GAMSAT - Graduate Australian Medical School Admissions Test


	Section III Unit 5 Questions 23 - 26: Question 23 B As stated the rate is a measure of the rate of formation of products or the rate at which reactants are used up. This is simply the rate of change of their concentration. Question 24 C To find the orders of each reactant look at the experimental data as follows. To find order of H⁺ from Expt 1-2 the conc. of H⁺ doubles and the rate increases x 4. Hence the order must be 2. For Br ^- from expt 4-2 the conc. of Br ^- doubles and the rate also doubles. Hence first order. For BrO₃^- use expts 2+3 in the same way. Question 25 C The slow step (RDS) determines which species must appear in the rate equation. In this case step 3 involves 2 moles of H⁺, I mole each of Br ^- and BrO₃^-. This would lead to the rate equation seen in the above question. Question 26 B Each pH increase of 1 unit causes a decrease in[H⁺] of a factor of 10. Hence a decrease of 2 units leads to a decrease in[H⁺] of 100 x and so the same rate decrease. NEXT SECTION