Basic Buffer Action

Q. $C{H}_{3}N{H}_2$ (0.1 mole $K_b$ = 5 $\times {10}^{-4})$ is added to 0.08 mole of HCl and the solution is diluted to one litre, resulting hydrogen ion concentration is

1. $5\times {10}^{-5}$
2. $1.6\times {10}^{-11}$
3. $8\times {10}^{-11}$
4. $8\times {10}^{-2}$

Q. $pH$ of resultant solution formed by mixing equal volumes of two solutions having $pH=5.8$ and $pH=12.8$ is

1. $12.5$
2. $5.5$
3. $6.1$
4. $13.1$

Q. Which will make a basic buffer?

1. $50mL$ of $0.1M$ $NaOH$ + $25mL$ of $0.1M$ $C{H}_{3}COOH$
2. $100mL$ of $0.1M$ $C{H}_{3}COOH$ + $100mL$ of $0.1M$ $NaOH$
3. $100mL$ of $0.1M$ $HCl$ + $200mL$ of $0.1M$ $N{H}_{4}OH$
4. $100mL$ of $0.1M$ $HCl$ + $100mL$ of $0.1M$ $NaOH$

Q. Calculate the ratio of $C{H}_{3}N{H}_2$ to $C{H}_{3}N{H}_3^{+}C{l}^{-}$ required to create a buffer with pH = 10.14
$K_{b}ofC{H}_{3}N{H}_2=4.4\times {10}^{-4}$
take $log2.27=0.356,log0.313=-0.504$

1. 0.5
2. 0.31
3. None of the above
4. 1.05

Q. Basic buffer is made up of ?

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

Q. Which will make basic buffer ?

1. $100mLof0.1MHCl+200mLof0.1MN{H}_{4}OH$
2. $100mLof0.1MC{H}_{3}COOH+100mLof0.1MNaOH$
3. $50mLof0.1MNaOH+25mLof0.1MC{H}_{3}COOH$
4. $100mLof0.1MHCl+100mLof0.1MNaOH$

Q. Calculate the weight in mg of HCl added to 100 ml of 0.1 N BOH to have its pH = 6.6 and $K_b=6.25\times {10}^{-8};$ Antilog $(-7.4)=3.98\times {10}^{-8}.$ (Assume there is no change in volume on addition of $HCl$)

1. 425
2. 223
3. 300
4. 100

Q. Calculate the concentration of $N{H}_{3}andN{H}_4^{+}C{l}^{-}$ present in the buffer solution of pH = 9, when total concentration of buffering reagents is 0.6 $mol{L}^{-1}.$ Take $p{K}_b$ for $N{H}_3=4.7,log2=0.3$

1. $\left[N{H}_4^{+}C{l}^{-}\right]=0.1M\text{and}\left[N{H}_3\right]=0.3M$
2. $\left[N{H}_4^{+}C{l}^{-}\right]=0.8M\text{and}\left[N{H}_3\right]=0.2M$
3. $\left[N{H}_4^{+}C{l}^{-}\right]=0.6M\text{and}\left[N{H}_3\right]=0.6M$
4. $\left[N{H}_4^{+}C{l}^{-}\right]=0.4M\text{and}\left[N{H}_3\right]=0.2M$

Q. Solution of 0.1 N $N{H}_{4}OH$ and 0.1 N $N{H}_{4}Cl$ has pH 9.25. $p{K}_b$ of $N{H}_{4}OH$ is :

1. 9.25
2. 4.75
3. 3.75
4. 8.25

Q. A $1L$ aqueous solution is made by mixing $N{H}_{4}OH$ and $HCl$ solution at ${25}^{\circ }C$.
This can act as a basic buffer when :

1. Molar concentration of weak base is more than the molar concentration of strong acid i.e $\left[N{H}_{4}OH\right]>\left[HCl\right]$
2. Molar concentration of weak base is equal to the molar concentration of strong acid i.e $\left[N{H}_{4}OH\right]=\left[HCl\right]$
3. A basic buffer is always formed by $N{H}_{4}OH$ and $HCl$
4. Molar concentration of weak base is less than the molar concentration of strong acid i.e $\left[N{H}_{4}OH\right]<\left[HCl\right]$