Conservation of mass and balanced equations

A student investigated how the surface area of magnesium affects the rate of the reaction between magnesium and hydrochloric acid.

Figure 11 shows the apparatus.

This is the method used.

1. Add 50 cm³ of hydrochloric acid to the conical flask.

2. Add 0.05 g of magnesium ribbon to the hydrochloric acid.

3. Insert the stopper into the conical flask as quickly as possible.

4. Start a stopclock.

5. Record the volume of gas collected in the gas syringe every 20 seconds for 100 seconds.

6. Repeat steps 1 to 5 with 0.05 g of magnesium powder.

Magnesium reacts with hydrochloric acid to produce magnesium chloride and hydrogen.

Balance the equation for the reaction.

What was the independent variable in the investigation?

Tick () one box.

Surface area of magnesium

Time interval

Volume of hydrochloric acid

Why was the stopper inserted into the conical flask as quickly as possible in step 3?

Figure 12 shows the results for magnesium ribbon.

Explain the trend for the volume of gas collected after 80 seconds.

Use Figure 12.

Figure 13 shows the results for magnesium ribbon.

The student then used 0.05 g of magnesium powder instead of 0.05 g of magnesium ribbon.

Draw a line on Figure 13 to show the expected results for the magnesium powder.

This question is about groups in the periodic table.

What name is given to the Group 0 elements?

Explain the reactivity of the Group 0 elements.

Describe the relationship between relative atomic mass and boiling point for the elements in Group 0.

Fluorine is an element in Group 7.

Complete Figure 5 to represent the electronic structure of fluorine.

Which is a correct statement about the elements in Group 7?

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The elements in Group 7 consist of single, non-bonded atoms.

The elements in Group 7 react with non-metals to form covalent compounds.

The melting points of the elements in Group 7 decrease going down the group.

The reactivity of the elements in Group 7 increases going down the group.

The elements in Group 1 react with water.

Give two observations you would see when a small piece of lithium is added to water.

Lithium reacts with water less vigorously than sodium reacts with water.

Explain why lithium is less reactive than sodium.

Complete the equation for the reaction of lithium with water.

You should balance the equation.

This question is about reactions involving gases.

Hydrogen gas consists of hydrogen molecules.

A hydrogen atom has one electron.

Complete the dot and cross diagram for a hydrogen molecule (H₂).

Hydrogen (H₂) reacts with chlorine (Cl₂) to produce hydrogen chloride (HCl).

Balance the equation for the reaction.

0.8 g of hydrogen reacts with chlorine to produce 29.2 g of hydrogen chloride.

Calculate the mass of chlorine that reacts.

Hydrogen reacts with nitrogen to produce ammonia.

Figure 3 represents a molecule of ammonia.

Ammonia reacts with hydrogen chloride to produce ammonium chloride.

The reaction is reversible.

Write the word equation for the reaction.

Include the symbol for a reversible reaction.

Which condition needs to be changed so that the direction of the reaction is reversed?

This question is about metals reacting with oxygen.

Calcium (Ca) reacts with oxygen (O₂) to produce calcium oxide (CaO).

Balance the equation for the reaction.

______ Ca + O₂ → 2 CaO

40 g of calcium reacts completely with oxygen to produce 56 g of calcium oxide.

Calculate the maximum mass of calcium oxide that could be produced from 10 g of calcium.

A student reacted different masses of magnesium with oxygen and measured the mass of magnesium oxide produced.

Figure 3 shows the results.

Why did the student ignore one of the points when drawing the line of best fit on Figure 3 ?

Predict the mass of magnesium oxide produced from 0.5 g of magnesium.

You should extend the line of best fit on Figure 3.

A different student reacted copper with oxygen and measured the mass of copper oxide produced.

The student did repeat measurements for each mass of copper.

Table 1 shows the results when 0.42 g of copper was reacted.

Calculate mean value X in Table 1.

The reaction between copper and oxygen is exothermic.

Which reaction profile represents this reaction?

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Calcium carbonate reacts with hydrochloric acid.

The equation for the reaction is:

CaCO₃(s) + 2 HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)

A student investigated the effect of changing the surface area of the calcium carbonate on the rate of this reaction.

The student used calcium carbonate in the form of lumps and of powder.

Figure 4 shows the apparatus.

The rate of reaction is determined by measuring the decrease in mass of the conical flask and contents at regular time intervals.

Give the reason why the mass of the conical flask and contents decreases.

The mean rate of reaction using the calcium carbonate lumps was 0.0012 g/s.

Calculate the time taken for the mass of the conical flask and contents to decrease by 0.36 g.

The results showed that calcium carbonate powder reacted faster than calcium carbonate lumps.

Explain why calcium carbonate powder reacted faster than calcium carbonate lumps.

The surface area of a calcium carbonate lump can be estimated by comparing the lump with a cube.

Figure 5 shows a cube and a similar-sized calcium carbonate lump.

Figure 5

Calculate the total surface area of the cube in Figure 5.

Total surface area = cm² ________________

The total surface area of the calcium carbonate lump in Figure 5 is estimated rather than measured.

Suggest one reason why.

This question is about the periodic table.

The halogens are in Group 7 of the periodic table.

Explain the trend in reactivity going down Group 7.

Explain how the electronic structure of calcium relates to calcium reacting as a metal.

Rubidium has an atomic number of 37.

Complete the equation for the reaction of rubidium with water.

You should balance the equation.

Use the periodic table.

______ Rb + ______ H₂O → ______________ + ______________

This question is about substances found in the Earth’s crust.

Aluminium silicate is a compound found in the Earth’s crust.

The formula of aluminium silicate is Al₂SiO₅

What is the total number of atoms in the formula Al₂SiO₅?

Tick (✓) one box.

3 5 7 8

Table 2 shows the percentage of some elements found in the Earth’s crust.

Calculate the simplest whole number ratio for the percentage of silicon to the percentage of aluminium in the Earth’s crust.

Simplest whole number ratio for: percentage of silicon: percentage of aluminium = _____________: _____________

Iron is found as iron oxide in the Earth’s crust.

Iron can be extracted by heating iron oxide with carbon.

Why is iron oxide reacted with carbon to extract iron?

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Iron is less reactive than carbon.

Iron has the same reactivity as carbon.

Iron is more reactive than carbon.

The word equation for the reaction to extract iron is:

iron oxide + carbon iron + carbon dioxide

Which reactant is reduced?

Tick (✓) one box.

Carbon

Carbon dioxide

Iron

Iron oxide

The symbol equation for the reaction to extract iron is:

What is the value of X ?

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2 3 4 5

Aluminium is found as aluminium oxide in the Earth’s crust.

Figure 8 shows the apparatus used for the process to extract aluminium from aluminium oxide.

Name the process used to extract aluminium from aluminium oxide.

What are the positive electrodes made of in this process?

Tick (✓) one box.

Aluminium

Carbon

Copper

Cryolite

Large amounts of energy are used in the process in Figure 8.

Give two ways energy is used in the process.

Diamond and silicon dioxide are also found in the Earth’s crust.

Figure 9 represents the structure of diamond and the structure of silicon dioxide.

Compare the structure and bonding of diamond with the structure and bonding of silicon dioxide.

This question is about magnesium oxide.

What type of substance is magnesium oxide?

Tick (✓) one box.

Compound

Element

Mixture

Magnesium reacts with oxygen to produce magnesium oxide.

Balance the equation for the reaction.

What does the state symbol ‘(s)’ represent?

A student reacted magnesium with oxygen.

Figure 9 shows the apparatus used.

Figure 9

This is the method used.

1. Measure the mass of the empty crucible and lid.

2. Put magnesium into the crucible.

3. Measure the mass of the crucible, lid and magnesium.

4. Heat the crucible strongly.

5. Lift the lid occasionally.

6. Heat until the magnesium stops glowing.

7. Measure the mass of the crucible, lid and magnesium oxide.

Give one safety precaution the student should use.

The magnesium reacted with oxygen.

Suggest where the oxygen comes from.

The student lifted the lid several times.

Why did lifting the lid allow the magnesium to react completely?

Table 3 shows the results.

Calculate the mass of magnesium put into the crucible.

Use Table 3.

Calculate the mass of oxygen that reacted with the magnesium.

Use Table 3.

This question is about iron and steel.

Figure 18 shows a flow chart for the production of iron and steel from iron ore.

Iron ore consists mainly of iron oxide.

In the blast furnace iron oxide reacts with carbon monoxide to form iron and carbon dioxide.

Complete the equation for the reaction between iron oxide and carbon monoxide.

You should balance the equation.

Iron oxide is reduced in the reaction with carbon monoxide.

What does ‘reduced’ mean in this reaction?

Cast iron is an alloy.

Cast iron contains carbon.

Figure 19 shows the arrangement of atoms in pure iron and in cast iron.

Explain why cast iron is harder than pure iron.

In addition to cast iron, scrap steel is added to the steel-making furnace.

Give three environmental advantages of recycling scrap steel in this way.

Hydrogen peroxide (H₂O₂) decomposes to produce oxygen gas and water.

Balance the equation for the reaction.

Two catalysts that can be used in the reaction are raw potato and

manganese dioxide.

A student compared the rate of decomposition of hydrogen peroxide using:

• a cube of raw potato as the catalyst

• crushed raw potato as the catalyst.

The student kept all other variables constant.

The hydrogen peroxide decomposed at a different rate when using a cube of raw potato compared with using crushed raw potato.

Explain why.

The student repeated the investigation using boiled potato instead of raw potato.

When boiled potato is added to hydrogen peroxide no bubbles of oxygen are observed.

Explain why.

The student then investigated the rate of decomposition of hydrogen peroxide using manganese dioxide as the catalyst.

The student measured the volume of oxygen produced every 5 seconds for 50 seconds.

Figure 12 shows the results.

Determine the rate of reaction at 15 s

A teacher extracted copper from copper oxide.

This is the method used.

1. Mix 1.30 g of zinc and 1.59 g of copper oxide.

2. Heat the mixture strongly.

3. When the mixture starts to glow, stop heating.

4. Let the glow spread through the mixture.

5. Leave the mixture to cool.

This reaction is exothermic.

Which part of the method shows the reaction is exothermic?

Tick one box.

The equation for the reaction between zinc and copper oxide is:

1.30 g of zinc fully reacted with 1.59 g of copper oxide to produce 1.62 g of zinc oxide.

What mass of copper was produced?

What is the physical state of zinc oxide in the reaction?

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Which substance has been oxidised in the reaction?

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What type of reaction takes place when zinc reacts with copper oxide?

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Copper is a metal.

Which structure represents the arrangement of atoms in pure copper?

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Copper is used in electrical wiring.

Give one reason why.

In the UK, 40% of the copper we use is recycled copper.

The other 60% is copper obtained by mining.

What is the simplest ratio of recycled copper to copper obtained by mining?

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What are two advantages of recycling copper?

Tick two boxes.