Chapter 17Reaction Rates

• Speed at which chemical reactions can vary greatly– Space rocket = fast– Concrete hardening = slow– Fossil fuels creation = really really slow

• At times it’s important to be more specific about how fast reactions occur

•Radioactive tracking devices help doctors diagnose problems

•Knowledge about fuel combustions help cars go fast and far

Reaction Rates• The speed at which the reaction goes is measured

against time– Sprinter = meters / second– Car = miles /hour– Reaction rate = concentration / time

= molarity / second = moles / L · s

timeMolarity ratereaction

• Time 1 = 5 seconds [NaCl] = 2 M

• Time 2 = 15 seconds [NaCl] = 8 M

• What is the reaction rate?

timeMolarity ratereaction

Reaction Rate Problems II

1. Determine the rate of reaction if a 1.0 M concentration of bromine when it changes during a reaction to a 0.0 M concentration of bromine in 29 seconds.

2. Determine the rate of reaction of a 4.0 M concentration of oxygen when it changes during a reaction to a 0.0 M concentration of hydrogen in 4 seconds.

3. Determine the rate of reaction of a 3.2 M concentration of sulfur when it changes during a reaction to a 1.3 M concentration of calcium in 18 seconds.

4. Determine the rate of reaction of a 6 M concentration of Na2SO4 when it changes during a reaction to a 2.1 M concentration of Na2SO4 in 1 minutes and 28 seconds.

5. Determine the reaction rate of a 1.8 M concentration of H2S when it changes to a 0.5 M concentration in 14 seconds.