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DGS S2 Science > Acids And Alkalis > Flashcards

Acids And Alkalis Flashcards

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1
Q

What do lemons contain that give them their sour taste?

A

Acids

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2
Q

List 8 foods that contain acids.

A

Soft drinks, tea, yoghurt, grapes, vinegar, spinach, apples, citrus fruits

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3
Q

List 4 personal care products that contain acids.

A

Toilet cleaner, body lotion, aspirin, hair conditioner

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4
Q

List the names of the acids soft drinks, vinegar, yoghurt, tea, and spinach contain respectively.

A 
Soft drinks: carbonic acid
Vinegar: Ethanoic acid
Yoghurt: lactic acid
Tea: tannic acid
Spinach: oxalic acid
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5
Q

List 3 types of acids found in school labs.

A

Hydrochloric acid, sulphuric acid, nitric acid

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6
Q

What are the properties of acids?

A

They have a sour taste, can conduct electricity, and they react with alkalis and other materials.

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7
Q

What are the uses of acids in daily life? List one example for each usage.

A

Used as preservatives: vinegar with ethanoic acid
Used to remove stains: toilet cleaners with hydrochloric acid to remove stains
Used for making industrial chemicals: sulphuric acid is used to make fertilisers, dyes, and paints.

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8
Q

What does soap contain to give it a slippery feel?

A

Alkalis

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9
Q

List 7 daily household products that contain alkalis.

A

Soaps, toothpastes, glass cleaners, kitchen cleaners, drain cleaners, baking soda, alkaline batteries

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10
Q

List 3 kinds of alkalis found in school labs.

A

Sodium hydroxide, ammonia solution, calcium hydroxide (limewater)

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11
Q

What are the properties of alkalis?

A

Alkalis have a bitter taste and a slippery feel. They can conduct electricity and react with acids.

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12
Q

What are the daily uses of alkalis? List one example for each usage.

A

Used for removing grease: kitchen cleaners that contain ammonia and drain cleaners that contain sodium hydroxide
Used for making industrial chemicals: potassium hydroxide is used in making batteries

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13
Q

What are the ways we can distinguish acids, alkalis, and neutral solutions?

A

By using natrual indicators, litmus paper, universal indicator (pH paper and universal indicator solution), pH meter, and pH sensor with data-logger.

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14
Q

Explain how natrual indicators can distinguish if a solution is acidic, alkaline, or neutral.

A

Natrual indicators have pigments that change colour in the presence of acids and alkalis. thr change to different colours when exposed to acids and alkalis.

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15
Q

List all types of litmus that can be used to test for acidic or alkaline solutions.

A

Red litmus paper, red litmus solution, blue litmus paper, blue litmus solution

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16
Q

Which litmus are used to test for acids and alkalis and how?

A

Acid: blue litmus paper/solution, turn red when in contact with acids
Alkalis: red litmus paper/solution, turn blue when in contact with alkalis

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17
Q

What is the primary material of litmus paper/solution?

A

Lichen

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18
Q

If a solution does not make red litmus change colour, what may it be? Should we carry on to determine whether it is an acid, alkaline, or a neutral solution? How?

A

The solution may be an acid or a neutral solution. We have to carry out the blue litmus test to see if the blue litmus changes colour to red. If it does, then it is an acidic solution; if it does not, then it is a neutral solution.

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19
Q

What is the range of pH values?

A

0-14

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20
Q

What are the possible pH values for acidic, alkaline, and neutral solutions respectively?

A

Acidic: 0-7
Neutral: 7
Alkaline: 7-14

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21
Q

What are the approximate colours of the pH paper in the presence of acids, alkalis, and neutral solutions respectively?

A 
pH 0-2 (acids): red to pink
pH 3-6 (acids): orange to yellow
pH 7 (neutral): light green
pH 8-11 (alkalis): green to dark green
pH 12-14 (alkalis): dark blue to dark purple
22
Q

Is tap water a neutral substance?

A

No, it is slightly acidic (pH~6.93)

23
Q

What type of substance is shampoo?

A

Alkaline substance

24
Q

What are the parts of a pH meter?

A

There is a probe connected to a digital display. Once the probe is immersed into the substance, the pH value of the substance will be shown on the display.

25
Q

Usually, what is the accuracy of a pH meter?

A

It is accurate to two decimal places.

26
Q

What are pH sensors usually used for?

A

A pH sensor is connected with a data-logger and the data recorded can be analysed and recorded in a computer. Therefore, it is often used to monitor the change of pH values.

27
Q

List three advantages of using pH meters to measure the acidity or alkalinity of a substance.

A
  1. More accurate result (rounded to 2 decimal places)
  2. Can be reused unlike natural indicators/pH paper/litmus
  3. Can be used to measure the pH value of substances with deep colour
28
Q

List two disadvantages of using pH meters to measure the pH values of substances.

A
  1. More expensive than pH paper

2. Relatively larger in size, more inconvenient to carry around

29
Q

What happens to the pH value of an acid after an alkalis is added to it?

A

It increases.

30
Q

What is the general form of the equation of neutralisation?

A

Acid+alkalis—>salt+water

31
Q

When nitric acid is added into sodium hydroxide, what is the name of the salt created?

A

Sodium nitrate

32
Q

When hydrochloric acid is added into calcium hydroxide, what is the name of the salt produced?

A

Calcium chloride

33
Q

List 6 uses of neutralisation in daily life.

A
  1. Untangle hair: Hair conditioner (acid) neutralises shampoo (alkaline)
    2a. Prevent tooth decay: Toothpaste (alkaline) neutralises the acids in the moith created by bacteria
    2b. Gum simulates saliva (alkaline) and saliva neutralises the acids in the moith created by bacteria
  2. Relieve stomach upset: Antacids neutralise excess acids in stomach
    4a. Treat insect stings/bites: Soap (alkaline) neutralises stings by ants, bees, and mosquitoes (acidic)
    4b. Vinegar (acidic) neutralises stings by wasps (alkaline)
  3. Treating industrial waste: waste from factories commonly of electroplating, dyeing, and electronic/chemical products are neutralised before being discharged
    6a. Regulating pH value of soil: slaked lime (calcium hydroxide) is added to too acidic soil
    6b. Sulphur is added to too alkaline soil to let natrual bacteria convert it into sulphuric acid
34
Q

What happens to some metals when acids are added to them?

A

They will be corroded.

35
Q

What is the general form of the equation when acids react with metals?

A

Acid+metal—>salt+hydrogen

36
Q

What is the test for hydrogen?

A

Burning splint test. If a burning splint is exposed to hydrogen, it burns with a ‘pop’ sound.

37
Q

What is the general form of the equation when acids react with calcium carbonate?

A

Acid+calcium carbonate—> salt+carbon dioxide+water

38
Q

What is the word equation of the reaction between zinc and sulphuric acid?

A

Zinc+sulphuric acid—>zinc sulphate+hydrogen

39
Q

List 5 substances that contain calcium carbonate.

A

Marble, limestone, eggshells, seashells, and pearls

40
Q

What are the gases that cause acid rain and how?

A

Sulphur dioxide and nitrogen oxides, they dissolve in water droplets and create sulphuric acid and nitric acid. The water droplets containing acids are then joined to form clouds and fall as acid rain.

41
Q

What is the main cause of acid rain?

A

Human activity (burning fossil fuels)

42
Q

Why does burning fossil fuels release sulphur dioxide?

A

Fossil fuels contain sulphur impurities. When burnt, the impurities react with oxygen and form sulphur dioxide.

43
Q

What are the effects of acid rain on the environment and living things?

A
  1. Buildings will be corroded: acid rain corrodes iron bridges/fences and statues/buildings made of metals or marble.
  2. Plants may be damaged: acid rain may destroy the leaves of the trees, making them unable to carry out photsynthesis and die. It also washes away the nutrients in the soil and make the soil more acidic, which results in less plants being able to grow well.
  3. Damage to aquatic life: the acidity of water will be increased by acid rain, which results in less aquatic life being able to survive/reprpduce normally. Some harmful minerals from the soil may also be washed into the lakes/rivers, slowing down the growth and reproduction of aquatic life.
44
Q

What are the four classes of acids and alkalis and how corrosive are they?

A

Strong acid, weak acid, strong alkali, weak alkali

Strong acids are more corrosive than weak acids, and strong alkalis are more corrosive than weak alkalis.

45
Q

List 3 examples for both strong acids and weak acids.

A

Strong acids: hydrochloric acid, nitric acid, sulphuric acid

Weak acids: citric acid, carbonic acid, ethanoic acid

46
Q

List 2 examples of strong alkalis and 1 exampls of weak alkalis.

A

Strong alkalis: potassium hydroxide, sodium hydroxide

Weak alkali: ammonia solution

47
Q

What can strong acids corrode? Are they stronger in concentrated or diluted form?

A

Metal, skin, and flesh

They are more corrosive in concentrated form.

48
Q

What is the proper procedure for diluting concentrated acids/alkalis?

A
  1. Dilute the acid/alkali in a well ventilated area.
  2. Wear safety goggles and protective gloves.
  3. Add the acid/alkali to a large amount of water slowly.
  4. Stir the solutino continuously and slowly when mixing.
49
Q

What are the things we should never do when diluting concentrated acids/alkalis?

A
  1. Never add water to the acid/alkalis.
  2. Never dilute the acid/alkali with bare hands.
  3. Never inhale acidic/alkaline vapour.
50
Q

Why should we handle concentrated acids/alkalis in a well ventilated area?

A

The acidic or alkaline vapour may corrode or irritate our respiratory tract, skin, or eyes.

51
Q

Why shouldn’t we add water to concentrated acids/alkalis for dilution?

A

When diluting acids/alkalis, a large amount of heat is released, which can cause the splashing out of the acids/alkalis.

DGS S2 Science (5 decks)

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