Topic 10

Question 1

Why can the calculated value for bond enthalpy change be different from the data book value

Answer 1

Some tables use the mean bond enthalpy

Question 2

With the equation of chlorine gas reacting with bromide ions to form bromine gas and chloride ions, what would be observed

Answer 2

Colourless to brown

Question 3

Two features of a system which has reached dynamic equilibrium

Answer 3

1. The forwards and backwards reactions occur at the same rate
2. The amount of products and reactants remain constant

Question 4

Carbon dioxide and water vapour both contain polar bonds, what effect does infrared radiation have on their bonds

Answer 4

Causes the bonds to vibrate more

Question 5

Outline the mechanism by which the molecules such as carbon dioxide and water cause global warming

Answer 5

• Heat is absorbed by greenhouse gases
• Heat is then re-emitted back to the earth

Question 6

In the haber process, why may the product be removed before its maximum concentrated is achieved

Answer 6

• The equilibrium position will shift to the right
• in an equilibrium removal of the product decreases the rate of formation of reactants
• the time to reach equilibrium may be too long
• unreacted reactants can be recycled

Question 7

Why does increasing pressure have no effect on the rate of a reaction