chem 2 - equilibrium

Question 1

reaction: iron (yellow) + thiocyanate ions (colourless) -> FeSCN (red)

if more drops of the colourless solution that has a high conc of thiocyanate ions are added to the orange equilibrium mixture
explain the colour change (3)

Answer 1

• becomes more red
• since the equilibrium moves to the right
• so that the conc of thiocyanate ions is reduced / counteracted

Question 2

reaction: iron (yellow) + thiocyanate ions (colourless) -> FeSCN (red)

orange equilibrium mixture placed in water bath that has a hot temp and becomes more yellow
why does this happen?
what changes about the position of equilibrium?

Answer 2

• position of equilibrium moves to the left, so an increase in Fe ions conc
• so that the temp is reduced
• meaning the forward reaction is exothermic

Question 3

4 main things to remember about the haber process

Answer 3

1. ammonia removed immediately
2. uses an iron catalyst
3. forward reaction is exothermic
4. reactants continually recycled into the mixture

Question 4

describe dynamic equilibrium (3)

Answer 4

-only happens ina closed system
-it is when the forward and backwards reaction rates are equal
-the conc of reactants and products are constant

Question 5

what does Le chateliers principle say (2)

Answer 5

• that if you change the conditions of a reversible reaction at equilibrium the system will try to counteract the change
• its used to predict the effect of any change in the reaction

Question 6

what does decreasing the conc of products do

Answer 6

it shifts the equilibrium to the right
since the system is trying to increase it again by reducing the amount of reactants

Question 7

what does decreasing the temp of a reaction do

Answer 7

it shifts the equilibrium in the exothermic reaction
to produce more heat

Question 8

what does decreasing the pressure of gas in a reaction do

Answer 8

it shifts the equilibrium to the side with more gas molecules

Question 9

what are the 2 compromises in the haber process

Answer 9

• temp 450 C - increases the rate of reaction, however not too high otherwise yield would be too low
• pressure 200 atm - too high of pressure would be too dangerous and requires more energy (which is expensive) to maintain