1A Rates

Question 1

What is a reaction rate

What unit it it usually measured in

Answer 1

The number of chemical reactions occurring in the system per reaction volume per time

mol/L x s

Question 2

If the reaction is A —> B: What is the reaction rate

Definition, Rate A, Rate B, Explain why one will be negative

Answer 2

1. Reaction rate is the number of mol/L of A that are converted to B every second
2. rate= -D[A]/Dt
3. rate=+D[B]/Dt
4. Because [A] decreases with time, D[A] is negative

Question 3

In the equation A —> B:
What sign will each slope be in terms of their concentration

Answer 3

+slope of [B]
- slope of [A]

Question 4

What sign will reaction rates ALWAYS be

Answer 4

Always a positive number because of the way it is defined. A rate is how fast a reaction goes.

Question 5

Difference between average and instantaneous rate

Answer 5

Average rate is the rate over a period of time whereas instantaneous rates are the rates at a specific time (dt=0)

Question 6

If the equation is 2A —> B:
1. What happens to the moles during the reaction
2. How do you get the reaction rate of A and B

Answer 6

1. 2 moles of A dissapeared, 1 mole of B formed
2. rate= (-1/2)D[A]/Dt
3. rate=D[B]/Dt

Question 7

What is the rate law

Answer 7

It expresses the relationship between the reaction rate and the concentrations of the reactants

Question 8

Given the equation: aA+bB –> cC+ dD:
1. What is the rate law (rate)
2. Define each part
3. Does the rate law include products
4. Units for rate
5. How do you find Units for rate constant

Answer 8

1. Rate= k[A]^x[B]^y
2. k is the reaction rate constant, xth order in A, yth order in B, and reaction is (x+y)th order overall
3. Rate law does not include products
4. Rate: M/s
5. K: M^(1-x-y)/s

Question 9

What is a qualitive way to see how fast a reaction occurs

Answer 9

Color change signifies a reaction has occurred

Question 10

For a reaction that looks like this: aA+bB –> cC+ dD
How can the reaction rate be calculated

Answer 10

Can be calculated from any of the concentrations
rate=-1/aD[A]/dt=-1/bD[b]/Dt=1/cD[C]/Dt=1/dD[D]/dt

Question 11

What is the overall order and unit of k for this rate law= k[X]^1[Y]^2

Answer 11

3rd Order and M^-2/s

Question 12

What are the 3 rate law properties

Answer 12

1. Rate laws are NORMALLY found experimentally/emperically
2. Reaction order is USUALLY defined in terms of reactant (NOT PRODUCT) concentrations
3. The order of a reactant ISNOT related to the stoichiometric coefficient (ie F2+2CLO2 but the rate=k[F2][ClO2}^1