OAT General Chemistry 3

Question 1

The Henderson-Hasselbalch equation is used to calculate:

Accepted Answer

pH of a buffer solution

Answer

The Henderson-Hasselbalch equation (pH = pKa + log([A⁻]/[HA])) calculates the pH of buffer solutions.

Question 2

Which of the following represents an endothermic process?

Accepted Answer

Dissolution of ammonium nitrate in water

Answer

Dissolution of NH4NO3 in water absorbs heat (feels cold), making it an endothermic process.

Question 3

What is the molarity of a solution made by dissolving 4.0 g of NaOH (MW = 40 g/mol) in enough water to make 500 mL of solution?

Accepted Answer

0.2 M

Answer

Moles of NaOH = 4.0/40 = 0.1 mol; Molarity = 0.1 mol / 0.5 L = 0.2 M.

Question 4

Which of the following is a Lewis acid?

Accepted Answer

BF3

Answer

BF3 is a Lewis acid because it is an electron pair acceptor (boron has an empty p orbital).

Question 5

In an electrochemical cell, oxidation occurs at the:

Accepted Answer

Anode

Answer

Oxidation (loss of electrons) always occurs at the anode in any electrochemical cell.

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