An acid-base indicator has a K a of 3 . 0 × 10 - 5 . If the acid form of the indicator is red and the basic form is blue, then

pH is 5 . 00 when indicator is 75 % blue.

pH is 5 . 00 when indicator is 75 % red.

pH is 4 . 05 when indicator is 75 % blue.

An acid-base indicator has K a = 3 . 0 × 10 - 5 . The acid form of the indicator is red and the basic form is blue. Then:

pH is 5.00 when indicator is 75% blue.

pH is 5.00 when indicator is 75% red.

pH is 4.05 when indicator is 75% blue.

Following is the titration curve of CH 3 COOH against NaOH added with phenolphthalein as the indicator. K In value of phenolphthalein is 4.0 x 10 -10 . Thus, incorrect statement is

It begins to change colour from the pH 9.4

It begins to change colour from acid colourless at pH 8.4 to the base form (reddish pink) at pH 10.4

Phenolphthalein is suitable indicator for CH 3 COOH-NaOH titration

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How to choose an indicator for an acid base titration?

Important Questions on Consequences

HARD

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

An acid-base indicator has a

K_{a}

3.0 \times 10^{- 5} .

If the acid form of the indicator is red and the basic form is blue, then

EASY

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

Name any two human-made indicators.

MEDIUM

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

When

K M n O_{4}

solution is titrated with a solution containing

F e^{2 +}

ion, the indicator used in this titration is

EASY

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

Write the quadrants in which the following points lie:

$(- 4, 7)$

MEDIUM

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

What is substance 'Y'?

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MEDIUM

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

4

-methyl benzene sulphonic acid reacts with sodium acetate to give

MEDIUM

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

How many of the following can turn moist red litmus blue?

$\mathrm{H}_{3} \mathrm{BO}_{3}, \mathrm{Na}_{2} \mathrm{B}_{4} \mathrm{O}_{7} \cdot 10 \mathrm{H}_{2} \mathrm{O}, \mathrm{CaCO}_{3}, \mathrm{Na}_{2} \mathrm{CO}_{3},$ Potash alum, $\mathrm{SnO}_{2}, \mathrm{NaNO}_{3}, \mathrm{Na}_{3} \mathrm{PO}_{4}, \mathrm{NaAlO}_{2}$

EASY

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

An element $E$ reacts with water to form a solution which turns phenolphthalein solution pink. The element $E$ is most likely to be:

MEDIUM

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

Which of the following indicators is used in the activity?

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HARD

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

An acid-base indicator has

K_{a} = 3.0 \times 10^{- 5}

. The acid form of the indicator is red and the basic form is blue. Then:

MEDIUM

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

You are given the dilute sulphuric acid. What is effect of it on the phenolphthalein?

MEDIUM

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

What is substance 'X'?

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HARD

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

Following is the titration curve of CH₃COOH against NaOH added with phenolphthalein as the indicator.

Question Image

K_In value of phenolphthalein is 4.0 x 10^-10. Thus, incorrect statement is

MEDIUM

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

Why does a pink colour appear upon gradually adding sodium hydroxide to a solution of acid having

2 - 3

drops of phenolphthalein?

HARD

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

What is pH of 1 M acetic acid solution? If volume one litre solution be diluted to

X \times 10^{4}

L so that pH of resulting solution is twice the original value (K_a = 1.8 x 10^{- 5} ). Find the value of X.

MEDIUM

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

An acid-base indicator(pK_a = 4.5271)has the acid form red and basic form blue. If we need 75% red to be converted into 75% blue form in solution, the change in pH of solution should be :

EASY

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

What will you observe when a drop of phenolphthalein is added to the solution of lime water.

HARD

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

An indicator has a pK_a of 7.5. What is the ratio of the concentration of the base form to the concentration of the acid form ([A^- ]/ [HA], in a buffer solution in which the pH is 6.5 ?

HARD

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

An indicator, HIn has a standard ionization constant of

9 \cdot 0 \times 1 0^{- 9}

. The acid colour of the indicator is yellow, and the alkaline colour is red. The yellow colour is visible when the ratio of yellow form to red form is

30 : 1

and the red colour is predominant when the ratio of red form to yellow form

2 : 1

. What is the

pH

range of the indicator? Hence, report

∆ pH

the difference in term

pH

values of the range.

HARD

Chemistry>Change>Consequences>Role of Indicators in Acid-base Reactions

What is the colour of this indicator in (a) Neutral (b) Acidic (c) Basic solution?
Phenolphthalein

How to choose an indicator for an acid base titration?

Important Questions on Consequences

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