Acids And Alkalis Flashcards
What do lemons contain that give them their sour taste?
Acids
List 8 foods that contain acids.
Soft drinks, tea, yoghurt, grapes, vinegar, spinach, apples, citrus fruits
List 4 personal care products that contain acids.
Toilet cleaner, body lotion, aspirin, hair conditioner
List the names of the acids soft drinks, vinegar, yoghurt, tea, and spinach contain respectively.
Soft drinks: carbonic acid Vinegar: Ethanoic acid Yoghurt: lactic acid Tea: tannic acid Spinach: oxalic acid
List 3 types of acids found in school labs.
Hydrochloric acid, sulphuric acid, nitric acid
What are the properties of acids?
They have a sour taste, can conduct electricity, and they react with alkalis and other materials.
What are the uses of acids in daily life? List one example for each usage.
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.
What does soap contain to give it a slippery feel?
Alkalis
List 7 daily household products that contain alkalis.
Soaps, toothpastes, glass cleaners, kitchen cleaners, drain cleaners, baking soda, alkaline batteries
List 3 kinds of alkalis found in school labs.
Sodium hydroxide, ammonia solution, calcium hydroxide (limewater)
What are the properties of alkalis?
Alkalis have a bitter taste and a slippery feel. They can conduct electricity and react with acids.
What are the daily uses of alkalis? List one example for each usage.
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
What are the ways we can distinguish acids, alkalis, and neutral solutions?
By using natrual indicators, litmus paper, universal indicator (pH paper and universal indicator solution), pH meter, and pH sensor with data-logger.
Explain how natrual indicators can distinguish if a solution is acidic, alkaline, or neutral.
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.
List all types of litmus that can be used to test for acidic or alkaline solutions.
Red litmus paper, red litmus solution, blue litmus paper, blue litmus solution
Which litmus are used to test for acids and alkalis and how?
Acid: blue litmus paper/solution, turn red when in contact with acids
Alkalis: red litmus paper/solution, turn blue when in contact with alkalis
What is the primary material of litmus paper/solution?
Lichen
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?
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.
What is the range of pH values?
0-14
What are the possible pH values for acidic, alkaline, and neutral solutions respectively?
Acidic: 0-7
Neutral: 7
Alkaline: 7-14
What are the approximate colours of the pH paper in the presence of acids, alkalis, and neutral solutions respectively?
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
Is tap water a neutral substance?
No, it is slightly acidic (pH~6.93)
What type of substance is shampoo?
Alkaline substance
What are the parts of a pH meter?
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.
Usually, what is the accuracy of a pH meter?
It is accurate to two decimal places.
What are pH sensors usually used for?
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.
List three advantages of using pH meters to measure the acidity or alkalinity of a substance.
- More accurate result (rounded to 2 decimal places)
- Can be reused unlike natural indicators/pH paper/litmus
- Can be used to measure the pH value of substances with deep colour
List two disadvantages of using pH meters to measure the pH values of substances.
- More expensive than pH paper
2. Relatively larger in size, more inconvenient to carry around
What happens to the pH value of an acid after an alkalis is added to it?
It increases.
What is the general form of the equation of neutralisation?
Acid+alkalis—>salt+water
When nitric acid is added into sodium hydroxide, what is the name of the salt created?
Sodium nitrate
When hydrochloric acid is added into calcium hydroxide, what is the name of the salt produced?
Calcium chloride
List 6 uses of neutralisation in daily life.
- 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 - 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) - 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
What happens to some metals when acids are added to them?
They will be corroded.
What is the general form of the equation when acids react with metals?
Acid+metal—>salt+hydrogen
What is the test for hydrogen?
Burning splint test. If a burning splint is exposed to hydrogen, it burns with a ‘pop’ sound.
What is the general form of the equation when acids react with calcium carbonate?
Acid+calcium carbonate—> salt+carbon dioxide+water
What is the word equation of the reaction between zinc and sulphuric acid?
Zinc+sulphuric acid—>zinc sulphate+hydrogen
List 5 substances that contain calcium carbonate.
Marble, limestone, eggshells, seashells, and pearls
What are the gases that cause acid rain and how?
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.
What is the main cause of acid rain?
Human activity (burning fossil fuels)
Why does burning fossil fuels release sulphur dioxide?
Fossil fuels contain sulphur impurities. When burnt, the impurities react with oxygen and form sulphur dioxide.
What are the effects of acid rain on the environment and living things?
- Buildings will be corroded: acid rain corrodes iron bridges/fences and statues/buildings made of metals or marble.
- 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.
- 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.
What are the four classes of acids and alkalis and how corrosive are they?
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.
List 3 examples for both strong acids and weak acids.
Strong acids: hydrochloric acid, nitric acid, sulphuric acid
Weak acids: citric acid, carbonic acid, ethanoic acid
List 2 examples of strong alkalis and 1 exampls of weak alkalis.
Strong alkalis: potassium hydroxide, sodium hydroxide
Weak alkali: ammonia solution
What can strong acids corrode? Are they stronger in concentrated or diluted form?
Metal, skin, and flesh
They are more corrosive in concentrated form.
What is the proper procedure for diluting concentrated acids/alkalis?
- Dilute the acid/alkali in a well ventilated area.
- Wear safety goggles and protective gloves.
- Add the acid/alkali to a large amount of water slowly.
- Stir the solutino continuously and slowly when mixing.
What are the things we should never do when diluting concentrated acids/alkalis?
- Never add water to the acid/alkalis.
- Never dilute the acid/alkali with bare hands.
- Never inhale acidic/alkaline vapour.
Why should we handle concentrated acids/alkalis in a well ventilated area?
The acidic or alkaline vapour may corrode or irritate our respiratory tract, skin, or eyes.
Why shouldn’t we add water to concentrated acids/alkalis for dilution?
When diluting acids/alkalis, a large amount of heat is released, which can cause the splashing out of the acids/alkalis.
