Kinetics

Question 1

Rate of reaction

Answer 1

the speed at which reactants are used up or products are formed, or the change in concentration of reactants or products per unit time

Question 2

instantaneous rate of reaction

Answer 2

the rate of a reaction at a specific time period when the concentrations of reactants and products change by a negligible amount

Question 3

initial rate of reaction

Answer 3

the speed at which reactants are used at the start of a reaction

Question 4

tangent line

Answer 4

the line through a pair of infinitely close points on the curve, used to find the instantaneous rate of reaction

Question 5

gradient

Answer 5

the derivative of the curve at that point, used to find the instantaneous rate of reaction. (slope of the tangent line)

Question 6

kinetic molecular theory

Answer 6

1. Gases are composed of a large number of particles that behave like hard, spherical objects in a state of constant, random motion.
2. These particles move in a straight line until they collide with another particle or the walls of the container.
3. These particles are much smaller than the distance between particles. Most of the volume of a gas is therefore empty space.
4. There is no force of attraction between gas particles or between the particles and the walls of the container.
5. Collisions between gas particles or collisions with the walls of the container are perfectly elastic. None of the energy of a gas particle is lost when it collides with another particle or with the walls of the container.
6. The average kinetic energy of a collection of gas particles depends on the temperature of the gas and nothing else.

Question 7

kinetic energy

Answer 7

a property of a moving object or particle and depends not only on its motion but also on its mass.

Question 8

collision theory

Answer 8

a method that is used to explain the variation of rate of reaction. A reaction can occur only when two particles collide in the correct orientation an with E > Ea

Question 9

unsuccessful collision

Answer 9

a collision that does not create a new bond

Question 10

successful collision

Answer 10

a collision that creates a new bond

Question 11

activation energy

Answer 11

the minimum energy that colliding particles must have before collision results in a chemical reaction

Question 12

energy profile

Answer 12

a representation of the most favourable energetic pathway for the reactants to be transformed into the products

Question 13

reaction coordiante

Answer 13

an abstract one-dimensional coordinate chosen to represent progress along a reaction pathway.

Question 14

transition state

Answer 14

a chemical reaction is a particular configuration along the reaction coordinate

Question 15

maxwell-boltzmann energy distribution curve

Answer 15

describes the distribution of speeds among the particles in a sample of gas at a given temperature. The distribution is often represented graphically, with particle speed on the x-axis and relative number of particles on the y-axis

Question 16

catalyst

Answer 16

a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change

Question 17

intermediate

Answer 17

a species which appears in the mechanism of a reaction, but not in the overall balanced equation. An intermediate is always formed in an early step in the mechanism and consumed in a later step.

Question 18

enzymes

Answer 18

catalysts that speed up the rate of reactions in biological chemistry. They are made of amino acids that react with substrates to form an enzyme-substrate complex