Amounts of substance in equations

Figure 8 shows part of the reactivity series of metals.

The method used to extract a metal from its ore is related to the metal’s position in the reactivity series.

Which metal is found in the Earth’s crust as an uncombined element?

Name one metal in Figure 8 that is normally extracted by electrolysis.

25 000 kg of an ore of iron was found to contain 10 050 kg of iron.

Calculate the percentage of iron in this ore of iron.

percentage of iron in ore =_........

When copper oxide is heated with carbon, the products are copper and carbon dioxide.

Write the word equation for this reaction.

In this reaction, copper oxide loses oxygen.

State the type of reaction when copper oxide loses oxygen.

In one reaction, 159.0 g of copper oxide was heated with excess carbon to produce 127.0 g of copper.

Use this information to calculate the mass of copper formed, in g, when 238.5 g of copper oxide is reacted with excess carbon.

mass of copper =_........ g

State why this reaction with copper oxide uses excess carbon.

A solution of zinc sulfate was made by dissolving 23.8 g of the compound in water and was made up to a total volume of 250 cm³ with water.

Calculate the concentration of this solution in g dm^–3.

Give your answer to 2 significant figures.

concentration =_........ g dm^–3

Malachite, Cu₂CO₃(OH)₂, is a mineral containing copper.

When heated, malachite decomposes to form copper oxide, carbon dioxide and water.

Which apparatus should be used to heat the malachite and test for carbon dioxide?

When carbon dioxide is bubbled through limewater, a precipitate forms. This precipitate solid makes the limewater cloudy.

Name the precipitate that makes the limewater cloudy.

The equation for the decomposition of malachite when it is heated is

Calculate the maximum mass of copper oxide that can be formed when 22.1 g of malachite is decomposed completely.

(relative atomic masses: Cu = 63.5, O = 16.0, C = 12.0, H = 1.0)

maximum mass of CuO =_........

Copper can be extracted from copper oxide by heating the copper oxide with carbon.

A student investigated two methods to extract the maximum mass of copper from copper oxide.

Figure 2 shows the two methods.

Comment on the strengths and weaknesses of these two methods.

A student carried out an investigation to determine the order of reactivity of four metals, W, X, Y and Z. A piece of metal W was added to a test tube containing excess dilute hydrochloric acid. This was repeated with the other three metals, X, Y and Z. In each case, the size of each piece of metal was the same. The student recorded observations on each reaction for three minutes.

The observations obtained are shown in Figure 6.

Use the information in Figure 6 to place the metals in order of reactivity from the least reactive to the most reactive.

The experiment was repeated using an excess of dilute sulfuric acid in place of the dilute hydrochloric acid.

metal + sulfuric acid metal sulfate + hydrogen

When metal Y reacts with dilute sulfuric acid, bubbles form quickly at first and then the reaction stops. Most of the solid metal remains.

Explain why the reaction between metal Y and excess dilute sulfuric acid stopped even though there was solid metal Y left.

The reactions between metals and dilute ethanoic acid are slower than reactions between metals and dilute hydrochloric acid. This is because ethanoic acid is a weak acid.

Explain the meaning of the term weak acid.

The formula of aluminium sulfate is Al₂(SO₄)₃.

Calculate the total number of atoms that combine to form 5.13 g of aluminium sulfate.

(relative atomic masses: O = 16.0, A l = 27.0, S = 32.0 Avogadro number = 6.0210²³)

number of atoms =_........

Iron is more reactive than lead. Iron reacts with lead nitrate solution to form solid lead. Two possible balanced equations for the reaction are

Equation 1 Fe + Pb(NO₃)₂ Fe(NO₃)₂ + Pb

Equation 2 2Fe + 3Pb(NO₃)₂ 2Fe(NO₃)₃ + 3Pb

In one experiment, it was found that 4.48 g of iron reacted with excess lead nitrate solution to form 24.84 g of lead.

Carry out a calculation, using the information above, to show which equation represents the reaction taking place.

(relative atomic masses: Fe = 56.0, Pb = 207)

This question is about gases.

When sodium is added to water, hydrogen gas is produced.

Which observation shows that a gas has been produced?

Some damp litmus paper is placed in a gas. The litmus paper is bleached.

Which gas bleaches damp litmus paper?

When calcium carbonate is heated it decomposes.

When 5.000 g of calcium carbonate is heated, the mass of solid remaining is 2.800 g.

Calculate the mass of carbon dioxide that has been released.

Give your answer to three significant figures.

mass of carbon dioxide =_........ g

A diagram of an atom of helium is shown in Figure 3.

Explain, using Figure 3, why helium is inert.

Helium is used to fill balloons.

State one property of helium, apart from it being inert, that makes it suitable for filling balloons.

Oxygen gas has the formula O₂.

Calculate the number of oxygen atoms in 3.50 mol of oxygen gas.

(Avogadro constant = 6.0210²³)

number of oxygen atoms =_........

This question is about oxygen.

The percentage of oxygen in today’s atmosphere is greater than the percentage of oxygen in the Earth’s early atmosphere.

Explain what caused this change to happen.

Magnesium reacts with oxygen from the air to form magnesium oxide.

A student carries out an investigation to determine the mass of magnesium oxide formed when a known mass of magnesium reacts completely with oxygen.

This is the method the student used.

step 1 find the mass of a crucible and lid

step 2 put a known mass of magnesium into the crucible and put the lid on

step 3 heat for five minutes using a roaring Bunsen burner flame

step 4 let the crucible, lid and contents cool down

step 5 find the final mass of the crucible, lid and contents

Explain how the student could check that the magnesium had reacted completely with oxygen.

In another experiment, it was found that 1.24 g of phosphorus reacted completely with 1.60 g of oxygen to form phosphorus oxide.

The relative formula mass of this phosphorus oxide is 284.

Deduce the molecular formula of this phosphorus oxide.

You must show your working.

(relative atomic masses: O = 16, P = 31)

molecular formula =_........

A student uses the apparatus shown in Figure 6 to investigate the percentage of oxygen in the atmosphere.

The apparatus was left for a few days.

Explain one change the student would see after a few days.

Explain one change that can be made to the apparatus in Figure 6 to allow the student to calculate the percentage of oxygen in the atmosphere.

This question is about some of the elements in group 7 of the periodic table.

Which row in the table correctly shows the colours and physical states of the elements at room temperature?

The compound phosphorus oxychloride has the formula POCl₃.

Calculate the percentage by mass of chlorine in phosphorus oxychloride.

(relative atomic masses: O = 16.0, P = 31.0, C l = 35.5)

percentage by mass of chlorine =_........

When iron reacts with chlorine, iron chloride is formed.

Two possible equations for this reaction are

A Fe + Cl₂ FeCl₂ B 2Fe + 3Cl₂ 2FeCl₃

In an experiment, 8.40 g iron reacts with chlorine to form 19.05 g iron chloride.

Show, using a calculation, which reaction, A or B, is taking place.

You must show your working.

(relative atomic masses: C l = 35.5, Fe = 56.0)

*(d) Group 1 metals react with the elements from group 7 to form salts.

Some examples of these reactions are shown in Figure 7.

You will find the position of these elements in their groups on the periodic table.

Explain, in terms of their electronic configurations and the relative reactivity of these elements, which of the reactions shown in Figure 7 would be the most violent.

Methane is a hydrocarbon fuel.

Complete the word equation for the complete combustion of methane in oxygen.

methane +_........ water +_........

The incomplete combustion of methane can produce carbon and carbon monoxide.

Give the reason why carbon and carbon monoxide are produced in the incomplete combustion of methane.

Crude oil is a complex mixture of hydrocarbons. Crude oil can be separated into useful fractions by fractional distillation.

Figure 7 shows a fractional distillation column and the fractions produced when crude oil is distilled.

Name the fraction in Figure 7 that is used to surface roads.

Name the fraction in Figure 7 that contains hydrocarbons with the lowest boiling point.

When crude oil is fractionally distilled, the demand for some fractions is more than the amount produced.

Figure 8 shows the relative amounts of each fraction in a crude oil and the relative demand for each of these fractions.

Which of the following shows the fractions where the relative demand is greater than the relative amount in the crude oil?

Cracking involves the breaking down of large hydrocarbon molecules into smaller hydrocarbon molecules.

Octane, C₈H₁₈, can be cracked to produce one molecule of ethene, C₂H₄, and one molecule of C_xH₁₄.

Determine the value of x in the molecule of C_xH₁₄.

x =_........

Dodecane is a large hydrocarbon molecule. When one molecule of dodecane is cracked the products are one molecule of octane and one molecule of butene.

dodecane octane + butene

Calculate the maximum mass of octane that could be produced when 340 g of dodecane is cracked in this reaction.

(relative formula masses: dodecane = 170, octane = 114)

mass of octane =_........ g

An aluminium atom has the atomic number 13 and the mass number 27.

Which row shows the numbers of subatomic particles present in an

Magnesium burns in excess oxygen to form magnesium oxide. The balanced equation for this reaction is

Starting with 1.35 g of magnesium, calculate the maximum mass of magnesium oxide that could be formed in this reaction. (relative atomic masses: O = 16.0, Mg = 24.0)

You must show your working.

mass of magnesium oxide =_........ g

Chlorine reacts with hydrogen to form hydrogen chloride.

Write the balanced equation for this reaction.

*(d) Sodium chloride is an ionic compound, containing sodium ions, Na⁺, and chloride ions, Cl^–.

Figure 10 shows the electronic configuration of sodium and chlorine.

Explain how sodium and chlorine atoms form the ions in sodium chloride and how the ions are arranged in the solid sodium chloride.

You may wish to use diagrams in your answer.

An aluminium atom has the atomic number 13 and the mass number 27.

Which row shows the numbers of subatomic particles present in an

Magnesium burns in excess oxygen to form magnesium oxide. The balanced equation for this reaction is

Starting with 1.35 g of magnesium, calculate the maximum mass of magnesium oxide that could be formed in this reaction. (relative atomic masses: O = 16.0, Mg = 24.0)

You must show your working.

mass of magnesium oxide =_........ g

Chlorine reacts with hydrogen to form hydrogen chloride.

Write the balanced equation for this reaction.

Sodium reacts with chlorine to form sodium chloride.

The electronic configuration of the sodium atom is 2.8.1 and the electronic configuration of the chlorine atom is 2.8.7.

Give the electronic configurations of the ions formed.

Na⁺_........

(a) A student placed a piece of metal P in a test tube containing excess dilute sulfuric acid. The student repeated this with three other metals, Q, R and S. All the pieces of all four metals were the same size.

The student recorded the observations until each metal had reacted with the acid for two minutes. The observations are shown in Figure 6.

Use this information to put the four metals in order of reactivity from the least reactive to the most reactive.

least reactive
most reactive

Acid solutions contain hydrogen ions.

Aluminium reacts with dilute hydrochloric acid to form a solution containing aluminium ions, Al³⁺.

Complete the balanced ionic equation for this reaction.

_........ +_........ H⁺ _........ Al³⁺ +_........

The hydrogen ion concentration in a solution is decreased by a factor of 10.

State how the pH of this solution changes.

Calculate the mass, in g, of a hydrogen atom, using the data below. (relative atomic mass: H = 1.00; Avogadro constant = 6.02 × 10²³)

mass of hydrogen atom =_........ g