Stoichiometry, Kinetics, and Equilibrium

Question 1

says that the mass of the reactants in a reaction must equal the mass of the products
chemical equations must be balanced so there are the same number of atoms of each element in the products as there are in the reactants

Answer 1

law of conservation of mass

Question 2

Strategy: Solve for how many grams of a reactant needed to form x number of grams of product

Answer 2

1. Determine number of moles of product you want to produce (moles = g / g per mol)
2. Set up molar ratio to determine number of moles of reactant you need to react w/ product (based on reaction coefficients)
3. convert moles of reactant to grams (grams = moles * molar mass)

Question 3

reactant that would be used up first if the reaction were allowed to run to completion
not necessarily the reactant of which you have the least
limits the amount of product that can be formed in the reaction

Answer 3

limiting reagent (reactant)

Question 4

Strategy: Determine limiting reagent

Answer 4

1. Balance the equation
2. Determine how many moles of each reactant we have: divide the mass of each by its molar mass
3. Based on molar coefficients, determine how many moles of one reactant is needed to react with the other reactant; Determine which will be depleted first

Question 5

actual series of steps through which a chemical reaction occurs

Answer 5

reaction mechanism

Question 6

a species that is formed for a very short period of time in a chemical reaction but does not appear in the overall net reaction equation

Answer 6

reaction intermediate

Question 7

step in reaction mechanism that determines the overall reaction rate
slowest step in a proposed mechanism in a rxn mechanism
imposes an upper limit on how fast a reaction can go

Answer 7

rate-determining step

Question 8

for nearly all forward, irreversible reactions, the rate is proportional to the product of the concentrations of the reactants of the rate determining step

Answer 8

rate law: (forward, irreversible reactions)

Question 9

Rate Law for general reaction: aA + bB —–> cC + dD

Answer 9

rate = k * [A]^x * [B]^y
Note: k = known constant; x and y = orders of reaction determined experimentally; [A] and [B] = molar concentrations of species A and B (reactants in chemical equation–mol/Liter)

Question 10

sum of the orders of the reaction (x + y)

sum of exponents in rate law

Answer 10

overall reaction order

Question 11

If the concentration of one reactant is doubled and the rate of reaction increases by a factor of 2, the reaction is _______ with respect to that reactant. The reactant receives an exponent of ____ in the rate law

Answer 11

first order; 1

Question 12

if the concentration of one reactant is doubled and the rate of the reaction increases by a factor of 4, the reaction is _______ with respect to that reactant. The reactant receives an exponent of ____ in the rate law

Answer 12

second order; 2

Question 13

if the concentration of one reactant is doubled and the rate of the reaction does not change, the reaction is _______ with respect to that reactant. The reactant receives an exponent of ____ in the rate law.

Answer 13

zero order; reactant does not appear in reaction rate law

Question 14

4 Factors that affect the reaction rate

Answer 14

reactant concentration
temperature
solvent
catalysts (enzymes)

Question 15

The greater the concentration of reactants (more particles per unit volume), the _____ will be the number of effective collisions per unit time, causing the reaction rate to _______.

Answer 15

greater

increase

Question 16

Reaction rate is _________ proportional to reaction concentration except for _____ reactions, when the reaction rate is not dependent on the concentration of reactants.

Answer 16

directly proportional

zero order reactions

Question 17

Reaction rate and temperature are __________

Answer 17

directly proportional

Question 18

As the temperature increases, the reactant molecules have more ______ and Ea will be reached more quickly.

Answer 18

Energy

Question 19

Catalysts increase the rate of chemical reactions by _____________

Answer 19

lowering the activation energy of the reaction

Question 20

a dynamic state at which the forward and reverse reaction rates are equal
molar concentrations of the reactants and products are usually not equal

Answer 20

equilibrium

Question 21

ratio of product to reactant concentrations
pure liquids and solids do not appear in the expression
characteristic of a given system at a given temperature

Answer 21

equilibrium expression (Keq)

Question 22

Equation: Equilibrium Experssion (Keq)
Rxn: aA + bB —-> cC + dD

Answer 22

Keq = [C]^c * [D]^d / [A]^a * [B]^b
(Rf = Rr)
Note: Raise the concentration of the molecules in the reaction to their stoiciometric coefficients

Question 23

If the value of Keq is very large compared to 1, then at equilibrium, there will be much more of the _________ than the ______.

Answer 23

more products than reactants

Question 24

________ and ______ do not appear in the equilibrium constant expression.

Answer 24

Pure solid

liquids

Question 25

If a stress is applied ot a system at equilibrium, the system will shift in such a way as to relieve the applied stress

Answer 25

Le Chatelier’s Principle

Question 26

Increasing the concentration of a species will shift the equilib ________ from the species that is added (to use it up)

Answer 26

away from that species

Question 27

An increase in the pressure of a system will shift the equilibrium so as to _____ the number of moles of gas present

Answer 27

decrease (decrease entropy)

Question 28

If the temp was increased, the ___________ rxn will shift to the right and the ______ rxn will shift to the left

Answer 28

endothermic shifts to the R

exothermic shifts to the L

Question 29

If the temp was decreased, the ______ rxn will shift to the left to produce more heat to raise the temp, and the _____ rxn will shift to the right, to produce more heat to raise the temp

Answer 29

endothermic rxn shifts to the L

exothermic rxn shifts to the R

Question 30

When we add an ionic compound to a water, it usually dissolved by dissociating into its _______

Answer 30

component ions

Question 31

solution that contains the maximum number of ionic particles before a precipitate forms

Answer 31

saturated solution

Question 32

when a solution is saturated, a dynamic equilibrium exists between the _______ and the _____.

Answer 32

solute (dissolved substance)

solid

Question 33

a dynamic equilibrium between dissolved and solid solute

Answer 33

saturated solution

Question 34

equilibrium constant for dissolution
greater this value, the more soluble the solute in that solvent
solid compounds do not appear in expression bc it is a pure solid
dependent on Temp

Answer 34

solubility product constant (Ksp)

Question 35

Equation: K(eq) / K(sp)
Rxn: Fe(OH)3 (s) —-> Fe3+(aq) + 3OH- (aq)

Answer 35

Keq = Ksp = [Fe3+][OH-]^3

Note: Concentration of ions are the concentration at saturation level

Question 36

The higher the Ksp, the _______ it is to reach saturation b/c more compound will dissolve

Answer 36

harder

Question 37

The solubility product constant (Ksp) is _________ proportional to temperature

Answer 37

directly proportional

solubility increases w/ temperature

Question 38

maximum number of moles of a compound that will dissolve in 1 L of solution

Answer 38

molar solubility

Question 39

Molar solubility corresponds to the _________ at that Molarity

Answer 39

concentration of that ion * number of moles of that ion present (stoichiometric coefficient / subscript of molecule)