- Reaction Rates -

 Discovered in 1847, nitroglycerine is an extremely unstable liquid – a physical shake can cause it to explode  In 1867, Alfred Nobel discovered that mixing it with silica paste to form a solid makes it more stable – he invented dynamite

 When detonated, the nitroglycerine undergoes a rapid and highly exothermic decomposition reaction, released an enormous amount of energy in less than a second!

 Dynamite was used extensively in the building of Canada’s railroads; nitroglycerine in its pure form was also used for tunnel blasting

 Nitroglycerine is also used as a heart medication  Treatment of angina, chest pain associated with clogged arteries and decreased blood flow, which reduces oxygen supply to the heart

 As a heart medication does not explode, it undergoes a different chemical reaction, which releases small amounts of nitric oxide (NO (g) )  Nitric oxide acts on the walls of the blood vessels to makes their diameter larger  This increases blood flow and relieves angina  Production of nitrous oxide gas occurs at the much slower rate, releasing far less energy, so not harmful

 Chemical kinetics is the branch of chemistry concerned with the rates of chemical reactions  A rate is a change in a measurable quantity over time  Different chemical reactions proceed from reactants to products at different rates (e.g. combustion of propane and oxidation of silver)

 The reaction rate of a chemical reaction is the change in concentration of a reactant or product per unit time  How do we determine the reaction rate of a specific chemical reaction?  Read and summarize p. 365 “Measuring Reaction Rates”

1) List 3 ways to make a chemical reaction go faster 2) Think of the Alka Seltzer reaction – how can you increase the rate of this reaction? 3) Think of the Mg + HCl reaction – how can you increase the rate of this reaction? 4) Think of methanol + O 2 – how can you increase the rate of this reaction? 5) Cars can produce more power (and therefore more speed) if they can combust the fuel faster – what can drivers/engineers do to increase the rate at which fuelburns? 6) Are there any chemical reactions that we want to slow down? 7) How could you slow the browning of an apple?

 How do we determine the rate at which a car travels?  Similarly, how can we determine the rate at which a chemical reaction occurs?  Let’s develop an equation:  Average rate of reaction = change in concentration elapsed time r = ∆c ∆t Complete the sample problems on page 360/361

 This graph shows the concentrations of both reactants and products as time elapses.  What do we notice about the curves? Explain this?  What measurement should be used for the concentration instead of number of molecules?

 Use a secant to determine the average rate of reaction.  Complete the sample question on page 363.

 Use a tangent to determine the instantaneous rate of reaction.  Complete the sample question on page 363.

 What types of equipment can we use? 1) Reactions that produce a gas: 2) Reactions that involve ions: 3) Reactions that change colour

 Assigned Questions ◦ p. 361 Practice UC # 1, 2 ◦ pp. 364 – 365 Practice UC # 3, 4, 5, 6 ◦ Read and Summarize p. 365 “Measuring Reaction Rates” ◦ pp. 365 – 366 Practice UC # 7, 8, 9, 11 ◦ Section 6.1 Questions UC # 1, 2  Assignment – p. 401 Lab Exercise – Determining a Rate of Reaction ◦ Students to complete Prediction, Analysis, Evaluation, Synthesis