Chemistry 12 Reaction Kinetics I. Name: Date: Block: 1. Calculating Rates 2. Measuring Rates 3. Factors Affecting Rates

Transcription

1 Chemistry 12 Reaction Kinetics I Name: Date: Block: 1. Calculating Rates 2. Measuring Rates 3. Factors Affecting Rates Monitoring and Calculating Reaction Rates Reaction Rate = Time units: Rate Units: Given the following equation and data: 2 HNO 3 (aq) + Cu (s) NO 2 (g) + H 2O (l) + CuNO 3 (aq) Mass of copper (g) Time (min) a) Does the reaction above have a constant rate? Explain why or why not. b) Calculate the rate in units of (g Cu/min). c) Calculate the rate in units of (mole Cu/min). d) Calculate the rate in moles HNO 3 consumed per minute (remember the mole ratio). e) Calculate the rate in units of (g/min) for HNO 3.

2 Thionyl chloride is a reactive compound used in a variety of organic synthesis reactions. Due to its potential to release dangerous gases explosively on contact with water, it is controlled under the Chemical Weapons Convention in the United States. It can be decomposed in solution with an organic solvent. [SO 2Cl 2] (mol/l) Time (seconds) What would the slope of this graph represent? 2. How does the slope of the graph change as passes? 3. What does this indicate about the reaction rate? 4. How does the rate at 500 s compare to the rate at 300 s?

3 Calculate the rate in units of (ml NO 2/sec). 2 HNO 3(aq) + Cu (s) NO 2(g) + H 2O (l) + CuNO 3(aq) Volume of NO 2 (ml) Time (sec) a) Calculate the rate in units of (L NO 2/min). b) Calculate the rate in units of (moles NO 2/min) at STP. c) Calculate the rate in units of (moles HNO 3/min) at STP (remember the mole ratio). Complete Worksheet Measuring Reaction Rates Changing rates of reactions can be found by measuring a change in one of the following properties: 1. Colour 2. Temperature 3. Pressure 4. Mass State five different methods for measuring the rate of the reaction of an iron nail in concentrated hydrochloric acid: a. What is the balanced chemical equation? (HCl is colourless; FeCl 2 is yellow-orange)

4 b. What properties would/could you monitor? Δ [HCl] Δ ph Δ Vol H 2 Δ P H 2 Δ mass H 2 Titrate ph meter Eudimeter Manometer Balance M/s ph units/s ml/s kpa/s g/s Hebden Workbook: Pg. 5 #9:

5 Factors Affecting Reaction Rates When the increases, then the rate. Reaction rates are affected by the following factors: 1. Temperature When the temperature is increased, the particles have energy. Will result in more frequent and more forceful collisions. The for the reaction to take place will. Therefore the reaction rate will. 2. Concentration As the reactant concentration increases, there are more particles to collide with each other. The reaction rate will. 3. Pressure An increase in pressure causes the particles to be together. Pressure is inversely proportional to. o An increase in pressure results in a of volume and vice versa. 4. Surface Area/Phase With a greater the surface area exposed, there is an increase in locations where the reaction can take place Most important in heterogeneous reactions when reactants are present in different states Ex: (ex. reacting with a solution or a gas)

6 Allows for in reaction rate Nature of the reactants Factors such as ionization energy, electronegativity, ionic and molecular polarity, size, complexity of structure, etc. In general, at room temperature the rate of aqueous > gas > liquid > solid. 6. Presence of a catalyst Substances that increase the rates of chemical reactions without being used up. (An inhibitor is a species that reduces the rate of a chemical reaction by combining with a reactant to stop it from reacting in its usual way.) The following reaction is taking place at a very slow rate in a closed container at room temperature: S (s) + O 2 (g) SO 2 (g) State what effect each of the following procedures will have on the rate of this reaction, and explain why the procedure has the stated effect. a) The temperature is decreased. b) More O 2 (g) is added in the same volume. c) The sulphur is ground up into a power. d) The volume of the container is increased.

7 Which of the following reactions is fastest at room temperature? List three ways to increase the rate of each reaction. a) H 2 (g) + I 2 (s) 2 HI (g) b) Ba 2+ (aq) + SO 4 2- (aq) BaSO 4 (s)