Upload
barnaby-golden
View
215
Download
0
Embed Size (px)
Citation preview
Energy Changes
Solutions Equilibrium IIEquilibriumReaction Kinetics
100 100 100100100
200 200 200200200
300 300 300300300
400 400 400400400
500 500 500500500
Energy Changes 100
If heat is written down in a chemical equation as a reactant, is the reaction endothermic or exothermic? Does the reaction have a positive or negative value of ΔH?
The reaction is endothermic, and it has a positive value of ΔH.
Energy Changes 200
Temperature is a measure of the average energy of a substance, while heat is actual energy moving from a warmer object to a
cooler object.
Explain the difference between heat and temperature.
Energy Changes 300
Which of the following is an endothermic change?
D. Ice melting requires the ice
to absorb energy.
a. Hot coffee cooling to room temperature
b. Steam condensing to water on a cold window
c. Frost forming on a windshield
d. Ice melting
Energy Changes 400
What is the first law of thermodynamics?
Energy cannot be created or destroyed – it can only change forms.
Energy Changes 500How would you solve the following problem
if it came up on a departmental exam?
Use Hess’ Law – all of the molecules are formed by reactions with their elements in their standard states.
Solutions 200
• When a solution has more solute in it than it is supposed to be able to hold at a given temperature, we call the solution ___________________.
Supersaturated
Solutions 300
• What is the key fact that allows for the derivation of the dilution equation, C1V1 = C2V2?
Before and after the dilution, the number of moles of solute are the same.
Solutions 400Daily Double
What is the mass of a 4.5% ethanol solution containing
0.6 g of ethanol?
13.3 grams
Solutions 500
HCl is added to a saturated solution of NaCl. Explain why NaCl precipitates out of the solution, using Le Chatelier’s Principle!
The solution contains a system of NaCl dissolving to form Na+ and Cl- at chemical
equilibrium. The adding of HCl is a stress that increases Cl-, and to offset it, NaCl is formed.
Reaction Kinetics 100
Is the reaction pictured in the diagram endothermic or exothermic? How can you tell?
Exothermic, energy of the products is lower than the energy of the reactants.
Reaction Kinetics 200
What is the transition state, or activated complex?
The transition state is the complex that exists between reactants and products, and
it has incredibly high energy and only lasts for a very short time.
Reaction Kinetics 300
According to the collision theory, what has to happen in order for two particles that collide to chemically react?
The particles must strike with enough energy, as well as with the proper orientation.
Reaction Kinetics 400
Catalysts increase the rate of a chemical reaction by decreasing the energy required for
an effective collision – in other words, they lower that energy hill.
What is the role of a catalyst in a chemical reaction? How does it affect
the energy of the transition state?
Reaction Kinetics 500
Imagine that you have a gaseous system that is reacting, but you can’t measure the concentration
of the chemicals involved. How else could you measure the speed of the reaction?
Measure the change in pressure of the system.
Equilibrium 100
Imagine that at chemical equilibrium, the rate of the forward reaction was greater than the rate of the reverse reaction. What would you say about that chemical equilibrium?
That’s impossible! At equilibrium, the rate of the forward reaction is ALWAYS equal to the
rate of the reverse reaction.
Equilibrium 200
When we are writing an equilibrium constant expression, what phases of matter do we leave out of it?
Solids and liquids.
Equilibrium 300A chemical equilibrium has a Keq value of approximately 5 x 1089. Which of the following is true?
a. The chemical reaction occurs very quicklyb. The reaction essentially goes to completion
c. There are virtually no products present at equilibriumd. The denominator of the equilibrium constant expression is very high
b. The reaction essentially goes to completion
Equilibrium 400
If you increase the pressure of a gaseous system, to which side of the chemical
equation will the equilibrium shift?
It will shift to the side with the fewest moles of gas.
Equilibrium 500Look at the following chemical reaction. Which of the following would NOT shift the position of
the equilibrium?H2O(l) + H2O(l) → H3O+
(aq) + OH-(aq)
a. Lowering concentration of OH-
b. Increasing volume of containerc. Increasing temperature
d. Adding a catalyst
Neither B or D will affect it – changing pressure only affects gases at equilibrium.
Equilibrium II 100
Imagine that you have a system that initially only has products in it. Initially, is the rate of the forward reaction faster or the reverse reaction faster?
The rate of the reverse reaction is faster – initially there are no reactants, so the forward
reaction can’t even occur.
Equilibrium 200
What is a steady-state process?
A process in which products are constantly removed and new
reactants are constantly added.
Equilibrium 300
What factor that shifts equilibrium also changes the value of the equilibrium constant?
Temperature
Equilibrium II 400Examine the following graph. Are the reactants or
products favoured at chemical equilibrium?
From what you are given, it is impossible to tell
Equilibrium II 500I wanted to put an I.C.E. box problem here, but decided that
would be hard to work out. What is the first step in solving an I.C.E. box problem if you know the concentrations of one chemical initially AND at equilibrium?
Calculate the changes in concentration of each species
based on the change in the one you know.