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Chemistry > Topic 4 -chemical changes > Flashcards

Topic 4 -chemical changes Flashcards

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1
Q

What is the PH scale

A

a measure of how acidic or alkaline a solution is .

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2
Q

What are the two ways of measuring the PH of a solution ?

A

An indicator- a dye that changes colour depending on the PH
A PH probe attached to a PH meter- the probe is placed into the solution you are measuring and the Ph is displayed as a numerical value.

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3
Q

What ions do acids form?

A

H+

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4
Q

what ions do alkalis form ?

A

OH-

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5
Q

what is the word and formula equation for neutralisation between acids and alkalis?

A

acid + base -> salt and water
H+ (aq) + OH-(aq) -> H20 (l)

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6
Q

describe how you would carry out a titration experiment to find the concentration of an alkali

A

1) use a pipette to measure 25 ml of your alkali and place it in a conical flask
2) Add 3 drops of a suitable indicator into the conical flask and place it on a white tile.
3) using a funnel , fill your burette with acid of a known concentration,(make sure this is done below eye level and safety glasses are being worn)
4) Record the initial volume of acid in the burette
5) complete a rough titration by slowly turning the tap and adding acid to the conical flask (swirl the flask at the same time)untill end point has been reached(colour change)
6)record the final volume of acid in the burette then repeat the experimet accurately several times untill you get concordant results.

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7
Q

describe the colour change with litmus indicator

A

blue in alkali
red in acid

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8
Q

describe the colour change with phenolphthalein indicator

A

pink in alkali
colourless in acid

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9
Q

describe the colour change with methyl orange indicator

A

yellow in alkali
red in acid

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10
Q

what is a strong acid?

A

an acid that fully ionises or dissociates in aqueous solution/water to form H+ ions

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11
Q

what is a weak acid

A

and acid that does not fully ionise or dissociate in a solution. only some particles dissociate to release h+ ions

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12
Q

The ionisation of a weak acid is a __________ reaction which sets up an e________ between the undissociated and dissociated acid.
The position of equilibrium lies well to the _____

A

reversible
equilibrium
left

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13
Q

Acid + metal oxide -> ____ + _______

A

acid + metal oxide -> salt+ water

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14
Q

Acid + metal hydroxide -> ______ + ______

A

acid + metal hydroxide -> salt + water

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15
Q

acid + metal carbonate -> ____ + ____ + ______ _______

A

acid + metal carbonate -> salt + water + carbon dioxide

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16
Q

describe the moethod for obtaining salt crystals in a reaction between an acid and base

A

1) gently heat your acid in a beaker using a bunden burner
2) add your insoluble base a bit at a time untill it is in excess
3) filter the solution using filter paper, to remove excess solid.
4) heat the solution in a water bath or evaporating basin untill the point of crystalaisation is reached.
5) Leave to cool then wash and dry to obtain pure crystals

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17
Q

Why are strong acids more reactive than weak acids of the same concentration?

A

In a strong acid the concentration of H+ ions is greater meaning that the rate of reaction is faster, so strong acids are more reactive than weak acids

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18
Q

What is the PH of an acid or alkali a measure of ?

A

the concentration of H+ ions in the solution

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19
Q

For every decrease of 1 on the PH scale, the concentration of H+ ions increases by a factor of ….

A

10

20
Q

Is the PH of a strong acid more than or less than the PH of a weaker acid with the same concentration?

A

Less

21
Q

What is the difference between acid strenght and concentration?

A

acid strength- tells you what proportion of the acid molecules ionise in water
acid concentration- measures how much acid there is in a certain volume

22
Q

The particular salt produced in any reaction between an acid and a base or alkali depends on:

A

the acid used (hydrochloric acid produces chlorides, nitric acid produces nitrates, sulfuric acid produces sulfates)

the positive ions in the base, alkali or carbonate.

23
Q

What is a metals reactivity determined by ?

A

how easily they lose electrons- forming positive ions

24
Q

What does it tell you if a metal is higher up in the reactivity series?

A

when metals react with water or acids they lose electrons to form positive ions. so the higher a metal is in the reactivity series, the more easily it reacts and loses electrons in water or acids.

25
Q

Name the reactivity series in order from most to least reactive

A

Potassium
Sodium
Lithium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen
Copper

26
Q

Some metals react with acids to produce salt and what gas?

A

hydrogen gas

27
Q

True or false:
potassium, sodium, lithium and calcium react with water

A

true

28
Q

True or false:
zinc, iron, copper react with water

A

false

29
Q

Name 3 ways you can test the reactivity of metals

A

react with acid:
- measure rate at which hydrogen gas is given off
- measure temperature change of the reaction
react with water

30
Q

Why cant you measure the reactivity of zinc, iron and copper in water?

A

they dont react in water

31
Q

What is oxidation?

A

loss of electrons
gain of oxygen

32
Q

What is reduction?

A

gain of electrons
loss of oxygen

33
Q

The formation of metal ore is an example of what reaction?

A

oxidation

34
Q

how cann Metals less reactive than carbon can be extracted from their oxides?

A

reduction using carbon

35
Q

Metals higher than carbon in the reactivity series are extracted by ….

A

electrolysis

36
Q

What happens in a reduction reaction between metal oxides (ores) and carbon?

A

the ore is reduced (oxygen is lossed) and the carbon is oxidised (gains oxygen)

37
Q

What does the mnemonic OIL RIG stand for?
(helps understand oxidation and reduction in terms of electrons)

A

Oxidation Is loss (of electrons)
Reduction Is Gain (of electrons)

38
Q

True or false:
reduction and oxidation happen at the same time

A

true

39
Q

Complete the redox reaction and explain it
Fe+ 2H2+ —–>

A

Fe+ 2H2+ —–> Fe2+ + H2
the iron atoms lose electrons. they are oxidised by the hydrogen ions
the hydrogen ions gain electrons. they are reduced by the iron atoms

40
Q

What is the rule for displacement reactions?

A

a more reactive metal will displace a less reactive metal from its compound

41
Q

What would happen if you put a more reactive metal into a solution of a weak dissolved metal compound?

A

the more reactive metal will displace the less reactive metal and replace it in the compound

42
Q

Complete the displacement reaction:
iron + copper sulfate ——>

A

iron + copper sulfate ——> iron sulfate +copper

43
Q

In displacement reactions, does the metal ion or metal atom gain electrons (becomes reduced)

A

metal ion

44
Q

In displacement reactions, does the metal ion or metal atom loose electrons (becomes oxidised)

A

metal atom

45
Q

In displacement reactions, does the metal ion or metal atom loose electrons (becomes oxidised)

A

metal atom

Chemistry (7 decks)

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