Q: A coffee cup calorimeter is used to measure the enthalpy change of a reaction. If 100 g of water absorbs 836 J of heat and the temperature increases by 2 °C, what is the specific heat capacity of water based on this experiment? Use $q = m c riangle T$.

$c = \frac{q}{m \triangle T} = \frac{836}{100 \times 2} = 4.18\ \mathrm{J/g\cdot ^\circ C}$

Q: A reaction has an enthalpy change of $\triangle H = -250\ \mathrm{kJ}$. What does this indicate about the reaction?

The reaction is exothermic and releases 250 kJ of heat.

Q: Which of the following is true regarding the application of Hess's Law?

Multiplying a reaction by a factor multiplies $\triangle H$ by the same factor.

Q: A solution has $[H^+] = 1.0 \times 10^{-5}\ \mathrm{M}$. What is its pH?

$pH = -\log(1.0 \times 10^{-5}) = 5$

Q: A buffer is made by mixing 0.10 mol of acetic acid (HA) and 0.10 mol of sodium acetate (A$^-$) in 1.0 L of water. If the $pK_a$ of acetic acid is 4.76, what is the pH of the buffer? Use the Henderson-Hasselbalch equation.

$pH = pK_a + \log \left( \frac{[A^-]}{[HA]} \right ) = 4.76 + \log(1) = 4.76$

Q: Which of the following will increase the buffer capacity of a solution?

Increasing the total concentration of acid and base.

Q: Which indicator would be most suitable for a titration with an equivalence point at pH = 9?

An indicator with $pK_a \approx 9$

Q: A buffer solution is destroyed when:

Either the weak acid or the conjugate base is completely consumed.

Q: Which of the following is a correct statement about the neutralization of a weak acid (HA) with a strong base (OH$^-$)?

HA + OH$^-$ $\rightarrow$ A$^-$ + H$_2$O

Question 1

A coffee cup calorimeter is used to measure the enthalpy change of a reaction. If 100 g of water absorbs 836 J of heat and the temperature increases by 2 °C, what is the specific heat capacity of water based on this experiment? Use $q = m c 	riangle T$.

Accepted Answer

$c = \frac{q}{m 	riangle T} = \frac{836}{100 	imes 2} = 4.18\ \mathrm{J/g\cdot ^\circ C}$

Question 2

Which of the following statements about exothermic and endothermic reactions is correct?

Accepted Answer

Exothermic reactions release heat to the surroundings ($q < 0$).

Question 3

A reaction has an enthalpy change of $	riangle H = -250\ \mathrm{kJ}$. What does this indicate about the reaction?

Accepted Answer

The reaction is exothermic and releases 250 kJ of heat.

Question 4

Which of the following is true regarding the application of Hess's Law?

Accepted Answer

Multiplying a reaction by a factor multiplies $	riangle H$ by the same factor.

Question 5

Which of the following acids is considered a strong acid?

Accepted Answer

HNO$_3$

Question 6

According to the Brønsted-Lowry definition, which statement is correct?

Accepted Answer

An acid is a proton donor.

Question 7

A solution has $[H^+] = 1.0 	imes 10^{-5}\ \mathrm{M}$. What is its pH?

Accepted Answer

$pH = -\log(1.0 	imes 10^{-5}) = 5$

Question 8

Which of the following is the correct relationship between $K_w$, $K_a$, and $K_b$ for a conjugate acid-base pair?

Accepted Answer

$K_w = K_a 	imes K_b$

Question 9

A buffer is made by mixing 0.10 mol of acetic acid (HA) and 0.10 mol of sodium acetate (A$^-$) in 1.0 L of water. If the $pK_a$ of acetic acid is 4.76, what is the pH of the buffer? Use the Henderson-Hasselbalch equation.

Accepted Answer

$pH = pK_a + \log \left( \frac{[A^-]}{[HA]} \right ) = 4.76 + \log(1) = 4.76$

Question 10

Which of the following will increase the buffer capacity of a solution?

Accepted Answer

Increasing the total concentration of acid and base.

Question 11

During a titration of a weak acid with a strong base, what is the pH at the half-equivalence point?

Accepted Answer

pH = pK_a

Question 12

Which indicator would be most suitable for a titration with an equivalence point at pH = 9?

Accepted Answer

An indicator with $pK_a \approx 9$

Question 13

A buffer solution is destroyed when:

Accepted Answer

Either the weak acid or the conjugate base is completely consumed.

Question 14

Which of the following is a correct statement about the neutralization of a weak acid (HA) with a strong base (OH$^-$)?

Accepted Answer

HA + OH$^-$ $\rightarrow$ A$^-$ + H$_2$O

Question 15

If the percent ionization of a weak acid is 2% and the initial concentration is 0.10 M, what is the concentration of $H^+$ ions?

Accepted Answer

$[H^+] = 0.10 	imes 0.02 = 0.002\ \mathrm{M}$

Question 16

Which of the following ions will make a solution acidic when dissolved in water?

Accepted Answer

NH$_4^+$

Question 17

What is the pOH of a solution with $[OH^-] = 1.0 	imes 10^{-3}\ \mathrm{M}$?

Accepted Answer

$pOH = -\log(1.0 	imes 10^{-3}) = 3$

Question 18

A student wants to prepare a buffer with pH = 5.0. Which acid should they choose?

Accepted Answer

An acid with $pK_a$ close to 5.0

Question 19

During the titration of a weak base with a strong acid, what is true at the equivalence point?

Accepted Answer

The solution contains the conjugate acid and pH < 7.

General Chemistry Study Notes: Thermochemistry, Acids & Bases, and Aqueous Ionic Equilibria

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