Ap Chem Tips
What should you do the night before the ap exam
sleep
what is a reversible reason
a reaction that can happen in both directions simultaneously
What is a reaction quotient/the purpose?
the reaction quotient (Q) is a measure of the concentrations of the reactants and products at a specific point in time.
What is an equilibrium constant?
The equilibrium constant, K, expresses the relationship between products and reactants of a reaction at equilibrium with respect to a specific unit.
What is Le Chatelier’s principle?
When a system at equilibrium is placed under stress, the system will undergo a change in such a way as to reduce the stress. If a system at equilibrium is disturbed by a change the system undergoes a temporary shift in order to restore equilibrium.
What concepts should you know for the ap exam
atomic structure, including electron configurations and periodic trends, molecular structure, and bonding
what is an irreversible reaction
a reaction in which the reactants convert to products and where the products cannot convert back to the reactants
How do you calculate Q?
Qc = [C]c[D]d / [A]a[B]b (using concentrations)
How do you calculate K?
K = [C]c[D]d / [A]a[B]b
What change can stress Equilibrium/Keq?
Temperature
What's a good way to study for the ap exam
khan academy, practice problems, and fiveable
How to solve a reversible reaction?
by setting up an equilibrium constant expression and solving for the unknown equilibrium concentrations using initial conditions and the equilibrium constant.
how do you find if it shifts left or right?
Check whether Q or K is greater or less than (use crocodile example)
If the equilibrium constant has a lot of reactants where does the equilibrium lie?
Equilibrium lies to the left
If you add products to the system which way, does it shift?
The equilibrium will shift to the left, favoring the formation of more reactants to consume the added products.
when is the AP exam?
May 6th
how can the direction of a reversible reaction be changed
how can the direction of a reversible reaction be changed
What is the answer to this problem (show a picture on a separate tab)
Q = 4.0 and shifts left
Consider the following reversible reaction. In a 3.00 liter container, the following amounts are found in equilibrium at 400 oC: 0.0420 mole N2, 0.516 mole H2 and 0.0357 mole NH3. Evaluate Kc.
N2(g) + 3H2(g) ⇌ 2NH3(g)
Kc=1.99
The following reaction is to reach equilibrium.
CaO(s) + CO2(g) ⇌ CaCO3(s)
What happens to the reaction when some CaCO3 (s) is removed?
Nothing: The reaction is still at equilibrium
What time does the AP exam start
8:00am
how does a catalyst affect a reversible reaction
A catalyst accelerates both the forward and reverse reactions in a reversible reaction equally, allowing the system to reach equilibrium faster, but without changing the equilibrium position or equilibrium constant
If Kc = 0.0142 and the initial concentrations are 1.0 M NOBr, 0.2M NO, and 0.8M Br₂, which way will the reaction progress to reach equilibrium?
Q = 0.032 and Q > 0.0142 ⇒ Q > K ⇒ the reaction will proceed to the left because we have passed K.
Nitrosyl chloride, NOCl, dissociates on heating as shown below. When a 1.50 gram sample of pure NOCl is heated at 350oC in a volume of 1.00 liter, the percent dissociation is found to be 57.2%. Calculate Kc for the reaction as written.
NOCl(g) ⇌ NO(g) + 1/2 Cl2(g)
Kc= 0.107
What would be the effect of reducing the volume of a container in which the following system was at equilibrium?
2NO(g) + O2(g) ⇌ 2NO2(g)
increase [NO2]