Chemical bonds

This question is about the noble gas xenon.

Xenon is unreactive.

Explain, in terms of its electronic configuration, why xenon is unreactive.

Under extreme conditions, xenon can be made to react with fluorine to form xenon tetrafluoride, XeF₄.

Write the balanced equation for this reaction.

Some information about xenon tetrafluoride is shown in Figure 7.

State and explain, with reasons, the type of structure and bonding in xenon tetrafluoride.

Under extreme conditions, xenon reacts with fluorine to form xenon hexafluoride.

The reaction is exothermic. The energy change for the reaction is –400 kJ mol^–1.

On Figure 8

• add a label to the y‑axis

• draw the reaction profile for this reaction

• label the energy change and the activation energy for the reaction.

Concrete is a composite material made of cement, sand and stone.

Different types of concrete are produced by changing the ratio of cement, sand and stone.

Figure 1 shows some information about three different types of concrete,

State how the amount of stone added to the mixture affects the compressive strength of concrete.

What mass of stone is in a sample of concrete B containing 5000 kg of sand?

Sand contains silicon dioxide.

Figure 2 shows part of the structure of silicon dioxide.

State the type of structure and bonding in silicon dioxide.

Which statement about nanoparticles is correct?

Some sunscreens contain nanoparticles of titanium dioxide.

Explain why nanoparticles of titanium dioxide are used in some sunscreens.

Ammonia can be produced from the reaction of hydrogen with nitrogen.

What is the percentage by mass of nitrogen in ammonia, NH₃?

(relative atomic masses: H = 1.0, N = 14)

The reaction between hydrogen and nitrogen is exothermic.

Figure 13 shows the reaction profile of this exothermic reaction.

Which arrow represents the activation energy for the reaction?

Describe what the reaction profile shows about the energy involved in bond breaking and bond making in this reaction.

Ammonia, NH₃, and silicon dioxide, SiO₂, are both compounds that are made of two non-metallic elements.

Ammonia has a boiling point of –33 °C. Silicon dioxide has a boiling point of 2230 °C.

Explain why the boiling points of ammonia and silicon dioxide are so different.

Bromine is a liquid at room temperature and vaporises readily. Bromine has a simple molecular structure.

Which row of the table shows the most likely melting and boiling points of bromine?

Part of the structure of graphene is shown in Figure 5.

Explain why graphene will be a good conductor of an electric current.

Part of the structure of potassium chloride is shown in Figure 6.

Potassium chloride has a melting point of 770 °C.

Explain why potassium chloride has a high melting point.

*(d) A molecule of methane can be represented in several different ways as shown in Figure 7. These representations have been labelled A – E to assist you in your answer.

Describe what information can be obtained from each representation including the limitations of these representations of methane.

An ion of element X can be represented as

This ion of element X has 54 electrons.

Calculate the number of protons and the number of neutrons in this ion.

A sample of silicon contains isotopes.

State, in terms of subatomic particles, how atoms of these isotopes are the same.

This sample of silicon contains three isotopes.

92% of the atoms are silicon-28 5% of the atoms are silicon-29 3% of the atoms are silicon-30

Calculate the relative atomic mass of silicon in this sample.

relative atomic mass =_........

*(c) Figure 6 shows some properties of three substances, A, B and C.

Deduce, using the information in Figure 6, the structure and bonding of substances A, B and C, explaining their properties in terms of their structure and bonding.

In the 19th century, Mendeleev arranged the elements known at the time to form his periodic table. Mendeleev’s periodic table is different from the modern periodic table.

State one difference between Mendeleev’s periodic table and the modern periodic table.

Aluminium oxide reacts with hydrochloric acid to form a salt and water.

State the name of the salt formed.

In this reaction aluminium oxide is a base.

State the type of reaction that takes place when an acid reacts with a base.

Gallium, Ga, is in the same group of the modern periodic table as aluminium.

The formula of aluminium oxide is Al₂O₃.

Predict the formula of gallium oxide.

Gallium oxide has a very high melting point. Gallium oxide does not conduct electricity when solid but does conduct electricity when molten.

What type of substance is gallium oxide?

Figure 5 shows the changes of state for gallium and the arrangement of particles in liquid gallium.

Complete the boxes for solid gallium and gaseous gallium by drawing the arrangement of the particles in each of these physical states.

Give the name of the change of state labelled Y in Figure 5.

Gallium metal is a conductor of electricity.

Explain how metals conduct electricity.

Calcium has an atomic number of 20. A calcium atom has a mass number of 40.

Which row of the table shows the number of protons and number of neutrons in this atom of calcium?

Figure 8 shows the arrangement of electrons in an atom of calcium.

Explain, using the information in Figure 8, in which period of the periodic table calcium can be found.

Calcium and potassium react with water in similar ways.

One similarity in the reactions is that hydrogen gas is produced.

State one other similarity in the products of the reactions of calcium and potassium with water.

Potassium is higher in the reactivity series than calcium and reacts more vigorously with water than calcium reacts with water.

State why potassium is higher in the reactivity series and reacts more vigorously with water than calcium.

*(c) Calcium chloride can be prepared by the reaction of calcium with chlorine gas.

Figure 9 shows some properties of calcium, chlorine and calcium chloride.

Explain, in terms of bonding and structure, why the properties of the product, calcium chloride, are different from the properties of the reactants, calcium and chlorine.

Alloy steels are made when iron is alloyed with other transition metals such as cobalt and chromium.

Which row of the table shows the typical properties of a transition metal?

Figure 1 shows the chain on a bicycle.

Explain how lubricating the chain with oil prevents corrosion of the steel chain.

Iron fences can be galvanised by coating them with a layer of zinc. When the layer of zinc is scratched exposing the iron to the weather, the iron does not rust.

Explain why the exposed iron does not rust.

Metals have high melting points.

Explain, in terms of their structure and bonding, why metals have high melting points.