HIGHER CHEMISTRY PAST PAPERS 2000 -2010 1 Lesmahagow High School Higher Chemistry Controlling the 

HIGHER CHEMISTRY PAST PAPERS 2000 -2010 1 Lesmahagow High School Higher Chemistry Controlling the Rate -Past Paper Homework HIGHER CHEMISTRY PAST PAPERS 2000 -2010 2 Rates of reaction 2000 1.Document Preview:

HIGHER CHEMISTRY PAST PAPERS 2000 – 2010 Lesmahagow High School Higher Chemistry Controlling the Rate – Past Paper Homework 1HIGHER CHEMISTRY PAST PAPERS 2000 – 2010 Rates of reaction 2000 1. Methanoic acid, HCOOH, can break down to carbon monoxide and water by two different reactions, A and B. Reaction A (catalysed) + + HCOOH(aq) + H (aq) ? CO(g) + H O(l) + H (aq) 2 Reaction B (uncatalysed) HCOOH(aq) ? CO(g) + H O(l) 2 + (a) (i) What is the evidence in the equation for Reaction A that the H (aq) ion acts as a catalyst? 1 (ii) Explain whether Reaction A is an example of heterogeneous or homogeneous catalysis. 1 (b) The energy diagram for the catalysed reaction is: 1 Draw a line on the diagram to show the reaction pathway for the uncatalysed reaction. (3) 2HIGHER CHEMISTRY PAST PAPERS 2000 – 2010 2001 2. In experiments with four different gases, a syringe was held vertically as shown with the weight of 3 the syringe piston applying a downward pressure on the gas. The times taken for 60cm of helium, methane, carbon dioxide and butane to escape through the pinhole were measured and the graph shows the results plotted against relative formula mass. 3 (a) Calculate the average rate of escape from the syringe of 60cm of methane, in 3 -1 cm s 1 (b) Name a hydrocarbon gas which would take 56s to escape. 1 (c) The error in a measurement decreases as the actual size of the measurement increases. Suggest one way of reducing the error in each of the time measurements. 3