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Chemistry > Topic 3- Chemical Changes > Flashcards

Topic 3- Chemical Changes Flashcards

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1
Q

Acids form… in water

A

H+ ions

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2
Q

Alkalis form…in water

A

OH- ions

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3
Q

Litmus indicates…
In acidic solutions?
In neutral solutions?
In alkaline solutions?

A

Acid- red
Neutral- purple
Alkaline- blue

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4
Q

Methyl orange indicates…
In acidic solutions?
In neutral solutions?
In alkaline solutions?

A

Acid- red
Neutral- yellow
Alkaline- pink

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5
Q

Phenolphthalein indicates…
In acidic solutions?
In neutral solutions?
In alkaline solutions?

A

Acid- colourless
Neutral- colourless
Alkaline- pink

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6
Q

Acid + base

A

Neutralisation

Produces salt and water

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7
Q

Calcium oxide and dilute hydrochloric acid neutralisation reaction:
Method?
Graph shape?

A
  1. Measure out the base intervals and acid out correctly
  2. Add the base into the acid
  3. Wait for the base to react completely and test the pH
  4. Repeat steps 1-3 until all the acid has reacted (when there is unreacted calcium oxide at the bottom of the flask)

Graph- not much change in pH but then the is a sudden change as you approach the point where the solution is neutral and then it levels off again (like a S shape)

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8
Q

All acids can …/… in solution which means that…

A

Ionise/dissociate which means splitting up to produce a hydrogen ion, H+ and another ion

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9
Q

Strong acid ionise…

Example of strong acids

A

Ionise completely in water i.e. a large proportion of the acid molecules dissociate to release H+ ions. They tend to have lower pHs (pH 0-2)
Eg. Sulfuric, hydrochloric and nitric acids

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10
Q

Weak acid ionise…

Example of weak acids

A

Do not fully ionise in solution i.e. only a small proportion of the acid molecules dissociate to release H+ ions. There pHs tend to be around pH 2-6
Eg. Ethanoic, citric and carbonic acids

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11
Q

Acid strength (strong or weak) tells you…

A

What proportion of the acid molecules ionise in water

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12
Q

Concentration measures…

A

How much acid there is in a litre of water

how watered down an acid is

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13
Q

An acid with a large number of acid molecules compared to the volume of water is said to be…
Whereas an acid with a small number of acid molecules compared to the volume of water is said to be…

A
  1. Concentrated - the more grams or moles of acid per dm (3) the more concentrated an acid
  2. Dilute
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14
Q

Concentration describes the total number of…

A

Dissolved acid molecules

NOT the number of molecules that produce hydrogen ions

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15
Q

If the concentration of H+ ions increases by a factor of 10, the pH…
Therefore if the concentration increases by a factor of 100 the pH…

A
  1. The pH will decrease by 1

2. The pH will decrease by 2

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16
Q

If the concentration of H+ ions decreases by a factor of 10, the pH…
Therefore if the concentration decreases by a factor of 100 the pH…

A
  1. The pH will increase by 1

2. The pH will increase by 2

17
Q

Acid + metal oxide

Produce what?

A

Acid + Metal Oxide = Salt + Water

18
Q

Acid + Metal Hydroxide

Produce what?

A

Acid + Metal Hydroxide = Salt + Water

19
Q

Acid + Metal

Produce what?

A

Acid + Metal = Salt + Hydrogen

20
Q

Acid + Metal Carbonate

Produce what?

A

Acid + Metal Carbonate = Salt + Water + Carbon Dioxide

21
Q

Test for Hydrogen

A

You test for hydrogen using a lighted splint
If there is hydrogen it will make a squeaky pop
Because the hydrogen is burning with the oxygen in the air to form water

22
Q

Test for Carbon Dioxide

A

To test to see whether a gas is carbon dioxide, you bubble it through limewater
If the gas is carbon dioxide, the limewater will turn cloudy

23
Q

Common salts of sodium, potassium and ammonium

Soluble or insoluble?

A

Soluble

24
Q

Nitrates

Soluble or insoluble?

A

Soluble

25
Q

Common chlorides

Soluble or insoluble?

A

Soluble

EXCEPT… silver chloride and lead chloride

26
Q

Common sulfates

Soluble or insoluble?

A

Soluble

EXCEPT… lead, barium and calcium sulfate

27
Q

Common carbonates and hydroxides

Soluble or insoluble?

A

Insoluble

EXCEPT… sodium, potassium and ammonium ones

28
Q

Making in soluble salts- precipitation reactions
What reacts?
Example?

A

Two soluble salts react together

Eg. Lead Nitrate + Sodium Chloride = Lead Chloride + Sodium Nitrate
Lead Chloride is an insoluble salt

29
Q

Precipitation method for getting Lead Chloride

4 steps

A
  1. Dissolve a spatula of Lead Nitrate in deionised water, in a test tube and do the same for Sodium Chloride in a separate test tube
  2. Tip the two solutions into a beaker and stir to mix it together- the Lead Chloride should precipitate out
  3. Filter the contents through a filter funnel and paper, the residue left behind is the precipitate
  4. Then leave the Lead Chloride to dry in an oven or desiccator
30
Q

Making soluble salts using …

Example?

A

An acid and insoluble base

Eg. Copper oxide + Sulfuric acid = Copper sulfate + Water

31
Q

Method for making soluble salts

5 steps

A
  1. Heat the acid in a water bath
  2. Add the base to the acid, this will produce a soluble salt and water
    (You know the acid has been neutralised when excess solid sinks to the bottom of the flask)
  3. Filter the excess solid, so the solution is just salt and water
  4. Heat the solution to evaporate the water, then leave the solution to cool and dry so the salts crystallise
  5. Then filter off the solid salt and leave it to dry
32
Q

Soluble salts can also be made from…

A

Acid and Alkali reactions

33
Q 
Titration method (acid and alkali = soluble salt)
(5 steps)
A
  1. Measure out a set amount of acid into a chronically flask using a pipette and add a few drops of indicator
  2. Slowly add alkali to the acid, until you reach an end point where the acid has been completely neutralised and the indicator changes colour
  3. Then carry the experiment out again using the exact same volumes of acid and alkaline but with no indicator
  4. The solution that remains after this only contains salt and water, therefore you evaporate off some of the water and then leave to crystallise
  5. Filter of the solid and dry it

Chemistry (4 decks)

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