Chapter 18 - Rates of Reactions

Question 1

How is the reaction rate at a specific time worked out using a concentration-time graph?

Answer 1

1. Draw a tangent at the given time value.
2. Calculate the gradient of the tangent using the x and y intercepts.
3. Gradient = Rate.

Question 2

What is the rate equation for 2 reactants, A and B.

Answer 2

Rate = k x [A] x [B]

A and B may be second order in which case you put ^2

Question 3

What is initial rate?

Answer 3

The instantaneous rate at the start of a reaction when time = 0

Question 4

What are 2 methods of continuous monitoring when a gas in produced in the reaction?

Answer 4

Mass of reactant lost

Volume of gas produced

Question 5

What is continuous monitoring?

Answer 5

When continuous measurements are taken during the course of a reaction and can be plotted on a graph.

Question 6

What is a way of using light to continuously monitor rate of reaction?

Answer 6

Use a colorimeter to measure the amount of light absorbed by a solution.

Question 7

In a conc-time graph, how can you tell if the reaction is first or second order?

Answer 7

Measure multiple half lives. If they are constant, it is first order. If not it’s second order.

Question 8

What is the Arrhenius Equation?

Answer 8

k = A x e^(-Ea/RT)

A = Pre exponential factor that takes into account orientation of colliding molecules

e^(-Ea/RT) = The proportion of molecules with sufficient energy for the reaction to take place

Question 9

What is the logarithmic form of the Arrhenius equation in the model of y = mx + c?

Answer 9

ln k = -Ea/R x 1/T + ln A