1.7 simple equilibria and acid-base reactions Flashcards
What is a reversible reaction?
one that can go in either direction depending on the conditions
What happens if reversible reactions take place in a closed system?
they will reach dynamic equilibrium
Define dynamic equilibrium
The rate of the forward reaction equals the rate of the backward reaction
What are the factors affecting equilibrium?
- temperature
- pressure of gaseous equilibrium
- concentration of reactant/product
What is Le Chatalier’s principle?
If a system at dynamic equilibrium is subjected to a change the position of equilibrium will shift to minimise said change.
In this reaction:
H2 + I2 ⇌ 2HI
if the concentration of the reactants are increased, what happens to the concentration of HI?
Concentration of HI increases to restore equilibrium and vice versa if HI increases, yield increases
In this reaction (general):
A +2B ⇌ C + D
if the concentration of the products is increased, what happens to eqm?
eqm shifts to LHS so yield decreases
What are the two types of pressure change?
- Change in partial pressure of chemicals
- Change in total pressure
What is change in partial pressure the same idea as?
the concentration in reactions, only applied to gases
What does a change in total pressure favour?
An increase in pressure favours the formation of fewer gas molecules
When determining a change in total pressure, what do you look at in an equation?
The large number before the compound/element
In an exothermic reaction what does raising the temp cause the eqm to do? Lowering temp?
raising temp: eqm shifts to LHS
lowering temp: eqm shifts to RHS
In an endothermic reaction what does raising the temo cause the eqm to do? Lowering the temp?
raising temp: eqm shifts to RHS
lowering temp: eqm shifts to LHS
What if the effect of catalysts on the eqm?
No effect on the position of the eqm but the eqm is reached faster
What is the eqm constant in terms of conc?
Kc
What can a an eqm reaction be represented as in general term? And then the kc at a given temp.
aA + bB ⇌ cC + dD
[C]^c x [D]^d divided by [A]^a x [B]^b
What should you do when calculating the value of K?
use the ICE method where
I: initial value
C: change in value
E: Equilibrium
Define what an acid is
a proton (H)+ donor
Define what a base is
a proton (H)+ acceptor
What is dissociating?
When an acid donates H+ ions (protons) in an acqueous solution
What are some common examples of a base?
NaOH
CaO
NH3
MgO
What is it called when a base dissolves in an acid?
it is called an alkali
Define a strong acid
fully dissociates in acqueous solutions
Define a weak acid
partially dissociates in acqueous solutions
What is the difference between a concentrated acid and a strong acid?
The strength refers to the extent of dissociation and not concentration whereas the concentration refers to the amount of acid dissolved in 1dm3 of solution
Define a concentrated acid
consists of a large quantity of acid and a small quantity of water
When an acid dissolves in water, what happens to the concentration of H+ ions? So the pH…
increases so the pH decreases
What is pH defined as?/ How do you calculate the pH?
-log10[H+]
What does the - in front of the pH equation mean?
results in pH decreasing as aq H+ ions increase
How do you calculate the [H+] of solutions?
[H+] = 10 ^-pH
In the pH the smaller the no…
the larger the no…
the smaller the no. the stronger the acid
the larger the no. the stronger the alkali
