Chemistry Revision Session 7

Equilibria  Define the term dynamic equilibrium (3)  Consider N 2(g) + 3H 2(g)  Fe  2NH 3 (g) ΔH=-100 kJ/Mol  Explain what will be the effect on the yield of ammonia if I increase the pressure (3)  Would changing concentrations or surface area increase yield of ammonia?  What about increasing the temperature?

More on equilbria  Even so a relatively high temperature is chosen is why (4 marks)  What type of catalysis is this example?  Use the following equilbria to explain what happens to the pH when CO 2 dissolves  CO 2 (g) CO 2 (aq)  CO 2 (aq) + H 2 O (l) H + (aq) + HCO 3 - (aq)

Global warming  Explain why increasing carbon dioxide concentrations leads to increased “global warming” Make sure your answer includes the term infra-red!  Name another greenhouse gas and explain a way it is made

CFCs  Draw out the full structural formula of chloro, fluoro methane.  Which bond would break first and explain how you made your choice.  What environmental problem did CFCs cause, and why was this a problem?  What type of radiation causes these bonds to break?

Ozone hole  Suggest a catalytic cycle of the breakdown of ozone using chlorine atoms.  Identify the catalyst and the intermediate.  Write the overall equation

An answer  Cl + O3  ClO + O2  ClO + O3  Cl + 2O2  2O3  3O2

Fission  Consider bromoethane:  Done that? Good- now write equations showing the products when bromoethane undergoes heterolytic fission and homolytic fission, guessing which is which of course!

 Define the term radical  Explain, using equations, how chlorine can chlorinate large amounts of ethane (forming chloroethane) (Free radical substitution mechanism)  Is chloroethane a polar molecule or not? In your answer you should include the term electronegativity and perhaps a diagram?

Just a thought  How much FANTASTIC chemistry are we covering AGAIN today?  Isn’t it marvellous?

Mechanism  Explain the mechanism for the reaction between ammonia and ethanol. (5 marks)  What type of mechanism is this (2 marks)  State the reagents and conditions needed for this reaction (don’t forget to learn this type of info!!)

Just a point  Note your syllabus expects you to “explain and use the terms nucleophile, hydrolysis, carbocation and substitution”  Finally name the following