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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
describe the combustion for hydrogen.
w.e.- hydrogen + oxygen -> water s.e.- 2H2(g) + O2 (g) -> 2H2O (l) observation - squeaky pop
26
what is the ion for Iron (II)?
Fe 2+
27
what is the ion for Silver?
Ag +
28
what is the ion for Iron (III)?
Fe 3+
29
what is the ion for Zinc ?
Zn 2+
30
what is the ion for Copper?
Cu 2+
31
what is the ion for lead?
Pb 2+
32
what is the chemical test for oxygen?
- glowing splint -> relights this is because the oxygen allows the wood in the splint to combust more efficiently.
33
what happens to oxides if they dissolve in water?
oxides tend to form an acidic or alkaline solution depending if the original element is a metal (alkaline) or non-metal (acidic)
34
what do metal oxides form when dissolved in water?
an alkaline solution
35
what do non-metal oxides form when dissolved in water?
an acidic solution.
36
how can you determine whether an unknown element is a metal or a non-metal?
1. combust it in oxygen 2. dissolve the oxide formed 3. check the pH of the solution with an indicator
37
what is the definition of an acid?
a H+ donor
38
what is the definition of a base?
a H+ acceptor - insoluble
39
what is the definition of an alkali?
an OH- donor - a soluble base
40
what do acids or alkalis describe?
a substance in terms of ions when mixed with water
41
what does acidic or alkaline describe?
a solution in terms of pH
42
what happens when acids dissolve in water?
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
what happens when alkalis dissolve in water?
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
what happens when bases dissolve in water?
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
what is the formulae for the following acids: - hydrochloric acid - nitric acid - sulphuric acid - phosphoric acid - carbonic acid
- HCl - HNO3 - ion formula: NO3 - - H2SO4 - ion formula: SO4 2- - H3PO4- ion formula: PO4 3- - H2CO3- ion formula: CO3 2-
46
what is the formulae for the following alkalis: - sodium hydroxide - potassium hydroxide - ammonium hydroxide - all soluble metal hydroxides
- NaOH -KOH -NH4OH - ion formula: NH4 + - ion formula: OH -
47
what is the formula for ammonia?
NH3
48
what can be an alkali?
all soluble metal hydroxides
49
what can be a base?
all metal oxides, all metal hydroxides
50
what is formed when a base reacts with an acid and what is it called?
acid + base -> salt + water neutralisation
51
what happens in an acid and base reaction if the salt is soluble?
it dissolves the water to form a salt solution
52
what are the soluble salts (alkalis)?
- 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
how can you tell if you use the titration method to make a salt?
if it is a soluble salt and if it can be made from an alkali (sodium, potassium or ammonium).
54
how can you tell if you use the insoluble base method to make a salt?
if it is a soluble salt and if it cannot be made from an alkali (sodium, potassium or ammonium)
55
how can you tell if you use the precipitation method to make a salt?
if it isn't a soluble salt.
56
describe the method of titration.
- 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
describe the insoluble base method.
- 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
describe the precipitation method.
- add a soluble salt of the cation (...nitrate) to the soluble salt of the anion (sodium....). - filter to collect salt
59
what do carbonates and metals reacting together form?
salt + water + carbon dioxide
60
describe an acid + carbonate reaction.
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
what is the chemical test for carbon dioxide?
limewater turning cloudy, this is because the CO2 reacts with the limewater to make an insoluble white solid.
62
what is the pH range for something strongly acidic?
0-3
63
what is the pH range for something weakly acidic?
4-6
64
what is the pH range for something weakly alkaline?
8-10
65
what is the pH range for something strongly alkaline?
11-14

IGCSE Chemistry (18 decks)

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