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This final lesson brings everything together. Instead of teaching a new technique, it walks you through a realistic mixed set of questions — the kind you meet across an OCR Gateway Chemistry paper — showing the thinking behind each one and a model answer. You will see a multiple-choice item, a short calculation, a data/graph question, a short structured question and a 6-mark extended response, so the whole toolkit from the earlier lessons comes together in one place.
All the questions below are original practice questions written in the OCR style. They are not reproduced from any real past paper.
By the end of this lesson you should be able to approach each question type with a clear routine, apply the right command-word response, show working with units, interpret data, and structure a 6-mark answer to reach the top band.
Exam Tip: Before the first question, spend two minutes scanning the whole paper, check no pages are missing, and note where the 6-mark question is so you can budget time for it. Remember the timing: roughly 1 minute per mark over the 90-mark, 105-minute paper, leaving about 10 minutes to check.
Which row correctly describes the bonding in sodium chloride and the particle that carries the charge when it conducts electricity?
A Covalent — electrons B Ionic — ions (when molten or dissolved) C Metallic — delocalised electrons D Ionic — electrons in the solid
The thinking: First answer it in your head — sodium chloride is ionic, and it conducts only when molten or dissolved, when the ions are free to move. Now check the options. A and C give the wrong bonding. D is wrong because solid ionic compounds do not conduct (the ions are fixed in the lattice). Only B matches both the bonding and the charge carrier.
Answer: B.
Exam Tip: Always read all four options and answer in your head first. Distractor D is deliberately "ionic but solid conducts" to catch anyone who forgets that the ions must be free to move — a reminder to read the whole row, not just the bonding type.
Calculate the relative formula mass (Mr) of magnesium nitrate, Mg(NO3)2. Use the relative atomic masses: Mg = 24, N = 14, O = 16.
The thinking: "Calculate" means show working. The bracket and subscript 2 multiply everything inside — so there are two nitrate groups.
Step 1 — count the atoms. Mg: 1. Inside the bracket, NO3 has 1 N and 3 O; with the subscript 2 there are 2 N and 6 O.
Step 2 — multiply by the relative atomic masses.
Mr=24+(2×14)+(6×16)
Step 3 — add up.
Mr=24+28+96=148
Answer: Mr=148 (no units — relative formula mass is a ratio).
Exam Tip: The subscript outside the bracket multiplies every atom inside it. Here it is easy to count only one nitrate and get 81; reading (NO3)2 as two nitrates (2 N, 6 O) is the whole skill. Mr has no units.
A student measured the volume of gas produced when magnesium reacted with hydrochloric acid. The results are plotted below. (a) Describe how the rate of reaction changes during the experiment. (2) (b) Use the graph to estimate the total volume of gas produced, and explain what has happened by the time the curve becomes flat. (2)
The thinking for (a): "Describe how the rate changes" — direction plus a comment on the gradient, no full mechanism needed. The curve is steepest at the start, then flattens.
Model answer (a): "The rate of reaction is fastest at the start (the curve is steepest), then slows down (the curve becomes less steep), and finally the rate is zero when the curve becomes flat. For example, about 40 cm³ of gas is produced in the first 20 s but very little is produced after 60 s." (2 marks: fastest at start/slows + supported with the gradient or figures.)
The thinking for (b): Read off the final (plateau) volume on the y-axis, then explain why the reaction has stopped.
Model answer (b): "The total volume produced is about 60 cm³ (where the curve levels off). The curve is flat because the reaction has finished — one of the reactants (the magnesium or the acid) has been completely used up, so no more gas is produced." (2 marks: read-off + a reactant used up.)
Exam Tip: The height of the plateau is the total volume of gas; the curve goes flat when a reactant is used up, not because the reaction "gets tired". Use a ruler to read the plateau precisely and back the read-off with that reason.
A student is given an unknown solution and asked to identify the ions in it. (a) Describe a test to show that the solution contains chloride ions, and give the result. (2) (b) Name the gas given off when dilute acid is added to a carbonate, and state the test for it. (1)
The thinking for (a): "Describe a test... and give the result" — the test for a halide ion is silver nitrate (with dilute nitric acid). 2 marks: the test and the positive result.
Model answer (a): "Add a few drops of dilute nitric acid, then silver nitrate solution. A white precipitate forms if chloride ions are present." (2 marks: silver nitrate test + white precipitate.)
The thinking for (b): A "name... and state the test" — 1 mark for both the gas and its test.
Model answer (b): "The gas is carbon dioxide; it turns limewater milky (cloudy)." (1 mark.)
Exam Tip: For "test and result" questions, always give both the reagent/method and the exact observation (white precipitate, limewater milky). Naming only the reagent, or only the colour, usually scores half. These are bankable recall marks if your tests are learned precisely.
Sodium and potassium are both in Group 1 of the periodic table. Explain how the reactions of the Group 1 metals with water change as you go down the group, and explain, in terms of electronic structure, why this trend occurs. (6 marks)
This is an explain question linking Group 1 trends with atomic structure (C2) — a typical synoptic 6-marker. The three responses below show it answered at three levels.
Mid-band response: "As you go down Group 1 the metals get more reactive. Lithium reacts gently with water, sodium reacts faster and potassium is very vigorous and can catch fire. This is because the atoms get bigger as you go down the group, so it is easier for them to lose their outer electron."
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