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Year 12 Chemistry > 2. The Acidic Environment > Flashcards

2. The Acidic Environment Flashcards

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1
Q

What is the colour range of Litmus?

A

RED 5

BLUE 7.6

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2
Q

What is the colour range of Phenolphthalein?

A

COLOURLESS 8.3

RED 10

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3
Q

What is the colour range of Methyl Orange?

A

RED 3.1

YELLOW 4.4

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4
Q

What is the colour range of Bromothymol blue?

A

YELLOW 6

BLUE 7.6

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5
Q

Describe the use of indicators to test soil

A
  • Azaleas and pineapples prefer basic soil while violets prefer basic
  • Acidic soil can be neutralised with limestone
  • To test, mix soil with inert solid (BaSO4) before adding indicator
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6
Q

Oxides of metals usually produce _____ oxides (include equation)

A

basic

MgO + H2O -> Mg(OH)2

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7
Q

Basic oxides react with acids to form ____

A

Salts

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8
Q

Oxides of non-metals form _____ oxides (include equation)

A

acidic
Acidic oxide + water -> Acid
CO2 + H2O -> H2CO3 (carbonic acid)

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9
Q

What is the trend in the periodic table for basic to acidic oxides?

A

Left to right
Metal to non-metal
Basic oxides to acidic oxides

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10
Q

Define Le Chatilier’s principle

A

If a system is in equilibrium, and is disturbed or changed in any way, then the system will adjust itself to minimise the amount of change

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11
Q

What are the main features of a system at equilibrium?

A
  • closed system (no energy enters or leaves)
  • macroscopic properties don’t change
  • reactant and product concentrations remain the same
  • rate of forward reaction equals rate of backwards reaction
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12
Q

If ∆H is negative, the forward reaction is ______

A

exothermic

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13
Q

How does temperature affect a system at equilibrium?

A

If the temperature increases, the equilibrium shifts towards the side that absorbs heat - the endothermic side

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14
Q

The reaction between CO2 and water is _____thermic, therefore with temperature increase, CO2 solubility ____

A

endothermic

decreases

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15
Q

The solubility of CO2 in water is dependent on _____ and _____

A

pressure

temperature

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16
Q

What are natural sources of sulfur dioxide?

A

Volcanic gases

bushfire smoke

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17
Q

What are industrial sources of sulfur dioxide?

A

burning fossil fuels

smeltering and refining sulfide ores

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18
Q

What are natural sources of nitrogen oxides?

A

lightning

action of certain bacteria in nitrogenous materials

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19
Q

What are some industrial sources of nitrogen oxides?

A

nitrogenous fertiliser

combustion in power stations and automobiles

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20
Q

What is the report showing atmospheric concentration of acidic oxides? what are two main statistics?

A

Environmental protection agency NSW, 2003 report

  • Peak 1-hour measurements of SO2 in Sydney are now less than 25% of the standard
  • the standard is 0.2ppm
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21
Q

Why is rainwater acidic?

A

Because water reacts with acidic oxides in the atmosphere

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22
Q

What are some effects of acid rain?

A
  • Plant growth - stunts growth, defoliation
  • Attacks metallic structures
  • Erosion of marble
  • Formerly insoluble materials can be dissolved by acid and release toxic metal ions into soil e.g. aluminium
  • Some animals are sensitive to changes
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23
Q

Describe the ionisation of acids in water

A
  • An acid in a solution produces hydrogen ions, which exist in a molecule with water in the form of H3O+
  • Ionisation is an EXOTHERMIC process
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24
Q

What is the systematic name and molecular formula for citric acid?

A

2-hydroxypropane-1,2,3tricarboxylic acid

C6H8O7

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25
Q

What does pH depend on? (4 things)

A
  • concentration
  • acid/base strength
  • the number of H+ ions the acid can release
  • temperature
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26
Q

Name four strong acids

A

Hydrochloric, HBr, nitric acid, sulphuric acid

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27
Q

Name two weak acids

A

Citric (C6H8O7) and acetic (CH3COOH)

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28
Q

What is the difference in strong and weak acids in terms of degree of ionisation?

A

Strong: almost all of the acid molecules ionise in water to hydronium ions
Weak: only some of the molecules ionise

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29
Q

What is the pH formula?

A

-log [H+]

[H+] = 10^-pH

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30
Q

Weak acids are at ________, which means that they ______

A

equilibrium

partially ionise in water

31
Q

Strong acids are virtually _____

A

complete

all acid molecules become ions

32
Q

Why are acids used as food additives?

A
  • they can improve the taste of foods
  • they can be used as preservatives
  • they are antimicrobials and antioxidants
33
Q

How is acetic acid used as a food additive?

A

Vinegar (4%) to preserve food (e.g. pickling) and add flavour

34
Q

How is lactic acid used as a food additive?

A

production of dairy products such as cheese and yoghurt

35
Q

Phosphoric acid

A

acidulation of soft drinks
manufacture of processed cheese
pH control in diet jelly

36
Q

Name 3 naturally occurring acids

A
  • Citric acid
  • Tartaric acid
  • Benzoic acid
37
Q

Name 2 naturally occurring bases

A
  • Calcium carbonate

- Calcium magnesium carbonate

38
Q

What is the source and chemical formula of citric acid?

A

citrus fruits, some vegetables

C6H8O7

39
Q

What is the source and chemical formula of tartaric acid?

A

grapes, pineapples

C4H6O6

40
Q

What is the source and chemical formula of benzoic acid?

A

prunes, plums, cranberries

C7H6O2

41
Q

What is the source and chemical formula of calcium carbonate?

A

limestone, marble

CaCO3

42
Q

What is the source and chemical formula of calcium magnesium carbonate?

A

dolomite

CaCO3.MgCO3

43
Q

When did Lavoisier write his acid definition and what is it?

A

1780
Believed that all acids contained oxygen, and that it was the oxygen that causes acidity
FAULT: many compounds containing oxygen are basic, and some acids don’t contain oxygen

44
Q

When did Davy write his acid definition and what is it?

A

1815
Acids are substances containing hydrogen. This hydrogen was shown to be replaceable, where metals could displace hydrogen to form salts
FAULT: there are many compounds containing hydrogen that are not acids, and this didn’t take into account acid strengths

45
Q

What was Arrhenius’ acid definition?

A
  • Acids are neutral and ionise in water to form H+
  • Bases ionise to form OH-
  • He acknowledged different acid strengths based on degree of ionisation
  • he explained neutralisation as the reaction between H+ and OH- of an acid and a base
    FAULTS
  • only applied to aqueous solutions
  • did not explain different strengths in different solvents
  • cannot explain amphoteric or amphiprotic acids
46
Q

What is the Broasted-Lowry acid/base theory?

A

1923

  • An acid is a proton donor
  • A base is a proton acceptor
47
Q

Describe the relationship between an acid and is conjugate base, and a base and its conjugate acid

A

After an acid has given up a proton, it is able to accept one, so it has become a (conjugate) base

48
Q

How do you write a conjugate base of an acid?

A
  1. Remove an H from the acid

2. Subtract one from charge

49
Q

How do you write a conjugate acid of a base?

A
  1. Add an H to the base

2. Add one to charge

50
Q

What is the relationship between strengths of conjugates?

A

A strong acid has a weak conjugate base, and vice versa

51
Q

How will a neutral salt form?

A

a reaction between a strong acid and strong base

52
Q

How will an acidic salt form?

A

reaction between a strong acid and a weak base

53
Q

How will a basic salt form?

A

reaction between strong base and weak acid

54
Q

What is an amphoteric substance?

A

one that can react with an acid and a base

55
Q

What is an amphiprotic substance?

A

one that can behave as a proton donor or acceptor

56
Q

What is a common amphiprotic substance?

A

Hydrogen carbonate ion
- in the presence of an acidic solution it acts as a base
HCO3- + H3O+ -> H2CO3 +H2O
- in the presence of a basic solution it acts as an acid
HCO3- + OH- -> CO3- + H2O

57
Q

What are the three main types of amphiprotic substances?

A

Water
ions of polyprotic acids
some metal hydroxides

58
Q

Neutralisation is always _______

A

exothermic

59
Q

What is the general naturalisation equation for acid+base

A

acid + base -> salt + water (+heat)

60
Q

What is the general naturalisation equation for acid + carbonate?

A

acid + carbonate -> salt + water + carbon dioxide (+heat)

61
Q

What is the net ionic equation for neutralisation reaction?

A

H+ + OH- -> H2O

62
Q

What are the features of an alkanol?

A
  • polar OH group making the molecules polar
  • soluble in water, decreasing with increasing chain length
  • higher melting and boiling point that corresponding alkanes/alkenes
63
Q

What are the features of an alkanoic acid?

A
  • polar due to COOH- groups
  • strong hydrogen bonds with nearby alkanolic acids -> water soluble
  • they are weak kids as they partially dissociate in water
    RCOOH (aq) RCOO- + H+
64
Q

How do you name esters?

A

Named in two parts

  • first comes from the alkanol e.g. ethyl comes from ethanol
  • the second part comes from the acid e.g. butanoate comes from butanoic acid
65
Q

First few members of alkane/alkenes are ____ because of their _____ caused by ______ forces

A

Gases
low boiling point
weak dispersion

66
Q

Alkaniols and carboxylic acid groups are polar and have strong intermolecular forces, therefore

A

None of them are gases

67
Q

Esterification is

A

the reaction between an alkanoic acid and an alkanol

68
Q

what is the general equation for esterification?

A

alkanoic acid + alkanol ester + water

69
Q

What is the catalyst in esterification, and what is its purpose?

A

The catalyst is an acid, as it absorbs the water produced, therefore shifting the equilibrium to the side of the forward reaction to replace the water

70
Q

Why does esterification require reflux?

A

It cools volatile gases and forces them back into the mixture, therefore preventing the loss of gaseous products

71
Q

Where do esters occur naturally?

A

flavouring agents in plants or fruits

animal fats and plant oils

72
Q

What are the two methods of ester production?

A

produced naturally in plants and animals

also produced commercially by heating an alkanoic acid in the presence of an alcohol and acid catalyst.

73
Q

What are some uses of esters?

A

flavouring and scents in foods
solvents and thinners (volatility, easy mixing)
plasticisers
alternative fuels (esters of natural fatty products used as biofuels)

74
Q

What is a common ester?

A

octyl ethanoate
main ester in oranges
1-octanol + ethanoic acid

Year 12 Chemistry (4 decks)

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