3.c - Reversible reactions and equilibria

Question 1

how is it shown that reactions are reversible

Answer 1

forward arrow + backward arrow as an = sign

Question 2

name to reversible reactions

Answer 2

dehydration of hydrated copper ( II ) sulphate

thermal decomposition of (effect of heat on) ammonium chloride

Question 3

describe the reversible reaction of the thermal decomposition of ammonium chloride

Answer 3

1. ammonium chloride = white solid
2. heated breaks down into the gasses ammonia + hydrogen chloride = forward reaction
3. if let it cool ammonia +hydrogen chloride react to re-form the solid = backward reaction

Question 4

describe the reversible reaction of dehydration of hydrated copper ( II ) sulphate

Answer 4

1. hydrated copper ( II ) sulphate = blue crystals
2. heat blue hydrated copper ( II ) sulphate crystals = drives water off
3. = white anhydrous copper ( sulphate powder ) = forward reaction
4. add couple of water to white powder = blue crystals back again = backward reaction

Question 5

PAPER 2

what can happen to a reaction in a sealed container ( closed system )

Answer 5

it can reach dynamic equilibrium

Question 6

PAPER 2

what are the characteristics of a reaction at dynamic equilibrium

Answer 6

1. forward + reverse reactions occur at the same rate

2. concentrations of reactants + products remain constant

Question 7

why does a catalyst not effect the position of equilibrium in a reversible reaction

Answer 7

catalyst speeds up the forward reaction and the backward reaction by the same amount

Question 8

what does an increase in temp do to the position of equilibrium

Answer 8

shifts in the direction of the endothermic reaction ( use up extra heat )

Question 9

what does an decrease in temp do to the position of equilibrium

Answer 9

shifts in the direction of the exothermic reaction ( give out more heat )

Question 10

what does an increase in pressure do to the position of equilibrium

Answer 10

shifts in the direction that produces fewer moles of gas

Question 11

what does an decrease in pressure do to the position of equilibrium

Answer 11

shifts in the direction that produces more moles of gas