equilibria I & II

Question 1

Features of dynamic equilibrium

Answer 1

• the forward and backward reactions are still happening.
• the rates of the forward and backward reactions are the same.
• the concentrations of the reactants and products remain constant (they do not change)
• in a CLOSED system

Question 2

Features of static equilibrium

Answer 2

• the forwards and backwards reactions have ceased
• in a CLOSED system
• no movement between products and reactants

Question 3

what affects Kc value?

Answer 3

if the temperature changes once equilibrium has been reached

Question 4

how can you tell whether a reaction’s equilibrium lies to the left or right based on its Kc value?

Answer 4

> 1 = lies to products (the fraction is top heavy)
<1 = lies to reactants (the fraction is bottom heavy)

Question 5

what do [XXX] brackets mean?

Answer 5

Concentration of XXX

Question 6

What is a proton?

Answer 6

a H+ ion

Question 7

Acids are proton…

Answer 7

donors

Question 8

Bases are proton…

Answer 8

acceptors

Question 9

How do you mathematically define pH?

Answer 9

pH = -log10 [H+ (aq)]

Question 10

What would be the [H+] in 1 mol dm^3 HCl

Answer 10

1 M

Question 11

What would be the [H+] in 1 mol dm^3 H2SO4

Answer 11

2 M

Question 12

What would be the [H+] in 1.5 mol dm^3 of HNO3

Answer 12

1.5 M

Question 13

does water become more acidic or alkaline when heated? why?

eq. in H2O is
H2O = H+ + OH-

Answer 13

• forwards reaction is endo
• so eq. will shift to left to counteract heat increase
• so more H+ and OH- is made
• so [H+] increases, which will decrease the pH even though more OH- is made too
• because we only care about [H+] concentration

Question 14

what is the the equilibrium constant for water and what is its value?

Answer 14

Kw

Kw = [H+(aq)][OH-(aq)]/ [H2O(l)]

so Kw = 1.0 x 10^-14 mol2 dm^-6

Question 15

What do strong acids do in solution in water

Answer 15

Strong acids fully ionise to produce H+ ions when in solution in water

Question 16

What do weak acids do in solution in water

Answer 16

Weak acids partially ionise to produce H+ ions in water

Question 17

what is le chateliers principle

Answer 17

If a constraint is imposed upon a system, the system
will act to counteract that constraint.

Question 18

what will happen if pressure is increased on this equilibrium?
CaF2 (s) + 2H (aq) + ⇌ Ca (aq)2+ 2HF (aq)

Answer 18

It is aqueous; pressure only affects gas

Question 19

What will happen if I increase the concentrations of the constituents on the left of my equilibrium

Answer 19

EQ. will shift right
- to oppose the effect and counteract the change

Question 20

What is the effect of catalysts on equilibrium?

Answer 20

• the position of equilibrium isn’t changed
• but the rate at which equilibrium is reached is quicker (increased)

Question 21

what is the effect of increasing the temperature on an equilibrium when the backwards reaction is endothermic.

Answer 21

EQ. shifts to the left with the endothermic reaction
- because it wants to counteract the change and keep its original conditions (at equilibrium)

Question 22

Give two characteristics of all reactions at
equilibrium.

Answer 22

• the [] of all reactants and products are the same
• the rate of the forwards reaction is equal to the backwards reactions