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WorksheetsChemical Reactions Assessment
Total questions: 38
Worksheet time: 19mins
Which of the following BEST describes a chemical reaction?
A change in the shape of a substance
A process where new substances are formed
A change in the state of matter only
Dissolving sugar in water
Which of the following is a sign that a chemical change has occurred?
Melting
Freezing
Permanent colour change
Evaporation
Which one is not a chemical change?
Burning of paper
Rusting of iron
Melting of ice
Digestion of food
In a chemical reaction, the substances that react are called ________.
Catalysts
Products
Reactants
Solutes
Which of the following represents a balanced chemical equation?
H₂ + O₂ → H₂O
2H₂ + O₂ → 2H₂O
H₂ + 2O₂ → H₂O
H₂O → H₂ + O₂
The formation of a new substance in a chemical change means ______.
The atoms disappear
New atoms are created
Atoms rearrange to form new substances
The mass increases
Which of the following is a chemical reaction?
Cutting of paper
Boiling water
Iron reacting with sulphur to form iron sulphide
Breaking glass
A chemical reaction that releases heat is called ______.
Endothermic
Exothermic
Reversible
Neutral
Which of the following proves the Law of Conservation of Mass?
Atoms are destroyed during reactions
The total mass before and after reaction stays the same
Mass always decreases
Reactions cannot be balanced
What happens to atoms during a chemical reaction?
They vanish
They are created
They rearrange
They melt
Which of the following is a physical change?
Burning wood
Cooking egg
Dissolving salt in water
Rusting iron
Which difference is correct?
Physical changes form new substances; chemical changes do not
Chemical changes form new substances; physical changes do not
Both physical and chemical changes form new substances
Neither forms new substances
2Mg + O₂ → 2MgO is an example of:
Decomposition reaction
Combination reaction
Displacement reaction
Neutralization reaction
Which of the following is a displacement reaction?
Zn + HCl → ZnCl₂ + H₂
CaCO₃ → CaO + CO₂
NaOH + HCl → NaCl + H₂O
H₂ + Cl₂ → 2HCl
Electrolysis is defined as:
Splitting of water by heat
Decomposition of an electrolyte by electricity
Formation of ions in solution
Production of heat by current
In electrolysis, the electrode where oxidation occurs is the:
Cathode
Anode
Salt bridge
Base
What is the time required to deposit 2g of Cu if 1g is deposited in 10 minutes (same current)?
5 minutes
10 minutes
20 minutes
30 minutes
Which equation represents Faraday's Second Law?
m = Zit
E = mc²
n₁C₁ = n₂C₂
P = IV
Why must chemical equations be balanced?
To satisfy the Law of Conservation of Mass
To make the answer look neat
To show the state symbols
To show the colour of reactants
During electrolysis of copper(II) sulfate solution using copper electrodes, the mass of the cathode:
Increases
Decreases
Stays the same
Melts completely
In electrolysis, reduction always occurs at the:
Anode
Cathode
Salt bridge
Electrolyte container
What is the product at the anode during electrolysis of molten aluminium oxide?
Aluminium
Carbon dioxide
Oxygen
Hydrogen
Which method can separate a soluble solid from a solution?
Filtration
Crystallisation
Evaporation
Chromatography
Which of the following is a mixture?
Sodium chloride
Pure water
Air
Carbon dioxide
Which change is exothermic?
Melting ice
Evaporation
Freezing water
Electrolysis
Which statement is correct about endothermic reactions?
They release heat
Temperature increases
They absorb heat
They always produce gas
A reaction releases 250 kJ of energy when forming products. What does this suggest about the bonds?
More energy was used to break bonds than was released
More energy was released when new bonds formed
The reaction is endothermic
Bond breaking releases energy
During electrolysis of aqueous copper(II) chloride using inert electrodes, which product forms at the anode and why?
Hydrogen, because hydrogen ions are discharged first
Oxygen, because it is formed from water when chloride ions are harder to discharge
Chlorine, because halide ions are preferentially discharged
Copper, because it is the least reactive
A student mixes solutions of lead nitrate and potassium iodide. A yellow solid appears. What type of reaction has occurred?
Oxidation
Neutralisation
Precipitation
Polymerisation
Why does graphite conduct electricity but diamond does not?
Diamond has a giant ionic structure
Graphite has free electrons that can move between layers
Diamond's atoms are arranged in layers
Graphite has no covalent bonds
Which reaction represents reduction?
Fe → Fe²⁺ + 2e⁻
Cu²⁺ + 2e⁻ → Cu
HCl → H⁺ + Cl⁻
Zn + Cu²⁺ → Zn²⁺ + Cu²⁺
If 3.2 g of copper is deposited during electrolysis, how many moles of electrons were used? (Relative atomic mass of Cu = 63.5, Cu²⁺ + 2e⁻ → Cu)
0.05 mol
0.10 mol
0.20 mol
0.40 mol
A student strongly heats blue copper(II) sulfate crystals. Which observation clearly shows a chemical change occurred?
The colour changes from blue to white
Steam is produced
The crystals become powdery
The beaker becomes warm
Iron filings are placed near a magnet. This is NOT a chemical change because:
No electrons are transferred
No new substance is formed
Iron cannot react with magnets
Mass decreases
In the reaction: 2KClO₃ → 2KCl + 3O₂ Which statement is correct?
The number of oxygen atoms increases
Mass of products is greater than reactants
The total mass remains constant
Potassium atoms disappear
Which factor does NOT affect the rate of a chemical reaction?
Temperature
Catalyst
Colour of reactants
Concentration
Which mixture can only be separated by fractional distillation?
Sand + water
Ethanol + water
Salt + water
Copper + sulfur
When heating copper carbonate, the green powder turns black. The black solid is:
Copper metal
Copper(II) oxide
Copper sulfate
Carbon
