Acidic Buffer Action

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 happens when an acid is added to a buffer?

Q.

How will you test pure chloroform?

Q. Which of the following aqueous solutions can act as an acidic buffer?

1. $0.1MC{H}_{3}COOH+0.1MC{H}_{3}COONa$
2. $0.5MHCl+0.5MNaCl$
3. $0.1MNaCl$
4. $0.1MC{H}_{3}COONa$

Q.

What is a stoichiometric point in the titration?

Q. Which of the following mixture which can acts as an acidic buffer solution ?

1. $HN{O}_3\text{and}C{H}_{3}COOH$
2. $HCl\text{and}C{H}_{3}COONa$
3. $H_{2}S{O}_4\text{and}C{H}_{3}COONa$
4. $C{H}_{3}COOH\text{and}C{H}_{3}COONa$

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

Q.

An acid type indicator, Hln differs in colour from its conjugate base ($I{n}^{-}$). The human eye is sensitive to colour differences only when the ratio $\frac{\left[I{n}^{-}\right]}{\left[Hln\right]}$ is greater than 10 or smaller than 0.1. What would be the minimum change in pH of the solution to observe a complete colour change ($K_a$ = $1.0\times {10}^{-5}$) ?

1. 2

2. 3.25

3. 6

4. 4

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

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. A buffer solution of $pH=5.74$ is to be prepared using $C{H}_{3}COOH$ and $C{H}_{3}COONa$. Find the concentration of sodium acetate to be added to $0.01M$ solution of $C{H}_{3}COOH$
$K_a\left(C{H}_{3}COOH\right)=1.8\times {10}^{-5}$
Take $log\left(1.8\right)=0.26$

1. 1 M
2. 1.5 M
3. 0.1 M
4. 0.5 M

Q. An unknown volume and unknown concentration of a weak acid $HX$ is titrated with $NaOH$ of unknown concentration. After addition of $10.0{\text{cm}}^3$ of the $NaOH$ solution, the $pH$ of the solution is 5.7. After the addition of $20.0{\text{cm}}^3$ of the $NaOH$ solution, the $pH$ is $6.3$. Calculate the $p{K}_a$ of the weak acid, HX. (Given: log2 = 0.3, log = 0.5)

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. 0.5
2. 0.75
3. 1
4. 2.5

Q. $2\text{g}$ of acetate ions in the form of sodium acetate are added to $500\text{mL}$ of a $0.10\text{M}$acetic acid solution of $p{K}_a\left(C{H}_{3}COOH\right)=4.74$. What is the $pH$ of the final solution?

1. $4.56$
2. $4.74$
3. $5.01$
4. $5.70$

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. Find the $pH$ of a $500mL$ solution containing 2.5 moles of $KCN$ and 2.5 moles of $HCN$ at ${25}^{o}C$.
Given:The $p{K}_b$ of cyanide ion $\left(C{N}^{-}\right)$ is 4.7

1. 9.3
2. 7.3
3. 10.3
4. 8.3

Q. Find the pH of the solution by mixing equal volumes of three acid solutions of $pH4,5,and6$ ?
$log\left(3.7\right)=0.57$

1. 6
2. 5.43
3. 5
4. 4.43

Q. Acidic buffer is made up of ?

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

Q. A $50mL$ solution of $0.2MC{H}_{3}COOH$ is titrated with $0.2MNaOH$. Find the $pH$ of solution when:
(a) $0mLNaOH$ is added ($p{H}_{initial}$)
(b) $10mL$ of $NaOH$ has been added ($p{H}_{10mL}$)

Given: $K_a\left(C{H}_{3}COOH\right)=1.8\times {10}^{-5}$

1. $p{H}_{initial}=2.72,p{H}_{10mL}=4.14$
2. $p{H}_{initial}=4.57,p{H}_{10mL}=2.17$
3. $p{H}_{initial}=5.7,p{H}_{10mL}=6.72$
4. $p{H}_{initial}=1.72,p{H}_{10mL}=7.28$

Q. 0.1 M $C{H}_3$COOH is titrated with 0.1M NaOH solution. What would be the difference in pH between $\frac{1}{4}$ and $\frac{3}{4}$ stages of neutralization of acid

1. $log\frac{1}{3}$
2. $2log\frac{1}{4}$
3. $2log\frac{3}{4}$
4. $2log3$

Q. Which of the following equimolar mixture can act as a salt buffer ?

1. $C{H}_{3}COOH+C{H}_{3}COONa$
2. $N{H}_{4}OH+N{H}_{4}Cl$
3. 
   $N{H}_{4}OH+C{H}_{3}COOH$
4. $HCl+NaOH$

Q. A $50mL$ solution of $0.2MC{H}_{3}COOH$ is titrated with $0.2MNaOH$. Find the $pH$ of solution when:
(a) $0mLNaOH$ is added ($p{H}_{initial}$)
(b) $10mL$ of $NaOH$ has been added ($p{H}_{10mL}$)

Given: $K_a\left(C{H}_{3}COOH\right)=1.8\times {10}^{-5}$

1. $p{H}_{initial}=2.72,p{H}_{10mL}=4.14$
2. $p{H}_{initial}=5.7,p{H}_{10mL}=6.72$
3. $p{H}_{initial}=1.72,p{H}_{10mL}=7.28$
4. $p{H}_{initial}=4.57,p{H}_{10mL}=2.17$

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 $pH=5$ is obtained ?

Given :$K_a$ value of acetic acid is $1.8\times {10}^{-5}$ ${\log }_{10}1.8=0.25\text{and}{10}^{\left(0.25\right)}=1.8$

1. $1:1.8$
2. $1.8:1$
3. $0.18:1$
4. $1:0.18$

Q. The $p{K}_a$ of a weak acid $\left(HA\right)$ is 4.5. The $pOH$ of an aqueous buffered solution of $HA$ in which 50% of the acid is ionized is:

1. 4.5
2. 2.5
3. 9.5
4. 7

Q. $20mL$ of $0.2M$ sodium hydroxide is added to $50mL$ of $0.2M$ acetic acid to give $70mL$ of the solution. Calculate the $pH$ of the solution.
The dissociation constant for $C{H}_{3}COOH$ is $1.8\times {10}^{-5}$.

1. 3.56
2. 4.56
3. 5.56
4. 6.56

Q. 8g of $NaOH$ was dissolved in 1 L of a solution containing one mole of acetic acid $C{H}_{3}COOH$ and one mole of sodium acetate $C{H}_{3}COONa$. Find the pH of the resulting solution.
The dissociation constant for $C{H}_{3}COOH$ is $1.8\times {10}^{-5}$.

1. 6.88
2. 4.92
3. 3.68
4. 5.76

Q. To produce a buffer solution that has a pH of 5.270 with already existing solution that contains 10.0 mmol of acetic acid in 1L of solution. How many millimoles of sodium acetate to added to this solutions?
When $p{K}_a$ of acetic acid is 4.752.
$log32.96=1.518$

1. 25
2. 10
3. 23
4. 33

Q. A certain buffer solution contains $X^{-}$ is twice the concentration of HX. If $K_a$ for HX is ${10}^{-6},$ then pH of buffer is

1. 7
2. 4.2
3. 6.3
4. 5.8