Introducing Chemical Reactions (OCR Gateway GCSE Chemistry: Combined Science)

The formula of an iron(III) ion is Fe³⁺ and the formula of the sulfate ion is SO₄^2-.

What is the formula of iron(III) sulfate?

Avogadro's constant has a value of 6.02 x 10²³.

How many hydrogen atoms are in 0.05 moles of hydrogen molecules?

Which equation shows the formation of a Group 5 non-metal ion?

X represents a Group 5 non-metal and e^- represents an electron.

A piece of iron wool is left in moist air and goes rusty.

Which graph shows how the mass of the iron wool changes?

A student wanted to make 15.0 g of zinc chloride. The equation for the reaction is:

ZnCO₃ + 2HCl →  ZnCl₂ + CO₂ + H₂O

What mass of zinc carbonate should the student add to the hydrochloric acid to make 15.0 g of zinc chloride?

Relative atomic masses (A_r): C = 12    Zn = 65   O= 16    Cl = 35.5     H= 1

Symbol equations always need to have the same number of atoms on both sides.

Which equation is correctly balanced?

How many moles are present in 9 kg of glucose, C₆H₁₂O₆?

Relative formula mass (M_r):       C₆H₁₂O₆ = 180

What is the mass of 0.25 moles of hydrated copper(II) sulfate, CuSO₄.5H₂O?

Relative formula mass (M_r):  H₂O = 18  CuSO₄ = 160

2.7 g aluminium reacts with 38.1 g of iodine, I₂, to make 40.8 g aluminium iodide, AlI₃.

Relative atomic masses (A_r):     Al = 27        I = 127

Relative formula mass (M_r):      AlI₃ = 408

What coefficients would balance the equation for the reaction?

Nitrogen and hydrogen react together to make ammonia.

N₂ + 3H₂  → 2NH₃

If 2.0 g of hydrogen is added to 12.0 g of nitrogen which substance is the limiting reactant and how much of the excess reactant remains?

Relative atomic masses (A_r): H = 1    N = 14

When 12 g of carbon (C) burns in oxygen (O₂), 44 g of carbon dioxide (CO₂) is formed.

What mass of C would burn to form 11 g of CO₂?

Lead nitrate contains lead ions, Pb²⁺, and nitrate ions, NO₃^-.

What is the formula for lead nitrate?

Hydrogen gas can be made by reacting methane and steam (H₂O).

CH₄ + H₂O 3H₂ + CO

6 g of hydrogen gas can be made from 18 g of steam, H₂O.

How much hydrogen gas can be made from 3.6 g of steam, H₂O?

Ethanol, C₂H₅OH, burns in oxygen. Carbon dioxide and water are made.

Which equation for this reaction is correctly balanced?

Oxygen reacts with 1.20 g of carbon. 4.40 g of carbon dioxide forms.

C + O₂ → CO₂

What mass of oxygen is used in this reaction?

The formula of a magnesium ion is Mg²⁺.

The formula of a nitrate ion is NO₃^-.

What is the formula of magnesium nitrate?

Higher Only

Urea, (NH₂)₂CO, is a fertiliser.

A student makes 1 mole of urea from 2 moles of ammonia.

What is the mass of urea that the student makes?

Magnesium reacts with chlorine. Magnesium chloride is made.

What is the balanced symbol equation for this reaction?

Which of these shows the balanced symbol equation for the reaction between potassium and chlorine to make potassium chloride?

Magnesium is heated in a crucible.

The mass of the crucible and magnesium increases.

Which statement is the best explanation for this?

Higher Only

A student neutralises nitric acid with potassium hydroxide solution.

Which equation shows the ionic equation for neutralisation?

Higher Only

What is the amount, in mol, of 15 g of carbonate ions, CO₃^2-?

The accurate relative atomic mass of aluminium is 26.9815385.

What is this number to 5 significant figures?

Look at the diagram.

It shows how the reaction between hydrochloric acid and marble chips (calcium carbonate) can be monitored.

The reading on the balance decreases during the reaction.

Which statement is the best explanation?

Higher Only

Avogadro’s constant has a value of 6.02 × 10²³.

How many oxygen atoms are in 0.25 moles of oxygen molecules?

Higher Only

Avogadro’s constant has a value of 6.02 × 10²³.

What is the number of atoms in 0.5 mol of water?

Higher Only

Methane burns in oxygen to form carbon dioxide and water.

CH₄ + 2O₂ → CO₂ + 2H₂O

Calculate the amount of carbon dioxide made when 6.4 g of methane is burnt.

Higher Only

Sodium hydroxide reacts with hydrochloric acid. Sodium chloride and water are made.

NaOH + HCl → NaCl + H₂O

What mass of sodium hydroxide would be needed to make 46.8 g of sodium chloride?

Phosphoric acid contains phosphate ions,

Phosphoric acid is completely neutralised by sodium hydroxide.

What is the formula of the salt that is made?