Reaction profiles

This question is about acids.

A student investigated the volume of an alkali needed to react completely with

Figure 10 shows the apparatus.

This is the method used.

1. Add 25 cm³ of the acid to a beaker.

2. Add a piece of universal indicator paper to the acid.

3. Add the alkali drop by drop to the acid until the universal indicator paper changes colour to green.

4. Record the number of drops of alkali added.

The method does not give an accurate volume of alkali needed to react completely with the acid.

Suggest two improvements to the method.

What is the pH of the solution when the universal indicator paper turns green?

Tick () one box.

What name is given to the reaction between an acid and an alkali?

Tick () one box.

Which ion do all acids contain?

Tick () one box.

Name the acid that reacts with sodium hydroxide to produce sodium nitrate.

Figure 11 shows a reaction profile for the reaction between an acid and an alkali.

What do labels A and B represent on Figure 11 ?

Choose the answers from the box.

Acids also react with insoluble solid substances to produce salt solutions.

When making a salt solution, excess solid is added to the acid.

Draw the apparatus used to separate the excess solid from the salt solution by filtration.

The apparatus should collect:

• the excess solid

• the salt solution.

Solid X reacts with hydrochloric acid to produce zinc chloride and hydrogen gas.

Name solid X.

Nitrogen reacts with hydrogen to produce ammonia (NH₃).

Complete the dot and cross diagram for an ammonia molecule.

The equation for the reaction between nitrogen and hydrogen to produce ammonia is:

Calculate the mass of hydrogen that is needed to produce 25 g of ammonia.

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

Figure 7 shows the displayed formulae equation for the reaction of nitrogen

with hydrogen.

In the reaction the energy released forming new bonds is 93 kJ/mol greater than the energy needed to break existing bonds.

Table 3 shows bond energies.

Calculate the bond energy X for the H — H bond.

Use Figure 7 and Table 3.

Energy is released from the reaction to produce ammonia.

Figure 8 shows part of the reaction profile for the reaction between nitrogen and hydrogen to produce ammonia.

Complete Figure 8.

You should:

• complete the profile line

• label the energy level of the reactants and the product

• label the overall energy change.

A student investigated the change in temperature when different masses of zinc were added to copper sulfate solution. This is the method used.

1. Measure the volume of copper sulfate solution using a measuring cylinder.

2. Pour the copper sulfate solution into a metal container.

3. Add 2 g of zinc.

4. Measure the temperature of the solution.

5. Repeat steps 1 to 4 with different masses of zinc.

Figure 7 shows the apparatus.

Give three improvements to the investigation to make the results more accurate.

Figure 8 shows part of the measuring cylinder.

What is the volume of copper sulfate solution in Figure 8 ?

When zinc was added to copper sulfate solution the temperature increased. Figure 9 shows the reaction profile.

What type of reaction is shown in Figure 9 ? Tick (✓) one box.

Figure 10 shows the results.

Determine the gradient of the line in Figure 10. Use the equation:

Suggest why the student should not use more than 10 g of zinc. Use Figure 10. You should extend the graph line.

This question is about energy change. A student investigated the temperature change when 10 g of ammonium nitrate was

This is the method used.

1. Measure the temperature of 100 cm³ of water.

2. Add 10 g of ammonium nitrate.

3. Stir once.

4. Measure the temperature of the solution every minute for 7 minutes.

Figure 3 shows the apparatus.

What is the dependent variable in this investigation?

Give three improvements to the investigation to make the results more accurate.

Figure 4 shows the results.

Explain the results.

Draw a reaction profile for an exothermic reaction. You should label:

• the energy level of the reactants and of the products

• the activation energy

• the overall energy change.

Methane, ethane, propane and butane all react with oxygen to produce carbon dioxide and water.

Suggest why a mixture of methane and oxygen does not react at room temperature. Answer in terms of particles.

Table 3 shows the energy released when methane, ethane and propane react with oxygen to produce carbon dioxide and water.

Predict the energy released when butane (C₄H₁₀) reacts with oxygen to produce carbon dioxide and water.

Propane reacts with oxygen to produce carbon dioxide and water. The displayed formula equation for the reaction is:

The reaction is exothermic. In the reaction, the energy released when forming new bonds is 1640 kJ/mol greater than the energy needed when breaking bonds. Table 4 shows bond energies.

Calculate the C––C bond energy (X).

This question is about energy changes.

Which of these items uses an endothermic reaction? Tick (✓) one box.

Figure 1 shows the reaction profile for an exothermic reaction.

Which letter represents the activation energy for the reaction? Tick (✓) one box.

Which letter represents the overall energy change for the reaction? Tick (✓) one box.

Complete the sentence. Choose the answer from the box.

In an exothermic reaction the energy of the products is the energy of the reactants.

A student measured the temperature at the start and at the end of a reaction. Name the apparatus used to measure the temperature.

Figure 2 shows the temperature at the end of the reaction.

Complete Table 1. Use Figure 2.

This question is about oxygen.

Hydrogen reacts with oxygen.

Figure 2 shows the relative energies of the reactants and products at a certain temperature.

Label the activation energy on Figure 2.

Determine the overall energy change for the reaction between hydrogen and oxygen shown in Question 03.1 Use Figure 2.

Oxygen is in Group 6 of the periodic table. Figure 3 shows the outer energy levels in one molecule of oxygen (O₂). Draw the electrons in the outer energy levels in Figure 3.

The equation shows the decomposition of hydrogen peroxide. 2 H – O – O – H → 2 H – O – H + O=O Table 1 shows the bond energies.

Calculate the overall energy change for the reaction.

This question is about sodium and chlorine. Figure 13 shows the positions of sodium and chlorine in the periodic table.

State one difference and one similarity in the electronic structure of sodium and of chlorine.

Sodium atoms react with chlorine atoms to produce sodium chloride (NaCl). Describe what happens when a sodium atom reacts with a chlorine atom. Write about electron transfer in your answer.

The reaction between sodium and chlorine is an exothermic reaction. Complete the reaction profile for the reaction between sodium and chlorine.

This question is about sodium and chlorine. Figure 2 shows the positions of sodium and chlorine in the periodic table.

State one difference and one similarity in the electronic structure of sodium and of chlorine.

Sodium atoms react with chlorine atoms to produce sodium chloride (NaCl). Describe what happens when a sodium atom reacts with a chlorine atom. Write about electron transfer in your answer.

The reaction between sodium and chlorine is an exothermic reaction. Complete the reaction profile for the reaction between sodium and chlorine.