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Reaction Rates
Catalysts
Reversible Reactions and Equilibrium
Shifts in Equilibrium
Misc.
100

What is the relationship between reaction rate and activation energy?

The higher the activation energy, the slower the reaction.

The lower the activation energy, the faster the reaction.

100
How does a catalyst affect activation energy?

Catalysts lower the activation energy

100

Define dynamic equilibrium

Dynamic equilibrium is when the rate of the forward reaction is equal to the rate of the reverse reaction (the rates of forward and reverse reactions are equal)
100

If a reaction is in equilibrium, what happens if the concentration of products is doubled?

The reaction will shift to the left to favor formation of the reactants

100

What is the effect of temperature on reaction rate?

Increased temperature increases the reaction rate
200

How does adding reactant (increasing concentration) affect the reaction rate?

Increasing the concentration of the reactant increases reaction rate by allowing for increased molecular collisions

200

Define homogenous and heterogenous catalysts

Homogenous catalysts are catalysts in the SAME phase as the reactants.

Heterogeneous catalysts are catalysts in a DIFFERENT phase than the reactants.

200

Given the following reaction:

N2(g) + 3H2(g) <----> 2NH3(g)

Write the equilibrium constant expression (Keq)

Keq = [NH3]2/[N2][H2]3

200

Given the following reaction at equilibrium:

H2 + I2 + 2.7kJ <---> 2HI 

What would happen to the amount of 2HI when the temperature of the system is increased?

Increased temperature would shift the reaction to the right in favor of product formation, so the amount of 2HI would increase

200

If ∆G is positive, is the reaction exergonic or endergonic?

Endergonic

300

In a spontaneous reaction, will the products have more or less energy than the reactants? Is ∆G positive or negative?

The products will have LESS energy than the reactants, and ∆G will be NEGATIVE

300

Between homogenous and heterogenous catalysts, which is more commonly used in industry and why?

Heterogenous catalysts are more commonly used in industry because they are more easily separated from the reactants

300

The following lists different states of matter. Identify which states are used in writing an equilibrium constant expression (Keq) and which are not:

Solids (s)

Liquids (l)

Gases (g)

Aqueous substances (aq)

Solids and liquids are NOT included in the equilibrium constant expression

Gases and aqueous substances ARE included in the equilibrium constant expression

300

Given the following reaction:

HCl (aq) <---> H+ (aq) + Cl-(aq)

What would happen if a large amount of sodium chloride (NaCl) was added to the solution?

The equilibrium would shift to the left, favoring the formation of the reactant HCl.  

300

How does pressure affect reaction rate?

Increasing pressure increases reaction rate IF the reactants contain more moles of gas than the products

400

Define collision theory

Particles must collide in order to react

400

Define enzymes. How is enzymatic activity regulated by the body?

Enzymes are biological catalysts (often proteins) that regulate cellular functions. The body uses feedback mechanisms to control enzyme activity.

400

Given the following reaction:

NH4NO3(s) <---> N2O(g) + 2H2O(l)

Write the equilibrium constant expression (Keq)

Keq = [N2O]

400

Given the following reaction at equilibrium: 

2H2(g) + O2 (g) <---> 2H2O (g)

What would be the effect of increasing the pressure of the system?

Increasing the pressure shifts the equilibrium toward fewer molecules. In this case, there are 3 molecules of reactant (2H2 + 1 O2) and 2 molecules of product (2H2O). So increasing the pressure would shift the equilibrium to the right favoring more product formation.

400

Define activation energy

Activation energy is the minimum amount of energy needed to initiate a chemical reaction
500

What are the two conditions needed for an effective collision between molecules?

Collisions must be energetic/have proper energy (1) and correct orientation (2)

500

Name one way that catalysts can increase reaction rate

Possible answers:

1) Hold reactant molecules in proper orientation to react

2) Provide alternative reaction pathway (form temporary reaction intermediates)

3) Weaken or break reactant bonds

500

Given the following reaction:

CO2(g) + 2H2(g) <---> CH3OH(g)

What is the value of the equilibrium constant (Keq) if the following concentrations are measured at equilibrium?

[CO2] = 0.50 M

[H2] = 0.25 M

[CH3OH] = 0.050

The value of Keq = [CH3OH]/[CO2][H2]2 = 1.6

500
Predict what will happen in the following scenarios:

1) Q < K

2) Q = K

3) Q > K

1) If Q<K, there is an overabundance of reactants. The system will shift towards the products. 


2) If Q=K, the reaction is at equilibrium; no shift will occur.

3) If Q>K, there is an overabundance of products. The system will shift towards the reactants.

500

Give a real-life example of the use of a catalyst

Lots of potential here:

- Catalytic converters in cars

- Specific enzymes in blood