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Chemistry Edexcel GCSE > Chemical Changes > Flashcards

Chemical Changes Flashcards

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1
Q

What is an alkali

A

A base that is soluble in water where the concentration of OH- is high(er)

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2
Q

What colours does litmus go

A

Red in acidic solutions
Purple in neutral solutions
Blue in alkaline solutions

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3
Q

What colours does methyl orange go

A

Red in acidic solutions
Orange in neutral Yellow in alkaline solutions

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4
Q

What colours does phenolphalein go

A

Colourless in acidic or neutral solutions
Pink in alkaline solutions

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5
Q

What is reaction between an acid and base called

A

Neutralisation

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6
Q

What do strong acids do in water

A

Fully (or close to) dissociate

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7
Q

What do weak acids do in water

A

Partially dissociate

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8
Q

How much does pH increase by

A

A factor of 10

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9
Q

What forms when an acid reacts with a metal (hydr)oxide

A

Salt + water

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10
Q

What forms when an acid reacts with a metal

A

Salt + Hydrogen

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11
Q

What forms when an acid react with a metal carbonate

A

Salt + Water + Carbon dioxide

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12
Q

How to test for CO2

A

bubble the gas through limewater and if present the limewater will turn cloudy then colourless again

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13
Q

Solubility rules

A

All sodium, potassium and ammonium salts are soluble

All nitrates are soluble

Most chlorides (except silver and lead) are soluble

Most sulphates (except lead, barium and calcium) are soluble

Most carbonates and hydroxides (except sodium, potassium and ammonium) are insoluble

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14
Q

What happens when an acid reacts with ammonia

A

An ammonium salt is formed

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15
Q

How to to make an soluble salt from an insoluble base

A

Excess base method

This cannot be used to make sodium, potassium and ammonium salts

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16
Q

Excess base method

A

Use the metal oxide and corresponding acid

eg. to make copper sulfate crystals use copper oxide + sulfuric acid

Add some of the acid to a beaker and then add excess base to ensure that all of the acid has been used up

Gently warm

Filter then evaporate

17
Q

What is the titration method used for

A

Making sodium, potassium and ammonium salts which are inseparable by filtration

18
Q

Titration method

A

Choose suitable chemicals
Alkaline + corresponding acid (similar to excess base)

Use glass pipette to place 25.0 cm ^3 of alkali into a conical flask

Add a few drops of phenolphthalein (it will turn pink)

Put the acid into the burette and add to the alkali a bit at a time + swirl

Measure where indicator goes colourless

Repeat and be careful + adjust volume

Heat the mixture and evaporate water

Leave to crystallise

Filter

19
Q

What is the precipitation method used for

A

To make insoluble salts and when both base and salt are solids

20
Q

Precipitation method

A

Use the metal nitrate and the sodium compound

eg. Barium nitrate and sodium sulfate to make barium sulfate

Mix the two solutions together in a beaker

Filter

Wash with distilled water

Leave to dry

21
Q

What is a precipitate

A

A solid made from reacting two solutions together

22
Q

What happens to the cations in electrolysis

A

reduction

23
Q

What happens to the anions in electrolysis

A

oxidised

24
Q

How to set up an electrochemical cell

A

2 inert electrodes (usually graphite)

Clean the surfaces using emery paper

Place into a beaker

Connect to a power supply using crocodile clips and wires

25
Q

What is formed at the cathode

A

Hydrogen gas
OR
If less reactive metal than hydrogen is present that will be formed

26
Q

What is formed at the anode

A

Oxygen
OR
Halides if they are present

27
Q

What is the half-equation at the anode is oxygen is formed

A

4OH- –> O2 + 2H2O +4e-

Chemistry Edexcel GCSE (9 decks)

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