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The rate of diffusion of a gas depends on its molecular mass and the temperature.
Which combination of molecular mass and temperature gives the slowest rate of diffusion? [Table_1]
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A student is asked to measure the time taken for 0.4g of magnesium carbonate to react completely with 25.0 cm^3 of dilute hydrochloric acid. Which pieces of apparatus does the student need?
555
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510
Substance Q was investigated using chromatography. The chromatogram is shown. The diagram is not drawn to scale. What is the $R_f$ value of Q?
503
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509
Which statement about an ionic compound is not correct?
548
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600
What is the total number of electrons in one molecule of ammonia, NH$_3$?
561
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512
Rubidium has two isotopes, $^{85}_{37}\text{Rb}$ and $^{87}_{37}\text{Rb}$.
Which statement explains why both isotopes have the same chemical properties?
579
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Which statement about the structure and properties of silicon(IV) oxide is not correct?
551
521
572
Which statement describes the structure of copper?
529
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568
Phosphorus reacts with oxygen to form phosphorus(III) oxide as shown.
$4P(s) + 3O_2(g) \rightarrow 2P_2O_3(s)$
Which mass of phosphorus(III) oxide is produced from 6.2 g of phosphorus?
580
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536
Calcium carbonate is heated. Calcium oxide and carbon dioxide gas are formed.
The equation for the reaction is shown.
$\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2$
225 kg of calcium carbonate is heated until there is no further change in mass.
The yield of calcium oxide is 85 kg.
What is the percentage yield?
510
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The diagram shows a simple cell.
Which pair of metals produces the largest voltage?
522
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521
What are the ionic half-equations for the electrode reactions during the electrolysis of concentrated aqueous sodium chloride? [Table_1]
566
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The temperature of the water in two beakers, X and Y, is measured as 21.5°C.
5 g of sodium chloride is dissolved in the water in beaker X. The temperature changes to 18.0°C.
5 g of calcium oxide is dissolved in the water in beaker Y. The temperature changes to 29.4°C.
Which types of process are occurring in beakers X and Y?
[Table_1]
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Which gases are used to generate electricity in a fuel cell?
548
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543
Which row identifies a chemical and a physical change? [Table_1]
530
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A sample of dilute nitric acid is added to lumps of limestone in a conical flask. The conical flask is placed on a balance and the loss in mass is measured. A second sample of nitric acid of a different concentration is separately tested. All other conditions are kept the same. The loss in mass in 1 minute at each concentration of nitric acid is shown. [Table_1]
Which row describes and explains the results obtained using $1.0 \text{ mol/dm}^3$ nitric acid compared with $0.5 \text{ mol/dm}^3$ nitric acid? [Table_2]
502
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510
When carbon monoxide reacts with hydrogen, methanol is formed.
$$\text{CO(g) + 2H}_2\text{(g)} \leftrightarrow \text{CH}_3\text{OH(g)}$$
The forward reaction is exothermic.
Which statements are correct?
1. There are more moles of gas on the left-hand side of the reaction.
2. Increasing the temperature increases the amount of methanol at equilibrium.
3. Increasing the pressure increases the amount of methanol at equilibrium.
4. Increasing the initial amount of hydrogen decreases the amount of methanol at equilibrium.
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In the blast furnace, iron is formed when iron(III) oxide reacts with carbon monoxide in a redox reaction.
\( ext{Fe}_2 ext{O}_3 + 3 ext{CO}
ightarrow 2 ext{Fe} + 3 ext{CO}_2 \)
Which substance is the oxidising agent and which substance is the reducing agent?
533
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Which oxide is classified as an amphoteric oxide?
588
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521
Which statement describes the properties of hydrochloric acid?
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A method used to make copper(II) sulfate crystals is shown.
1 Place dilute sulfuric acid in a beaker.
2 Warm the acid.
3 Add copper(II) oxide until it is in excess.
4 Filter the mixture.
5 Evaporate the filtrate until crystals start to form.
6 Leave the filtrate to cool.
What are the purposes of step 3 and step 4?
534
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Lead(II) sulfate is an insoluble salt.
Which reaction produces a mixture from which lead(II) sulfate is obtained by filtration?
562
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525
Helium is a noble gas.
Which statement about helium is correct?
592
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504
Which pair of elements reacts together most violently?
521
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Iron (II) ions can be oxidised to iron (III) ions by hydrogen peroxide. Which statement explains why iron is a transition element?
540
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Some properties of substance X are listed.
• It conducts electricity when molten.
• It has a high melting point.
• It burns in oxygen and the oxide dissolves in water to give a solution with pH 11.
What is X?
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Which row describes the uses of aluminium, copper and mild steel?
[Table]
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The properties of four metals are listed.
• Metal W does not react with dilute hydrochloric acid.
• Metal X reacts with dilute hydrochloric acid.
• Metal Y displaces metal X from an aqueous solution of its ions.
• Metal Z reacts with water and dilute hydrochloric acid.
What is the order of reactivity of the metals?
[Table_1]
591
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Which statement about the extraction of aluminium from aluminium oxide is correct?
548
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548
River water contains soluble impurities, insoluble impurities and bacteria.
River water is made safe to drink by filtration and chlorination.
Which statement is correct?
518
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570
Which process is used to separate nitrogen and oxygen from air?
534
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524
The apparatus shown is set up and left for a week.
Which diagram shows the level of the water at the end of the week?
518
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500
The diagram represents an outline of the carbon cycle.
Which processes are X and Y?
543
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510
Ammonium sulfate is used as a fertiliser. It is made from ammonia and sulfuric acid. Which words complete gaps 1, 2 and 3? The ......1...... is made by the ......2...... process in which ......3...... is used as a catalyst.
501
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580
Which statement about limestone and lime is correct?
535
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524
Some fractions obtained from petroleum are listed.
[Table_1]
Which rows are correct?
525
569
554
Which products are obtained by the cracking of an alkane?
[Table_1]
532
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Ethanol is produced by fermentation or by the reaction of ethene with steam. Which row is correct? [Table_1]
549
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The diagram shows the structure of a monomer and of the polymer made from it.
What are the monomer and polymer?
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591
The structure of a naturally occurring polymer, X, is shown.
What is X?
540
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