Collision Theory
Reaction Rates/
PE Diagrams
PE Diagrams
PE Diagrams II
Equilibrium
Micellaneous
100
DOUBLE JEOPARDY!
A chemical reaction occurs when reactant particles
A) are separated by great distances
B) have no attractive forces between them
C) collide with proper energy and proper orientation
D) convert chemical energy into nuclear energy
C) collide with proper energy and proper orientation
100
Which mathematical expression represents the heat of reaction for a chemical change?
A) (PE of the products) – (PE of the reactants)
B) (PE of the products) + (PE of the reactants)
C) (PE of the products) ÷ (PE of the reactants)
D) (PE of the products) × (PE of the reactants)
A) (PE of the products) – (PE of the reactants)
100
Which equation represents a physical equilibrium?
A) CO2(g) <--> CO2(s)
B) C(s) + O2(g) --> CO2(g)
C) N2(g) + 3H2(g) <--> 2NH3(g)
D) N2(g) + O2(g) --> 2NO(g)
A) CO2(g) <--> CO2(s)
100
Double Jeopardy!
Common household bleach is an aqueous solution containing hypochlorite ions. A closed container of bleach is an equilibrium system represented by the equation below.
Explain why the container must be closed to maintain equilibrium.
– The container must be closed so that no matter can enter or leave, thus distributing the equilbrium.
– If the container is open, Cl2 gas escapes.
– to keep the concentration of the reactants and products constant
100
Which phrase describes what happens to the reaction pathway and activation energy of a reaction to which a catalyst is added?
A) the same pathway with the same activation energy
B) the same pathway with a lower activation energy
C) a different pathway with the same activation energy
D) a different pathway with a lower activation energy
D) a different pathway with a lower activation energy
200
An enzyme acts as a catalyst to speed up a reaction by providing an alternate reaction pathway that has a
A) higher activation energy
B) lower activation energy
C) higher heat of reaction
D) lower heat of reaction
B) lower activation energy
200
Based on Table I, which compound dissolves in water by an exothermic process?
A) NaCl
B) NaOH
C) NH4Cl
D) NH4NO3
NaOH
200
Double Jeopardy!
Which potential energy diagram represents the change in potential energy that occurs when a catalyst is added to a chemical reaction?
B)
200
Which statement describes a reaction at equilibrium?
A) The mass of the products must equal the mass of the reactants.
B) The entropy (disorder) of the reactants must equal the entropy of the products.
C) The rate of formation of the products must equal the rate of formation of the reactants.
D) The number of moles of the reactants must equal the number of moles of the products.
C) The rate of formation of the products must equal the rate of formation of the reactants.
When equilibrium is reached, the rates are equal and the concentrations are constant
200
Double Jeopardy!
Given the equation representing a system at equilibrium:
N2O4(g) <--> 2NO2(g)
Which statement describes the concentration of the two gases in this system?
A) The concentration of N2O4(g) must be less than the concentration of NO2(g).
B) The concentration of N2O4(g) must be greater than the concentration of NO2(g).
C) The concentration of N2O4(g) and the concentration of NO2(g) must be equal.
D) The concentration of N2O4(g) and the concentration of NO2(g) must be constant.
D) The concentration of N2O4(g) and the concentration of NO2(g) must be constant.
300
A 5.0-gram sample of Fe(s) is to be placed in 100 milliliters of HCl(aq). Which changes will result in the fastest rate of reaction?
A) increasing the surface area of Fe(s) and increasing the concentration of HCl(aq)
B) increasing the surface area of Fe(s) and decreasing the concentration of HCl(aq)
C) decreasing the surface area of Fe(s) and increasing the concentration of HCl(aq)
D) decreasing the surface area of Fe(s) and decreasing the concentration of HCl(aq)
A) increasing the surface area of Fe(s) and increasing the concentration of HCl(aq)
300
In the early 1900s, scientists developed a process to produce ammonia from hydrogen and atmospheric nitrogen on an industrial scale. The balanced equation below represents this reaction.
N2(g) + 3H2(g) --> 2NH3(g) + 91.8 kJ
a) Draw a potential energy diagram for the reaction.
b) Explain, based on the equation, how you know whether this is an endothermic/exothermic rxn.
Heat is located on the product side of the equation
300
In a chemical reaction, the difference between the potential energy of the products and the potential energy of the reactants is equal to the
Heat of reaction or delta H
300
Hydrogen gas is needed for many industrial chemical reactions. An equilibrium system that includes the use of a catalyst produces hydrogen from methane and steam is shown in equation 1 below.
Equation 1:
CH4(g) + H2O(g) + 210 kJ <--> CO(g) + 3H2(g)
Compare the rate of the forward reaction to the rate of the reverse reaction for the equilibrium system at equilibrium represented by equation 1.
— In equation 1, the rate of the forward reaction equals the rate of the reverse reaction at equilibrium.
300
Double Jeopardy!
During a laboratory activity, a student dissolves 20.0 grams of solid ammonium chloride, NH4Cl(s), in 100.0 grams of water at 25°C. After thorough stirring, no undissolved NH4Cl(s) remains. During this laboratory activity, appropriate safety equipment is used and safety procedures are followed.
State evidence from Table I that indicates that this dissolving process is endothermic.
— The delta H for this dissolving is +14.78 kJ/mol
400
A 3% hydrogen peroxide solution, H2O2(aq), is commonly used as a disinfectant. Hydrogen peroxide, H2O2, decomposes as represented by the balanced equation below.
State how increasing the temperature of the H2O2 affects the rate of the reaction.
Possible answers:
— The increase in temperature of the reactant will increase the reaction rate.
— The reaction will happen faster after the temperature increases.
— Higher temperature, faster rate.
400
The activation energy is _________ kJ and the reaction is _________________ (endo/exothermic).
PE of reactant = 40
Activated Complex = 50
50 - 40 = 10 kJ
EXOTHERMIC
400
Which interval represents the heat of reaction?
4
400
Nitrogen dioxide gas, NO2(g), can reach equilibrium with dinitrogen tetroxide gas, N2O4(g), in a closed system. At 1.0 atmosphere, the boiling point of N2O4is 21°C. The equation below represents this system.
2NO2(g) <--> N2O4(g) + energy
State how the equilibrium shifts when the pressure on the equilibrium system is increased at constant temperature.
— Increasing the pressure favors the forward reaction.
— Equilibrium shifts to the right.
400
In each of the four beakers shown below, a 2.0-centimeter strip of magnesium ribbon reacts with 100 milliliters of HCl(aq) under the conditions shown.
In which beaker will the reaction occur at the slowest rate?
A) lowest concentration, lowest temperature
500
The balanced equation below represents the reaction between a 5.0-gram sample of zinc metal and a 0.5 M solution of hydrochloric acid. The reaction takes place in an open test tube at 298 K and 1 atm in a laboratory activity.
Zn(s) + 2HCl(aq) --> H2(g) + ZnCl2(aq) + energy
State one change in reaction conditions, other than adding a catalyst, that will increase the rate of the reaction.
Possible answers:
— Increase the surface area of the zinc.
— Increase the temperature of the reaction.
— Use a more concentrated HCl(aq) solution.
500
The activation energy for the reverse reaction is represented by
Letter ______ + ______
Activation Energy of the reverse rxn goes from the PE of the product to the highest point (activated complex)
B + C
500
Given the potential energy diagram and equation representing the reaction between substances A and D
According to Table I, substance G could be
A) HI(g) B) H2O(g) C) CO2(g) D) C2H6(g)
Endothermic Rxn
Look on Table I in Chem Ref Table to find a heat of reaction value (delta H) as positive
A) HI(g)
500
Given the equation representing a system at equilibrium:
PCl5(g) + energy <--> PCl3(g) + Cl2(g)
Which change will cause the equilibrium to shift to the right?
A) adding a catalyst
B) adding more PCl3(g)
C) increasing the pressure
D) increasing the temperature
D) increasing the temperature
500
Given the equation representing a system at equilibrium:
N2(g) + 3H2(g) ↔ 2NH3(g) + energy
Which changes occur when the temperature of this system is decreased?
A) The concentration of H2(g) increases and the concentration of N2(g) increases.
B) The concentration of H2(g) decreases and the concentration of N2(g) increases.
C) The concentration of H2(g) decreases and the concentration of NH3(g) decreases.
D) The concentration of H2(g) decreases and the concentration of NH3(g) increases.
The concentration of H2(g) decreases and the concentration of NH3(g) increases.