Lecture 6-8 (Ch. 14): Rxn Rates, Instantaneous/Relative/Avg Rate, Rate Law, Half Life

Question 1

rxn rate

Answer 1

• change in reactant or product conc. w/ time
• unit: M/s (usually)
• rate values are always positive
• reactant always neg., product always positive

Question 2

average rxn rate

Answer 2

• change in conc. of rxt or prdt over a specific time interval
• calculating the slope

Question 3

instantaneous rate

Answer 3

• change in conc. of a rxt or prdt at a specific time point
• calculated from slope of 1 pnt tangent to a graph
• measure initial rate since rate changes w time (con.c values also better known at beg. of rxn)

Question 4

rate law def. & equation

Answer 4

-compares rxn rate to reactant conc.
Rate=k[A]^m[B]^n
-Rate: typically M/s
-k: rate constant (units vary)
-m & n: rxn order of reactants

Question 5

rxn order

Answer 5

• exponent to which a reactant is raised
• not from coefficients
• indicates how the rate depends on reactant conc.
• usually positive integers

Question 6

overall rxn order

Answer 6

-sum of rxn orders (m + n)

Question 7

zero order

Answer 7

• if you double a conc., the rxn rate is constant
• [A]t vs t
• -k

Question 8

first order

Answer 8

• if you double a conc., the rxn rate is doubled
• ln[A]t vs t
• -k

Question 9

second order

Answer 9

• if you double a conc., the rxn rate is quadrupled
• 1/[A]t vs t
• +k

Question 10

initial rate method to find reaction orders

Answer 10

• calculates m & n by changing 1 rxt conc. & keeping other rxt conc. constant to see what happens to rate
• can use logs to help bring exponents down

Question 11

graphical rate method to find reaction orders

Answer 11

must convert rate law equation to an integrated rate law equation that relates conc and time

Question 12

which orders do half life depend on concentration?

Answer 12

• zero: does
• first: doesn’t
• second: does

Question 13

rate law

Answer 13

-how rate depends on conc.

Question 14

integrated rate law

Answer 14

-how conc. depends on time