unit 9 Flashcards
(116 cards)
1
Q
what acid is in soft drinks
A
carbonic acid
2
Q
what acid is in vinegar?
A
ethanoic acid
3
Q
what acid is in milk and yoghurt?
A
lactic acid
4
Q
what acid is in tea?
A
tannic acid
5
Q
what acid is in spinach
A
oxalic acid
6
Q
what acid is in lemon, orange, etc?
A
citric acid
7
Q
3 things that contain acid found in daily life
A
- personal care products (eg body lotions, hair conditioner)
- household cleaners (eg toilet cleaner)
- some drugs (eg aspirin)
8
Q
3 kinds of strong acids
A
- hydrochloric acid
- nitric acid
- sulphuric acid
9
Q
where is concentrated nitric acid commonly stored in?
A
brown reagent bottle
10
Q
why is nitric acid commonly stored in brown reagent bottle?
A
the chemical is easily decomposed by light
11
Q
4 properties of acids
A
- have a sour taste
- can conduct electricity
- react with alkalis
- react with many materials including metals
12
Q
3 uses of acids
A
- as preservatives
- removing stains (cleaning agents)
- making industrial chemicals
13
Q
why can food be preserved by soaking them in acids?
A
food may go bad due to microorganisms, which cannot grow or reproduce in acidic conditions. some acids may kill them
14
Q
what kind of acid is found in toilet cleaners?
A
hydrochloric acid
15
Q
which industrial chemical products can sulphuric acid be used to make?
A
fertilisers, dyes, paints
16
Q
7 daily household products that contain alkali
A
- glass cleaners
- kitchen cleaners
- drain cleaners
- baking soda
- toothpaste
- soaps
- alkaline batteries
17
Q
3 kinds of alkalis in school laboratories
A
- sodium hydroxide
- ammonia solution
- calcium hydroxide (limewater)
18
Q
4 properties of alkalis
A
- have a bitter taste
- have a slippery feel
- can conduct electricity
- react with acids
19
Q
2 uses of alkalis
A
- removing grease
- making industrial chemicals
20
Q
2 types of cleaners that ammonia is commonly found in
A
kitchen cleaners and glass cleaners
21
Q
why is sodium hydroxide commonly found in drain cleaners?
A
a large amount of heat is released when it is dissolved in water. the hot alkaline solution can remove substances like grease or hair in the drain.
22
Q
how is alkali used in making industrial chemicals
A
potassium hydroxide is used in making batteries
23
Q
use of acid in food processing except as preservatives?
A
acids can speed up the fermentation process of milk to produce cheese
24
Q
use of alkali in food processing
A
alkalis can be used in making century eggs (preserved eggs)
25
what should we pour acidic or alkaline waste into?
chemical waste bottle
26
what should we do if an accident involving acids or alkalis occurs
wash the affected area under slow running water for at least 10 minutes
27
what should we do if we get acid or alkali in our eyes
wash it with the eye wash bottle for at least 10 minutes
28
what do we use to make red cabbage leaves as natural indicators
mortar and pestle
29
how does the colour of the red cabbage extract change in acids
purple -> red
30
How does the colour of the red cabbage extract change in alkalis
purple -> green
31
why can red cabbage be used as a natural indicator?
it contains pigments which change colour in the presence of an acid or an alkali
32
where is litmus extracted from
lichen
33
how is litmus paper prepared?
by soaking strips of filter paper in litmus solution and drying them before use
34
which kind of litmus do we use to test acidic solutions?
blue litmus
35
how does blue litmus change in acidic solutions?
blue to red
36
which kind of litmus do we use to test alkaline solutions?
red litmus
37
how does red litmus change in alkaline solutions
red to blue
38
how would a neutral solution affect the litmus
the blue or red litmus will not change colour
39
what is the range of the pH scale?
0-14
40
what pH value would an acidic solution have?
less than 7
41
what pH value would an alkaline solution have?
greater than 7
42
what pH value would a neutral solution have?
7
43
what is the pH value of sulphuric acid
1
44
what is the pH value of cola?
2
45
what is the pH value of orange juice?
3
46
what is the pH value of black coffee?
5
47
what is the pH value of distilled water?
7
48
what is the pH value of detergent
9
49
what is the pH value of glass cleaner
11
50
what is the pH value of limewater?
12
51
what is the pH value of drain cleaner
14
52
which 2 methods can we use to measure pH value more accurately?
1. pH meter
2. pH sensor connected with a data logger
53
3 advantages of using a pH meter or pH sensor connected with a data logger?
1. can measure the pH value of a substance more accurately
2. can be reused
3. can be used to measure the pH value of a liquid with a dark colour
54
3 disadvantages of using a pH meter or a pH sensor conncected with a data logger?
1. more expensive
2. larger -> less convenient to carry around
3. has to be calibrated (rinse with distilled water) before use and it need to be cleaned after use
55
what is neutralization
acids and alkalis react with each other when they are mixed together
56
what is an end point in neutralization?
where the alkali/acid completely neutralises the acid/alkali
57
how to find the end point in neutralisation?
(pH value of the acid + pH value of the alkali) / 2
58
what is the use of a burette?
to drop a small amount of liquid continuously
59
what is an advantage of using a pH sensor connected with a data logger in neutralisation?
it can help monitor the change in pH value of the solution during the experiment. the results are more accurate and the pH curve is plotted automatically
60
what are reactants?
substances which take part in a chemical reaction
61
what are products?
substances formed as a result of the chemical reaction
62
what are the products in neutralization?
salt and water, and heat is released
63
which 2 substances react to form sodium chloride
hydrochloric acid + sodium hydroxide
64
what is sodium chloride
tablesalt to add flavour to food
65
which 2 substances react to form potassium nitrate
nitric acid + potassium hydroxide
66
what is the use of potassium nitrate?
to make fertilizers
67
which 2 substances react to form calcium sulphate?
sulphuric acid + calcium hydroxide
68
what is the use of calcium sulphate?
to make tofu
69
word equation of neutralization?
acid + alkali -> salt + water
70
5 applications of neutralization
1. prevention of tooth decay
2. relieving stomach upset
3. treatment of insect stings and bites
4. treatment of industrial waste containing acids or alkalis
5. regulation of pH value of soil
71
why are there acids in our mouth after eating
there are a lot of bacteria in our mouths which convert sugar in the food residue into acids
72
how is neutralisation used in brushing teeth?
toothpaste is slightly alkaline which can neutralise the acids in our mouths
73
how is neutralisation used in chewing sugar-free gum
chewing sugar-free gum can help stimulate the production of saliva in our mouths, which is slightly alkaline so it can neutralise the acids in the mouth
74
what acid is produced by our stomachs to digest food?
hydrochloric acid
75
how is neutralisation applied in relieving stomach upset?
antacids contain alkalis which can neutralise the excess acids in stomachs, so it can be used to relieve stomach upset
76
how is neutralisation applied in the treatment of insect stings and bites
stings or bites of some insects contain acidic or alkaline substances that cause the affected area to be itchy or painful. we can apply acidic or alkaline substances to the affected area to treat insect stings or bites
77
what could industrial waste that contain acids or alkalis cause if they are discharged without proper treatment
water pollution
78
what alkali is used to neutralise acidic wastes
calcium hydroxide
79
what acid is used to neutralise alkaline wastes
sulphuric acids
80
why do farmers need to neutralise the soil
because many plants do not grow well in soil which is too acidic or too alkaline
81
what would farmers add to the soil if it is too acidic
slaked lime which is calcium hydroxide as it is an alkali
82
what would farmers add to the soil if it is too alkaline
sulphur
83
what will happen to sulphur if it is in the soil
natural soil bacteria can convert sulphur into sulphuric acid
84
why shouldn't we store an acidic drink in a metal flask?
it may corrode the metal
85
what are produced when an acid react with a metal?
a salt and hydrogen
86
what do we use to test for hydrogen?
a burning splint
87
what will happen to hydrogen when a burning splint is placed over a test tube containing hydrogen
the hydrogen will burn with a 'pop' sound
88
the reactivity of metals in decreasing order
potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, copper, mercury, silver, gold, platinum
89
which metals do not react with acids
copper, mercury, silver, gold, platinum
90
word equation for reactions between acids and metals
acid + metal -> salt + hydrogen
91
5 substances that contain calcium carbonate
1. marble
2. limestone
3. pearls
4. seashells
5. eggshells
92
why should we avoid using acidic cleaners to clean marble surfaces
acids will corrode the material
93
what are produced during the reaction between acids and calcium carbonate
salt, carbon dioxide, and water
94
word equations for reactions between acids and calcium carbonate
acid + calcium carbonate -> salt + carbon dioxide + water
95
what is the pH value of natural rainwater
5.6
96
what is the pH value of acid rain
less than 5.6
97
which 2 air pollutants will the burning of fossil fuels release?
sulphur dioxide and nitrogen oxides
98
3 places that fossil fuels burn
power stations, factories, vehicles
99
what are sulphur dioxide and nitrogen oxides?
acidic gases
100
what will happen when sulphur dioxide and nitrogen oxides are released into the atmosphere?
they dissolve into water droplets and sulphuric acid and nitric acid are produced respectively
101
what will happen to the acidic droplets in the atmosphere?
they will join to form clouds and fall as acid rain
102
how is sulphur dioxide produced in the burning of fossil fuels
fossil fuels contain sulphur impurities that will react with oxygen when burning, producing sulphur dioxide
103
what are some natural causes of acid rain
erupting volcanoes emit sulphur dioxide
104
3 effects of acid rain on the environment and living things
1. corroding metal objects and building materials
2. damaging plants
3. causing harm to aquatic life
105
how does acid rain damage plants in 3 factors
1. destroys the leaves of plants directly -> die as they cannot carry out photosynthesis
2. dissolves and washes away the nutrients in the soil -> cannot get enough nutrients for growth -> grow slowly or even die
3. increases the acidity of the soil -> many plants cannot grow well in acidic soils
106
how does acid rain cause harm to aquatic life in 2 factors
1. it increases the acidity of the water -> most aquatic life cannot survive
2. dissolves minerals in the soil, washes them out and carries them into rivers and lakes
some minerals are harmful -> slow down the growth and reproduction of aquatic life
107
3 examples of strong alkali
1. sodium hydroxide
2. potassium hydroxide
3. calcium hydroxide
108
1 example of a weak alkali
ammonia solution
109
what can strong acids corrode
metal, skin, flesh
110
are concentrated or diluted strong acid/alkali more corrosive?
concentrated
111
why should we use acidic or alkaline cleaners in well ventilated areas?
the acidic or alkaline vapour can irritate or corrode our respiratory tract, skin, and eyes
112
why shouldn't we mix acidic or alkaline cleaners together?
they may react to produce toxic vapours
113
why do we need to dilute some household cleaners before use?
some of them are in concentrated form which is very dangerous
114
why should we add concentrated the acidic or alkaline cleaners slowly to a large amount of water and not the other way round?
because a lot of heat is released while diluting the acidic or alkaline cleaners. since water is a good absorber of heat, adding the concentrated acid into the water won't cause the liquid to splash out, but the heat is absorbed. if it is the other way around, it will be very dangerous
115
why shouldn't we use a stopper to stop the test tube with an acid reacting with a metal?
hydrogen gas is released which causes great pressure, so the stopper may shoot out
116
what should we use instead of a stopper to cover the test tube with an acid reacting with a metal?
we should cover the test tube loosely with an inverted stopper or cotton wool
