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: 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}$$) = 5$$

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 ($$q \u003c 0).$$

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$$^-$$ $$\rightarrow A$^- + H$_2O$$

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 \u003c 7.

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

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