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Chemistry > C4 - Chemical Changes > Flashcards

C4 - Chemical Changes Flashcards

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1
Q

Metals oxides (2)

A
  • Are produced when metals react with oxygen

* These reactions are oxidation because metal gains oxygen

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2
Q

Reduction

A

Is the gain if electrons

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3
Q

Oxidation

A

Is the loss of electrons

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4
Q

What happens when potassium, sodium, lithium and calcium react with water (3)

A
  • Fizz
  • Give off hydrogen gas
  • Leave an alkaline solution of metal hydroxide
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5
Q

What happens when potassium, sodium, lithium and calcium react with dilute acid

A

Explode

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6
Q

What happens when magnesium, aluminium, zinc and iron react with water

A

Very slow reaction

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7
Q

What happens when metals react with other substances

A

The metal atoms form positive ions

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8
Q

What is the reactivity of a metal related to and how are they arranged (2)

A
  • Its tendency to form positive ions

* in order of their reactivity in a reactivity series

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9
Q

What happens when magnesium, zinc and iron react with dilute acids

A

React less violently than potassium,sodium,lithium and calcium

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10
Q

What happens when copper react with dilute acids

A

No reaction

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11
Q

How is the reactivity of metals in water or dilute acid related to the tendency of the metal to form its positive ion (2)

A
  • When metals react with water or acid, they lose electrons and form positive ions
  • So the higher a metal is in the reactivity series, the more easily it reacts with water or acid
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12
Q

What is the reaction of metals with water and acids limited to (2)

A
  • Room temperature

* Do not include reaction with steam

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13
Q

How can metals which are less reactive than carbon be extracted from their oxides

A

By reduction with carbon

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14
Q

Reduction (2)

A
  • Involves the loss of oxygen

* Gain of electrons

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15
Q

Oxidation (2)

A
  • Is the loss of electrons

* Gain of oxygen

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16
Q

How are metals which are higher than carbon extracted from their oxides

A

By using electrolysis

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17
Q

What happens when acids react with some metals

A

Produce salts and hydrogen

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18
Q

How are acids neutralised (2)

A
  • By alkalis (e,g soluble metal hydroxides) and bases (e.g insoluble metal hydroxides and metal oxides) to produce salts and water
  • And by metal carbonates to produce salts, water and carbon dioxide
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19
Q

What does the particular salt produced in any reaction between an acid and a bass or alkali depend on (2)

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
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20
Q

Soluble salts

A
  • Can be made from acids by reacting them with solid insoluble substances, such as metals, metal oxides, hydroxides or carbonates
  • The solid is added to the acid until no more reacts and the excess solid is filtered off to produce a solution of the salt
21
Q

How are solid salts produced

A

Salt solutions can be crystallised

22
Q

How to make soluble salts using an insoluble base - required practical (5)

A
  • Gently warm the dilute acid using a bunsen burner then turn off
  • Add the insoluble base to acid a bit at a time, until no more reacts (i.e the base is in excess) - acid is neutralised as the excess solid will just sink to the bottom
  • Then filter out the excess solid to get the salt solution
  • To get pure, solid crystals of the salt gently heat the solution using a water bath or electric heater to evaporate the water
  • Then stop heating and allow the solution to cool - then crystals should form
23
Q

What do acids produce in aqueous solutions

A

Hydrogen ions (H+)

24
Q

What do aqueous solutions of alkali’s contain

A

Hydroxide ions (OH-)

25
Q

The pH scale (3)

A
  • From 0 to 14
  • Is a measure of the acidity or alkalinity of a solution
  • can be measured using universal indicator or ph probe
26
Q

What do pH value do aqueous solutions of acids have

A

Less than 7

27
Q

What do pH value do aqueous solutions of alkalis have

A

Greater than 7

28
Q

Equation for the reaction between an acid and an alkali in terms of H+ and OH- ions

A

H+(aq) + OH- (aq) –> H2O(l)

29
Q

The use of a wide range indicator to measure the approximate pH of a solution

A

Wide range indicators contain a mixture of dyes that means they gradually change colour over a board range of pH

30
Q

The use of a universal indicator to measure the approximate pH of a solution

A

Universal indicator is a dye that changes colour depending on whether its above or below a certain pH

31
Q

Strong acid

A
  • Is a completely ionised in aqueous solution

* Examples: hydrochloric, nitric and sulfuric acids

32
Q

Weak acid

A
  • Is only partially ionised in aqueous solution

* Examples: ethanoic, citric and carbonic acids

33
Q

What is the relationship between acid and pH in a given concentration of aqueous solution

A

The stronger an acid the lower the pH

34
Q

What happens when the pH decreases by one unit

A

The hydrogen ion concentration of the solution increases by a factor of 10

35
Q

Explain dilute in terms of amount of substance

A

Dilute means not very concentrated - so little acid in a certain volume of water

36
Q

Explain concentration in terms of amount of substance (2)

A
  • Concentration measures how much acid there is in a certain volume of water
  • The larger the amount of acid there is in a certain volume of liquid, the more concentrated the acid is
37
Q

Explain weak in terms of degree of ionisation

A

• Is a reversible reaction - sets up an equilibrium between the undissociated and dissociated acid

38
Q

Explain strong in terms of degree of ionisation

A
  • If the concentration of H+ ions is higher the rate of reaction is faster
  • So strong acids will be more reactive than weak acids in the same concentration
39
Q

Electrolytes

A

Are liquids and solutions which are able to conduct electricity when an ionic compound is melted or dissolved in water, as the ions are free to move about within the liquid or solution

40
Q

What happens when electric current passes through electrolytes - electrolysis (5)

A
  • Causes ions to move to the electrodes
  • Positively charged ions move to the negative electrode (cathode)
  • Negatively charged ions move to the positive electrode (anode)
  • Ions are discharged at the electrodes producing elements
  • This process is called electrolysis
41
Q

What happens when a single ionic compound (e,g lead bromide) is electrolysed in the molten state using inert electrodes (2)

A
  • The metal (lead) is produced at the cathode

* The non metal (bromine) is produced at the anode

42
Q

How can metal be extracted from molten compounds

A

Using electrolysis

43
Q

Extraction process

A

Requires large amounts of energy to melt the compounds and to produce the electrical current

44
Q

Why is a mixture used at the electrolyte

A
  • Molten mixture contains free ions - so it’ll conduct electricity
  • Also it lowers the melting point
45
Q

Why must the positive electrode be constantly replaced

A

Anode is made of carbon and needs to be replaced regularly because it reacts with oxygen to produce carbon dioxide

46
Q

What do the ions discharged in when aqueous solution is electrolysed using inert electrodes depend on

A

The relative reactivity of the elements involved

47
Q

What happens at the negative electrode (cathode) - electrolysis of aqueous solution

A

Hydrogen is produced if the metal is more reactive than hydrogen

48
Q

What happens at the positive electrode (anode) - electrolysis of aqueous solution

A

Oxygen is produced unless the solution contains halide ions when the halogen is produced

49
Q

What do water molecules do in aqueous solutions to cause what happens at the electrodes to happen (2)

A
  • Water molecules break down producing hydrogen ions

* Hydroxide ions are discharged

Chemistry (9 decks)

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