chemical equilibrium

Question 1

forward reaction

Answer 1

initial reactants are used up quickly but slow down as the concentration drops

Question 2

backward reaction

Answer 2

initially reactants are reformed slowly but speed up as the concentration of products increases

Question 3

le chatiliers principle

Answer 3

if a reaction is at equilibrium is subjected to a change in pressure or temperature or conc
portion of equilibrium will move to counteract the change

Question 4

eq shift left

Answer 4

make more reactants

Question 5

eq shift right

Answer 5

make more products

Question 6

change of concentration
3h2 + n2 → 2nh3

Answer 6

increased concentration of reactant or product
Equilibrium shifts to reduce the concentration
3h2 + n2 → 2nh3
increase in h3 conc equilibrium will shift right to use it up and reduce the concentration and more nh3 is produced
increase in the nh3 concentration equilibrium shifts left to use it up and reduce the concentration so more h2 and n2 produced

Question 7

changing temperature
3h2 + n2 → 2nh3

Answer 7

3h2 + n2 → 2nh3
increase temperature equilibrium will shift to reduce the temp in the endothermic direction so more n2 or h2 produced
decrease in temp equilibrium shifts in exothermic direction increasing the temp and more nh3 produced

Question 8

catalysts

Answer 8

no effect on equilibrium
speeds up forward and backward reaction equally so no effect on yield

Question 9

making ethanol

Answer 9

c2h4 + h2o→ c2h5oh
pressure 60
temp 300
phosphoric acid catalyst
forward reaction is exothermic so decreases temp equilibrium shifts right producing more ethanol

Question 10

low temp

Answer 10

lower rate of a reaction
300 is a compromise between yield and rate

Question 11

pressure

Answer 11

high pressure means equilibrium shifts right producing more ethanol
less moles of gas on right so equilibrium shits right to reduce pressure
high pressure increases rate
hp environment expensive due to thick and robust vessels and pipes needed
compromise between yield speed and cost

Question 12

temp effect on KC

Answer 12

only valid for one temp
change in temp = change in equilibrium concentration so kc changes too
if temp change causes equilibrium to shift right ks increases
if temp change causes equilibrium to shift left kc decreases