Covalent bonding

Lithium reacts with chlorine to produce lithium chloride.

Figure 10 shows models of chlorine and of lithium chloride.

Draw one line from each substance to the type of bonding in the substance.

Lithium chloride can also be produced by reacting lithium carbonate with an acid.

Which acid reacts with lithium carbonate to produce lithium chloride?

Tick () one box.

Hydrochloric acid

Nitric acid

Sulfuric acid

What type of substance is lithium chloride?

Tick () one box.

Acid

Alkali

Salt

Figure 11 shows the electrolysis of lithium chloride solution.

Lithium chloride solution contains Li⁺ ions and Cl⁻ ions.

Chloride ions move to the positive electrode to produce chlorine.

Explain why chloride ions move to the positive electrode.

Hydrogen gas and chlorine gas are produced during the electrolysis of lithium chloride solution.

Draw one line from each gas to the result of the test for that gas.

Why is hydrogen gas produced at the negative electrode?

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Hydrogen is less reactive than lithium.

Hydrogen has the same reactivity as lithium.

Hydrogen is more reactive than lithium.

Hydrogen reacts with chlorine to produce hydrogen chloride. A hydrogen atom has 1 electron in the outer shell.

A chlorine atom has 7 electrons in the outer shell.

Complete the dot and cross diagram for a hydrogen chloride molecule.

Use the symbols O and X to represent electrons.

This question is about reactions involving gases.

Hydrogen gas consists of hydrogen molecules.

A hydrogen atom has one electron.

Complete the dot and cross diagram for a hydrogen molecule (H₂).

Hydrogen (H₂) reacts with chlorine (Cl₂) to produce hydrogen chloride (HCl).

Balance the equation for the reaction.

0.8 g of hydrogen reacts with chlorine to produce 29.2 g of hydrogen chloride.

Calculate the mass of chlorine that reacts.

Hydrogen reacts with nitrogen to produce ammonia.

Figure 3 represents a molecule of ammonia.

Ammonia reacts with hydrogen chloride to produce ammonium chloride.

The reaction is reversible.

Write the word equation for the reaction.

Include the symbol for a reversible reaction.

Which condition needs to be changed so that the direction of the reaction is reversed?

This question is about ammonium chloride.

Ammonium chloride (NH₄Cl) decomposes to produce ammonia (NH₃) and hydrogen chloride (HC l).

The reaction is reversible.

The equation for the reaction is:

What is the state of hydrogen chloride in this reaction?

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Aqueous

Gas

Liquid

Solid

How does the equation show that the reaction is reversible?

What is the total number of atoms in the formula NH₄C඀?

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3 4 5 6

When does a reversible reaction reach dynamic equilibrium?

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When the forward reaction is slower than the reverse reaction.

When the forward reaction and the reverse reaction have the same rate.

When the forward reaction is faster than the reverse reaction.

How must the apparatus for the reaction be designed so that dynamic equilibrium can be reached?

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So all of the substances can escape.

So none of the substances can escape.

So only ammonia and hydrogen chloride can escape.

Figure 7 represents the electronic structure of a chlorine atom (C ඀).

Which diagram represents the electronic structure of a chloride ion (C ඀ −)?

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Ammonia has the formula NH₃

Calculate the percentage (%) by mass of nitrogen (N) in NH₃

Relative atomic mass (A_r): N = 14

Relative formula mass (M_r): NH₃ = 17

Give your answer to 2 significant figures.

Figure 8 represents ammonia.

What does ‘ ’ represent in Figure 8?

What type of particle is ammonia?

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Atom

Ion

Molecule 11

This question is about bonds.

Compare the bonding in hydrogen gas (H₂) with the bonding in copper metal.

Hydrogen reacts with oxygen to produce water.

The equation for the reaction is:

The energy released in forming new bonds is 486 kJ/mol greater than the energy needed to break the existing bonds.

Table 2 shows some bond energy values.

Y is the bond energy of a H‒H bond.

Calculate Y.

This question is about the industrial process used to produce ammonia.

Ammonia is produced from nitrogen and hydrogen.

Complete the dot and cross diagram for the ammonia molecule shown in Figure 11.

Show only the electrons in the outer shell of each atom.

Hydrogen is obtained from natural gas.

One stage in the process is to react carbon monoxide with steam.

The equation for the reaction is:

The forward reaction is exothermic.

In the industrial process, the reaction occurs at approximately 400 °C

The reaction between carbon monoxide and steam reaches dynamic equilibrium.

Which statement describes dynamic equilibrium?

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The reaction between carbon monoxide and steam is faster at 600 °C than at 400 °C

Explain why a temperature of 600 °C is not used in the industrial process.

Predict the effect of increasing the pressure on the yield of hydrogen.

Give one reason for your answer.

Give two reasons why a catalyst is used in the reaction between carbon monoxide and steam.

The carbon dioxide produced in this reaction can be used in fizzy drinks.

In fizzy drinks carbon dioxide gas dissolves in water to form an aqueous solution of carbonic acid.

Carbonic acid is a weak acid.

Explain the difference between a weak acid and a strong acid.

The equation for the production of ammonia from nitrogen and hydrogen is:

1.275 × 10¹¹ kg of ammonia is used each year to manufacture fertilisers.

This is 85% of the ammonia produced each year.

Calculate the mass of nitrogen needed to manufacture the total mass of ammonia produced each year.

Relative atomic masses (A_r): H = 1 N = 14

This question is about polymers and plastics.

Figure 12 shows the displayed formula for poly(chloroethene).

What does ‘n’ represent in the displayed formula for poly(chloroethene)?

The representation of poly(chloroethene) in Figure 12 does not show the actual structure of the molecule.

Give one reason why.

Poly(chloroethene) is commonly known as PVC.

PVC does not decompose in the ground.

Many polymer plastics like PVC become pollutant waste in the oceans.

In the oceans, PVC can break into smaller pieces.

The smaller pieces are called PVC nanoplastic.

A piece of PVC nanoplastic has a thickness of 50 nm

Calculate the thickness of the PVC nanoplastic in metres.

Give your answer in standard form.

1 nm = 0.000 000 001 m

Suggest two reasons why PVC nanoplastic can be harmful to marine life.

Suggest two ways to reduce plastic waste.

This question is about polymers and plastics.

Figure 1 shows the displayed formula for poly(chloroethene).

What does ‘n’ represent in the displayed formula for poly(chloroethene)?

The representation of poly(chloroethene) in Figure 1 does not show the actual structure of the molecule.

Give one reason why.

Poly(chloroethene) is commonly known as PVC.

PVC does not decompose in the ground.

Many polymer plastics like PVC become pollutant waste in the oceans.

In the oceans, PVC can break into smaller pieces.

The smaller pieces are called PVC nanoplastic.

A piece of PVC nanoplastic has a thickness of 50 nm

Calculate the thickness of the PVC nanoplastic in metres.

Give your answer in standard form.

1 nm = 0.000 000 001 m

Suggest two reasons why PVC nanoplastic can be harmful to marine life.

Suggest two ways to reduce plastic waste.

A 1 kilogram mass is made from a mixture of metal A and metal B.

Figure 3 represents part of the structure of the 1 kilogram mass.

Figure 3

What is the ratio of metal A atoms to metal B atoms in Figure 3 ?

What is a mixture of metals called?

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A silicon sphere has a mass of 1 kilogram.

The largest impurity in the silicon sphere is copper.

There are 7 × 10^–5 g of copper in the silicon sphere.

What is the mass of copper in kilograms in the silicon sphere?

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An atom of silicon has 14 electrons.

What is the electronic structure of silicon?

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Silicon dioxide is a compound of silicon and oxygen.

Figure 4 represents part of the giant structure of silicon dioxide.

Figure 4

Which two words describe the bonding in silicon dioxide?

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How many silicon atoms are bonded to each oxygen atom in silicon dioxide?

Use Figure 4.

Tick (✓) one box.

Which symbol represents the state of silicon dioxide at room temperature?

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This question is about hydrocarbons.

Figure 6 represents hydrocarbon A.

Complete the chemical formula of hydrocarbon A.

C₅

What do the links between the atoms in Figure 6 represent?

Hydrocarbon A is a fuel. Hydrocarbon A is completely combusted in air.

Which two substances are produced?

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Some students investigated how changing the temperature of a hydrocarbon affects the viscosity of the hydrocarbon.

Figure 7 shows the apparatus used.

The students recorded the time it took for 25 cm³ of the hydrocarbon to flow through the hole in the viscometer.

Table 3 shows a student’s results at 60 °C

Calculate the mean value X.

Another student investigated a different hydrocarbon.

Table 4 shows the results.

Complete Figure 8.

You should:

• plot the data from Table 4

• draw a line of best fit.

Describe the pattern shown on Figure 8.

The viscosity of a substance is linked to how fast the substance flows.

The lower the viscosity, the faster the substance flows.

Complete the sentence.

Choose the answer from the box.

As the temperature increases, the viscosity of

the hydrocarbon.

A 1 kg mass is made from a platinum and iridium alloy.

The platinum and iridium alloy is harder than pure platinum.

Explain why alloys are harder than the pure metal.

The 1 kilogram mass consisted of 900 g platinum and 100 g iridium.

What was the ratio of platinum atoms to iridium atoms in the alloy?

Relative atomic masses (A_r): Pt = 195
Ir = 192

Tick (✓) one box.

The Avogadro constant is the number of atoms in 1 mole of a substance.

What is the value of the Avogadro constant?

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Scientists could use a sample of silicon to define the Avogadro constant.

Copper is an impurity in the silicon sample.

There are 70 nanograms of copper in 1 g of the sample.

Calculate the mass of copper in grams in 1 kg of the sample.

Give your answer in standard form.

1 nanogram = 10^–9 g

Silicon mainly occurs in the Earth’s crust as silicon dioxide.

Figure 8 represents part of the structure of silicon dioxide.

Determine the empirical formula of silicon dioxide.

Use Figure 8.

Describe the structure and bonding in silicon dioxide.

This question is about hydrogen chloride.

A hydrogen atom contains 1 electron and a chlorine atom contains 17 electrons.

Complete Figure 1 to show a dot and cross diagram for a hydrogen chloride molecule.

Show the outer electrons only.

Hydrogen gas (H₂) reacts with chlorine gas to produce hydrogen chloride.

Complete the balanced chemical equation for the reaction between hydrogen and chlorine.

Figure 2 shows the reaction profile diagram for the reaction between hydrogen and chlorine.

What do A and B represent on Figure 2 ?

How does the reaction profile diagram show that the reaction is exothermic?

Hydrogen chloride gas dissolves in water to form hydrochloric acid.

Hydrochloric acid contains hydrogen ions and chloride ions.

Explain why hydrogen chloride gas does not conduct electricity but hydrochloric acid is able to conduct electricity.