Unit 3 Equilibrium (Acids and Bases) Flashcards
What is equilibrium in chemical reactions?
- rate of the forward reaction is equal to the rate of the backwards reactions
- concentrations of reactants and products are constant
- only happens in a closed system (i.e. contained system)
Which reaction is in equilibrium?
a. H2 + N2 –> NH3
b. SO2 + NO2 ⇌ NO + SO3
b. Note the equilibrium arrows in the reaction (i.e. the reaction goes forwards and backwards)
What is an acid?
an acid either has a H in the front or a COOH in the back
ex. H2SO4
ex. C2H5COOH
acids are H donors (aka proton donors)
What is a base?
a base is a metal and a OH group or a conjugate base of a weak acid
ex. NaOH
ex. Mg(OH)2
ex. NH3
a base is a H acceptor (aka proton acceptor)
What is an ion?
an atom or molecule with a charge on it
ex. sodium ions = Na+
ex. chlorine ions = Cl-
What is a conjugate acid?
after a base reacts with an acid, it forms a conjugate acid
ex. H3PO4(aq) + H2O(l) ⇌ H2PO4-(aq) + H3O+(aq)
On the reactant side, the water (H2O) is the base and after it reacts forms H3O+ which is a conjugate acid
What is a conjugate base?
after a acid reacts with a base, it forms a conjugate base
ex. H3PO4(aq) + H2O(l) ⇌ H2PO4-(aq) + H3O+(aq)
On the reactant side, the H3PO3(aq) is the acid and after it reacts forms H2PO4-(aq) which is a conjugate base
What are the six strong acids? (hint: look at the acid table in your data booklet)
the acids at the top of the table are the strong acids:
HClO4, HI, HBr, HCl, H2SO4, HNO3
Why are the six strongest acids considered strong?
a. they completely dissolve, creating a high concentration of H3O+
b. they dissolve slightly, creating a low concentration of OH-
a. they completely dissolve, creating a high concentration of H3O+
Which acid is stronger?
a. H2CO3
b. HCOOH
b. HCOOH (it has a smaller Ka, so it dissolves better than H2CO3)
you can also remember that the higher on the acid table in your data booklet, the stronger the acid
Identify the acid, base, conjugate base, conjugate acid for this reaction:
NH3(aq) + HF(aq) ⇌ NH4+(aq) + F-(aq)
NH3(aq) + HF(aq) ⇌ NH4+(aq) + F-(aq)
NH3(aq) = base HF(aq) = acid NH4+ = conjugate acid F- = conjugate base
Predict whether the forward or reverse reaction is favoured (hint: compare the strengths of the two acids)
NH4+(aq) + H2PO4 2-(aq) ⇌ NH3(aq) + H3PO4(aq)
favours reverse reaction since H3PO4 is a stronger acid than NH4+
What is Le Chatelier’s principle?
if you make a change to an equilibrium reaction, the system will try to balance out.
Which reaction is favoured (the forward or reverse) in an endothermic reaction if you add heat?
A + B + heat ⇌ C + D
if you add heat, it would favour the forward reaction
Which reaction is favoured (the forward or reverse) in an endothermic reaction if you remove heat (cool it down)?
A + B + heat ⇌ C + D
then the reverse reaction would be favoured
Which reaction is favoured (the forward or reverse) in an exothermic reaction if you add heat?
A + B ⇌ C + D + heat
adding heat, it will favour the reactants (reverse reaction)
Which reaction is favoured (the forward or reverse) in an exothermic reaction if you remove heat (cool it down)?
A + B ⇌ C + D + heat
cooling down, it favours the products (forward reaction)
A + B ⇌ C + D
If you increase the concentration of A, will the forward or reverse reaction be favoured?
forward reaction favoured
A + B ⇌ C + D
If you decrease the concentration of B, will the forward or reverse reaction be favoured?
reverse reaction favoured
2A + B ⇌ C + D
If you increase the pressure of the container, will the forward or reverse reaction be favoured?
forward reaction, goes to the side with less molecules
2A + B ⇌ C + D
If you decrease the pressure of the container, will the forward or reverse reaction be favoured?
reverse reaction, goes to side with more molecules
2A + B ⇌ C + D
If you increase the volume of the container, will the forward or reverse reaction be favoured?
increasing the volume = decreasing the pressure
the reverse reaction will be favoured
2A + B ⇌ C + D
If you decrease the volume of the container, will the forward or reverse reaction be favoured?
decreasing volume = increasing pressure
the forward reaction will be favoured
If you decrease the volume, what happens to the pressure?
decreasing volume = pressure goes up
visualize: if you cover part of a water hose with your finger, you decrease the volume (i.e. it’s spraying narrower than before) and the pressure is higher (it’s spraying harder)
What is an amphiprotic molecule?
can act as an acid or a base
Which is an amphiprotic molecule?
a. NaOH
b. H2PO4-
c. PO4 3-
b. H2PO4-
What is a buffer?
- a buffer is a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid.
- buffers resist pH change when small amounts of acid of base are added to them.
What are the strong bases?
group 1 ions with OH or NH4OH (look at the solubility table for OH-)
ex. NaOH, KOH, LiOH, RbOH, CsOH, FrOH, NH4OH
What is a multiprotic acid?
acid that has more than one H it can donate
ex. H3PO4
ex. C3H5O(COOH)3
What is a monoprotic acid?
acid that can only donate one H
ex. HCl
ex. HBr
What is the one base you need to memorize (hint: common cleaning product)?
NH3 (ammonia)
Does a catalyst affect equilibrium?
no, it helps reach equilibrium faster but doesn’t affect equilibrium
