SCIENCE (CHEMISTRY)

The method contains three mistakes.
Complete Table 1.2 to identify each mistake and to state what the student should do instead.

Complete Table 2.1.

Another atom of iron has 26 protons and 31 neutrons.
Write the nuclide symbol for this atom.

Bronze is an alloy of copper and tin.
Complete box E in Fig. 3.1 to show the arrangement of the atoms in bronze. Use the key.

Table salt, sodium chloride, melts at 801 °C. Oxygen melts at −218 °C.
Explain this difference in melting point. Use ideas about structure and bonding in your answer.

The student has Universal Indicator solution and magnesium ribbon, as well as the usual laboratory apparatus.
Describe an experiment that the student can do to decide which liquid is more acidic. In your answer, include what you would observe or measure and how you would reach your conclusion.

In experiment 2, the student repeats experiment 1 with the vinegar at 40 °C. All other conditions are the same.
Draw a curve on Fig. 5.1 to show the results of experiment 2. Label your curve X.

Explain why the rate of reaction in experiment 2 is higher than in experiment 1.
Use ideas about particles in your answer.

In another experiment, the student mixes baking soda and vinegar in a plastic cup. The temperature of the mixture falls from 22.0 °C to 18.0 °C.
State whether the reaction is exothermic or endothermic. Give a reason for your answer.

Suggest why more carbon monoxide is made when the flame is yellow than when it is blue.

State why carbon monoxide is harmful to people.

A gas hob can also make oxides of nitrogen, NO and NO₂.
State one natural source of oxides of nitrogen.

Some cafes keep food warm with gel burners that contain bioethanol, made from the sugar in sugar cane. Table 6.2 compares 100 kg of this fuel with 100 kg of natural gas.
State what is meant by the term carbon neutral.

Use Table 6.2 to calculate the net amount of carbon dioxide added to the air by burning 100 kg of bioethanol.

A cook pours hydrogen peroxide solution on a chopping board. A gas is given off that relights a glowing splint.

Dried apricots are warmed with dilute acid. The gas given off turns acidified purple potassium manganate(VII) colourless.

Aluminium foil is dissolved in dilute hydrochloric acid. The solution gives a white precipitate with aqueous sodium hydroxide that dissolves in excess, and a white precipitate with aqueous ammonia that does not dissolve in excess.

Eggshell is dissolved in dilute hydrochloric acid. The solution gives a white precipitate with aqueous sodium hydroxide that does not dissolve in excess, and no precipitate with aqueous ammonia.

A green coating on a copper pan is dissolved in dilute sulfuric acid. The solution gives a light blue precipitate with aqueous sodium hydroxide.

Rust from an old knife is dissolved in dilute hydrochloric acid. The solution gives a red-brown precipitate with aqueous sodium hydroxide.

Water from a kettle is acidified with dilute nitric acid and aqueous barium nitrate is added. A white precipitate forms.

Write a balanced chemical equation, including state symbols, for the formation of the precipitate in any one of (c), (d), (e), (f) or (g).
You may write an ionic equation.

State what is meant by the term relative atomic mass, A_r.

Calculate the relative formula mass, M_r, of sodium chloride.

Use Fig. 8.1 to calculate the amount, in moles, of silver nitrate needed to react with all of the sodium chloride.

Use your answer to (c) to calculate the mass of sodium chloride in the 25.0 cm³ of stock.

Complete Table 9.1.

State what is meant by the term homologous series.

Name the reagent used to show that ethene is unsaturated.

PTFE is made from tetrafluoroethene, C₂F₄, which has a C=C double bond.
Name the type of polymerisation by which PTFE is made from its monomer.

Describe how the reactivity of the Group 1 metals with cold water changes from lithium to potassium. Use data from Table 10.1 to support your answer.

State which observation in Table 10.1 shows that Group 1 metals have a lower density than water.

Name the gas that burns with a lilac flame when potassium reacts with cold water.

A teacher gives the student three unlabelled pieces of grey metal. They are lithium, sodium and potassium. The apparatus available is: a large trough of cold water, forceps, a knife and white tile, filter paper, a safety screen and eye protection.
Plan an experiment, using water and the information in Table 10.1, to find out which piece of metal is which. In your plan, state what you would do and what you would observe for each metal, and state one safety precaution.

Potassium has proton number 19. State the electronic configuration of a potassium atom.

Potassium reacts with chlorine to form potassium chloride, an ionic compound. Draw a 'dot-and-cross' diagram to show the bonding in potassium chloride. Show only the outer shell electrons. Include the charge on each ion.

The equation for the reaction between potassium and chlorine is shown.

Complete Table 11.1.

Magnesium reacts with dilute hydrochloric acid to form hydrogen and one other product. Name the other product.

Iron knives rust. Iron rusts only when water and one other substance are both present. Name the other substance.

A wire dish rack is made of iron with a plastic coating. A scratch in the coating exposes the iron, as shown in Fig. 11.1. Explain why the coating stops the iron from rusting, and why rust forms at the scratch when the rack is left wet on a draining board.

Deduce which metal in Table 11.1 is the easiest to obtain from its ore. Give a reason for your answer.

Natural gas is used for cooking. Natural gas is mainly methane, CH₄, a covalent compound. Draw a 'dot-and-cross' diagram to show the bonding in a molecule of methane. Show only the outer shell electrons.

The ionic equation for the reaction between zinc and dilute hydrochloric acid is shown.