Tag: properties of acids and bases

Quizzes (0) Questions (142)

Questions Related to properties of acids and bases

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

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

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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. 

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

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

  1. $CH _{3}COOH+NaOH$
  2. $H _{2}C _{2}O _{4}+NaOH$
  3. $HCl+NaOH$
  4. $CH _{3}COOH+NH _{4}OH$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  1. HCL
  2. ${ H } _{ 2 }{ SO } _{ 4 }$
  3. $CH _{ 3 }COONa\quad$

  4. Any of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

CH3COOH is a weak acid. Adding CH3COONa provides a common ion (CH3COO-), which shifts the equilibrium of the weak acid dissociation to the left, suppressing it according to Le Chatelier's principle.

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

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

  1. Potassium permanganate

  2. Phenolphthalein

  3. Litmus

  4. Methyl orange
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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 $7.4 - 9.0$
  1. $(I)$
  2. $(II)$
  3. $(III)$
  4. $(IV)$
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $(II)$

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

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

  1. $\frac { \Pi }{ \sqrt [ 3 ]{ 2 } }$
  2. $\frac { \Pi }{ \sqrt [ 4 ]{ 2 } }$
  3. $\frac { \Pi }{ 4 }$
  4. $\frac { \Pi }{ 6 }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In a simple cubic unit cell, the atoms touch along the edge. The edge length a = 2r. The volume of the atom is (4/3)pi*r^3 and the volume of the cell is a^3 = (2r)^3 = 8r^3. Packing fraction = ((4/3)pi*r^3) / 8r^3 = pi/6.

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

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.

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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).

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

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

  1. Acetic acid against $NaOH$
  2. Aniline hydrochloride against $NaOH$
  3. Sodium carbonate against $HCl$

  4. Barium hydroxide against oxalic acid
Reveal answer Fill a bubble to check yourself
C Correct answer
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)