Reaction profiles

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 3.

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 4

• 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.

The relative atomic mass of argon is 40 and the relative atomic mass of potassium is 39 but potassium appears after argon in the periodic table.

State why potassium appears after argon in the periodic table.

Potassium reacts with water to form two products.

Give the formulae of both products.

_........ and_........

The reaction of potassium with water is exothermic.

On Figure 6, draw and label the reaction profile diagram for this reaction, labelling the activation energy.

Some reactions are endothermic.

Explain, in terms of bond breaking and bond forming, why some reactions are endothermic.

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 8 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.

In some chemical reactions, bonds are broken in the reactant molecules and new bonds are formed to make the product molecules.

Which row is correct about the energy changes for these processes?

Hydrogen reacts with fluorine.

Figure 7 shows the bond energies for the bonds in the three molecules in the equation.

Calculate the energy change for this reaction.

energy change =_........ kJ mol

*(b) The reaction profile for an uncatalysed exothermic reaction is shown in Figure 8.

Using some examples of catalysts you have met in chemistry, discuss what catalysts do and their effect on the activation energy of a reaction.

You can use Figure 8 to illustrate your answer.

The concentration of a solution can be calculated using the equation

A student dissolved 9.25 g of ammonium chloride in water and made up the

Use the equation to calculate the concentration of this solution in gdm⁻³.

concentration =_........ g dm⁻³

Dissolving ammonium chloride in water is an endothermic process. Figure 10 shows part of the reaction profile for this process.

Explain how Figure 10 shows that dissolving ammonium chloride in water is an endothermic process.

Complete the reaction profile in Figure 10 and label the activation energy.

Ammonia gas is toxic.

Which symbol should be placed on a container of a toxic gas?

Give one safety precaution that should be taken when working with toxic gases in the laboratory.

The concentration of a solution can be calculated using the equation

A student dissolved 9.25 g of ammonium chloride in water and made up the

Use the equation to calculate the concentration of this solution in gdm⁻³.

concentration =_........ g dm^–3

Dissolving ammonium chloride in water is an endothermic process. Figure 1 shows part of the reaction profile for this process.

Explain how Figure 1 shows that dissolving ammonium chloride in water is an endothermic process.

Complete the reaction profile in Figure 1 and label the activation energy.

A student investigated the reaction between potassium iodide and lead nitrate.

Solutions of potassium iodide and lead nitrate were mixed together. Lead iodide and potassium nitrate were formed.

Complete the word equation.

The student recorded the total mass of the reactants and the total mass of the products.

The results are shown in Figure 2.

State how the results in Figure 2 show that mass is conserved in this reaction.

In another experiment, a student investigated the temperature decrease when different amounts of ammonium nitrate crystals were dissolved in 100 cm³ of water.

The apparatus used is shown in Figure 3.

The student used the following method.

step N $pour 100 cm³ of water into the polystyrene cup

step 2 add one spatula of ammonium nitrate crystals to the water

step 3 stir the mixture

step 4 use the thermometer to record the lowest temperature reached by the mixtur e

step 5 repeat steps 1 to 4 using different amounts of ammonium nitrate

Name a piece of apparatus that should be used to measure the 100 cm³ of water in step 1.

The student cannot work out the temperature decrease using the method described.

State what the student must do before step 2 to be able to work out the temperature decrease.

State why a polystyrene cup is used in this experiment.

Figure 4 shows the reaction profile for this reaction.

Use the words from the box to complete the labels on Figure 4.

Crude oil is a complex mixture of substances.

Crude oil can be separated into useful fractions by fractional distillation.

Figure 3 shows a fractional distillation column and the fractions produced when a sample of crude oil is distilled.

The properties of these fractions vary from the top of the column to the bottom of the column.

Which of the following is a trend in a property of the fractions obtained from the top of the column to those obtained from the bottom?

Most of the substances in crude oil are alkanes.

Which of the following is the general formula of an alkane?

Explain why alkanes are described as hydrocarbons.

Figure 4 shows a graph of the boiling points of some alkanes against the number of carbon atoms in one molecule of each alkane.

Explain the pattern shown by this graph.

Use the information in Figure 5 to give the name of the fraction that is most likely to need to be cracked.

_........

In a cracking reaction, reactants are heated to form products. This reaction is endothermic.

On the axes provided, draw the reaction profile of this reaction. Label the energy of the reactants, the energy of the products and the activation energy of the reaction.

Dodecane, C₁₂H₂₆, can be cracked to form useful products.

Complete the equation for the cracking of dodecane by filling in the formula of the single molecule needed to balance the equation.

C₁₂H_{26 ........} + 3C₂H₄