Acidic Buffer Action

Q.

Which of the following is an example of basic buffer?

1. 1M solution of NaOH

2. A mixture of CH₃COOH and OH₃COONa

3. A mixture of NH₄Cl and NH₄OH

4. A mixture of HCl and NaOH

Q. Acidic buffer is made up of ?

1. Weak base and weak acid
2. Weak acid and its conjugate salt with weak base
3. Strong acid and its conjugate salt
4. Weak acid and its conjugate salt with strong base

Q. N factor of Na2S2O3 in acidic, basic and neutral medium.

Q.

On the addition of a small amount of an acid or a base, the pH value of a buffer solution:

1. increases

2. decreases

3. remains unaltered

4. none of these

Q. How much sodium formate $(HCOONa,68.0069gmo{l}^{-1})$ is to be added to 400 mL of 1.00 M formic acid for a pH=3.50 buffer. Given $K_a=1.77\times {10}^{-4}$
$log1.77=0.248\text{and log}0.56=-2.52$

1. 20.25 g
2. 15.23 g
3. 30.34 g
4. 5.50 g

Q. $C{H}_{3}COOH$ is titrated with $NaOH$ solution. Find the ratio $\left(\frac{\left[C{H}_{3}COONa\right]}{\left[C{H}_{3}COOH\right]}\right)$ when the volume of $NaOH$ added is half that of equivalence point.

1. 2.5
2. 0.5
3. 0.75
4. 1

Q. $1\text{L}$ of a buffer solution contains one mole each of $C{H}_{3}COOH$ & ${\left(C{H}_{3}COO\right)}_2\text{Ba}$. Which of the following options are correct? $(p{K}_a\text{of}C{H}_{3}COOH=4.7,\text{log}2=0.3)$

1. pH = 4.7
2. pH = 5
3. pOH = 9
4. pOH = 9.3

Q. give one example of each
1. acidic buffer
2. basic buffer

Q. A $30mL$ solution of $0.2MN{H}_{4}OH$ is titrated with $0.2MHCl$. Find the $pH$ of the solution when $10mL$ of $HCl$ has been added.
Given $p{K}_b\left(N{H}_{4}OH\right)=4.74$

1. 4.44
2. 9.56
3. 5.44
4. 8.56

Q. Find the dissociation constant $K_a$ of a weak monobasic acid which is 3.5% dissociated in a $\frac{N}{10}$ solution at ${25}^{\circ }C$

1. $1.269\times {10}^{-4}$
2. $1.269\times {10}^{-5}$
3. $2.269\times {10}^{-4}$
4. $2.269\times {10}^{-5}$

Q. $pH$ of the solution containing equimolar amount of $C{H}_{3}COOH$
$(p{K}_a=4.74)\text{and}C{H}_{3}CO{O}^{-}$ at ${50}^{\circ }C$ is:

1. Less than 4.74
2. More than 4.74
3. Equal to 4.74
4. None of these

Q. Which one of the following mixture is considered as an acidic buffer solution ?

1. $HCN+NaCN$
2. $HCN+N{H}_{4}CN$
3. $HCl+NaCl$
4. $C{H}_{3}COOH+HCOOK$

Q. Which one of the following pairs of solution is not an acidic buffer?

1. $H_{2}C{O}_3$ and $N{a}_{2}C{O}_3$
2. $H_{3}P{O}_4$ and $N{a}_{3}P{O}_4$
3. $HCl{O}_4$ and $NaCl{O}_4$
4. $C{H}_{3}COOH$ and $C{H}_{3}COONa$

Q. What will be the new $pH$ if $0.01mol$ of $NaOH$ is added to a $1L$ buffer solution that is $0.1M$ in acetic acid $\left(C{H}_{3}COOH\right)$ and $0.1M$ in sodium acetate $\left(C{H}_{3}COONa\right)$ ?
Dissociation constant $K_a$ of acetic acid at ${25}^{\circ }C$ is $1.8\times {10}^{-5}$

1. 5.52
2. 4.92
3. 4.1
4. 6.13

Q. All solution are at ${25}^{\circ }C$
$\begin{array}{cc}\text{Column I}& \text{Column II}\\ \text{(I) A solution containing weak acid 0.1 M HA}(K_a={10}^{-5}\&0.1\text{M NaA)}& \text{(P) Buffer solution}\\ \text{(II) In a mixture of 200 ml 0.5 M}N{a}_{3}P{O}_4\text{and 400 ml 0.5 M HCl}& \text{(Q) pH = 10}\\ (\text{for}{H}_{3}P{O}_4{K}_1={10}^{-3},K_2={10}^{-7},K_3={10}^{-12})& \\ \text{(III) An aqueous solution of sparingly soluble}A\left(OH{)}_3\right(K_{sp}=27\times {10}^{-40})& \text{(R) Acidic solution}\\ \text{(IV) 0.1}MN{a}_{2}A\left(K_{a_1}\right(H_{2}A)={10}^{-3}),K_{a_2}\left(H_{2}A\right)={10}^{-7}\text{solution}& \text{(S) pH is closer to 7}\\ & \text{(T) pH = 5}\end{array}$
Which of the following options has the correct combination considering LIst - I and List - II?

1. (I), (Q)
2. (III), (P)
3. (IV), (Q)
4. (II), (S)

Q. In blood ($pH=7.4$), aspirin has $p{K}_a$ of 3.4. What is the ratio of $A^{-}$ to $HA$?

1. 1:10000
2. 1000:1
3. 10000:1
4. 100:1

Q. Calculate the pH of an acidic buffer solution containing $1.2MC{H}_{3}COONa$ and $0.8MC{H}_{3}COOH$.
For acetic acid $K_a=1.8\times {10}^{-5}$

1. 4.92
2. 3.66
3. 6.89
4. 5.88

Q. A student prepares a buffer solution which contains $0.05\text{mol}d{m}^{-3}$ $HCOOH$ and $0.250mold{m}^{-3}$ $HCO{O}^{-}N{a}^{+}.$ The $K_a$ of $HCOOH$ is $1.78\times {10}^{-4}.$ Calculate the pH of the solution.
$log1.78=0.250,log5=0.699$

1. 12.5
2. 4.45
3. 6.2
4. 7.5

Q. When 100 $mL$ of 1.0 $M$ $HCl$ was mixed with 100 $mL$ of 1.0 $M$ $NaOH$ in an insulated beaker at constant pressure, a temperature increase of ${5.7}^{\circ }C$ was measured for the beaker and its contents (Expt 1). Because the enthalpy of neutralization of a strong acid with a strong base is a constant (-57.0 $kJmo{l}^{-1}$), this experiment could be used to measure the calorimeter constant. In a second experiment (Expt 2), 100 $mL$ of 2.0 $M$ acetic acid $(K_a=2.0\times {10}^{-5})$ was mixed with 100 $mL$ of 1.0 $M$ $NaOH$ (under identical conditions to Expt 1) where a temperature rise of ${5.6}^{\circ }C$ was measured.
(Consider heat capacity of all solutions as $4.2J{g}^{-1}{K}^{-1}$ and density of all solutions as $1.0gm{L}^{-1}$)

Enthalpy of dissociation (in $kJ$ $mo{l}^{-1}$) of acetic acid obtained from the Expt. 2 is:

1. 1
2. 10
3. 24.5
4. 51.4

Q. Acidic buffer means weak acid and its salt with strong base. Then how sodium acetate and acetic acid form acidic buffer? They both are weak acids and bases.

Q. To maintain the $pH$ of $7.4$ for blood at normal condition which is $2M$ in $H_{2}C{O}_3$ (at equilibrium), what volume of $7.8MNaHC{O}_3$ solution is required to mix with $10\text{mL}$ of blood?
$\text{Given}:K\left(H_{2}C{O}_3\right)=7.8\times {10}^{-7};{10}^{7.4}=2.511\times {10}^7$

1. $25.11\text{mL}$
2. $100.44\text{mL}$
3. $50.22\text{mL}$
4. $5.022\text{mL}$

Q. Match the (solution) given in List I with their characteristics in List II.

Q. In a buffer solution consisting of a weak acid and its salt, the ratio of concentration of salt to acid is increased tenfold, then the $pH$ of the solution will:

1. Increase by one
2. Increase tenfold
3. Decrease by one
4. Decrease tenfold

Q. Consider an acidic buffer solution of acetic acid and sodium acetate at ${25}^{o}C$. What should be the ratio of concentration of sodium acetate and acetic acid so that $pH=4$ is obtained ?

Given :$K_a$ value of acetic acid is $1.8\times {10}^{-5}$ $\text{and}{10}^{(-0.75)}=0.18$

1. $0.18:1$
2. $1:0.18$
3. $1:1.81$
4. None of the above

Q. $C{H}_{3}COOH$ is titrated with $NaOH$ solution. Find the ratio $\left(\frac{\left[C{H}_{3}COONa\right]}{\left[C{H}_{3}COOH\right]}\right)$ when the volume of $NaOH$ added is half that of equivalence point.

1. 2.5
2. 0.5
3. 0.75
4. 1

Q. Any buffer can be used as a buffer up to:

1. $1pH$ units
2. $2pH$ units
3. $10pH$ unts
4. $5pH$ units

Q. What is the pH of the solution when 0.2 mol of $HCl$ is added to one litre of a solution containing 1M acetic acid and acetate ions. Assume that the total volume is one litre. $K_a\left(C{H}_{3}COOH\right)=1.8\times {10}^{-5}$
$log\left(1.8\right)=0.255,log\left(0.66\right)=-0.181$

1. 9.04
2. 4.56
3. 7.2
4. 6.5

Q. The standard hydrolysis constant of anilinium acetate at ${25}^{\circ }\text{C}$ is $\left(K_a\right(C{H}_{3}COOH)=1.8\times {10}^{-5}M,K_b(\text{Aniline})=4.6\times {10}^{-10})$

1. 1
2. 1.21
3. 1.35
4. 2.6

Q. How much sodium formate $(HCOONa,68.0069gmo{l}^{-1})$ is to be added to 400 mL of 1.00 M formic acid for a pH=3.50 buffer. Given $K_a=1.77\times {10}^{-4}$
$log1.77=0.248\text{and log}0.56=-2.52$

1. 20.25 g
2. 15.23 g
3. 30.34 g
4. 5.50 g

Q. When 100 $mL$ of 1.0 $M$ $HCl$ was mixed with 100 $mL$ of 1.0 $M$ $NaOH$ in an insulated beaker at constant pressure, a temperature increase of ${5.7}^{\circ }C$ was measured for the beaker and its contents (Expt 1). Because the enthalpy of neutralization of a strong acid with a strong base is a constant (-57.0 $kJmo{l}^{-1}$), this experiment could be used to measure the calorimeter constant. In a second experiment (Expt 2), 100 $mL$ of 2.0 $M$ acetic acid $(K_a=2.0\times {10}^{-5})$ was mixed with 100 $mL$ of 1.0 $M$ $NaOH$ (under identical conditions to Expt 1) where a temperature rise of ${5.6}^{\circ }C$ was measured.
(Consider heat capacity of all solutions as $4.2J{g}^{-1}{K}^{-1}$ and density of all solutions as $1.0gm{L}^{-1}$)

Enthalpy of dissociation (in $kJ$ $mo{l}^{-1}$) of acetic acid obtained from the Expt. 2 is:

1. 1
2. 10
3. 24.5
4. 51.4