The law of conservation of energy states that
energy cannot be created or destroyed.
Catalysts accelerate a reaction by
lowering the energy of activation.
Catalysts
increase the rate of a chemical reaction, lowers the activation energy of a chemical reaction and is recovered unchanged in the reaction it catalyzes.
Energy is
the capacity to do work.
Le Ch�telier's principle is
a general rule used to explain the effect of a change in reaction conditions on equilibrium.
An equilibrium constant with a value of 4.0 x 10^6 indicates that at equilibrium
the products are favored (because the value is greater than 1)
1000 kcalorie=1 calorie
Calorie = 1000 Kcalories
An equilibrium constant with a value of 4.0 x 10^-6 indicates that at equilibrium
the reactants are favored (because the value is less than 1) .
When the pressure of a reaction at equilibrium decreases, in which direction does the equilibrium shift?
The equilibrium shifts in the direction that increases the number of moles of gas.
what will increase the rate of a reaction?
Increasing the temperature, increasing the concentration of a reactant. adding a catalyst, ensuring that the reactants are properly aligned when they collide
When ?H is negative
the bonds formed in the products are stronger than the bonds broken in the reactants.
Heat is absorbed in an
endothermic reaction.
Which bond is the strongest?
H-H=+104
Cl-Cl=+58
The most positive the stronger
In an exothermic reaction
the products are lower in energy than the reactants
As a general rule, a reaction rate
doubles for each 10 degrees C the temperature is raised.
Which bond is the weakest?
H-H=+104
Cl-Cl=+58
The least positive is the weaker
When reactants can come together and form products, and products can come together to re-form reactants, the reaction is called a
reversible reaction.
When heat is added to an exothermic equilibrium reaction, the reaction
shifts to form more reactants
Consider the reversible reaction at equilibrium: M2(g) + K2(g)<==> 2 MK(g).
What is the effect of removing some M2(g) from the equilibrium system?
the concentration of K2(g) increases
In the reaction: C2H6(g) + O2(g) ? CO2(g) + H2O(g), increasing the concentration of C2H6(g) (the reactants) will
increase the reaction rate.
For an endothermic reaction at equilibrium, increasing the temperature
increases the rate of the forward reaction to form more products.
Which statement concerning the reversible reaction 2 NO2(g)<===> N2O4(g) is true?
As the forward reaction progresses and more N2O4 is formed, the reverse reaction rate increases.
A chemical reaction requires 62.29 kJ. How many kilocalories does this correspond to?
1 kcal=4.184kj
62.29 kj/4.184 kj
14.88 kcal
A chemical reaction releases 1055.2 kcal. How many kilojoules does this correspond to?
1Kcal =4.184Kj
(1055.2 kcal)(4.184 kj)
4414.9 kj
Which of the following energy quantities is equivalent to 878 J?
1Kcal =4.184Kj
1kj = 1000 J
Which Kj energy quantities is equivalent to 14.9 kcal?
1Kcal =4.184Kj
Which of the following energy quantities is equivalent to 258 Cal?
1Kcal =4.184Kj
1 calorie= 1000 kcalories
Energy Diagram Labels
B = ?H
C = Transition state
D = products
E = reactants
Which quantity represents the largest amount of stored energy?
fat, carbohydrate or protein
Energy is stored in the body as fat
Fat= 9cal/gm, Protein and carbohydrate= 4cal/gm
A peanut butter and jelly sandwich contains 12.00 g of fat, 8.00 g of protein, and 25.0 g of carbohydrate. How many Calories does this sandwich provide?
Fat= 9cal/gm, Protein and carbohydrate= 4cal/gm
(12�9)+(8�4)+(25�4)
240 calories
Walking at a brisk pace burns off about 110 Cal/mile. How far would you have to walk to burn off the Calories obtained from eating a candy bar that contained 4 g of protein, 16 g of fat, and 9 g of carbohydrates?
Fat= 9cal/gm, Protein and carbohydrate= 4cal/gm
(16�9)+(4�4)+(9�4)= 196 calories
196/110= 1.78 miles
The activation energy for the reaction is ______
100 kJ
Endothermic describes a reaction in which the energy of the products is
higher than the energy of the reactants
Consider the reaction: C3H8(g) + 5 O2(g) 3 CO2(g) + 4 H2O(g), where H = -531 kcal. Which statement concerning this reaction is true?
The bonds formed in the products are stronger than the bonds broken in the reactants because the heat change is negative
Consider the reaction, C2H4(g) + H2(g) ? C2H6(g), where H = 130 kJ. How many kilojoules are released when 2.5 mol of C2H4 reacts?
2.5mol x 130Kj = ____________
325?
A catalytic converter uses a catalyst to catalyze three reactions that clean up the exhaust from an auto engine. The elements used as a catalyst in catalytic converters are
platinum, rhodium, and palladium
It is always necessary for a chemical reaction to occur between two reactants.
A and B must collide with the proper orientation and with a certain minimum amount of energy
Which of the following is NOT a reasonable assumption about the chemical reaction whose energy diagram is depicted below?
The rate of a chemical reaction increases with an increase in the concentration of one or more reactants, as the higher concentration of reactants increases the frequency of collisions between molecules.
The rusting of iron is described by the reaction:
4 Fe(s) + 3 O2(g)---> 2 Fe2O3(s).
The formation of rust has a low
reaction rate.
The formation of rust has a high
activation energy.
The formation of rust would occur more slowly at
higher altitudes where the concentration of oxygen is lower.
The formation of rust would occur faster in
the warmer summer months than in the cooler winter months.
A reversible reaction has reached equilibrium when
the condition is established of the forward and reverse reaction rates become equal
The hydrolysis of sucrose depicted below has K = 1.4 x105. Which of the following is a reasonable assumption about this reaction once equilibrium is established?
sucrose + H2O glucose + fructose
The equilibrium mixture contains mostly glucose and fructose.
What is the expression for the equilibrium constant for the reaction: 2 C2H6(g) + 7 O2(g)<==> 4 CO2(g) + 6 H2O(g)?
[ CO2] 4 [H2O]5
--------------------------
[ C2H6]2 [O2]
What is the gas phase chemical reaction that corresponds to the equilibrium constant expression shown below?
K= [ C] 2
----------------
[ A]4 [B]2
4 A + 2 B<==> 2 C
Consider the reaction: M3(g) + Kl2(g)<==> MKl5(g). If [M3] = 0.39 M, [Kl2] = 0.22 M, and [MK5] = 0.44 at equilibrium, what is the value of K?
K= [ MK]5
------------------ = ???
[ M]3 [Kl]2
Ammonia (NH3) is synthesized by the reaction of nitrogen and hydrogen in the presence of an iron catalyst according to the equation below.
Removing the iron catalyst would decrease the reaction rate.
Breaking a chemical bond requires
energy.
An endothermic reaction is one in which
energy is absorbed and ?H is pos (+).
Bond dissociation energies are always
positive numbers.
Bond breaking is
endothermic.
Exothermic reactions involve the formation of
products having lower energy than the reactants.
The stronger the bond, the higher its
bond dissociation energy.
Changes in potential energy occur in
chemical reactions.
The energy of the reacting molecules affects
whether a particular collision will lead to a chemical reaction.
The difference in energy between the reactants and the transition state is called
the energy of activation, symbolized by Ea.
Reactions with high Ea are generally
slow reactions.
Chemical reactions are considered favorable if
the products have a lower energy than the reactants.
Activation energy is the
minimum amount of energy necessary for a reaction to occur.
Increasing the concentration of the reactants in a chemical reaction increases
the number of collisions and the reaction rate.
Increasing the temperature of a reaction mixture usually results in
increase/decrease in the reaction rate.
Enzymes are proteins that act as
biological catalysts.
Once equilibrium is reached in a chemical reaction, reactants
may continue forming products.
Kinetic energy is the energy associated with
movement
Potential energy is
the energy inherent in an object due to its position or composition.
Consider the reaction: 2 C2H6(g) + 7 O2(g) 4 CO2(g) + 6 H2O(g).
Decreasing the concentration of C2H6(g) will decrease the reaction rate.
Consider the reversible reaction: M(g) + Kl2(g)<==> MKl2(g).
The reverse reaction is MKl2(g) ? M(g) + Kl2(g).
When the equilibrium constant for a reversible reaction is much greater than one (K > 1), the equilibrium is said to lie to
the right.