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HKDSE Chemistry > 14: Acids and Alkalis > Flashcards

14: Acids and Alkalis Flashcards

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1
Q

Name 3 acids in the laboratory.

A

Hydrochloric acid (HCl), sulphuric acid (H2SO4), nitric acid (HNO3)

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2
Q

List out 5 properties of acids.

A
  1. They taste sour.
  2. They are conductors of electricity.
  3. They react with reactive metals.
  4. They react with bases.
  5. They react with metal carbonates and hydrogencarbonates.
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3
Q

What is the word equation for metals’ reactions with dilute acid?

A

metal + acid -> salt + hydrogen

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4
Q

What is the balanced chemical equation for alkali metals’ reactions with dilute hydrochloric acid?

A

2M + 2HCl -> 2MCl + H2

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5
Q

What is the balanced chemical equation for alkaline earth metals’ reactions with dilute hydrochloric acid?

A

M + 2HCl -> MCl2 + H2

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6
Q

What is the balanced chemical equation for iron’s reaction with dilute hydrochloric acid?

A

Fe + 2HCl -> FeCl2 + H2

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7
Q

What is the balanced chemical equation for iron’s reaction with dilute sulphuric acid?

A

Fe + H2SO4 -> FeSO4 + H2

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8
Q

What is the definition of base?

A

A base is a substance that reacts with an acid to form a salt and water only.

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9
Q

What is the definition of neutralisation?

A

Neutralisation refers to a reaction of an acid and a base.

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10
Q

Describe two observations seen when copper(II) oxide granules are put into a beaker of dilute sulphuric acid.

A
  1. The colour of the solution turns from colourless to blue.
  2. The size of the copper oxide granules decreases.
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11
Q

Why do the size of copper(II) oxide granules decrease after they are put into a beaker of dilute sulphuric acid?

A

The insoluble copper(II) oxide reacts to form soluble copper(II) sulphate, which is then dissolved in water, so its size decreases.

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12
Q

Are metal carbonates and metal hydrogencarbonates classified as bases?

A

No, because alongside with giving out salt and water in their reaction with acids, they also give out carbon dioxide.

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13
Q

Describe two observations seen when calcium carbonate granules are put into a test tube containing dilute hydrochloric acid.

A
  1. Effervescence occurs / gas bubbles are produced.
  2. The size of the calcium chloride granules decreases.
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14
Q

What is the word equation for metal hydrogencarbonates’ reactions with dilute acid?

A

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

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15
Q

What is the word equation for metal carbonates’ reactions with dilute acid?

A

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

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16
Q

Why do the size of calcium carbonate granules decrease after they are put into a beaker of dilute hydrochloric acid?

A

The insoluble calcium carbonate reacts to form soluble calcium chloride, which is then dissolved in water, so its size decreases.

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17
Q

Why does effervescence occur after calcium carbonate granules are put into a beaker of dilute hydrochloric acid?

A

Calcium carbonate reacts with hydrochloric acid to produce calcium chloride, water, and carbon dioxide. The carbon dioxide is released as bubbles in the acid.

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18
Q

A solution of calcium compounds reacts with acid to form calcium chloride, water, and carbon dioxide. Determine the calcium compound in the original solution.

A

Calcium hydrogencarbonate, since calcium carbonate is insoluble in water and cannot be made into a solution.

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19
Q

What is the definition of acid?

A

An acid is a compound which produces hydrogen ions as the only positive ions when dissolved in water.

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20
Q

What is the basicity of an acid?

A

The basicity of an acid is the maximum number of hydrogen ions that can be produced by one molecule of the acid.

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21
Q

What is the basicity of CH3COOH?

A

It is monobasic as only the hydrogen atom in the COOH bond can be released.

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22
Q

Which arrow should be used for the dissociation of sulphuric acid to hydrogensulphate ion and hydrogen ion in water?

A

single arrow, since all sulphuric acid molecules dissociate.

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23
Q

Which arrow should be used for the dissociation of hydrogensulphate ion to sulphate ion and hydrogen ion in water?

A

double arrow, since hydrogensulphate ions partially dissociate.

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24
Q

Which arrow should be used for the dissociation of phosphoric acid to dihydrogenphosphate ion and hydrogen ion in water?

A

double arrow, since phosphoric acid molecules partially dissociate.

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25
Q

What is the basicity of phosphoric acid?

A

It is tribasic.

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26
Q

What is the basicity of sulphuric acid?

A

It is dibasic.

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27
Q

What is the difference between alkalis and bases?

A

Alkalis are bases which are soluble in water.

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28
Q

What is the definition of alkalis?

A

An alkali is a base which releases hydroxide ions when dissolved in water.

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29
Q

When making aqueous ammonia in a lab, how does using an inverted filter funnel facilitate the process?

A

It increases the area over which ammonia gas can dissolve, and prevents sucking back.

30
Q

When making aqueous ammonia in a lab, how does using an inverted filter funnel prevent sucking back?

A

Since the gas dissolves in water quickly, the gas pressure inside the tube is lower than that outside the tube. Water is sucked into the tube. When the opening of the tube is wider, the external water level quickly drops below the brim and air goes in, stopping the suckback.

31
Q

List out 6 properties of dilute alkalis.

A
  1. They feel slippery to touch.
  2. They taste bitter.
  3. They are conductors of electricity.
  4. They react with acids.
  5. They react with solutions containing certain metal ions to form precipitates.
  6. They react with ammonium compounds.
32
Q

Describe the observations when excess dilute sodium hydroxide solution is added to a solution of calcium ions.

A
  1. White precipitate is formed.
  2. The precipitate does not re-dissolve.
33
Q

Describe the observations when excess dilute sodium hydroxide solution is added to a solution of magnesium ions.

A
  1. White precipitate is formed.
  2. The precipitate does not re-dissolve.
34
Q

Describe the observations when excess dilute sodium hydroxide solution is added to a solution of aluminium ions.

A
  1. White precipitate is formed.
  2. The precipitate re-dissolves to give a colourless solution.
35
Q

Describe the observations when excess dilute sodium hydroxide solution is added to a solution of lead(II) ions.

A
  1. White precipitate is formed.
  2. The precipitate re-dissolves to give a colourless solution.
36
Q

Describe the observations when excess dilute sodium hydroxide solution is added to a solution of zinc ions.

A
  1. White precipitate is formed.
  2. The precipitate re-dissolves to give a colourless solution.
37
Q

Describe the observations when excess dilute sodium hydroxide solution is added to a solution of iron(II) ions.

A
  1. Green / dirty green precipitate is formed.
  2. The precipitate does not re-dissolve.
38
Q

Describe the observations when excess dilute sodium hydroxide solution is added to a solution of iron(III) ions.

A
  1. Reddish brown precipitate is formed.
  2. The precipitate does not re-dissolve.
39
Q

Describe the observations when excess dilute sodium hydroxide solution is added to a solution of copper(II) ions.

A
  1. Pale blue precipitate is formed.
  2. The precipitate does not re-dissolve.
40
Q

What is the name of the product made after reacting aluminium ions with excess dilute sodium hydroxide solution?

A

Tetrahydroxoaluminate ion

41
Q

What is the chemical formula of the product made after reacting aluminium ions with excess dilute sodium hydroxide solution?

A

[Al(OH)4]-

42
Q

What is the name of the product made after reacting lead(II) ions with excess dilute sodium hydroxide solution?

A

Tetrahydroxoplumbate(II) ion

43
Q

What is the chemical formula of the product made after reacting lead(II) ions with excess dilute sodium hydroxide solution?

A

[Pb(OH)4]2-

44
Q

What is the name of the product made after reacting zinc ions with excess dilute sodium hydroxide solution?

A

Tetrahydroxozincate ion

45
Q

What is the chemical formula of the product made after reacting zinc ions with excess dilute sodium hydroxide solution?

A

[Zn(OH)4]2-

46
Q

What is the ionic equation of the reaction of metal ion M with charge n+ with dilute sodium hydroxide solution?

A

Mn+(aq)+OH-(aq) -> M(OH)n(s)

47
Q

What is the ionic equation of the reaction of metal ion M with charge n+ with dilute ammonia solution?

A

Mn+(aq)+OH-(aq) -> M(OH)n(s)

48
Q

Describe the observations when excess dilute ammonia solution is added to a solution of magnesium ions.

A
  1. White precipitate is formed.
  2. The precipitate does not re-dissolve.
49
Q

Describe the observations when excess dilute ammonia solution is added to a solution of aluminium ions.

A
  1. White precipitate is formed.
  2. The precipitate does not re-dissolve.
50
Q

Describe the observations when excess dilute ammonia solution is added to a solution of lead(II) ions.

A
  1. White precipitate is formed.
  2. The precipitate does not re-dissolve.
51
Q

Describe the observations when excess dilute ammonia solution is added to a solution of zinc ions.

A
  1. White precipitate is formed.
  2. The precipitate re-dissolves to give a colourless solution.
52
Q

Describe the observations when excess dilute ammonia solution is added to a solution of iron(II) ions.

A
  1. Green / dirty green precipitate is formed.
  2. The precipitate does not re-dissolve.
53
Q

Describe the observations when excess dilute ammonia solution is added to a solution of iron(III) ions.

A
  1. Reddish brown precipitate is formed.
  2. The precipitate does not re-dissolve.
54
Q

Describe the observations when excess dilute ammonia solution is added to a solution of copper(II) ions.

A
  1. Pale blue precipitate is formed.
  2. The precipitate re-dissolves to give a dark blue / prussian blue solution.
55
Q

Describe the observations when excess dilute ammonia solution is added to a solution of silver ions.

A
  1. Grey precipitate is formed.
  2. The precipitate re-dissolves to give a colourless solution.
56
Q

What is the name of the product made after reacting zinc ions with excess dilute ammonia solution?

A

Tetraamminezinc ion

57
Q

What is the chemical formula of the product made after reacting zinc ions with excess dilute ammonia solution?

A

[Zn(NH3)4]2+

58
Q

What is the name of the product made after reacting silver ions with excess dilute ammonia solution?

A

Diamminesilver(I) ion

59
Q

What is the chemical formula of the product made after reacting silver ions with excess dilute ammonia solution?

A

[Ag(NH3)2]+

60
Q

What is the name of the product made after reacting copper(II) ions with excess dilute ammonia solution?

A

Tetraamminecopper(II) ion

61
Q

What is the chemical formula of the product made after reacting copper(II) ions with excess dilute ammonia solution?

A

[Cu(NH3)4]2+

62
Q

What is the ionic equation of the reaction between zinc hydroxide and dilute ammonia solution?

A

Zn(OH)2(s) +4NH3(aq) -> [Zn(NH3)4]2+(aq) + 2OH-(aq)

63
Q

What is the ionic equation of the reaction between copper hydroxide and dilute ammonia solution?

A

Cu(OH)2(s) +4NH3(aq) -> [Cu(NH3)4]2+(aq) + 2OH-(aq)

64
Q

What are the products formed after reacting ammonium chloride with potassium hydroxide solution?

A

Ammonia gas, potassium chloride, water

65
Q

How can ammonia gas be tested?

A

It turns a moist red litmus paper from red to blue, and it turns a moist pH paper from yellow to blue / purple.

66
Q

Why can ammonia gas be collected by upward delivery?

A

It is less dense than air, so it displaces the air originally in the collection flask.

67
Q

What is the meaning of hygroscopic?

A

A hygroscopic substance absorbs water vapour from air and increases its volume.

68
Q

What is the meaning of deliquescent?

A

A deliquescent substance absorbs water vapour and forms a very concentrated solution over time.

69
Q

List 3 common drying agents.

A
  1. Sulphuric acid
  2. Anhydrous calcium chloride
  3. Calcium oxide
70
Q

Which drying agent is used for drying ammonia and why?

A

Calcium oxide, since ammonia reacts with sulphuric acid and calcium chloride.

HKDSE Chemistry (28 decks)

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