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Acids and Bases

Description: This test is standardised achievment test in chemistry suitable for the students of cbse,icse and all other boards of class 7 and also useful for the students of different competitions and olympiads.
Number of Questions: 16
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Which of the following is not a base?

  1. Sodium hydroxide

  2. Magnesium hydroxide

  3. Ammonium hydroxide

  4. Calcium carbonate

  5. Ferric oxide


Correct Option: D
Explanation:

Copper carbonate is a salt because bases are oxides or hydroxides of metals, but a salt is a compound made up of an acid, when a metal takes the place of the hydrogen in the acid. Calcium carbonate is formed by the reactions of calcium and carbonic acid.

The pH value of a weak acid is

  1. 9

  2. 1

  3. 7

  4. 5

  5. 14


Correct Option: D
Explanation:

The pH of the solution is a measure of the replaceable hydrogen ions present in it.  The larger the value of pH, the lesser is the amount of hydrogen ions and less acidic is the solution. Hence, solution with pH 5 denotes a weak acid.   

Which of the following is an acidic salt?

  1. ZnSO4

  2. Pb(OH)Cl

  3. NaCl

  4. NaHSO4

  5. CuSO4.5H2O


Correct Option: D
Explanation:

Acidic salts are those, which contain hydrogen ion. NaHSO4 contains hydrogen ion. Hence, it is an acidic salt.

Which of the following statements is not true about bases and alkalis?

  1. All alkalis and bases are bitter in taste.

  2. All alkalis and bases turn red litmus blue.

  3. All alkalis and bases have a soapy feel.

  4. All bases are alkalies.

  5. All bases and alkali react with acids to give salt and water.


Correct Option: D
Explanation:

It is not true because bases, which dissolve in water are called as alkali. Hence, all alkalies are bases but all bases are not alkali.

Which of the following is not an acid-base indicator?

  1. Blue litmus

  2. Methyl orange

  3. Phenophthalein

  4. Turmeric

  5. Magnesium hydroxide


Correct Option: E
Explanation:

It is used as an antacid to neutralise the excessive acidity in the stomach. It is sold as 'milk of magnesia'.

Which of these metals cannot be used to prepare hydrogen by the action of an acid?

  1. Sodium

  2. Iron

  3. Zinc

  4. Copper

  5. Calcium


Correct Option: D
Explanation:

Copper does not react with acid, so it is not used to prepare hydrogen by the action of an acid.

How many molecules of water of crystallisation are present in a molecule of Plaster of Paris?

  1. Six

  2. Two

  3. Five

  4. Seven

  5. Ten


Correct Option: B
Explanation:

A molecule of Plaster of Paris contains two molecules of water of crystallisation. Plaster of Paris is known as calcium sulphate.

Which one of the following substances is different from others on the basis of acidity?

  1. Barium hydroxide

  2. Calcium hydroxide

  3. Magnesium hydroxide

  4. Sodium hydroxide

  5. Zinc hydroxide


Correct Option: D
Explanation:

The number of hydroxyl ions present in one molecule of base is called its acidity. In sodium hydroxide, only one hydroxyl ion is present, so its acidity is 1 while others have 2 hydroxyl ions, so the acidity is 2. The number of hydroxyl ions present in one molecule of base is called its acidity. In sodium hydroxide, only one hydroxyl ion is present, so its acidity is 1 while others have 2 hydroxyl ions, so the acidity is 2.Zinc hydroxide contain 2 hydroxyl ions, so its acidity is also 2.

Which of the following substances is used by milk vendors to prevent curdling in hot climates?

  1. Sodium carbonate

  2. Sodium hydroxide

  3. Calcium carbonate

  4. Sodium hydrogen carbonate

  5. Lactic acid


Correct Option: D
Explanation:

Sodium hydrogen carbonate, commonly known as baking soda, is added to the milk. This in turn, neutralises lactic acid and the milk does not curdle.

Which statement about acids or alkalis is true?

  1. Acids are not safe enough to be used in food preparations because they are too sour in taste.

  2. Antacids in indigestion mixtures are weak acids.

  3. Acids and alkalis are not made safer by diluting with water.

  4. Oven spray cleaners can be moderately alkaline.

  5. Orange juice is a strongly acid solution.


Correct Option: D
Explanation:

Yes, most of oven sprays contain ammonia solution, which are completely alkaline.

From which of the following sources, litmus solution is obtained?

  1. Animals

  2. Bacteria

  3. Virus

  4. Fungi

  5. Lichen


Correct Option: E
Explanation:

The litmus is extracted from lichen plants found in the Tundra region.

The hydroxides of _____ are used in the manufacture of an antidote for acid poisoning.

  1. sodium

  2. calcium

  3. potassium

  4. magnesium

  5. ammonium


Correct Option: B
Explanation:

Calcium hydroxide is used as an antidote for acid poisoning.

The formula for oil of vitriol is

  1. H2SO4

  2. CuSO4

  3. FeSO4

  4. ZnSO4

  5. CaSO4


Correct Option: A
Explanation:

Concentrated sulphuric acid is known as oil of vitriol.

Which of the following substances is used in cleaning sink and sanitary wares?

  1. Nitric acid

  2. Sulphuric acid

  3. Hydrochloric acid

  4. Magnesium hydroxide

  5. Calcium phosphate


Correct Option: C
Explanation:

Hydrochloric acid is used in cleaning kitchen sink and sanitary wares.

Which of the following acids is responsible for the 'fizz' in soft drinks?

  1. Lactic

  2. Carbonic

  3. Citric

  4. Tartaric

  5. Malic


Correct Option: B
Explanation:

Carbonic acid is responsible for the 'fizz' in soft drinks.

Which substance can be classified as an Arrhenius acid?

  1. NaCl

  2. KOH

  3. LiOH

  4. HCl

  5. ZnSO4.7H2O


Correct Option: D
Explanation:

According to the definition, an Arrhenius acid yields hydrogen ions as the only positive ions in the aqueous solution. Here, HCl forms H+ ions. Therefore, it is an Arrhenius acid.

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