1. Answer the following :
(a) What are bases? Differentiate the terms ‘bases’ and ‘alkalis ’with suitable examples.
(b) What do you understand by acidity of a base?
(c) State the acidity of the following bases: sodium oxide, calcium hydroxide, magnesium oxide,
aluminium hydroxide and ferric oxide.
(d) Name three bases which may react with an alkali beside an acid to give salt and water as the only
product. Also write balanced chemical equations for reactions of these bases with respective alkalis giving salt and water.
2. Write suitable balanced chemical equation for the preparation of the following bases as per the instruction: (a) Magnesium oxide [direct combination]
(b) Potassium hydroxide [using water]
(c) Ferrous hydroxide [by precipitation]
(d) Copper (II) oxide [from carbonate] (e) Lead monoxide [from nitrate]
3. State the name of a base which (only chemical names are acceptable): (a) is soluble in an acid as well as an alkali.
(b) Is yellow when hot and white when cold.
(c) Is obtained as a reddish-brown precipitate.
(d) Is reddish-yellow in colour and fuses with the glass of the test-tube when heated. (e) Is completely non-metallic.
Answers
Answer:
jkxgxod9yeodoxiyxosos9xxlhxoydos5
igclcpfufpf7
Explanation:
Which of the following is not an acid-base indicator?
(a) blue litmus
(b) methyl orange
(c) phenolphthalein
(d) Digene
ANSWER:
(d) digene
Digene is not an acid–base indicator but an antacid (base). It is used as a medicine to reduce acidity of the stomach by neutralising it.
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Question 2:
Which of the following is a strong acid?
(a) nitric acid
(b) citric acid
(c) acetic acid
(d) tartaric acid
ANSWER:
(a) nitric acid
Nitric acid is highly corrosive in nature. It can burn our skin severely.
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Question 3:
Which of the following is not a base?
(a) sodium hydroxide
(b) magnesium hydroxide
(c) copper carbonate
(d) ammonium hydroxide
ANSWER:
(c) copper carbonate
Copper carbonate is not a base but an ionic salt.
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Question 4:
Which of these metals cannot be used to prepare hydrogen by the action of an acid?
(a) sodium
(b) iron
(c) calcium
(d) copper
ANSWER:
(d) copper
Copper is a less reactive metal; therefore, it cannot displace and liberate hydrogen from acids.
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Question 5:
What is the common name of sodium bicarbonate?
(a) phitkari
(b) caustic soda
(c) baking soda
(d) blue vitriol
ANSWER:
(c) baking soda
Baking soda is the common name for sodium bicarbonate.
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Question 6:
Lime juice will turn
(a) blue litmus red
(b) methyl orange yellow
(c) red litmus blue
(d) phenolphthalein pink
ANSWER:
(a) blue litmus red
Lime juice contains citric acid; therefore, it will turn a blue litmus paper red.
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Question 7:
Sodium chloride will turn
(a) blue litmus red
(b) methyl orange yellow
(c) red litmus blue
(d) none of the above
ANSWER:
d) none of the above
Sodium chloride is a salt, and salts are neutral in nature. Thus it will induce no change to the acid-base indicators.
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Question 8:
Acids
(a) have sour taste
(b) are corrosive in nature
(c) are soluble in water
(d) have all of these properties
ANSWER:
(d) have all these properties
Acids have a sour taste and are extremely corrosive in nature. They also dissolve easily in water.
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Question 9:
Alkalis
(a) have sour taste
(b) are soluble in water
(c) turn blue litmus red
(d) have all of these properties
ANSWER:
(b) are soluble in water
All alkalis are water soluble bases.
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Question 1:
Which of these is neutral-hydrochloric acid, sodium hydroxide, sodium chloride?
ANSWER:
Sodium chloride is neutral in nature as it is a salt. It does not possess the properties of acids or bases.
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Question 2:
If a liquid turns blue litmus red, is it an acid, base or salt?
ANSWER:
If a liquid turns blue litmus red, then it is an acid.
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Question 3:
Methyl orange has________colour in an acidic solution
ANSWER:
Methyl orange has red colour in an acidic solution.
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Question 1:
What is an acid-base indicator? Give one example.
ANSWER:
Acid-base indicators are special substances which are used to detect the acidity or basicity of other substances. The change in colour of the indicators help us in understanding which substance is acidic and which one is basic.
Example: Litmus paper is a natural acid-base indicator.
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Question 2:
Name one each of acidic, basic and neutral substances.
ANSWER:
Acidic substance: Lemon juice is an acidic substance, as it contains citric acid.
Basic substance: Baking soda is basic in nature, as it contains sodium bicarbonate.
Neutral substance: Common salt is a neutral substance, as it is made of sodium chloride.
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Question 3:
What happens when dilute sulphuric acid is added to zinc?
ANSWER:
Zinc will react with dilute sulphuric acid to form zinc sulphate salt and hydrogen gas. The reaction is given below: