Chapters 10-12- Equilibria in Action

Question 1

How do you find the molarity of a solution?

Answer 1

Molarity (c) = amount of solute (mol) / volume of solution (l)

Question 2

How do you find the molality of a solution?

Answer 2

Molality (b) = amount of solute (mol) / mass of solvent (kg)

Question 3

How do you find the molar fraction of A?

Answer 3

xA = moles of A / total moles

Question 4

What makes dissolution spontaneous?

Answer 4

ΔG = ΔH − TΔS < 0
In creating a mixture, ΔS > 0
so spontaneity depends upon whether ΔH < TΔS

Question 5

What factors need to be considered with enthalpy change?

Answer 5

Breaking the solute–solute interactions and creating solute–solvent interactions

Question 6

What types of solids don’t dissolve in water?

Answer 6

Non-polar organic solids, such as hydrocarbons,

Question 7

What types of solids do dissolve in water?

Answer 7

Polar organic solids, such as alcohols and amines

Question 8

Define the term ‘Solute’

Answer 8

The dissolved substance contained in a solution

Question 9

Define the term ‘solvent’

Answer 9

The liquid component of a solution

Question 10

Define the term ‘solution’

Answer 10

A homogeneous mixture in which all the particles are of the size of atoms, small molecules or ions.

Question 11

Define the term ‘homogeneous’

Answer 11

Denoting a process involving substances in the same phase (solid, liquid, or gaseous)

Question 12

Define the term ‘heterogeneous’

Answer 12

Of or denoting a process involving substances in different phases (solid, liquid, or gaseous).

Question 13

Formula for the solubility product, Ksp, for the equation M(a)X(b) ⇌ aM^b+ + bX^a-

Answer 13

Ksp = [M^b+][X^a-]

Question 14

How does the presence of a solute affect the boiling point and melting point?

Answer 14

The presence of a solute lowers the freezing point and raises the boiling point of a solvent

Question 15

What’s the Brønsted–Lowry definition of acids?

Answer 15

Acids are proton donors

Question 16

What’s the Brønsted–Lowry definition of bases?

Answer 16

Bases are proton acceptors

Question 17

What are conjugate pairs?

Answer 17

A conjugate pair is an acid-base pair that differs by one proton in their formulas. A conjugate pair is always one acid and one base.

Question 18

Standard reaction of an acid in water

Answer 18

HA + H2O ⇌ H3O+ + A–

Question 19

Ka =

Answer 19

[H3O+][A-] / [HA]
In the absence of any other ions [H3O+] = [A-] so
Ka = ([H3O+]^2) / [HA]

Question 20

pKa=

Answer 20

− log(Ka)

Question 21

What’s the main difference between weak and strong acids?

Answer 21

Strong acids dissociate almost completely, so that Ka ≫ 1, pKa < 0
Weak acids dissociate only sparingly, so that Ka ≪ 0, pKa > 0