1. Reaction Rates and Equilibrium Standard Review
Worksheet #7 Answers
Reaction Rates and Equilibrium Standard Review

2. Standard 8a: Students know the rate of reaction is the decrease in concentration of reactants or the increase in concentration of products with time.
 1. As a reaction proceeds the concentration of reactants decreases as the concentration of products increases.
2. Which would not be an accurate way of measuring the rate at which Mike makes peanut butter sandwiches?
a. # of sandwiches made in 1 hour c. # of jars of peanut butter used in 30 minutes
b. # of knives dirtied in 1 hour d. # of bread slices used every 15 minutes

3. Standard 8b: Students know reaction rates depend on such factors as concentration, temperature, and pressure.
6H20 + 6CO2  C6H12O6 + 6O2 (reaction of photosynthesis) 3. For each change decide if the reaction rate increases or decreases – a. Adding water - inc c. Making it colder – dec b. Removing glucose - inc d. Adding in oxygen – dec 4. If pressure is increased, would gases react faster or slower? faster

4. Standard 8c: Students know the role a catalyst plays in increasing reaction rate. Standard 8d: Students know the definition and role of activation energy in a chemical reaction.
5. Why does a catalyst speed up a chemical reaction?
It lowers the activation energy (A) (makes the hill up shorter)
6. Is the catalyst used up in the reaction? No
7. Which letter of the graph would be changed by a catalyst and how would it change? A, become shorter (lower)

5. Standard 8c: Students know the role a catalyst plays in increasing reaction rate. Standard 8d: Students know the definition and role of activation energy in a chemical reaction.
8. Is the reaction endothermic or exothermic and how can you tell?
Exothermic because the energy of the products (D) is lower than the energy of the reactants (C)
9. Which letters are used to represent the products? AB + C or in area D
10. What is the activation energy used for?
To start the reaction

6. Standard 9a: Students know how to use Le Chatelier’s principle to predict the effect of changes in concentration, temperature, and pressure on chemical equilibrium.
3AB(g) + 2CD(g) + heat energy  AD(g) + CB(g) 11. Equilibrium only can occur in a reversible reaction. How can you tell that this reaction is reversible? The double arrow 12. Decide if equilibrium will shift to the left (back to reactants) or to the right (toward products) a. Adding heat (increase temp) - right (to products) b. Adding AB - right (to products) c. Removing CB – right (to products) d. Removing CD - left (to reactants)

7. 3AB(g) + 2CD(g) + heat energy  AD(g) + CB(g)
13. What are the 2 criteria that must be met before a pressure change will affect equilibrium of a reversible reaction? All reactants and products are gases and the # of moles of reactants compared to products is not equal 14. In the reaction above, there are 5 moles of reactants and 2 moles of products. 15. If pressure is decreased on the above reaction, will equilibrium shift towards the products or towards the reactants? It will shift towards reactants because reducing the pressure, reduces the weight on the mole heavy side (side with more moles)

8. 16. Equilibrium is when RATE forward = RATE reverse
Standard 9b: Students know how equilibrium is established when forward and reverse reaction rates are equal
16. Equilibrium is when RATE forward = RATE reverse
NOTE!!! - EQUILIBRIUM IS NOT concentration of products = concentration of reactants OR amount of products = amount of reactants