Acids, Bases and Salts Quiz: Clerkship 2024
A little practice. A step forward.
10 questions on acids, bases, salts and the pH scale, each with an explanation. 📖 Read the detailed topic
Which acid makes sour curd taste sour?
When milk sets into curd, bacteria turn the milk sugar into lactic acid, which makes curd sour. Citric acid is in lemon, tartaric acid in tamarind and formic acid in ant stings.
- Lactic acid in sour curd and buttermilk
- Citric acid in lemon and orange
- Tartaric acid in tamarind
- Curd = lactic
| Acid | Where found |
|---|---|
| Citric | Lemon, orange |
| Acetic | Vinegar |
| Lactic | Sour curd |
| Tartaric | Tamarind |
| Formic | Ant sting |
| Hydrochloric | Gastric juice |
What is the pH of pure water?
The pH scale runs from 0 to 14. 7 is neutral, and pure water has this value. Below 7 a solution is acidic, above 7 it is basic.
- pH scale: 0 to 14
- 7 = neutral
- Below 7 acidic, above 7 basic
- 7 in the middle, acids to the left, bases to the right
Which acid in our stomach helps digest food?
Gastric juice contains dilute hydrochloric acid (HCl). It makes food ready for digestion and kills harmful germs. Acetic acid is found in vinegar.
- Stomach acid = HCl
- Excess acid causes acidity
- Stomach = HCl
What is the chemical formula of baking soda?
Baking soda is sodium hydrogen carbonate, NaHCO3. Na2CO3 is washing soda, NaCl is common salt and CaCO3 is limestone.
- Baking soda = NaHCO3
- Used to raise cakes and as an antacid
- Mixing up baking soda (NaHCO3) and washing soda (Na2CO3)
- Baking soda has an H, washing soda has none
| Compound | Formula | Use |
|---|---|---|
| Common salt | NaCl | Cooking, preserving |
| Baking soda | NaHCO3 | Raising cakes, antacid |
| Washing soda | Na2CO3 | Washing clothes, softening water |
| Bleaching powder | CaOCl2 | Disinfecting, bleaching |
| Plaster of Paris | CaSO4.½H2O | Bone-setting casts, statues |
Which acid causes the burning from an ant sting?
The sting of ants and nettle leaves contains formic (methanoic) acid. A mild base such as baking soda eases the burning because a base neutralises the acid.
- Formic acid = ants, nettle
- A mild base relieves the sting
- Formic from formica (ant)
Which substance is used as an antacid to relieve acidity?
Excess acid in the stomach is neutralised by a mild base. Magnesium hydroxide, known as milk of magnesia, is a mild base. An acid or vinegar would make acidity worse.
- Antacid = mild base
- Milk of magnesia = Mg(OH)2
- Anti-acid = enemy of acid, so a base
What colour does phenolphthalein give in a basic solution?
Phenolphthalein is colourless in acidic and neutral solutions and turns pink in a basic solution. Red and yellow belong to methyl orange (red in acid, yellow in base).
- Phenolphthalein: colourless in acid, pink in base
- Methyl orange: red in acid, yellow in base
- Mixing up phenolphthalein and methyl orange
- Phenolphthalein turns pink in base
| Indicator | In acid | In base |
|---|---|---|
| Blue litmus | Red | Blue (no change) |
| Red litmus | Red (no change) | Blue |
| Phenolphthalein | Colourless | Pink |
| Methyl orange | Red | Yellow |
Heating gypsum gives which substance?
When gypsum (CaSO4.2H2O) is heated to about 100°C, it loses some water and becomes plaster of Paris (CaSO4.½H2O). It sets hard again when mixed with water, so it is used for bone-setting casts.
- Gypsum gives plaster of Paris
- Sets hard with water
- Used in casts and statues
- Gypsum heated = plaster
What is the reaction of an acid with a base to form salt and water called?
The reaction of an acid with a base that forms salt and water is called neutralisation. For example HCl and NaOH give NaCl and water.
- Acid + base = salt + water
- HCl + NaOH = NaCl + H2O
- Acid meets base, salt and water appear
What is the pH of acid rain usually?
Normal rain is slightly acidic because it dissolves carbon dioxide, with a pH of about 5.6. When oxides of sulphur and nitrogen dissolve in it and the pH falls below 5.6, it is called acid rain.
- Acid rain: pH below 5.6
- Caused by oxides of sulphur and nitrogen
- Below 5.6 means acid rain
At what mouth pH does tooth decay begin?
Bacteria in the mouth make acid from the sugar in food. When the pH of the mouth falls below 5.5, tooth enamel starts to decay. A basic toothpaste neutralises that acid.
- Decay begins below pH 5.5
- Basic toothpaste neutralises acid
- Rinse after sweets
📊 Topic Analysis
10 questions on acids, bases, salts and the pH scale, each with an explanation.
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