Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry > 8 — acids and bases > Flashcards

8 — acids and bases Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

Acid

A

An acid is a substance that dissociates/ionises in water to produce Hydrogen ions, H+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why acids cannot be dissolved in organic solvents but can dissolve in water

A

When acid molecules r dissolved in organic solvents, there is no dissociation to give H+ ions.
Acid molecules dissociates/ionises in water to produce H+ ions. Properties of acid r due to the present of H+ ions in acid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Properties of acid

A

Sour taste
Produces ions when dissolved in water hence able to conduct electricity due to the presence of mobile ions
Turns blue litmus paper red

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Acid reactions

A

acid + reactive metal/carbonates/bases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Acid w reactive metals

A

Acid + reactive metals -> salt + H2 (g)

Effervescence observed, metal dissolves.
Confirmation test:
1. Use a lighted splint
2. In the presence of H2 gas, lighted splint will extinguish w a ‘pop’ sound

Unreactive metals:
Lead
Copper
Silver
Gold

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Lead reaction w acid

A

Lead appears to react w HCl and H2SO4 but reaction stops halfway because the initial reaction betw lead and acid produces an insoluble layer of lead (II) chloride/sulfate which prevents further reaction from taking place.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Acid reaction w bases

A

Acid + metal oxide ->. Salt + water
Acid + metal hydroxide -> salt + water

Solid base dissolves, resulting mixture feels warm to touch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Acid reaction w carbonates

A

Acid + metal carbonate -> salt + CO2 (g) + H2O

Effervescence observed and metal carbonate dissolves.
Confirmation test:
1. Bubble gas into limewater (Ca(OH)2)
2. In the presence of CO2 (g), white precipitate (CaCO3) forms in limewater

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Neutralisation reactions

A

Water is the only product apart from the formation of a salt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Strength of an acid

A

Strength of an acid refers to the extent of dissociation/ionisation of the acid when dissolved in water

Comparing HCl and CH3COOH of the same concentration, the no. Of H+ ions in each dm^3 of solution/concentration of H+ ions is higher in HCl than that in CH3COOH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Strong and weak acids

A

A strong acid is an acid that completely dissociates/ionises in water t give a high concentration of hydrogen (H+) ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Weak acid

A

A weak acid is an acid that partially dissociates/ionises in water to give a low concentration of hydrogen (H+) ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Concentration

A

Concentration refers to the amount of solute dissolved in 1 dm^3 of water or solvent

strength of an acid is not affected by its concentration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Basicity of acids

A

Basicity of acids refer to the no. Of hydrogen ions that can be produced by the ionisation of one molecule of the acid when dissolved in water

— monobasic
— dibasic
— tribasic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Base

A

A base is any metal oxide or metal hydroxide. They contain either the oxide (O^2-)ion or the hydroxide (OH^-) ion.

Acid + bases -> salt and water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Alkali

A

An alkali is a soluble base that ionises/dissociates in water to produce hydroxide (OH^-) ions

17
Q

Strong and weak alkalis

A

A strong/weak alkali is an alkali that completely/partially ionises or dissociates in water to give a high/low concentration of hydroxide (OH-) ions

18
Q

Properties of alkalis

A

Bitter taste
Feels slippery and soapy
Produces ions when dissolved in water hence alkalis r able to conduct electricity
Turns red litmus paper blue

19
Q

Alkali reaction w acids

A

Acid + alkali -> salt + water

20
Q

Alkali reaction w ammonium salts

A

Alkali + ammonium salt -> salt + ammonia gas + water

Effervescence observed and pungent gas produced
Confirmation test:
1. Use a piece of moist/damp red litmus paper
2. In presence of ammonia gas, moist/damp red litmus paper turns blue

21
Q

Universal indicator

A

Universal indicator changes colour from green to _)

Strong acid: red
Weak acid: orange/yellow
Neutral: green
Weak alkali: blue
Strong alkali: purple/violet

22
Q

An ammonium chloride fertiliser was added to provide nutrients to the soil. Explain why the farmer should not add slaked lime to the soil after adding the fertiliser.

A

Calcium hydroxide in slaked lime will react w ammonium chloride to form ammonia gas, which results in the loss of nitrogen, an important nutrient for plants. The fertiliser thus will not provide nutrients to the soil.

23
Q

Controlling pH of soil

A

Plants need nitrogen, potassium and phosphorus as essential nutrients to grow.
Most plants grow best when the soil is neutral or slightly acidic.

PH of the soil may become unsuitable for plant growth due to too much fertiliser added, env pollution such as acid rain

Soil too acidic -> slaked lime
Too much slaked lime -> soil too alkaline

24
Q

Classification of oxides

A

-> basic oxides
- most metal oxides
- insoluble in water, only a few oxides eg NO and KO dissolve readily in water to form alkalis

-> amphoteric oxides
- metallic oxides that react w both acids and bases to form salt and water
- ZAP:
ZnO, Al2O3, PbO

-> acidic oxides
- non-metal oxides
- React w alkalis to form salt n water

-> neutral oxides
- insoluble in water
- show neither acidic nor basic properties
- non-metal
- CO NO H2O

25
Q

Why rate of reaction between CH3COOH and X is slower than rate of reaction between HCl and X.

A

Ethanoic acid is a weak acid that dissociates partially in after to give a low concentration of H+ ions but HCl is a strong acid which dissociates completely in water to give a high concentration of H+ ions. Lesser reactant particles per unit volume reduces the frequency of effective collisions, causing slower rate of reaction.

26
Q

Why CO2 gas and concentrated NaOH has to be removed.

A

CO2 gas is a greenhouse gas which causes global warming.
Concentrated NaOH increases soil pH to above 7 such that it is too alkaline for plant growth, causing harm to the ecosystem.

27
Q

Explain why B turns universal indicator solution orange.

A

B is a carboxylic acid which is a weak acid that dissociates partially in water to give a low concentration of H+ ions. [1]

28
Q

Explain what can be deduced about this acid: oxalic acid.
1. Aqueous oxalic acid as a pH 4.
2. One mole of oxalic acid reacts with 2 moles of aqueous NaOH

A
  1. Oxalis acid is a weak acid
  2. Oxalis acid is a dibasic acid which produces 2 moles of hydrogen ions when dissociated in water
29
Q

Fizzing is observed. Explain why.

A

Effervescence is observed due to the formation of HYDROGEN GAS

30
Q

Explain each of the observations

A

Metal oxide reacts with water to give hydroxide ions when hydroxide dissociates in water, thus turning red litmus indicator solution blue
Solution turns colourless due to formation of hydrogen peroxide which bleaches the red litmus solution. O2 gas is produced, effervescence occurs thus bubbles are observed.

31
Q

Which acids fit the general formula H.A. and which do not, explain [2]

A

HCl and CH3COOH fits the general formula while H2SO4 does not.
HCl and ethanoic acid are monobasic acids where one mole of acid dissociates in water to produce 1 mole of H+ ions and H+ ions and Cl- or CH3COO- ions are in 1:1 ratio. [1]
H2SO4 is a dibasic acid where one mole of acid dissociates in after to produce 2 moles of H+ ions and the ratio of H+ to SO4^2- ions are in 2:1, which does not follow the general formula.

32
Q

State and explain the factors that affect the pH of an acid [3]

A

The concentration of H+ ions affect the pH value of the acid, which depends on the concentration, basicity and strength of the acid.

Comparing hydrochloric acid and ethanoic acid with concentration of 0.01 mol/dm’, the pH of hydrochloric acid is lower at 2.0 than ethanoic acid at 3.4 as hydrochloric acid is a strong acid that dissociates completely in water to give a higher concentration of H+ ions (0.01 mol/dm3) than ethanoic acid which is a weak acid (0.0004 mol/dm3) [1].

Comparing hydrochloric acid and sulfuric acid, despite the same concentration of 0.01 mol/dm sulfuric acid which is a dibasic acid has twice the concentration of H* ions (0.02 mol/dm”) than hydrochloric acid and hence has a lower pH value of 1.7 [1].

Comparing concentration of hydrochloric acid where it increases from 0.01 mol/dm’ to 0.20
mol/dm, the pH of the acid is lowered from 2.0 to 0.7 [1]

33
Q

Explain why dilute nitric acid can be used to remove compounds of lead but not dilute hydrochloric or sulfuric acid. [2]

A

Lead (II)nitrate is soluble in the water is formed whenPb reacts with dilute nitric acid.
Insoluble lead(II) chloride and lead(II) sulfate is formed when lead reacts with HCl and H2SO4, that coats lead, preventing further reaction of lead with the acids.

34
Q

Give a reason why hypochlorite bleaches can cause people to have adverse reactions but hydrogen peroxide bleaches are less likely to do so. [1]

A

Hypochlorite bleaches reacts with ammonia in human waste, nitrogen compounds containing chlorine are formed which is irritating and toxic to people.
When H2O2 is used, it oxidises and breaks down compounds and produces water which is not harmful to people.

Chemistry (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions