CBI2 - Fundamentals of Chemistry II

Question 1

What are the three ways of describing concentration, including units.

Answer 1

Molar concentration ( mol/dm3). Mass concentration (g/dm3). Volume concentration (v/v %).

Question 2

Difference between dilution ratio and dilution factors.

Answer 2

Dilution ratio 1:10 means 11 parts total (1 part sample, 10 parts solvent).
Dilution factor 1:10 means 10 parts total (1 part sample, 9 parts solvent).

Question 3

Define serial dilution.

Answer 3

Where solution made is used as stock solution for following dilution.

Question 4

Formulas for calculation concentration/volume with two solutions.

Answer 4

C1 x V1 = C2 x V2

Question 5

Define Ka.

Answer 5

Acid dissociation constant for weak acids.

Question 6

Why is water ignored in acid dissociation constant.

Answer 6

Very large concentration/activity therefore its effect is considered constant.

Question 7

Define and discuss ionic product of water.

Answer 7

Kw = [H+][OH-]

Used to calculate pH of strong bases. Value of 1 x 10-14 at room temperature.

Question 8

Define Bronstred Lowry acids and bases.

Answer 8

Acid - proton donor. Base - proton acceptor.

Question 9

Is high pKa associated with strong or weak acids.

Answer 9

High pKa = low Ka = weak acid.

Question 10

How to calculate pH of strong acid.

Answer 10

Use pH = -log[H+].

Question 11

How to calculate pH of weak acids.

Answer 11

Use formula for Ka. Assume [H+] = [A-]. Rearrange for [H+] and calculate pH.

Question 12

How to calculate pH of strong base.

Answer 12

Use Kw = [H+][OH-]. Rearrange for [H+] and calculate pH.

Question 13

Define relationship between pH and pOH.

Answer 13

pH + pOH = 14.

Question 14

Define buffer solution.

Answer 14

A solution that maintains its pH when small amounts of acid or base are added to it. Works best with +/- 1 of pKa.

Question 15

How are buffers produced.

Answer 15

Weak acid and conjugate base.

Weak base and conjugate acid.

Question 16

How does a weak acid and conjugate base result in a buffer solution.

Answer 16

Weak acid partially dissociates releasing some conjugate base. Salt of acid added provided more conjugate base until complete dissociation.

Question 17

Define Henderson-Hasselbach equation.

Answer 17

pH = pKa +log[A-]/[HA].

Question 18

When does pH = pKa.

Answer 18

Using HH equation, when concentration of undissociated acid is equal to conjugate base concentration. Point is known as half neutralisation point.

Question 19

Define Avogadro’s constant.

Answer 19

Number of a species in a mole. 6.022x10*23/mol.

Question 20

Define and give value of Avogadros constant.

Answer 20

6.022 X 10^23. Defines number of particles in a mole.

Question 21

Define molarity.

Answer 21

Same as molar concentration. Moles divided by volume.

Question 22

Difference between formula and molecular mass.

Answer 22

Molecular mass - mass of one molecular of a substance.

Formula weight - used when substance does not exist as one molecule e.g. ionic lattices.

Question 23

Notations for avogadros constant.

Answer 23

Na or L

Question 24

What is a stock solution.

Answer 24

Initial solution used to create a serial dilution.

Question 25

Discuss activity vs concentration.

Answer 25

Concentration and activity are similarly linked. Activity has no units.

Question 26

Value for ionic product of water.

Answer 26

Kw = 1.0 X 10^-14

Question 27

Define Lewis acids and bases.

Answer 27

Electron pair acceptor. Electron pair donor.

Question 28

What does a low Ka indicate.

Answer 28

Low Ka = high pKa = weak acid.

Question 29

Is Ka/pKa high or low for strong acids?

Answer 29

High Ka, low pKa.

Question 30

Discuss Henderson Hasselbach equation.

Answer 30

pH = pKa + log([base]/[acid])
pH = pKa at half neutralisation point.