chloropentane with time
Question 3 (25 marks)
This question carries 25% of the marks for this assignment.
Advice on answering Question 3
This question relates to Topic 1, Part 1, Section 1.9 Representing a chemical reaction; Topic 2, Maths skill: Plotting graphs; Topic 4, Part 3, Section 3.7.1 Maths skill: Quantifying amounts and concentrations of solutions; Topic 9, Part 1, Section 1.1 What are chemicals and where they come from?; Topic 11, Part 3, Section 3.2.4 Maths skill: Drawing tangents to curves; and Maths for science, Section 7.1 Graphical representations.
a. Pentane is a volatile, colourless liquid with a characteristic smell that reacts with chlorine liquid (a diatomic molecule) in the presence of a catalyst. Liquid chloropentane is formed through the substitution of hydrogen with chlorine.
Write a balanced chemical equation for this reaction and explain how you balanced it. Hydrogen chloride gas is also a product of this chemical reaction. Note: ignore the presence of the catalyst. (3 marks)
b. Chloropentane has three constitutional isomers (1-, 2-, 3-chloropentane). Draw the skeletal forumula for each isomer and write the chemical formula for each isomer. (4 marks)
c. In any manufacturing process, reaction monitoring ensures that a chemical reaction proceeds as expected. Table 1 shows the monitoring data for the formation of chloropentane, collected using a technique called gas chromatography.
Note that the concentrations of the chloropentane solutions are given in millimoles per litre (mmol l–1). The abbreviation mM (millimolar) is frequently used. Plot a graph of the data in Table 1, and include the graph as your answer to this question. (6 marks)
Table 1 Concentration of chloropentane with time.
d. Annotate your graph to show how you could determine the rate of reaction at 5 hours by drawing a tangent to the curve. Include your annotated graph in the answer and use the values from it to calculate the rate of reaction at 5 hours. Show your calculation in full. (6 marks)
e.How many grams of chloropentane are there in 0.500 litre of a 70 mM solution? Show your calculations in full. (6 marks)