11. Consider the following statements:
(a) Both acids and bases change colour of all indicators.
(b) If an indicator gives a colour change with an acid, it does not give a change with a base
(c) If an indicator changes colour with a base, it does not change colour
with an acid.
(d) Change of colour in an acid and a base depends on the type of the
indicator
Which of these statements are correct?
(1) All four
(11) a and d
(iii) b. c and d
(iv) only d
Answers
Answer :
4) Only d
Explanation :
Change of colour of acid or base depends upon the nature of indicator.
An indicator may change of colour of both or may change colour of only one - either acid or both .
Let us consider all other three options .
Option A :
Both acids and base change colour of all indicators .
One such indicator that opposes this statement is phenolphthalein . It is naturally colourless and remains colourless in acidic solution and becomes pink in basic .
Option B :
If an indicator gives a colour change with an acid , it does not give a change with a base .
Methyl orange opposes this statement . It is orange in colour and changes its colour to red in acid and yellow in base .
Option C :
If an indicator changes colour with a base , it does not change colour with an acid .
This is the same case of methyl orange that changes colour with both acid and base .
Therefore , option d that it depends upon nature of indicator is correct .