equillibria + acid base

Question 1

what is Le Chatelier’s principle

Answer 1

if a reaction at equilibrium is subjected to a change in pressure, temperature or concentration, the position of equilibrium will move to counteract the change

Question 2

what happens if you increase conc in homogenous reversible reaction

Answer 2

equillibrium will shift to try and reduce the conc (use up the increased conc)

Question 3

what happens if you increase pressure in homogenous reversible reaction

Answer 3

equilibrium will shift to try and reduce the pressure (shifts to side with fewest number of gas particles)

Question 4

what happens when you increase the temp in homogenous reversible reaction

Answer 4

equilibrium shifts to endothermic direction to reduce temp

Question 5

conditions for making ethanol

Answer 5

60atm pressure
300C temperature
phosphoric acid catalyst, H3PO4

Question 6

what is dynamic equilibrium

Answer 6

when both the rate of the forward and backward reaction are equal, the conc of reactants and products remain constant

Question 7

what do catalysts do to equilibrium

Answer 7

they affect forward and backward reaction equally, allowing equilibrium to be reached faster

Question 8

what states do we use in Kc expressions

Answer 8

aqueous + gases
only in homogenous equillibria

Question 9

what is the one thing that affects Kc

Answer 9

if temperature changes
if anything else shifts equillibria the conc of reactants and products stay in same ratio

Question 10

why does changing the concentration of a species not affect Kc

Answer 10

increasing 1 species will shift equilibrium to restore the conc to be proportional so same ratio of reactants and products are still in equilibrium

Question 11

how to work out Kc in opposite direction

Answer 11

1/ Kc for other reaction

Question 12

what is the partial pressure of a gas

Answer 12

the pressure the gas would exert if it alone occupied the volume of the mixture

Question 13

in exothermic reaction what happens to Kc/Kp when temp is increased

Answer 13

become smaller as position of equilibrium moves to the left so less products over reactants

Question 14

why do catalysts not affect Kp or Kc

Answer 14

they affect the rate of reaction but not the position of equilibrium, so they are only affecting how fast the system reaches equilibrium

Question 15

what is a Bronsted Lowry base

Answer 15

proton acceptor

Question 15

what is a Bronsted Lowry acid

Answer 15

proton donor

Question 16

is a Bronsted Lowry conjugate acid positive / negative

Answer 16

positive, accepts protons

Question 17

is a Bronsted Lowry conjugate base positive / negative

Answer 17

negative, donates protons

Question 18

define pH

Answer 18

-log H+ concentration

Question 19

what is a strong acid

Answer 19

an acid that completely dissociates into ions in a solution, releasing the greatest number of hydrogen ions

Question 20

what is a weak acid

Answer 20

an acid that only partially dissociates in water to produce hydrogen ions

Question 21

define the ionic product of water Kw

Answer 21

the product of the molar concentrations of hydrogen ions and hydroxide ions in water at a specific temperature

Question 22

define pKa

Answer 22

10^ -Ka

Question 23

what does buffer solution mean

Answer 23

a solution that resists changes in pH when small volumes of an acid or base is added to it

Question 24

explain the use of blood being a buffer

Answer 24

carbon dioxide dissolved in the blood forms carbonic acid

so carbonic acid will shift right forming more H+ and hydrogencarbonate ions

large reservoir of hydrogencarbonate ions will react with H+ to restore pH

Question 25

why is the enthalpy of neutralisation less for weak acids

Answer 25

only partially dissociate/ionise
some H+ are not free to react with OH- ions

Question 26

why are solids and liquids not in Kc expression

Answer 26

we assume that their concentrations remain constant

Question 27

whats total pressure

Answer 27

sum of all the pressures of the individual gases

Question 28

what affect does changing temperature have on Kp

Answer 28

if temperature change causes equilibrium to shift right then Kp will increase