filter the mixture.

6. Warm the filtrate gently until crystals start to appear.

7. Leave the solution to cool and crystallise.

Complete the word equation for the reaction.

copper + sulfuric → + + carbon

Give one observation the student could make during Step 4 which shows that the copper carbonate is in excess.

Give one reason for filtering the mixture in Step 5.

Name the equipment that can be used to warm the filtrate gently in Step 6.

The maximum theoretical mass of the salt that could be produced using 50 cm³ of the sulfuric acid is 12.5 g.

The percentage yield of the salt is 92.8%.

Calculate the mass of salt actually produced.

Use the equation:

Some salts can be produced by reacting sulfuric acid with a metal.

Neither copper nor sodium is used to produce a salt with sulfuric acid.

Give one reason why each metal is not used.

This question is about the extraction of metals.

Tungsten is a metal. The symbol of tungsten is W Tungsten is produced from tungsten oxide by reaction with hydrogen. The equation for the reaction is:

Calculate the percentage atom economy when tungsten is produced in this reaction. Use the equation:

Relative formula masses (M_r): WO₃ = 232 H₂ = 2

Aluminium is extracted from aluminium oxide.

38% of a rock sample is aluminium oxide. Calculate the mass of aluminium oxide in 40 kg of the rock sample.

The formula of aluminium oxide is Al₂O₃ Calculate the relative formula mass (M_r) of aluminium oxide. Relative atomic masses (A_r): O = 16 Al = 27

60.0 kg of aluminium oxide produces a maximum of 31.8 kg of aluminium. In an extraction process only 28.4 kg of aluminium is produced from 60.0 kg of aluminium oxide. Calculate the percentage yield. Give your answer to 3 significant figures.

Use the equation:

Extracting metals by electrolysis is a very expensive process. Explain why aluminium is extracted using electrolysis and not by reduction with carbon.

The halogens are elements in Group 7.

Bromine is in Group 7.

Give the number of electrons in the outer shell of a bromine atom.

Bromine reacts with hydrogen. The gas hydrogen bromide is produced.

What is the structure of hydrogen bromide?

Tick one box.

What is the formula for fluorine gas?

Tick one box.

A student mixes solutions of halogens with solutions of their salts.

Table 1 shows the student’s observations.

Explain how the reactivity of the halogens changes going down Group 7.

Use the results in Table 1.

A company uses chlorine to produce titanium chloride from titanium dioxide.

What is the relative formula mass (M_r) of titanium dioxide, TiO₂ ?

Relative atomic masses (A_r): O = 16 Ti = 48

Tick one box.

The company calculates that 500 g of titanium dioxide should produce 1.2 kg of titanium chloride.

However, the company finds that 500 g of titanium dioxide only produces 900 g of titanium chloride.

Calculate the percentage yield.

Titanium is a transition metal. Titanium is extracted from titanium dioxide in a two stage industrial process. Stage 1 TiO₂ + 2 C + 2 Cl₂ TiCl₄ + 2 CO Stage 2 TiCl₄ + 4 Na Ti + 4 NaCl

Suggest one hazard associated with Stage 1.

Water must be kept away from the reaction in Stage 2. Give one reason why it would be hazardous if water came into contact with sodium.

Suggest why the reaction in Stage 2 is carried out in an atmosphere of argon and not in air.

Titanium chloride is a liquid at room temperature. Explain why you would not expect titanium chloride to be a liquid at room temperature.

In Stage 2, sodium displaces titanium from titanium chloride.

Sodium atoms are oxidised to sodium ions in this reaction. Why is this an oxidation reaction?

Complete the half equation for the oxidation reaction.

In Stage 2, 40 kg of titanium chloride was added to 20 kg of sodium. The equation for the reaction is:

Relative atomic masses (A_r): Na = 23 Cl = 35.5 Ti = 48 Explain why titanium chloride is the limiting reactant. You must show your working.

For a Stage 2 reaction the percentage yield was 92.3% The theoretical maximum mass of titanium produced in this batch was 13.5 kg. Calculate the actual mass of titanium produced.