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Year 12 Chemistry > 2. The Acidic Environment > Flashcards

2. The Acidic Environment Flashcards

(74 cards)

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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
What does pH depend on? (4 things)
- concentration - acid/base strength - the number of H+ ions the acid can release - temperature
26
Name four strong acids
Hydrochloric, HBr, nitric acid, sulphuric acid
27
Name two weak acids
Citric (C6H8O7) and acetic (CH3COOH)
28
What is the difference in strong and weak acids in terms of degree of ionisation?
Strong: almost all of the acid molecules ionise in water to hydronium ions Weak: only some of the molecules ionise
29
What is the pH formula?
-log [H+] | [H+] = 10^-pH
30
Weak acids are at ________, which means that they ______
equilibrium | partially ionise in water
31
Strong acids are virtually _____
complete | all acid molecules become ions
32
Why are acids used as food additives?
- they can improve the taste of foods - they can be used as preservatives - they are antimicrobials and antioxidants
33
How is acetic acid used as a food additive?
Vinegar (4%) to preserve food (e.g. pickling) and add flavour
34
How is lactic acid used as a food additive?
production of dairy products such as cheese and yoghurt
35
Phosphoric acid
acidulation of soft drinks manufacture of processed cheese pH control in diet jelly
36
Name 3 naturally occurring acids
- Citric acid - Tartaric acid - Benzoic acid
37
Name 2 naturally occurring bases
- Calcium carbonate | - Calcium magnesium carbonate
38
What is the source and chemical formula of citric acid?
citrus fruits, some vegetables | C6H8O7
39
What is the source and chemical formula of tartaric acid?
grapes, pineapples | C4H6O6
40
What is the source and chemical formula of benzoic acid?
prunes, plums, cranberries | C7H6O2
41
What is the source and chemical formula of calcium carbonate?
limestone, marble | CaCO3
42
What is the source and chemical formula of calcium magnesium carbonate?
dolomite | CaCO3.MgCO3
43
When did Lavoisier write his acid definition and what is it?
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
When did Davy write his acid definition and what is it?
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
What was Arrhenius' acid definition?
- 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
What is the Broasted-Lowry acid/base theory?
1923 - An acid is a proton donor - A base is a proton acceptor
47
Describe the relationship between an acid and is conjugate base, and a base and its conjugate acid
After an acid has given up a proton, it is able to accept one, so it has become a (conjugate) base
48
How do you write a conjugate base of an acid?
1. Remove an H from the acid | 2. Subtract one from charge
49
How do you write a conjugate acid of a base?
1. Add an H to the base | 2. Add one to charge
50
What is the relationship between strengths of conjugates?
A strong acid has a weak conjugate base, and vice versa
51
How will a neutral salt form?
a reaction between a strong acid and strong base
52
How will an acidic salt form?
reaction between a strong acid and a weak base
53
How will a basic salt form?
reaction between strong base and weak acid
54
What is an amphoteric substance?
one that can react with an acid and a base
55
What is an amphiprotic substance?
one that can behave as a proton donor or acceptor
56
What is a common amphiprotic substance?
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
What are the three main types of amphiprotic substances?
Water ions of polyprotic acids some metal hydroxides
58
Neutralisation is always _______
exothermic
59
What is the general naturalisation equation for acid+base
acid + base -> salt + water (+heat)
60
What is the general naturalisation equation for acid + carbonate?
acid + carbonate -> salt + water + carbon dioxide (+heat)
61
What is the net ionic equation for neutralisation reaction?
H+ + OH- -> H2O
62
What are the features of an alkanol?
- 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
What are the features of an alkanoic acid?
- 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
How do you name esters?
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
First few members of alkane/alkenes are ____ because of their _____ caused by ______ forces
Gases low boiling point weak dispersion
66
Alkaniols and carboxylic acid groups are polar and have strong intermolecular forces, therefore
None of them are gases
67
Esterification is
the reaction between an alkanoic acid and an alkanol
68
what is the general equation for esterification?
alkanoic acid + alkanol ester + water
69
What is the catalyst in esterification, and what is its purpose?
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
Why does esterification require reflux?
It cools volatile gases and forces them back into the mixture, therefore preventing the loss of gaseous products
71
Where do esters occur naturally?
flavouring agents in plants or fruits | animal fats and plant oils
72
What are the two methods of ester production?
produced naturally in plants and animals | also produced commercially by heating an alkanoic acid in the presence of an alcohol and acid catalyst.
73
What are some uses of esters?
flavouring and scents in foods solvents and thinners (volatility, easy mixing) plasticisers alternative fuels (esters of natural fatty products used as biofuels)
74
What is a common ester?
octyl ethanoate main ester in oranges 1-octanol + ethanoic acid

Year 12 Chemistry (4 decks)

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