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IGCSE Chemistry > Acids and Alkalis - 3rd > Flashcards

Acids and Alkalis - 3rd Flashcards

1
Q

what is the pH for acids?

A

<7

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2
Q

what is the pH for neutral?

A

7

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3
Q

what is the pH for alkaline?

A

> 7

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4
Q

what colour is methyl orange in an acid?

A

red

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5
Q

what colour is methyl orange in a neutral substance?

A

yellow

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6
Q

what colour is methyl orange in an alkaline?

A

yellow

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7
Q

what colour is phenolphthalein in an acid?

A

colourless

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8
Q

what colour is phenolphthalein in a neutral substance?

A

colourless

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9
Q

what colour is phenolphthalein in an alkaline?

A

pink

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10
Q

what colour is red litmus in an acid?

A

red

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11
Q

what colour is red litmus in a neutral substance?

A

(stays red)

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12
Q

what colour is red litmus in an alkaline?

A

blue

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13
Q

what colour is blue litmus in an acid?

A

red

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14
Q

what colour is blue litmus in a neutral substance?

A

(stays blue)

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15
Q

what colour is blue litmus in an alkaline?

A

blue

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16
Q

what are the colours on the universal indicator from 1-14?

A

0-2 : red
3-4: orange
5-6: yellow
7: green
8-10: light blue
11-13: dark blue
14: purple

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17
Q

what is air composed of?

A

nitrogen- 78%
oxygen- 21%
argon- 0.96%
carbon dioxide- 0.04%

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18
Q

what is an experiment to measure the percentage of oxygen in the air ?

A

react oxygen with copper / any metal, the air gradually decreases in volume until all of the oxygen has been added to the metal. SEE FLASHCARD 1(A+A)

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19
Q

If in an experiment to measure the percentage of oxygen in the air, the results don’t show 21% of oxygen in the air, why must this be?

A
  • the metal wasn’t heated for long enough for all the oxygen to be reacted
  • there’s a leak in the apparatus
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20
Q

what is element combustion?

A

when an element reacts with oxygen to produce an oxide.
element +oxygen-> element oxide

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21
Q

what would be the oxide name and state symbol for a metal?

A

metal oxide - solid

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22
Q

what would be the oxide name and state symbol for non-metal?

A

non-metal dioxide - gas

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23
Q

describe the combustion for magnesium.

A

w.e.- magnesium + oxygen -> magnesium oxide
s.e.- 2MG(s) + O2 (g) -> 2MgO (s)
observation - bright white light and white powder formed

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24
Q

describe the combustion for sulphur.

A

w.e.- sulphur + oxygen -> sulphur dioxide
s.e.- S(s) + O2 (g) -> SO2 (g)
observation - blue flame

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25
Q

describe the combustion for hydrogen.

A

w.e.- hydrogen + oxygen -> water
s.e.- 2H2(g) + O2 (g) -> 2H2O (l)
observation - squeaky pop

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26
Q

what is the ion for Iron (II)?

A

Fe 2+

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27
Q

what is the ion for Silver?

28
Q

what is the ion for Iron (III)?

29
Q

what is the ion for Zinc ?

30
Q

what is the ion for Copper?

31
Q

what is the ion for lead?

32
Q

what is the chemical test for oxygen?

A
  • glowing splint -> relights
    this is because the oxygen allows the wood in the splint to combust more efficiently.
33
Q

what happens to oxides if they dissolve in water?

A

oxides tend to form an acidic or alkaline solution depending if the original element is a metal (alkaline) or non-metal (acidic)

34
Q

what do metal oxides form when dissolved in water?

A

an alkaline solution

35
Q

what do non-metal oxides form when dissolved in water?

A

an acidic solution.

36
Q

how can you determine whether an unknown element is a metal or a non-metal?

A
  1. combust it in oxygen
  2. dissolve the oxide formed
  3. check the pH of the solution with an indicator
37
Q

what is the definition of an acid?

A

a H+ donor

38
Q

what is the definition of a base?

A

a H+ acceptor - insoluble

39
Q

what is the definition of an alkali?

A

an OH- donor - a soluble base

40
Q

what do acids or alkalis describe?

A

a substance in terms of ions when mixed with water

41
Q

what does acidic or alkaline describe?

A

a solution in terms of pH

42
Q

what happens when acids dissolve in water?

A

acids dissolve and then donate (release) H+ ions into the water. this is what causes the solution to have a pH < 7 and for it to be labelled acidic.

43
Q

what happens when alkalis dissolve in water?

A

alkalis dissolve and then donate (release) OH- ions into the water. This is what causes the solution to have a pH > 7 and for it to be labelled alkaline.

44
Q

what happens when bases dissolve in water?

A

bases dissolve and then accept (take) H+ ions from the H2O (water) molecules. but when a H2O molecule loses an H+ ion, what is leftover is an OH- ion. It is these OH- ions which cause the solution to have a pH > 7 and for it to be labelled alkaline.

45
Q

what is the formulae for the following acids:
- hydrochloric acid
- nitric acid
- sulphuric acid
- phosphoric acid
- carbonic acid

A
  • HCl
  • HNO3 - ion formula: NO3 -
  • H2SO4 - ion formula: SO4 2-
  • H3PO4- ion formula: PO4 3-
  • H2CO3- ion formula: CO3 2-
46
Q

what is the formulae for the following alkalis:
- sodium hydroxide
- potassium hydroxide
- ammonium hydroxide
- all soluble metal hydroxides

A
  • NaOH
    -KOH
    -NH4OH - ion formula: NH4 +
  • ion formula: OH -
47
Q

what is the formula for ammonia?

48
Q

what can be an alkali?

A

all soluble metal hydroxides

49
Q

what can be a base?

A

all metal oxides, all metal hydroxides

50
Q

what is formed when a base reacts with an acid and what is it called?

A

acid + base -> salt + water
neutralisation

51
Q

what happens in an acid and base reaction if the salt is soluble?

A

it dissolves the water to form a salt solution

52
Q

what are the soluble salts (alkalis)?

A
  • all sodium, potassium and ammonium salts are soluble
  • all nitrates are soluble
  • all sulphates except barium and lead are soluble
  • all chlorides except silver and lead are soluble
53
Q

how can you tell if you use the titration method to make a salt?

A

if it is a soluble salt and if it can be made from an alkali (sodium, potassium or ammonium).

54
Q

how can you tell if you use the insoluble base method to make a salt?

A

if it is a soluble salt and if it cannot be made from an alkali (sodium, potassium or ammonium)

55
Q

how can you tell if you use the precipitation method to make a salt?

A

if it isn’t a soluble salt.

56
Q

describe the method of titration.

A
  • place a measured quantity of alkali (NaOH, KOH, aq NH3) into a flask
  • add indicator
  • add acid from a burette until the indicator just changes colour
  • note the burette reading
  • pour contents of flask away and repeat using same quantities of acid and alkali, but without indicator
  • evaporate to 1/3 of the original volume and leave to crystallise.
57
Q

describe the insoluble base method.

A
  • place the acid in a 100cm^3 beaker and heat gently
  • add the base (or carbonate or appropriate metal) until it no longer dissolves and we see some salt forming
  • filter the mixture to remove excess solid
  • evaporate and leave to crystalise
  • dry crystals using paper towel
58
Q

describe the precipitation method.

A
  • add a soluble salt of the cation (…nitrate) to the soluble salt of the anion (sodium….).
  • filter to collect salt
59
Q

what do carbonates and metals reacting together form?

A

salt + water + carbon dioxide

60
Q

describe an acid + carbonate reaction.

A

observations:
- the carbonate disappears : this is because it is used up in the reaction
- there is fizzing: this is because a gas (carbon dioxide) is formed
- if the salt is soluble it dissolves into the water to form a salt solution

61
Q

what is the chemical test for carbon dioxide?

A

limewater turning cloudy, this is because the CO2 reacts with the limewater to make an insoluble white solid.

62
Q

what is the pH range for something strongly acidic?

63
Q

what is the pH range for something weakly acidic?

64
Q

what is the pH range for something weakly alkaline?

65
Q

what is the pH range for something strongly alkaline?

IGCSE Chemistry (18 decks)

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