Question

class 7 ncert solution science
please give me formulas all
chapter 5 acids bases and salts​

Answer 1

LET’S UNDERSTAND

I. Objective type questions

A.
1. Strong
2.
Bases
3.
Sulphuric
4.
Sodium hydroxide

5.
Blue, red






B.
1.
(d) Sulphuric acid
2.
(c) Acetic acid
3.
(a) Carbonic acid
4.
(b) Calamine lotion

5.
(c) Sugar
6.
(d) Both a and c
7.
(b) Hydrochloric acid


8.
(c) KOH
9.
(d) pH = 13
10.
(a) High melting point

C.
1.
(c) Acetic acid
2.
(a) Silver nitrate
3.
(d) Ammonium nitrate


4.
(e) Calcium hydroxide

5.
(b) Calcium carbonate

II. Very short answer type questions





1.
Alkalis
2.
Indicator
3.
pH paper
4.
Neutral salts

5. Hydrated salts

BI. Short answer type questions

1. Acids are sour to taste and are corrosive in nature. Acids are soluble in water. Bases are bitter to taste. Solutions of bases are slippery to touch.
2. To neutralise the soil

3. The reaction in which an acid reacts with a base to form salt is called a neutralization reaction. For example, hydrochloric acid reacts with sodium hydroxide to form sodium chloride.

4. On heating, hydrated salts lose their water of crystallization. The hydrated salts that have lost their water of crystallization are called anhydrous salts. For example, when blue crystals of copper sulphate are heated, they lose their water of crystallization to form white powder of anhydrous copper sulphate.

IV. Long answer type questions

1. Indicators can be prepared very easily from brightly coloured parts of plants such as flowers (china rose, rose), roots (beetroot), stems (turmeric), and leaves (red cabbage. Indicator solutions can be prepared by boiling coloured parts of the plant, such as petals, in water for some time and straining out the plant part. This solution gives a different colour in acidic and basic solutions. For example, red cabbage juice will change to deep red with acids, to purple with neutrals, and to green and yellow with bases.


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2

2. a. Most microorganisms cannot live in an acidic environment. An acidic environment either slows down their activities or can also kill them. This is why vinegar is found in many commonly packaged food items such as pickles, sauce, ketchups.

b. Liquid waste from factories often contains acid. If it reaches a river, the acid will kill aquatic life. This is prevented by neutralizing the waste by adding a base such as slaked lime.

c. To digest food, the liquid in the stomach must be acidic. But too much acidity leads to indigestion. One takes antacids, which usually contain baking soda or magnesium hydroxide, to neutralize the excess acid.

d. Strong bases are very corrosive and can burn the skin. Acids can also burn human tissues upon contact and damage clothes, paper, etc. Thus, one should handle strong acids and bases with care.

3. Generally, salts are found as crystals with water molecules present in them. This water is called the water of crystallization and such salts are called hydrated salts.
For example,
Copper sulphate crystal has five molecules of water for each copper sulphate molecule. This is written as CuSO4.5H2O. This water of crystallization gives the crystal its shape. It also gives colour to some crystals. For example, copper sulphate is also called blue vitriol due to its blue colour. On heating, hydrated salts lose their water of crystallization and, as a result, the crystals lose their shape and colour and change to a powdery substance. The hydrated salts that have lost their water of crystallization are called anhydrous salts. When hydrated copper sulphate is heated, it gives out water molecules to form white powdery anhydrous copper sulphate. On addition of water, this substance can convert back to a hydrated copper sulphate solution again.

LET’S RECALL




Substances


Acidic substance
Basic substance
Salts

Indicators









Properties:





Properties:




Properties:

Examples:


1. Bitter in taste





1. Sour in taste




1. High melting

1. Litmus


2. Slippery to touch





2. Corrosive in nature




and boiling

2. Phenolphthalein


3. May or may not be





3. Soluble in water




points

3. Methyl orange


soluble in water










2. Generally























soluble in water




Strong base





Mineral acid




3. Found as




Example:





Example: Nitric acid




crystals with




Sodium hydroxide










water molecules




















Weak base

present in them


Organic acid















Example:




Example: Acetic acid








Ammonium hydroxide