PHS Edexcel Combined Science H Feb 2020 Chem Mock Revision 2

Magnesium and calcium are in group 2 of the periodic table. They are less reactive than the metals in group 1.

Calcium reacts with water to form calcium hydroxide, Ca(OH)₂, and hydrogen, H₂.

Ca(s) + 2H₂O(l) → Ca(OH)₂(s) + H₂(g)

Describe what would be seen when a piece of calcium is dropped into a container of water

• Hydrogen gas would be produced so would see bubbling.

• Calcium moves around

• A lilac flame

• Calcium decreases in size

When zinc reacts with copper sulfate solution, zinc sulfate solution and copper are formed.

(i) An experiment was carried out to measure the temperature change when zinc powder reacts with copper sulfate solution.

initial temperature of copper sulfate solution = 20 °C

final temperature of mixture after the reaction = 46 °C

Explain what the temperature readings show about the type of heat change that occurs during this reaction.

• The temperature increased, so the reaction is endothermic

• The temperature increased, so the reaction is exothermic

• The temperature decreased, so the reaction is endothermic

• The temperature decreased, so the reaction is exothermic

Use the graph to explain how the rate of this reaction changes as the concentration of hydrochloric acid increases.

• As the concentration of the hydrochloric acid decreases, the time taken to react decreases so the rate of reaction increases

• As the concentration of the hydrochloric acid increases, the time taken to react increases so the rate of reaction increases

• As the time increases the concentration of the hydrochloric acid decreases so the rate of reaction increases.

• As the concentration of the hydrochloric acid increases, the time taken to react decreases so the rate of reaction increases

The dissolving of this solid in water is an exothermic change.

The experiment is repeated a number of times.

Compared with the initial temperature of the water, the final temperature of the solution is

• always higher

• always lower

• sometimes higher sometimes lower

• always unchanged

Lithium, sodium and potassium are reactive metals in group 1 of the periodic table.

In an experiment equal-sized pieces of lithium, sodium and potassium are added to separate samples of water.

A flame is produced only with potassium because potassium

• Is the softest metal

• has the lowest melting point

• is the most reactive

• is the only flammable metal

The electronic configurations of magnesium and calcium are

magnesium 2.8.2

calcium 2.8.8.2

When magnesium and calcium react with water they form positive ions.Suggest an explanation, in terms of their electronic configurations, why calcium is more reactive than magnesium.

• In calcium the outer most electrons are further away from the nucleus therefore there is a stronger attraction between the nucleus and the electrons.

• In calcium the inner most electrons are closer to the nucleus so there is a stronger attraction between the nucleus and the electrons.

• In calcium the outer most electrons are further away from the nucleus therefore there is less attraction between the nucleus and the electrons.

A student poured 50 cm³ water into a beaker and measured the water's temperature.

The student added 1.00 g calcium chloride to the water, stirred the mixture and then recorded the temperature.

The student's results were

temperature of water at start = 21 °C

temperature of mixture after stirring = 32 °C

Explain, using these results, the type of heat energy change that occurs when calcium chloride dissolves in water.

• The temperature increases as it is an exothermic process

• The temperature increases as it is an endothermic process.

The reaction between calcium carbonate and dilute hydrochloric acid is exothermic.

Explain, in terms of bond breaking and bond making, why some reactions are exothermic.

• Breaking bonds releases energy and is exothermic and making bonds needs energy and is endothermic. More energy is given out than is taken in.

• Breaking bonds needs energy and is endothermic and making bonds releases energy and is exothermic. More energy is given out than is taken in.

When solid ammonium chloride is added to water a colourless solution is formed.

During the process the temperature of the liquid decreases.

Describe how you would measure the change in temperature.

• Use a measuring cylinder to measure the volume.

• Use a thermometer to measure the initial and final temperature

• Use a thermometer to measure the final temperature

• Use a set of weighing scales to measure the mass.

When solid ammonium chloride is shaken with water, a colourless solution forms and the temperature changes from 20°C to 16°C.

Give the name of the type of heat change occurring.

• Endothermic

• Exothermic

• Biothermic