Question 1

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

Accepted Answer

NaF

Question 2

A buffer solution is best described as:

Accepted Answer

A solution that resists changes in pH when small amounts of acid or base are added

Question 3

Which of the following pairs can be used to make a buffer solution with a pH close to 9.25? (Assume $$pK_b of NH$_3 is 4.75)$$

Accepted Answer

NH$$_3$$ and NH$$_4Cl$$

Question 4

What is the pH of a buffer solution made by mixing 0.10 M acetic acid ($$CH_3COOH) $$and 0.10 M sodium acetate ($$NaCH_3COO$$)? ($$pK_a of $$acetic acid = 4.74)

Accepted Answer

$$pH = 4.74$$

Question 5

Which of the following best explains why the conjugate base of a strong acid does not affect the pH of a solution?

Accepted Answer

It is too weak to accept a proton from water

Question 6

Calculate the pH of a buffer solution containing 0.050 M $$CH_3COOH$$ and 0.100 M $$NaCH_3COO$$. ($$K_a$$ for acetic acid = $$6.5 	imes 10$$^{-5}$$)

Accepted Answer

$$pH = 4.96$$

Question 7

Which of the following statements about the equivalence point in a titration of a weak acid with a strong base is correct?

Accepted Answer

The moles of added base equal the moles of weak acid originally present

Question 8

A 25.0 mL sample of 0.10 M formic acid ($$HCOOH) is $$titrated with 0.10 M NaOH. What is the pH after adding 10.0 mL of NaOH? ($$K_a$$ for formic acid = $$1.8 	imes 10$$^{-4}$$)

Accepted Answer

$$pH = 3.75$$

Question 9

Which of the following is the correct form of the Henderson-Hasselbalch equation?

Accepted Answer

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

Question 10

Which of the following best describes the energy change when a system absorbs heat and does work on the surroundings?

Accepted Answer

$$\Delta E_{sys} = q + w$$, where $$q \u003e 0$$ and $$w \u003c 0$$

Question 11

How much heat (in J) is absorbed by a 3.10 g copper penny when its temperature increases from $$-80.0^\circ C to$$ $$37.0^\circ C$$? ($$C_s$$ for Cu = $$0.385 \frac{J}{g \cdot ^\circ C})$$

Accepted Answer

$$53.7\ J$$

Question 12

Which of the following is true about the standard enthalpy of formation ($$\Delta H_f^\circ) $$for an element in its most stable form?

Accepted Answer

$$\Delta H_f^\circ = 0$$

Question 13

A reaction releases 713.8 kJ of heat when 15.4 g of $$C_3H_8 is $$burned in excess $$O_2. $$What is the enthalpy change per mole of $$C_3H_8$$? (Molar mass $$C_3H_8 = 44.1\ g/mol)$$

Accepted Answer

$$-2044\ kJ/mol$$

Question 14

Which of the following best describes an open system in thermodynamics?

Accepted Answer

A system that can exchange both energy and matter with its surroundings

Question 15

If 1.5 kJ of work is done on a system and the system releases 0.75 kJ of heat, what is the change in internal energy ($$\Delta E$$)?

Accepted Answer

$$\Delta E = 0.75\ kJ$$

Question 16

Which of the following is the correct relationship for work done by a system at constant external pressure?

Accepted Answer

$$w = -P_{ext} \Delta V$$

Question 17

Which of the following statements about buffers is FALSE?

Accepted Answer

A buffer is made by mixing a strong acid and its conjugate base

Question 18

Which of the following best describes the enthalpy change ($$\Delta H) $$for an exothermic reaction?

Accepted Answer

$$\Delta H \u003c 0$$

Acids, Bases, Buffers, and Thermochemistry: General Chemistry Study Notes

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