Physical Chemistry

Question 1

Equilibrium constant

Answer 1

K. A measure of the ratio of the concentration of products to reactants at equilibrium– the position of the equilibrium

Question 2

Increasing/ decreasing K

Answer 2

The only thing that affects K is temperature

Question 3

Definition of an acid

Answer 3

It donates H+ ions

Question 4

Definition of a base

Answer 4

It accepts H+ ions

Question 5

Conjugate acid/ base

Answer 5

What is formed on the other side of the reaction e.g. acid is conjugate base. The stronger the acid, the weaker the conjugate base

Question 6

H+ ions

Answer 6

Just a proton. Forms a cluster in water, simplest being H30+, or hydronium (dative covalent bond between H+ and H2O)

Question 7

PKw

Answer 7

14

Question 8

Strength of acid/ base depends on?

Answer 8

How well they dissociate in water

Question 9

Strong acids

Answer 9

Dissociate completely into ions. Have a higher conductivity, lower pH and faster reaction rate due to higher H+ concentration

Question 10

Weak acids

Answer 10

Don’t completely dissociate into ions

Question 11

Examples of strong acids

Answer 11

HCL, HNO3, H2SO4

Question 12

Examples of weak acids

Answer 12

Ethanoic acid, methanoic acid, carbonic acid, and sulphurous acid

Question 13

Ka

Answer 13

acid dissociation constant. The larger the Ka, the more the acid breaks down, so the stronger it is

Question 14

PH

Answer 14

Depends on Ka, concentration of acid and salt

Question 15

Strong bases examples

Answer 15

Sodium hydroxide, potassium hydroxide, lithium hydroxide

Question 16

Weak bases examples

Answer 16

Basically anything with Amm in it e.g. ammonia

Question 17

PH of a salt solution

Answer 17

Depends on strength of the acid and base from which it was formed (pH depends on which one is strongest)

Question 18

Equilibrium of when a solvent is soluble in two different solvents

Answer 18

K= [solute] in solvent A divided by
[solute] in solvent B

Question 19

Soap

Answer 19

Salt formed from a fatty acid (weak) and Na or K hydroxide

Question 20

Amphoteric substance

Answer 20

Can act as acids or bases e.g. water

Question 21

Ka of dissociated ions

Answer 21

Ka= [H+] [A]
—————-
[HA]

Question 22

Buffer solutions

Answer 22

Has a pH which remains constant (ish) despite the addition of small amounts of H+ or OH- ions

Question 23

Base added to buffer solutions

Answer 23

H+ ions are removed and excess x molecules break up to replace them

Question 24

Equilibrium in a chemical reaction

Answer 24

when the composition of the reactants and the products remains constant indefinitely

Question 25

Endothermic reactions and K

Answer 25

a rise in temperature causes an increase in K and the yield of the product is increased

Question 26

Exothermic reactions and K

Answer 26

a rise in temperature causes a decrease in K and the yield of the product is decreased

Question 27

catalyst and K

Answer 27

a catalyst does not affect the value of K

Question 28

indicators

Answer 28

weak acids

Question 29

standard enthalpy of formation

Answer 29

the enthalpy change when one mole of a substance is formed from its elements in their standard states

Question 30

positive S

Answer 30

the greater the degree of disorder, the greater the entropy

Question 31

second laws of thermodynamics

Answer 31

the total entropy of a reaction system and its surroundings always increases for a spontaneous process

Question 32

exothermic reactions and entropy

Answer 32

heat energy released increases the entropy

Question 33

endothermic reactions and entropy

Answer 33

heat energy absorbed decreases the entropy

Question 34

the third law of thermodynamics

Answer 34

the entropy of a perfect crystal at 0K is zero

Question 35

-- Gibb's

Answer 35

the reaction is feasible

Question 36

order of a reaction

Answer 36

can only be determined through experimental data

Question 37

rate determining step

Answer 37

the slowest step of the reaction, which the rate of the reaction is dependent on

Question 38

reaction feasibility for reversible reactions

Answer 38

equilibrium will lie to the left

Question 39

reaction feasibility for non-reversible reactions

Answer 39

equilibrium will lie to the right