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Substance M is a solid at 30°C.
The substance is heated to 80°C and its temperature measured as it cools down to room temperature.
The cooling curve is shown.
Between which times is substance M freezing?
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Which gas has the fastest rate of diffusion?
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There are two stable isotopes of bromine. The mass number of isotope 1 is 79. The mass number of isotope 2 is 81. Which statement is correct?
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Which statement about ions and ionic bonds is correct?
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Part of the Periodic Table is shown. Which type of chemical bonding is present in the oxide of F and in the oxide of G?
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Elements X and Y react to form a compound.
Element X loses two electrons and element Y gains one electron.
What is the charge on the ions of elements X and Y and what is the formula of the compound?
[Table_1: Table with charges and compound formulas]
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Which statement about graphite explains why it is used as an electrode?
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Methane, CH_4, burns in air to form carbon dioxide and water. What is the balanced equation for this reaction?
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The equation for the thermal decomposition of sodium hydrogencarbonate is shown.
$$2\text{NaHCO}_3 \rightarrow \text{Na}_2\text{CO}_3 + \text{H}_2\text{O} + \text{CO}_2$$
The $M_r$ of sodium hydrogencarbonate, NaHCO$_3$, is 84.
The $M_r$ of sodium carbonate, Na$_2$CO$_3$, is 106.
In an experiment, 2.1 g of sodium hydrogencarbonate is heated but not all of it decomposes. All of the carbon dioxide is collected and measured at room temperature and pressure. The total volume of carbon dioxide produced is 0.21 dm$^3$.
The volume of 1 mole of a gas at room temperature and pressure is 24 dm$^3$.
Which statement is correct?
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An electrolysis experiment is done using carbon electrodes. Hydrogen and oxygen are formed at the electrodes. What is the electrolyte?
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Concentrated aqueous copper(II) sulfate is electrolysed using copper electrodes. Which ionic half-equation describes the reaction taking place at the cathode?
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When powdered sodium carbonate and aqueous ethanoic acid are mixed, the temperature of the mixture falls. Which statement about this reaction is correct?
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Magnesium powder reacts with an excess of dilute hydrochloric acid to produce hydrogen gas.
Which statements about this reaction are correct?
1. The smaller the particles of magnesium powder, the more slowly the hydrogen is produced.
2. The higher the temperature, the faster the magnesium powder disappears.
3. The lower the concentration of dilute hydrochloric acid, the faster the rate of reaction.
4. The faster the magnesium powder disappears, the faster the rate of reaction.
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The reaction between two aqueous compounds, X and Y, is slow and exothermic. The graph shows how the rate of this reaction changes with time. A student suggests that the rate of reaction decreases with time because: 1. the activation energy decreases 2. the speed of the molecules of X and Y decreases 3. the concentration of both X and Y decreases with time. Which suggestions are correct?
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Hydrogen reacts with iodine to form hydrogen iodide. $$\text{H}_2(g) + \text{I}_2(g) \rightarrow 2\text{HI}(g)$$ Which statements explain why the reaction is faster when the pressure is increased, at constant temperature? 1. At higher pressure, the molecules are moving faster. 2. At higher pressure, more of the molecules have the required activation energy. 3. At higher pressure, the molecules are closer together. 4. At higher pressure, the molecules collide more frequently.
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Ammonium sulfate is used as a fertiliser. It is made from ammonia and sulfuric acid. The ......1...... is made by the ......2...... process in which ......3...... is used as a catalyst. Which words complete gaps 1, 2 and 3? [Table_1]
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The reversible reaction shown takes place in a closed system at constant temperature. $$ \text{P(g) + Q(g) + R(g) } \rightleftharpoons \text{S(g) + T(g)} $$ When the reaction has reached equilibrium, more T is added. After the addition of T, which other substances increase in concentration?
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In which equation is the underlined substance acting as a reducing agent?
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An aqueous solution reacts with a solid. The products are an alkaline gas, a salt and water. What are the aqueous solution and the solid? [Table_1]
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Butanoic acid partially dissociates in aqueous solution.
Which row about butanoic acid is correct?
[Table_1]
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Copper(II) sulfate is prepared by adding excess copper(II) carbonate to sulfuric acid. Why is an \textbf{excess} of copper(II) carbonate added?
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Part of the Periodic Table is shown.
Which element has two electrons in its outer shell and three electron shells?
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Elements in Group I and Group II show the same trends in their reactions with water and in their density. Which row shows how the properties of barium compare with calcium? [Table_1]
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Which pair of compounds shows a transition element in two different oxidation states?
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Which description of brass is correct?
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What is the symbol of the metal used in the manufacture of aircraft because of its low density?
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Which substances react to form hydrogen gas?
1. calcium and water
2. silver and dilute hydrochloric acid
3. magnesium and steam
4. zinc and dilute hydrochloric acid
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Coke (carbon) and limestone are two raw materials used in the extraction of iron from hematite. Which type of reaction occurs when each substance is heated during the process? [Table_1]
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Some combustion reactions produce pollutant gases. Which reactions produce a pollutant gas that is not present in clean air?
1. \(2CH_4 + 3O_2 \rightarrow 2CO + 4H_2O\)
2. \(2H_2 + O_2 \rightarrow 2H_2O\)
3. \(C + O_2 \rightarrow CO_2\)
4. \(N_2 + O_2 \rightarrow 2NO\)
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One mole of alkane Y produces 72 \text{ dm}^3 of carbon dioxide when burned in excess oxygen, measured at room temperature and pressure. What is Y?
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The structure of organic compound X is shown. What is X?
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What is the structural formula of the compound formed in the addition reaction of propene with bromine?
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Ethanol is produced industrially by fermentation and also by a catalysed addition reaction involving steam.
Which row describes one advantage of each process?
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Carboxylic acids react with alcohols when warmed with an acid catalyst. Which type of substance is formed in this reaction?
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Nylon is formed by condensation polymerisation. Which structure represents nylon?
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Which structure represents the repeat unit of the addition polymer formed from but-1-ene?
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2.00 g of powdered calcium carbonate is added to 50.0 cm^3 of hydrochloric acid.
Which apparatus is used to measure these quantities of calcium carbonate and hydrochloric acid?
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The diagram shows a chromatogram obtained from the colours of three different sweets, X, Y and Z. How many different red dyes are present in the sweets?
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A mixture contains sand and an aqueous solution of sodium chloride. Which processes are used to obtain a sample of solid sand and a sample of solid sodium chloride from the mixture?
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A student tests an unknown compound M. The compound: - produces a lilac flame using a flame test - produces a gas which turns limewater cloudy when dilute hydrochloric acid is added. What is M?
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