OCR GCSE Chemistry B (21st Century) Paper 4 June 2018 question paper

Kai works in a research laboratory for a company that produces organic carbon compounds.

Kai has three unlabelled samples of different compounds. All are colourless liquids.

Kai thinks that one of the compounds might be an alkene. He thinks that another of the compounds might be a carboxylic acid. He thinks the third compound is neither an alkene nor a carboxylic acid.

Describe some simple experiments that Kai could use to find out which compound is which.

Include two tests and the expected results in your answer.

At what concentrations is ethanoic acid harmful, but not corrosive?

Suggest a concentration at which ethanoic acid is flammable.

Kai adds very concentrated ethanoic acid to ethanol and heats the mixture.

Suggest some safety procedures for Kai to use to make sure that he is safe during this experiment.

About 150 years ago, Dimitri Mendeleev developed an early version of the Periodic Table. His Periodic Table had eight groups. He put elements with similar properties into the same group.

The table shows some of the elements that Mendeleev grouped together.

Some of Mendeleev’s groups contain similar elements to groups in the modern Periodic Table.

Which group in Mendeleev’s table contains the elements now found in Group 14 of the modern Periodic Table?

None of the elements from Group 18 of the modern Periodic Table are shown on Mendeleev’s table.

Suggest a reason why.

Mendeleev put some of the transition metals into his Group 8.

He put some other transition metals into the other groups.

Give the symbols for three transition metals in Mendeleev’s table that he did not put in Group 8.

The transition metals are in the same block of the modern Periodic Table because their properties are similar to each other.

Which property do all the transition metals have?

Tick (✓) one box.

Transition metal salts are acidic.

Sundip does an experiment to test the acidity of some solutions of transition metal salts. She uses Universal Indicator and a colour chart to find the pH of each salt.

These are Sundip’s results.

Describe how Sundip uses Universal Indicator to test the pH of the solutions of the salts.

Sundip thinks her results do not show the difference in pH between the salts. She thinks she needs to improve the precision of her pH results.

Explain why she needs to improve her precision and suggest how she can change her experiment to do this.

Mauritius is a country of small islands surrounded by sea. There is almost no fresh water in Mauritius.

Seawater cannot be used as drinking water because it contains a large amount of salt.

Which stage removes the salt from the seawater?

Explain your answer.

Stage........

Explanation........

Explain why there are no harmful bacteria in the water after stage 2.

Explain why stage 3 is needed.

The diagram shows the arrangement of electrons in an atom of an element, element X.

Use the diagram and the Periodic Table to identify the element and to complete the missing information in the table.

The diagram below shows the arrangement of electrons in an ion of another element from the same group, element Y.

What is the charge on the ion?

Explain your answer.

Charge........

Explanation........

Explain how you can tell from the diagrams that element X and element Y are in the same group of the Periodic Table.

The table shows some information about diamond and carbon dioxide.

The structures of diamond and carbon dioxide are different, but the bonds are similar.

Write down some similarities between the bonds in diamond and carbon dioxide.

Explain why diamond is a solid and carbon dioxide is a gas at room temperature and pressure.

Diamond is an allotrope of carbon.

Graphite is another allotrope of carbon.

Carbon dioxide is not an allotrope of carbon.

Explain why diamond and graphite are allotropes but carbon dioxide is not.

The table shows the names and chemical formulae of some alkanes and alkenes.

An alkene called ‘methene’ cannot exist.

Explain why.

All the alkenes are members of the same homologous series.

How do the formulae of the alkenes show that they are from the same homologous series?

How do the formulae of the alkanes and alkenes show that they are from different homologous series’?

The general formula for an alkane is C_nH_(2n+2).

Use this general formula to predict the chemical formula for an alkane which contains 50 carbon atoms.

Use the general equation to write a balanced equation for the combustion of butene, C₄H₈.

Explain your reasoning for each part of the equation.

Equation........

Reasons........

This general equation can be used to balance equations for the complete combustion of alkenes, but does not work for alkanes.

Give one reason why the equation does not work for alkanes.

A new type of salt for using on food is called ‘Lo-So salt’.

Nina wants to find out what elements ‘Lo-So salt’ contains.

She does some experiments to find the emission spectra of some compounds of Group 1 elements. She also does an experiment to find the emission spectrum of ‘Lo-So salt’.

She puts small samples of each element and the salt in a spectroscopy machine and looks at the print-out of results.

Here are Nina’s results.

Element
Emission spectrum

* Nina says that she thinks she needs to do further experiments to identify all the elements in ‘Lo-So salt’.

State which elements ‘Lo-So salt’ does and does not contain, giving your reasons, and describe what further experiments Nina needs to do to identify all the elements in ‘Lo-So salt’.

The label for ‘Lo-So salt’ claims that it is ‘low in sodium’.

Nina says that she cannot use spectroscopy to check this claim because spectroscopy is a qualitative, not a quantitative technique.

Explain why Nina is right.

Alex does some experiments to make some salts.

In his first experiment, he uses 0.2 moles of magnesium oxide. He works out the mass of magnesium oxide in 0.2 moles.

He uses this equation: number of moles = mass of substance (g) ÷ relative formula mass (g)

Use the equation and the Periodic Table to work out the mass of magnesium oxide in 0.2 moles.

Give your answer to 1 decimal place.

In another experiment, Alex reacts 4.0 g copper oxide with hydrochloric acid to make copper chloride. This is an equation for the reaction.

copper oxide + hydrochloric acid copper chloride + water

Alex works out the mass of copper chloride he can make in the experiment.

He uses these relative formula masses.

What mass of copper chloride can be made from 4.0 g of copper oxide?

Use the relative formula masses and the equation to help you.

Give your answer to 2 decimal places.

Alex adds 4.0 g of solid copper oxide to 25.0 cm³ dilute hydrochloric acid. (c)

At the end of the experiment, Alex sees that there is a problem because he has some unreacted solid left.

How will this problem affect his actual yield?

How could Alex change his experiment to solve this problem?

Eve measures the volume of gas given off when solid calcium carbonate reacts with a dilute acid.

Fig. 9.1 shows a graph of her results.

She draws a tangent at the start of her graph.

Calculate the rate of reaction at the start by calculating the gradient of the tangent.

Rate =........ cm³/s

Draw a new tangent on the graph at time = 60 s.

How do the tangents show that the rate of reaction has changed from the start to 60 s?

Eve does some more experiments.

This time she finds out the rate of reaction at the start when she reacts different concentrations of acid with solid calcium carbonate.

She plots a graph of rate of reaction against concentration, as shown in Fig. 9.2.

Using the graph in Fig. 9.2 estimate the rate of reaction when acid of concentration 3.0 mol / dm³ is used.

Rate of reaction =........ cm³ / s

* Both companies show that the same material is likely to cause the least harm to the environment when used for making containers.

Use the information in Table 10.1 and Fig. 10.1 to state and explain which material is best to use for containers and identify any differences in the information from the two companies.

The way that plastic bottles are collected for recycling has changed over time.

In the past, people had to sort their waste plastic bottles and take them to bins in towns or supermarket car parks.

Now, over 90% of local authorities collected waste plastic bottles directly from homes.

Suggest how this change affects the life cycle assessment of plastic bottles.

Company 1 and Company 2 both manufacture drinks containers from polymers.

Some people want to ban the use of all non-biodegradable packaging, including polymers.

Explain why these people have different views to the polymer companies about the use of non-biodegradable materials

Nitrogen oxides are pollutant gases that are produced when coal is burned in a power station.

Which statements about nitrogen oxides are true and which are false ?

Put a tick (✓) in one box in each row.

The graph shows information about the concentration in parts per billion (ppb) of nitrogen oxides in the air between 1980 and 2012.

A scientist comments that the daily concentration of nitrogen oxides in 2012 has fallen by more than 50% compared to 1980.

To what extent does the data support this statement?

Use the data to explain your reasoning.

The concentration of nitrogen oxides is measured in ppb.

1 ppb = 0.000 001 mg / cm³

What was the lowest daily concentration of nitrogen oxides in 1980?

Tick (✓) one box.

Scientists first collect data about the concentration of nitrogen oxides in the air from a monitoring station near a power station.

They then set up 30 monitoring stations to collect data to work out a mean daily concentration of nitrogen oxide across the whole country.

Suggest some factors the scientists should consider when they choose where to set up these monitoring stations.