Kinetics

Question 1

The gas-phase reaction between hydrogen and chlorine is very slow at room temperature.
* Give one reason why the reaction between hydrogen and chlorine is very slow at room temperature. (1)
* Explain why a small increase in temperature can lead to a large increase in the rate of reaction between hydrogen and chlorine. (2)
* Give the meaning of the term catalyst.

Answer 1

• few molecules have sufficient energy to react
• many more molecules have energy greater than activation energy
• so increased frequency of successful collisions
• speeds up a reaction but is chemically unchanged at the end

Question 2

Explain why an increase in temperature increases the rate at which the gas is decomposed. (2)

Answer 2

• increase in proportion of molecules with E>= Ea
• higher frequency of successful collisions

Question 3

MB curve when at a higher temperature

Answer 3

M1 maximum peak height is lower and displaced to the right of the original
M2 all of the following:
* starts at the origin but does not follow the original line
* shows separation as soon as possible from the original line
* crosses the original curve once only
* similar area to original curve
* an attempt has been made to draw the new curve correctly towards the energy axis above the original curve but not to touch the original curve (or axis)