C5 Chemical Changes (Chemistry AQA Seperate)
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191 Terms
What is oxidation?
The gain of oxygen or the loss of electrons.
What is reduction?
The loss of oxygen or the gain of electrons.
What does OIL RIG stand for?
Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons).
What is a redox reaction?
A reaction in which oxidation and reduction happen at the same time.
What is the reactivity series?
A list of metals arranged in order of reactivity.
What determines a metal's reactivity?
How easily it loses electrons to form positive ions.
Why are more reactive metals placed higher in the reactivity series?
They lose electrons more easily.
Name the metals in the GCSE reactivity series from most to least reactive.
Potassium, Sodium, Lithium, Calcium, Magnesium, Aluminium, Carbon, Zinc, Iron, Tin, Lead, Hydrogen, Copper, Silver, Gold, Platinum.
Which non-metal is included in the reactivity series?
Carbon.
Why is carbon included in the reactivity series?
To show which metals can be extracted using carbon.
Why is hydrogen included in the reactivity series?
To compare metals with acids.
Which metals react with dilute acids?
Metals above hydrogen.
Which metals do not react with dilute acids?
Metals below hydrogen.
What happens when a metal reacts with an acid?
A salt and hydrogen gas are produced.
What test identifies hydrogen gas?
A lit splint produces a squeaky pop.
What is a displacement reaction?
A more reactive metal displaces a less reactive metal from its compound.
When does displacement occur?
When the added metal is more reactive than the metal in the compound.
Why do displacement reactions happen?
The more reactive metal loses electrons more easily.
What happens if a less reactive metal is added to a more reactive metal's compound?
No reaction occurs.
What is the ionic equation for zinc displacing copper?
Zn + Cu²⁺ → Zn²⁺ + Cu.
Why is copper deposited during displacement?
Copper ions gain electrons.
What colour is copper sulfate solution?
Blue.
What happens to blue copper sulfate solution when zinc is added?
It fades as copper ions are removed.
What colour is iron sulfate solution?
Pale green.
What colour is zinc sulfate solution?
Colourless.
What is a metal ore?
A rock containing enough metal compound for extraction to be worthwhile.
How are metals below carbon extracted?
By reduction with carbon.
How are metals above carbon extracted?
By electrolysis.
Why can't carbon extract aluminium?
Aluminium is more reactive than carbon.
Which metals are extracted by electrolysis?
Potassium, sodium, lithium, calcium, magnesium and aluminium.
What is reduction during extraction?
Removal of oxygen from a metal oxide.
What reduces iron oxide in the blast furnace?
Carbon monoxide.
What is the formula of iron(III) oxide?
Fe₂O₃.
What is the word equation for iron extraction?
Iron oxide + carbon monoxide → iron + carbon dioxide.
Why is electrolysis expensive?
It requires large amounts of electrical energy.
What is electrolysis?
The decomposition of an ionic compound using electricity.
What must an ionic compound be for electrolysis to occur?
Molten or dissolved in water.
Why can't solid ionic compounds conduct electricity?
The ions cannot move.
What are electrodes?
Conductors that allow current to enter and leave the electrolyte.
What is the positive electrode called?
The anode.
What is the negative electrode called?
The cathode.
Which ions move to the cathode?
Positive ions (cations).
Which ions move to the anode?
Negative ions (anions).
What happens at the cathode?
Reduction (gain of electrons).
What happens at the anode?
Oxidation (loss of electrons).
What is the electrolyte?
The molten or aqueous ionic substance being electrolysed.
What forms at the cathode during electrolysis of molten lead bromide?
Lead.
What forms at the anode during electrolysis of molten lead bromide?
Bromine.
What is the half equation for lead ions at the cathode?
Pb²⁺ + 2e⁻ → Pb.
What is the half equation for bromide ions at the anode?
2Br⁻ → Br₂ + 2e⁻.
What colour are bromine fumes?
Brown.
What is produced at the cathode during electrolysis of molten sodium chloride?
Sodium.
What is produced at the anode during electrolysis of molten sodium chloride?
Chlorine.
What is the half equation for sodium formation?
Na⁺ + e⁻ → Na.
What is the half equation for chlorine formation?
2Cl⁻ → Cl₂ + 2e⁻.
What products form when molten aluminium oxide is electrolysed?
Aluminium and oxygen.
What is cryolite used for?
To lower the melting point of aluminium oxide.
Why is cryolite added in aluminium extraction?
It reduces energy costs.
What is the half equation for aluminium ions?
Al³⁺ + 3e⁻ → Al.
Why must carbon anodes be replaced during aluminium extraction?
They react with oxygen to form carbon dioxide.
What is produced at the anode during aluminium extraction?
Oxygen.
Why is aluminium extraction costly?
High electricity demand and carbon anodes need replacing.
What happens at the cathode during electrolysis of aqueous solutions?
The less reactive of hydrogen and the metal is produced.
Which metals are less reactive than hydrogen?
Copper, silver and gold.
If copper chloride solution is electrolysed, what forms at the cathode?
Copper.
If sodium chloride solution is electrolysed, what forms at the cathode?
Hydrogen.
What happens at the anode if halide ions are present?
A halogen is produced.
Which halogens can form at the anode?
Chlorine, bromine or iodine.
What happens at the anode if no halide ions are present?
Oxygen forms.
What gas is produced at the anode from dilute sulfuric acid?
Oxygen.
What gas is produced at the cathode from dilute sulfuric acid?
Hydrogen.
What is electroplating?
Using electrolysis to coat an object with a thin layer of metal.
Why is electroplating used?
To improve appearance or prevent corrosion.
What is the cathode during electroplating?
The object being coated.
What is the anode during electroplating?
The pure coating metal.
What electrolyte is used for copper plating?
Copper sulfate solution.
What happens to the anode during electroplating?
It dissolves into the electrolyte.
What is an acid?
A substance that produces H⁺ ions in water.
What is an alkali?
A soluble base that produces OH⁻ ions in water.
What is a base?
A substance that neutralises acids.
What is neutralisation?
An acid reacting with a base to produce a salt and water.
What is the ionic equation for neutralisation?
H⁺ + OH⁻ → H₂O.
What pH is a neutral solution?
7.
What pH is an acidic solution?
Less than 7.
What pH is an alkaline solution?
Greater than 7.
What colour is universal indicator in a strong acid?
Red.
What colour is universal indicator at pH 7?
Green.
What colour is universal indicator in a strong alkali?
Purple.
What is hydrochloric acid's formula?
HCl.
What is nitric acid's formula?
HNO₃.
What is sulfuric acid's formula?
H₂SO₄.
Which acid forms chloride salts?
Hydrochloric acid.
Which acid forms nitrate salts?
Nitric acid.
Which acid forms sulfate salts?
Sulfuric acid.
What is a strong acid?
An acid that completely ionises in water.
What is a weak acid?
An acid that partially ionises in water.
Do strong acids always have a low concentration?
No.
Do weak acids always have a high pH?
No.
What is concentration?
The amount of dissolved substance per unit volume.
Can a dilute acid be strong?
Yes.