Test 6: Chemical Equilibrium

Question 1

What is dynamic equilibrium?

Answer 1

2 changes are opposites and they cancel each other out so it appears that nothing is happening.

Question 2

What is phase equilibrium?

Answer 2

A single substance exists in more than one phase.

Question 3

What is solubility equilibrium?

Answer 3

In an oversaturated solution, solute is dissolving and precipitating at the same rate.

Question 4

What is chemical equilibrium?

Answer 4

A reversible chemical reaction is occurring in a closed system at contant temperature and pressure.

Question 5

Give examples of irreversible reactions.

Answer 5

• Wood burning
• Candle burning
• Food rotting
• Cooking an egg

Question 6

What are the conditions necessary for chemical equilibrium?

Answer 6

• A closed system
• Reversible reaction
• No visible changes (temp, pressure, colour, pH, volume, concentration, excess solute)
• Invisible changes (molecular activity)

Question 7

What is the formula for the equilibrium law?

Answer 7

Kc = [C]^c [D]^d / [A]^a [B]^b

There’s also a partial pressures of gases formula that’s the same thing but I don’t think we’ve ever used it before.

Question 8

What is Le Chatelier’s Principle?

Answer 8

A system at equilibrium is subjected to change, the system will oppose them until a new equilibrium is reached.

Question 9

What are changes that can affect equilibrium?

Answer 9

• Concentration
• Temperature
• Pressure
• Catalyst (only the speed, not the quantities)

Question 10

When the concentration increases in one of the reactants, what happens to the other chemicals?

Answer 10

A up + B down —- C up + D up

Question 11

When the concentration decreases in one of the reactants, what happens to the other chemicals?

Answer 11

A down + B up —- C down + D down

Question 12

When the concentration increases in one of the products, what happens to the other chemicals?

Answer 12

A up + B up —- C up + D down

Question 13

When the concentration decreases in one of the products, what happens to the other chemicals?

Answer 13

A down + B down —- C down + D up

Question 14

When the temperature (energy) increases in an endothermic reaction, what happens to the other chemicals?

Answer 14

A down + B down + energy up —- C up + D up

Question 15

When the temperature (energy) decreases in an endothermic reaction, what happens to the other chemicals?

Answer 15

A up + B up + energy down —- C down + D down

Question 16

When the temperature (energy) increases in an exothermic reaction, what happens to the other chemicals?

Answer 16

A up + B up —- C down + D down + energy up

Question 17

When the temperature (energy) decreases in an exothermic reaction, what happens to the other chemicals?

Answer 17

A down + B down —- C up + D up + energy down

Question 18

What are the conditions that need to be met that allows the changing of pressure to affect a system?

Answer 18

• There are components that are gas in the reaction (doesn’t need to be all of them)
• There’s a different number of moles of gas on the reactant and products sides (if they’re the same on both sides, changing pressure won’t have an affect)

Question 19

When the pressure increases, what happens to the chemicals?

Answer 19

The side with the fewer moles is favoured (up).

Question 20

When the pressure decreases, what happens to the chemicals?

Answer 20

The side with the most moles is favoured (up).

Question 21

What’s the formula for finding pH using concentration?

Answer 21

pH = - log [?]

Question 22

What’s the formula for finding concentration using pH?

Answer 22

[?] = 10 ^ -pH

Question 23

What are the other formulas in the acids and base slides?

Sorry I really don’t know how to ask this

Answer 23

pH + pOH = 14
Kw = [OH-] [H+]
Kw = 10 ^ -14

Question 24

What happens when you add acid to the system?

Answer 24

H2O up —- H up + OH down

Question 25

What happens when you add base to the system?

Answer 25

H2O up —- H down + OH up