Chemical Reactions and Equilibrium

Question 1

What is a chemical reaction?

Answer 1

A process in which as least one new substance is produced as a result of chemical change.

Occurs when new bonds form or old bonds break. Foundation of all life processes.

Question 2

What are reactants and products.

Answer 2

Reactants - starting substances.
Products - end substance.

Number of atoms in each element is same before and after reaction

Question 3

What are the 5 major chemical reactions types?

Answer 3

combination, decomposition, displacement, exchange and combustion reactions

Question 4

What is the Law of Conversion Matter?

Answer 4

Matter cannot be created or destroyed during a chemical reaction

Question 5

What is activation energy?

Answer 5

Initial energy investment needed to start a reaction.

Reactants must absorb enough energy for their chemical bonds to become unstable and form new combinations

As new bonds form, energy is released into surroundings

Question 6

What is a combustion reaction?

Answer 6

Most common type of reaction - between substance and oxygen, creates heat and light

Oxygen tends to take away electrons
Hydrogen tends to give electrons

Question 7

What is a redox reaction?

Answer 7

Oxidation-reduction

A chemical reaction in which there is a transfer of electrons from one reactant to another. One undergoes oxidation, another undergoes reduction

Question 8

What is the oxidation number?

Answer 8

Represents the change that an atom has when electrons in each bond it is participating in are assigned to the more electronegative of the two

Question 9

What are the oxidation number rules?

Answer 9

1. Oxidation number of an element is zero
2. ON of monatomic ion is equal to charge of ion
3. ON of groups IA is 1+ and IAA is 2+
4. ON of hydrogen is 1+ in most hydrogen containing compounds
5. ON of oxygen is 2- in most oxygen containing compounds
6. In binary molecular compounds, the more electronegative element is assigned a negative ON equal to its charge
7. For a compound, the sum of the individual ON is equal to zero. For polyatomic ion, sum is equal to charge on ion

Question 10

What are the electron transfers of the following terms:

Oxidation
Reduction
Oxidising agent
Reducing agent

Answer 10

Oxidation: loss of electrons
Reduction: gain of electrons
Oxidising agent (substance reduced): electrons gained
Reducing agent (substance oxidised): electrons lost

Question 11

OIL RIG

Answer 11

Oxidation is loss (of electrons)
Reduction is gain (of electrons )

Question 12

What is an oxidising agent?

Answer 12

The reactant that causes oxidation of another by accepting electrons from it

Question 13

What is a reducing agent?

Answer 13

The reactant in redox reaction that causes reduction of another by providing electrons for other to accept

Question 14

What is collision theory?

Answer 14

1. Reactant molecules must collide with each other
2. Colliding reactants must possess certain minimum amount of energy
3. Colliding reactant must be oriented in a specific way for reaction to occur

Question 15

What is an exothermic chemical reaction?

Answer 15

Releases energy as the reaction occurs

Question 16

What is an endothermic chemical reaction

Answer 16

Requires input of energy as reaction occurs

Question 17

What is chemical equilibrium?

Answer 17

Rate of forward reaction is equal to the rate of reverse reaction.

Both processes occurring simultaneously, even though there is no observable change

Question 18

What is equilibrium constant?

Answer 18

Concentration of reactants and products at equilibrium

Question 19

What is equilibrium position?

Answer 19

Relative amounts of reactants and products present in a system at equilibrium.

Question 20

What is Le Chateliers principle?

Answer 20

If a stress (change in conditions) is applied to a system in equilibrium, the system will readjust (change the equilibrium position) in the direction that best reduces the stress imposed on the system

Question 21

What does is mean if the equilibrium shifts to the right or the left?

Answer 21

Right = more products have been produced
Left = more reactants form

Question 22

Concentration change on reactions

Answer 22

• More particles of matter present, greater chance they will collide
• concentration increases when more are added to a space or pressure on space increases

Question 23

Temperature change on reactions

Answer 23

As the temperature rises, particles more more rapidly, more forcefully particles collide/greater chance of collision

Question 24

What are catalysts?

Answer 24

Chemical compounds that speed up chemical reactions by lowering the activation energy needed for a reaction to occur

Helps to orient colliding particles, interacting at precise spots to make reaction happen

Catalyst itself is unchanged at end of reaction

Question 25

What are some factors that increase chemical reaction rates?

Answer 25

Increase in concentration, temperature, adding catalyst, state of subdivision