Tag: properties of acids and bases

Questions Related to properties of acids and bases

Choose the correct answer form the alternatives given.
The chemical name of baking soda is

chemistry acids and alkalis acids with carbonates reactions of acids and bases properties of acids and bases

  1. Sodium carbonate

  2. Sodium bicarbonate

  3. Sodium chloride

  4. Sodium nitrate

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Correct Option: B

1 kg of NaOH is added to 10 ml of 0.1N HCl, the resulting solution will:

chemistry further aspects of equilibria indicators and acid-base titration study of indicators properties of acids and bases

  1. turn blue litmus red

  2. turn phenolphthalein solution pink

  3. turn methyl orange red

  4. will have no effect on red or blue litmus paper

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Correct Option: B
Explanation:

The final solution is strongly basic. Phenolphthalein is an indicator used in acid-base reactions which turns pink in basic solution. Therefore, phenolphthalein turns pink. 

From the following in which titration methyl orange is a best indicator?

chemistry further aspects of equilibria indicators and acid-base titration study of indicators properties of acids and bases

  1. $CH _{3}COOH+NaOH$

  2. $H _{2}C _{2}O _{4}+NaOH$

  3. $HCl+NaOH$

  4. $CH _{3}COOH+NH _{4}OH$

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Correct Option: A
Explanation:

In the titration of acetic acid with a strong base such as sodium hydroxide the indicator used in the titration is methyl orange changed to yellow.

Dissociation of ${ CH } _{ 3 }COOH$ is suppressed by adding

chemistry further aspects of equilibria indicators and acid-base titration study of indicators properties of acids and bases

  1. HCL

  2. ${ H } _{ 2 }{ SO } _{ 4 }$

  3. $CH _{ 3 }COONa\quad$

  4. Any of the above

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Correct Option: C

Which one of the following indicatprs works in the pH range $8-9.8$?

chemistry further aspects of equilibria indicators and acid-base titration study of indicators properties of acids and bases

  1. Litmus

  2. Phenolphthalein

  3. Methyl red

  4. Methyl orange

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Correct Option: B
Explanation:

Phenolphthalein works in $pH$ range of $8.3-10.0$

Methyl Red works in $pH$ range of $4.4-6.5$
Methyl Orange works in $pH$ range of $3.2-4.5$

For the titration between oxalic acid and sodium hydroxide, the indicator used is

chemistry further aspects of equilibria indicators and acid-base titration study of indicators properties of acids and bases

  1. Potassium permanganate

  2. Phenolphthalein

  3. Litmus

  4. Methyl orange

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Correct Option: B
Explanation:

Oxalic acid is titrated against NaOH. Phenolphthalein is chosen because it changes color in a pH range between 8 – 10. It appears pink in basic solutions and colourless in acidic solutions.

In the case of a strong acid-strong base titration, this pH transition would take place within a fraction of a drop of actual neutralization, since the strength of the base is high.

Select the best indicator from the given table for titration of $20\space mL$ of $0.02\space M\space CH _3COOH$ with $0.02\space M\space NaOH$. Given $pK _a\ \text{of}\ CH _3COOH= 4.74)$

Indicator $pH$ range
(I) Bromothymol blue $6.0 - 7.6$
(II) Thymolphathalein $9.3 - 10.5$
(III) Malachite green $11.4 - 13$
(IV) M-Cresol purple $7.4 - 9.0$
chemistry further aspects of equilibria indicators and acid-base titration study of indicators properties of acids and bases

  1. $(I)$

  2. $(II)$

  3. $(III)$

  4. $(IV)$

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Correct Option: B
Explanation:

Since $pH=\left( SW+WA \right) =7+1/2\left( pKa+logC \right) $    {at equilance pointer}

             $C=0.01$  after mixing
  $\therefore \quad pH=7+1/2\left( 4.74+log0.01 \right) $
  $\therefore \quad pH=8.37$
So, it lies in range of $(IV)$ and somenehat of $(II)$

The fraction of total volume occupied by by the atoms present in a simple cube is

chemistry further aspects of equilibria indicators and acid-base titration study of indicators properties of acids and bases

  1. $\frac { \Pi }{ \sqrt [ 3 ]{ 2 } }$

  2. $\frac { \Pi }{ \sqrt [ 4 ]{ 2 } }$

  3. $\frac { \Pi }{ 4 }$

  4. $\frac { \Pi }{ 6 }$

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Correct Option: D

Assertion: In general, phenolphthalein is used as an indicator for the titration of weak acid (HA) against strong base (NaOH).
Reason: At equivalent point, solution is basic.

chemistry further aspects of equilibria indicators and acid-base titration study of indicators properties of acids and bases

  1. Both Assertion and Reason are correct and Reason is the correct explanation of Assertion

  2. Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion

  3. Assertion is correct but Reason is not correct


  4. Assertion is not correct but Reason is correct

  5. Both Assertion and Reason are not correct

Show answer
Correct Option: B
Explanation:

The phenolphthalein  indicator changes color over pH range 8.0 to 9.8.
During titration of weak acid (HA) against strong base (NaOH), at equivalence point complete neutralization occurs and a salt NA of weak acid (HA) with strong base (NaOH) is obtained.
The hydrolysis of this salt gives alkaline solution in the pH range 8.0 to 9.8.
Hence, in general phenolphthalein is used as an indicator for the titration of weak acid (HA) against strong base (NaOH).

A certain indicator (an organic dye) has $p{K} _{a} = 5$. For which of the following titrations it may be suitable?

chemistry further aspects of equilibria indicators and acid-base titration study of indicators properties of acids and bases

  1. Acetic acid against $NaOH$

  2. Aniline hydrochloride against $NaOH$

  3. Sodium carbonate against $HCl$

  4. Barium hydroxide against oxalic acid

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Correct Option: C
Explanation:

Give $pK _a$ of indicator $= 5$


This $pK _a$ value corresponds to methyl red indicator. Methyl red is a suitable indicator for titrating carbonates of weak acids (ex. $H _2CO _3$ salt $Na _2CO _3$) with strong acid $HCl$.


 Above titration reaction complated in following steps.

a) $Na _2 CO _3 (aq) + HCl (aq) \rightarrow NaHCO _3 (aq) + NaCl (aq)$

b) $NaHCO _3 (aq) + HCl(aq) \rightarrow NaCl (aq) + CO _2 (g) + H _2O(aq)$

Correct option (C)