Unit 3 Term 1

Question 1

what is homogeneous equilibrium?

Answer 1

reactions in which all components are in the same phase (liquid, gas, solid)

Question 2

what is heterogeneous equilibrium?

Answer 2

reactions in which components are in different phases (liquid + solid)

Question 2

what is dynamic equilibrium?

Answer 2

a state which occurs after a reverse reaction when concentrations and product/reactant ratios become constant and reverse/forward reactions occur at the same rate

Question 2

what is an open system?

Answer 2

a reaction vessel which does not have a lid, allowing reactants or products to be lost to the atmosphere

Question 3

what is a closed system?

Answer 3

a reaction vessel that is closed off or has a lid, meaning reactants and products aren’t lost to the atmosphere

Question 4

what is activation energy?

Answer 4

the minimum amount of energy required in a collision for a reaction to occur

Question 5

what is enthalpy?

Answer 5

the energy stored within chemical substances, referred to as its chemical or heat content

Question 6

what is a forward reaction?

Answer 6

the reaction between reactants to form products

Question 7

what is a reverse reaction?

Answer 7

the backwards reaction in which the products react to reform the reactants

Question 8

what is Le Châtelier’s Principle?

Answer 8

the theory that a system at equilibrium will adjust to minimise the disturbance to it (equilibrium will shift to oppose change)

Question 9

which factors impact changes to the equilibrium?

Answer 9

concentration
pressure
temperature
volume
catalysts

Question 10

what changes result in a net forward reaction?

Answer 10

decrease in product concentration
increase in reactant concentration

Question 11

what changes result in a net backwards reaction?

Answer 11

increase in product concentration
decrease in product concentration

Question 12

what effect does a catalyst have on a reaction?

Answer 12

it will initially lower the activation energy, before equilibrium is reached faster, however concentrations stay the same so no net reaction occurs.

Question 13

what is the formula for the equilibrium constant?

Answer 13

kc = [products]^p/[reactants]^r

excludes liquids and solids

Question 14

What do different values for kc mean?

Answer 14

kc>1, then the concentration of products is greater than that of the reactants
kc<1, then the concentration of reactants is greater than that of the products
kc=1 then ratios are equal

Question 15

How is Q different to kc?

Answer 15

Q is a trial expression, it uses the same equation as kc, however it uses practical values whereas kc uses theoretical values.

Question 16

What do different values for Q mean?

Answer 16

Q>kc, too far right, system will shift left
Q<kc, too far left, system will shift right
Q=kc system is at equilibrium

Question 17

What is an organic acid?

Answer 17

they’re carbon based acids such as, lactic, acetic, and citric (COOH) “-oic”

Question 18

What are some inorganic acids?

Answer 18

• hydrochloric HCL
• carbonic H2CO3
• nitric HNO3
• sulphuric H2SO4

Question 19

What is the Bronsted-Lowry theory?

Answer 19

• acids are proton donors
• bases are proton acceptors

Question 20

Describe monoprotic acids

Answer 20

• one proton
  HCL => H+ => Cl-
  HNO3 => H+ => NO3-

Question 21

Describe diprotic acids

Answer 21

• two protons
  H2SO4 => 2x H+ => SO4^2-

Question 22

Describe polyprotic acids

Answer 22

• many protons
  H3PO4 => 3x H+ => PO4^3-

Question 23

when is water pure?

Answer 23

kw= 1 x 10-14 at 25°C

Question 24

What does the end point represent in a titration?

Answer 24

the point in a titration when the indicator changes colour

Question 25

What does the equivalence point represent in a titration?

Answer 25

when system is at perfect equilibrium (pH 7)

Question 26

What does concordant refer to?

Answer 26

the three titre volumes which must be within 0.1ml of each other