Question 1

Which of the following acids has the strongest conjugate base? Use the $K_a$ values below:

$\begin{array}{l|c}
	ext{Acid} & K_a \
\hline
	ext{HNO}_3 & 4.5 	imes 10^0 \
	ext{HClO}_4 & 1.0 	imes 10^1 \
	ext{HCN} & 4.9 	imes 10^{-10} \
	ext{HCOOH} & 1.8 	imes 10^{-4} \
\end{array}$

Accepted Answer

HCN

Question 2

A solution of 0.01 M CH$_3$COOH (acetic acid) has a $K_a = 1.8 	imes 10^{-5}$. What is the concentration of H$_3$O$^+$ ions at equilibrium?

Accepted Answer

$4.2 	imes 10^{-4}$ M

Question 3

Which of the following statements is true about strong acids?

Accepted Answer

They completely dissociate in water.

Question 4

Calculate the pH of a 0.025 M HNO$_3$ solution. Assume complete dissociation.

Accepted Answer

pH = $-\log(0.025) = 1.60$

Question 5

A buffer is made by mixing 0.10 mol of NH$_3$ and 0.10 mol of NH$_4$Cl in 1.0 L of solution. If $K_b$ for NH$_3$ is $1.8 	imes 10^{-5}$, what is the pH of the buffer? ($K_w = 1.0 	imes 10^{-14}$)

Accepted Answer

pH = $9.25$

Question 6

Which of the following combinations would be best to prepare a buffer with a pH of 9.5?

Accepted Answer

NH$_3$ and NH$_4$Cl

Question 7

What is the solubility (in mol/L) of PbI$_2$ in water if $K_{sp} = 8.5 	imes 10^{-9}$?

Accepted Answer

$1.3 	imes 10^{-3}$

Question 8

Which of the following salts will produce a basic solution when dissolved in water?

Accepted Answer

NaNO$_2$

Question 9

A 0.10 M solution of a weak acid HA has a $K_a = 1.0 	imes 10^{-5}$. What is the pH of the solution?

Accepted Answer

pH = $3.00$

Question 10

Which of the following is the best indicator for a titration of a weak acid with a strong base?

Accepted Answer

Phenolphthalein

Question 11

Which of the following is true about the relationship between acid strength and conjugate base strength?

Accepted Answer

A strong acid has a weak conjugate base.

Question 12

Calculate the pH at the equivalence point for the titration of 0.100 M CH$_3$COOH with 0.100 M NaOH. ($K_a$ for CH$_3$COOH = $1.8 	imes 10^{-5}$)

Accepted Answer

pH = $8.72$

Question 13

Which of the following is the correct expression for the solubility product constant ($K_{sp}$) for Ca$_3$(PO$_4$)$_2$?

Accepted Answer

$K_{sp} = [Ca^{2+}]^3[PO_4^{3-}]^2$

Question 14

A solution is prepared by mixing 0.10 M NH$_3$ and 0.10 M NH$_4$Cl. What is the ratio $\dfrac{[NH_3]}{[NH_4^+]}$ when the pH equals the p$K_a$ of NH$_4^+$?

Accepted Answer

1

Question 15

Which of the following will increase the solubility of AgCl in water?

Accepted Answer

Adding NH$_3$

Question 16

A 0.10 M solution of a weak base B has a $K_b = 1.0 	imes 10^{-5}$. What is the pOH of the solution?

Accepted Answer

pOH = $5.00$

Question 17

Which of the following is the best choice for a buffer with a pH near 5?

Accepted Answer

CH$_3$COOH and CH$_3$COONa

Question 18

Which of the following is the correct formula for calculating the pH of a weak acid solution?

Accepted Answer

$pH = -\log([H_3O^+])$

Question 19

A 0.10 M solution of HCN ($K_a = 4.9 	imes 10^{-10}$) is prepared. What is the pH of the solution?

Accepted Answer

pH = $5.00$

Acids, Bases, and Equilibrium: General Chemistry Study Notes

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