Physical Chemistry

Question 1

is bond-breaking endothermic or exothermic?

Answer 1

endothermic

Question 2

is bond-making endothermic or exothermic?

Answer 2

exothermic

Question 3

why is a reaction exothermic?

Answer 3

more energy is given out when bonds form than taken in to break bonds
negative enthalpy change

Question 4

why is a reaction endothermic?

Answer 4

more energy is taken in to break bonds than given out when bonds form
positive enthalpy change

Question 5

how is a dynamic equilibrium reached?

Answer 5

reversible reaction in sealed container:
concentration of reactants decreases so rate of forward reaction decreases
concentration of products increases so rate of backward reaction increases
until rate of forward reaction = rate of reverse reaction
& concentration of reactants & products stay the same

Question 6

what are the characteristics of a reaction at dynamic equilibrium?

Answer 6

rate of forward reaction equals the rate of reverse reaction
concentration of reactants & products stay constant

Question 7

what is the effect of a catalyst on position of equilibrium & why?

Answer 7

no effect
it speeds up the forward & reverse reaction by the same amount
equilibrium might be reached raster

Question 8

how does an increase in temperature affect the position of equilibrium?

Answer 8

increase in temperature shifts equilibrium to decrease temperature in endothermic direction
then say which direction

Question 9

how does a decrease in temperature affect the position of equilibrium?

Answer 9

decrease in temperature shifts equilibrium to increase temperature in exothermic direction

Question 10

how does an increase in pressure affect the position of equilibrium?

Answer 10

increase in pressure shifts equilibrium to decrease pressure in direction that produces fewer gas moles

Question 11

how does a decrease in pressure affect the position of equilibrium?

Answer 11

decrease in pressure shifts equilibrium to increase pressure in direction that produces more gas moles