ACIDS BASES AND SALTS EXTRA QUESTION

It is based on class 7 education

1. EXTRA QUESTIONS
CHAPTER 5
VERY SHORT ANSWER TYPE
Question 1.
What is the test for acids and bases using
litmus paper?
Answer:
Acids turn blue litmus paper red while bases
turn red litmus paper blue.

Question 2.
What name is given to those substances
which do not change the colour of either
red or blue litmus paper?
Answer:
The solutions or substances which do not

2. change the colour of either red or blue
litmus paper are neutral.

Question 3.
Write the name of two indicators which
occur naturally.
Answer:
 Turmeric
 China rose

Question 4.
Name the acid present in lemon juice and
tomato.
Answer:
Citric acid in lemon juice and oxalic acid in
tomato.

3. Question 5.
Name a substance which is used to cure the
discomfort caused by indigestion due to
over eating.
Answer:
Milk of magnesia which contains
magnesium hydroxide (base) is used to
neutralise the effect of excessive acid in
stomach.

Question 6.
Why does a turmeric stain on white shirt is
turned to red when it is washed with soap?
[HOTS]
Answer:
Turmeric stain on white shirt is turned to
red when it is washed with soap because
the soap solution is basic in nature.

4. Question 8.
Is lime water an acidic or basic solution?
Answer:
Lime water (calcium hydroxide) is a basic
solution.

Question 9.
Name the reaction when an acid is mixed
with base.
Answer:
Neutralization reaction.

Question 10.
Which acid is injected into our body by an
ant sting that causes pain? [HOTS]
Answer:

5. The acid is formic acid which is injected into
the skin of a person when an ant bites.

Question 11.
Name the salt formed when hydrochloric
acid reacts with sodium hydroxide solution
(a base).
Answer:
When hydrochloric acid reacts with sodium
hydroxide solution, then sodium chloride
salt is formed.

Question 12.
Write two basic substances which we use in
our daily life.
Answer:
 Baking soda

6.  Soap or detergent

Question 13.
Name one acid which is responsible for acid
rain.
Answer:
Carbonic acid.

Question 14.
Name two gaseous pollutants which are
responsible for acid rain.
Answer:
Two gaseous pollutants are nitrogen dioxide
(NO2) and sulphur dioxide (SO2).

Question 15.
(a) Name one indicator which turns red on

7. adding an acid.
(b) Name one indicator which turns red on
adding a base.
Answer:
(a) Litmus (blue litmus paper)
(b) Turmeric

Question 16.
Form a sentence using the following words:
baking soda, ant bite, moist, effect,
neutralised, rubbing [NCERT Exemplar;
HOTS]
Answer:
The effect of an arft bite can be neutralised
by rubbing moist baking soda.

SHORT ANSWER TYPE

8. Question 1.
Write the characteristics of acids by which
we can identify acids.
Answer:
Characteristics of acids are
 They are sour in taste.
 They turn blue litmus paper/solution to
red.
 Dilution of acid in water is an
exothermic reaction, i.e. heat energy is
evolved.
Question 2.
Look at the figure which shows solutions
taken in test tubes A, B, C and D. What
colour is expected, when a piece of red
litmus paper is dropped in each test tube?
Nature of the solutions is given in the table

9. for your help.

Test tube Nature of
solution
Change in
colour of red
litmus
A Neutral
B Basic
C Acidic
D Neutral
[NCERT Exemplar]
Answer:
Nature of solution is given below:
Test tube Nature of
solution
Change in
colour of red
litmus
A Neutral No change

10. B Basic Turn blue
C Acidic No change
D Neutral No change
Question 3.
While playing in a park, a child was stung by
a wasp. Some elders suggested applying
paste of baking soda and others lemon juice
as remedy. Which remedy do you think is
appropriate and why? [NCERT Exemplar;
HOTS]
Answer:
Wasp sting inject a liquid in the skin which
is acidic in nature. Hence, baking soda is the
appropriate remedy as it is basic in nature
and neutralises the acid.
Question 4.
Which of the following are acidic and which
are basic?

11. Lime water, Vinegar, Toothpaste, Stomach
juices, Lemon juice, Baking soda solution,
Milk of magnesia, Ammonia solution.
Answer:
Acidic in nature Basic in nature
Vinegar Lime water
Stomach juices Toothpaste
Lemon juice Baking soda solution
Milk of magnesia
Ammonia solution
Question 5.
A small amount of hydrochloric acid is
always produced in the stomach. Is it useful
or harmful for us? If excess of acid is
produced in the stomach, what should we
do?
Answer:
A small amount of hydrochloric acid
produced in the stomach is useful as it can

12. kill the harmful bacteria that may enter into
the stomach along with the food.
However, if excess of acid is produced,
there is a burning sensation in the stomach.
We should take milk of magnesia as an
antacid medicine to neutralise the excess
acid.
Question 6.
Write the effect of China rose petals on
acidic and basic solutions.
Answer:
China rose petals when added to warm
water, form a light pink coloured solution
which may be used as an indicator. This
indicator turns acidic solution to magenta
(deep pink) and basic solution to green.
Question 7.
To test the presence of an acid in any

13. substance, what methods can be used?
Answer:
Acid can be tested in any substance by the
following methods
 Take a drop of the dilute solution of the
substance on the tips of your tongue. If
tastes sour, it is acidic.
 Dip a blue litmus paper in the solution. If
the colour of the litmus paper turns red,
the solution is acidic.
Question 8.
Why are sodium bicarbonate and lemon
juice used during indigestion?
Answer:
Sodium bicarbonate neutralises the acidity
in the stomach. Hence, it is used during
indigestion. Lemon contains acid. It reacts
with undigested food and suffers it.

14. Question 9.
After carrying out the neutralisation
reaction, the test tube immediately found
to be somewhat hot. Explain why.
Answer:
In neutralisation reaction, heat is always
produced or evolved. The evolved heat
raises the temperature of the reaction
mixture. Therefore, if we touch the test
tube immediately after the neutralisation
reaction, it is found to be hot.
Acid + Base → Salt + Water (heat is evolved)
Question 10.
Name three acids used in the laboratory.
Answer:
Acids which are mostly used in laboratory
as below
 Hydrochloric acid (HCl)

15.  Sulphuric acid (H2SO4)
 Nitric acid (HNO3)
Question 11.
Paheli is suffering from indigestion due to
acidity. Is it advisable to give her orange
juice in this situation and why? |NCERT
Exemplar; HOTS]
Answer:
No, because orange juice is acidic in nature.
Excess of acid in the stomach causes
indigestion. We take an antacid such as milk
of magnesia which contains magnesium
hydroxide.
Question 12.
Explain two neutralisation reactions related
to daily life situations.
Answer:
(i) Ant bite When an ant bite injects the

16. acidic liquid (formic acid) into the skin, the
effect of the acid can be neutralised by
rubbing moist baking soda (sodium
hydrogen carbonate) or calamine solution,
which contains zinc carbonate.
(ii) Indigestion Our stomach contains
hydrochloric acid. It helps us to digest food
but too much of acid in the stomach causes
indigestion. Sometimes, indigestion is
painful. To relieve indigestion, we take an
antacid such as milk of magnesia which
contains magnesium hydroxide.
It neutralises the effect of excessive acid.
Question 13.
How lime water is prepared in the
laboratory?
Answer:
To prepare lime water, dissolve some lime

17. (chuna) in water in a bottle. Stir the solution
and keep it for sometime. Pour a little more
from the top. This is lime water.
Question 14.
Name three types of salts. Give one
example of each type of salt.
Answer:
Type of salts
 Neutral salts e.g. sodium chloride (NaCl)
 Acidic salts e.g. Ammonium chloride
(NH4Cl)
 Basic salts e.g. sodium hydrogen
carbonate (NaHCO3)
Question 15.
Paheli observed that most of the fish in the
pond of her village were gradually dying.
She also observed that the wastes of a
factory in their village are flowing into the

18. pond which probably caused the fish to die.
(a) Explain why the fish were dying?
(b) If the factory waste is acidic in nature,
how can it be neutralised? [NCERT
Exemplar; HOTS]
Answer:
(a) If the wastes of a factory flow into
waterbodies, it can cause a threat to the
lives of sea creatures and to anybody who
drink the water. Since, factory wastes may
contain acids or bases and it can kill the
fish.
(b) If the factory waste is acidic in nature, it
can be neutralised by adding basic
substances.
Question 16.
What is a salt? Name any salt and give their
formulae.

19. Answer:
A substance formed by the neutralisation of
an acid with a base is called salt. Salt may
be acidic, basic or neutral in nature.
For example,
Hydrochloric acid (HCI) +
(Acid)
Sodium hydroxide (NaOH) →
(Base)
Sodium chloride (NaCI) + Water (Salt)
(Salt)
Question 17.
Look at the given reaction.
Hydrochloric acid + Sodium hydroxide
(base) → Sodium chloride (salt) + Water
Sodium chloride formed in this reaction
remains in solution form. Can we get solid
sodium chloride from this solution? Suggest

20. a method (if any). [NCERT Exemplar]
Answer:
We can get solid sodium chloride by
evaporation method. Evaporation is the
process by which water changes from a
liquid to a gas or vapour.
Rate of evaporation increases with
temperature.
Question 18.
Name three bases used in the laboratory
with their formulae.
Answer:
Bases which are mostly used in laboratory
as below
 Sodium hydroxide (NaOH)
 Calcium hydroxide [Ca(OH)2]
 Ammonium hydroxide (NH4OH)
LONG ANSWER TYPE

21. Question 1.
A farmer was unhappy because of his low
crop yield. He discussed the problem with
an agricultural scientist and realised that
the soil of his field was either too acidic or
too basic. What remedy would you suggest
the farmer to neutralise the soil? [HOTS]
Answer:
The reason for low crop yield in farmer’s
field was that the soil at a place is either too
acidic or too basic. The soil may be acidic or
basic naturally. The excessive use of
fertilisers in the fields also makes the soil
too acidic. When the soil is too acidic, it is
treated with base such as quicklime
(calcium oxide) or slaked lime (calcium
hydroxide) which neutralises the excess
acid present in the soil and reduces its

22. acidic nature. If the soil is too basic, then
decaying organic matter (called manure or
compost) is added it. The decaying organic
matter releases acid which neutralises the
excess bases present in the soil and reduces
its basic nature.
Question 2.
You are provided with three test tubes A,
Sand Cas shown in figure with different
liquids. What will you observe when you
put
(a) a piece of blue litmus paper in each test
tube?
(b) a piece of red litmus paper in each test
tube?
(c) a few drops of phenolphthalein solution
to each test tube?

23. Answer:
Test tube Effect on
blue
litmus
paper
Effect on
red
litmus
paper
Effect on
phenolph
thalein
solution
A Turns red Remains
red
Colourles
s
B Remains
blue
Turns
blue
Pink
colour
C Remains
blue
Remains
red
Colourles
s
Question 3.
Boojho, Paheli and their friend Golu were
provided with a test, each containing China
rose solution which was pink in colour.
Boojho added 2 drops of solution ‘A’ in his

24. test tube and got dark pink colour. Paheli
added 2 drops of solution ‘S’to her test tube
and got green colour. Golu added 2 drops of
solution ‘C but could not get any change in
colour. Suggest the possible cause for the
variation in their results. [HOTS]
Answer:
China rose (gudhal) is an acid-base
indicator.
China rose solution in different medium
shows following changes:
China rose + acid → Give dark pink colour,
hence A is an acidic solution.
China rose + base → give green colour,
hence 6 is a basic solution.
China rose + neutral → No change in colour,
hence C is a neutral solution.

25. Question 4.
Nitesh was playing with his friends in the
garden. Suddenly, Nitesh was stung by a
honeybee and was in great pain.
Immediately, his friends call his mother. She
applied baking soda solution on the
affected area and then took him to the
doctor.
Read the above passage and answer the
following questions:
(a) What could be the reason for this
burning pain?
(b) Why did his mother applied baking soda
solution on the affected area?
(c) What values are shown by Nitesh’s
friends? [Value Based Question]
Answer:
(a) The reason for this burning pain is

26. honeybee sting which causes pain and
irritation. This is due to the acidic liquid
(formic acid) injected into the skin by the
honeybee.
(b) The effect of acid can be neutralised by
rubbing the affected area by baking soda
solution which is a mild base.
(c) Nitesh’s friends are caring , supportive
and helpful.
Question 5.
One day Rahul’s mother after taking meal
felt pain and irritation in her stomach. His
father was out of station. Rahul was an
intelligent boy. He remembered his
teacher’s statement and gave his mother
some baking soda solution Which gave her
a relief from pain and irritation of stomach.
Read the above passage and answer the

27. following questions.
(a) Which information given by Rahul’s
teacher that helped him to select the baking
soda as remedy?
(b) Why he selects baking soda as a cure?
(c) What values are shown by Rahul? [Value
Based Question]
Answer:
(a) Rahul knows that our stomach contains
hydrochloric acid. It helps us to digest food.
But, too much acid in the stomach causes
indigestion. Sometimes, indigestion is
painful and some mild base should be taken
to relief from this pain. So, this information
given by his teacher helped him.
(b) He gave her mother baking soda
solution which was available in the kitchen
easily. He selects baking soda because it is a

28. mild base and neutralises the excess acid in
the stomach and it will give relief from pain.
(c) Rahul is very intelligent and caring boy.