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GCSE Chemistry Paper 1 v2 > Chemical Changes > Flashcards

Chemical Changes Flashcards

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1
Q

What is PH?

A

A measurement of how acid or alkaline a substance is

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2
Q

What are the most acidic and alkaline PHs?

A

PH 0 and PH 14

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3
Q

What are the ways to measure the PH of a solution?

A
  • Use an indicator

- Use a ph probe connected to a ph meter

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4
Q

What happens when you react an acid and a base?

A

acid + base → salt + water

The acid and base neutralise each other.

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5
Q

What is an acid?

A

An aqueous solution with a ph less than 7

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6
Q

What ions do acids form in water?

A

H+

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7
Q

What is a alkali?

A

An aqueous solution with a ph above 7

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8
Q

What ions do alkalis form in water?

A

OH-

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9
Q

What is the purpose of titration?

A

It calculates the exact concentration of acid needed to neutralise a base and vise versa.

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10
Q

What is the method for titration?

A

Say you want to find the concentration of acid it takes to neutralise an alkali:

  • First use a pipette and a pipette filter to measure out a set volume of alkali into a conical flask,
  • Add two or three drops of indicator
  • Use a funnel to fill a burette with some acid of known concentration,
  • Record the initial volume of the acid
  • Slowly drip down the acid so that you can tell what volume is left in the burette,
  • Do this until the solution changes colour, this means the solution has neutralised,
  • Record the final volume of the acid and find the amount of acid dripped down into the solution by finding the difference. This is the volume of a certain concentration of acid to neutralise the known volume of alkali.
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11
Q

How do you increase the accuracy of your titrations?

A
  • Take several readings
  • Ignore anomalies
  • Take a mean of your trials
  • Use a high resolution burette.
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12
Q

What indicators can you use for titration?

A

> Litmus (blue in alkali → red in acids)
Phenolphthalein (pink in alkalis → colourless in acids)
Methyl Orange (yellow in alkalis → red in acids)

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13
Q

What are strong acids?

A

Acids that ionise fully in water, all the acid particles disassociate to release H+ ions.

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14
Q

What are weak acids?

A

Acids don’t ionise fully in water, not all the acid particles disassociate to release H+ ions.

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15
Q

Which acid forms a reversible reaction? (Strong or Weak)

A

Weak, it cause an equilibrium.

e.g. CH3COOH ⇌ H+ + CH3COOH-

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16
Q

Why are strong acids more reactive?

A

There are more H+ ions to react in the solution, so, the rate of reaction is faster because there are more reactants.

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17
Q

What is the relation between PH and concentration of H+ ions in an acid?

A

Factor H+ ion concentration changes by = 10^-x

so if the the PH falls from 7 to 4 the PH changes by -3 so 10^-(-3) = 10^3 = 1000, so the concentration of H+ ions has increased by 1000

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18
Q

What is the difference between strong acids and concentrated acids?

A

Acid concentration is the proportion of acid in the aqueous solution,
Acid strength is the proportion of molecules in the acid that ionise in water

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19
Q

What are the products of Acid + Metal oxide?

A

Acid + Metal oxide → Salt + Water

20
Q

What are he products of Acid + Metal hydroxide?

A

Acid + Metal hydroxide → salt + water

21
Q

What are the products of Acid + Metal carbonate?

A

Acid + Metal carbonate → salt + water + Carbon dioxide

22
Q

How do you make soluble salts using an insoluble base?

A
  • You need to pick the right acid and insoluble base,
  • Gently heat up the dilute acid using a Bunsen burner, then turn of the Bunsen burner,
  • Add the insoluble base to the warm acid a bit at a time,
  • You know when the reaction is done because the excess insoluble solid will sink to the bottom,
  • Then filter out the excess solid to get a salt solution,
  • Use crystallisation to get the pure solid crystals of he salt.
23
Q

What is the reactivity series? (definition not order)

A

Lists the metals in order of their reactivity towards other substances.

24
Q

What is the order of the reactivity series?

A 
Potassium
Sodium
Lithium
Calcium
Magnesium
Carbon > non-metal
Zinc
Iron
Hydrogen > non-metal
Copper
25
Q

What are the products of Acid + metal?

A

Acid + Metal → salt + hydrogen

26
Q

What are the products of Metal + Water?

A

Metal + Water → Metal Hydroxide + Hydrogen

27
Q

What is Reduction?

A

The gain of electrons

28
Q

What is Oxidation?

A

The loss of electrons

29
Q

How can you remember reduction and oxidation?

A 
> O - oxidation
> I - is
> L - loss
> R - reduction
> I - is 
> G - gain
30
Q

`What reactions is this:

2Mg + O2 → 2MgO

A

Oxidation:

reacting in oxygen, electrons are lost

31
Q

What reaction is this:

2CuO + C → 2Cu + CO2

A

Reduction:

Separating a metal oxide, electrons are gained

32
Q

How do you extract metals form metal oxides under carbon in the reactivity series?

A

Use carbon to displace the metal in a reduction reaction, this looks like:
Metal oxide + Carbon → Metal + Carbon Dioxide

33
Q

What method is used to extract metals that are of higher reactivity than carbon?

A

Electrolysis

34
Q

How do extract metals that are not very reactive at all?

A

They tend to be found naturally pure because they don’t react with anything.

35
Q

What is a Redox reaction?

A

A reaction where electrons are transferred:
e.g. Fe + 2H+ → Fe2+ + H2
The Fe takes two electrons from the H2 it becomes reduced
The H2 loses 2 electrons so it oxidises.

36
Q

What is an example of a Redox reaction?

A

A displacement reaction:

In this reaction, the metal always gains electrons is reduced

37
Q

What is the difference between an ionic equation and a regular balanced equation?

A

Ionic equations only focus on the ions/ important sections of the equation.

38
Q

What is electrolysis?

A

This is the process of passing direct current through a solution of melted ionic compound to move the ions apart and so break the compound down and discharge some of the elements at the electrodes.

39
Q

What is an electrolyte?

A

A molten ionic compound.

40
Q

What is the method of electrolysis?

A
  • A circuit is created by dipping an anode and a cathode into an electrolyte. The electrolyte can conduct electricity because they have free flowing ions and will therefore complete the circuit.
  • The Anode is positively charge and lacks electrons,
    The Cathode is negatively charged and has an abundance of electrons,
  • The ions form the electrolyte (Positive metal and negative electron) attract to the anode and cathode,
  • The anion (non-mental) attracts to the anode and the cation (metal) attracts to the cathode.
  • The molten metal is now neutral form taking electrons from the cathode and sinks to the bottom of the electrolysis tank where it can be collected.
41
Q

What side of the battery/power pack is the anode connected to?

A

Positive

42
Q

What side of the battery/power pack is the cathode connected to?

A

Negative

43
Q

What are the electrodes usually made of?

A

A nonreactive substance such as: graphite or expensive platinum metal.

44
Q

What bonds are used in an electrolyte?

A

Ionic bonds

45
Q

Why don’t solid ionic compounds conduct electricity?

A
  • They do not have free flowing ions because they are rigid in place since the structure of a solid is an organised arrangement.
  • Therefore, there is little movement of the ions, this means electricity cannot be conducted.

GCSE Chemistry Paper 1 v2 (5 decks)

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