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Flashcards in Test 2 Deck (33):

Change in heat of a solution

change in heat(1) + change in heat(2) + change in heat(3)


Exothermic reaction

Change in heat of solution < 0


Endothermic reaction

Change in heat of solution > 0



Molarity = moles of solute / liters of solution


Percent mass of solute

% mass of solute = (mass solute/mass of soln) * 100%



The number of moles of solute per Kg of solvent.
m = #moles of solute / Kg of solvent


Mole Fraction

If a solution contains components A and B, then:
Xa + Xb = 1
Xa = moles A / total moles
Xb = moles B / total moles


Solid solubility in relation to temperature

generally increases with increase in temperature


Gas solubility in relation to temperature

generally decreases with increase in temperature


External pressure in relation to solubility of liquids and solids

has no influence on the solubility of liquids and solids


LeChatellier's principle

When a system in equilibrium is disturbed by a change of temperature, pressure, or concentration variable, the system shifts in equilibrium composition in a way that tends to counteract this change of variable, i.e., the system will shift left if the right side increases and vice-versa.


Henry's law

The solubility of a gas in a liquid is proportional to the P of the gas over the liquid.
c = kP, where:
c = molar concentration of the dissolved gas (mol/L, i.e., molarity)
k = constant value depending only on temperature (mol/L *atm)
P = pressure, in atm, of the gas over the solution


Rauolt's Law

P1 = X1 * Pnot1
change in P = X2 * Pnot1


Vapor pressure of a solution, P(total) =

Pt = Xa * PnotA + XbPnotB
A = solvent
B = solute


Boiling point elevation

change in temp boiling = i * Kb * Cm
i = van't Hoff factor
Kb = molal boiling point constant
Cm = concentration (molality)


Freezing point depression

change in temp freezing = i* Kf * Cm
i = van't Hoff factor
Kb = molal freezing point constant
Cm = concentration (molality)


Osmotic pressure

pi = iMRT
pi = osmotic pressure
i = van't Hoff factor
M = molarity of the solution
R = gas constant, 0.0821 L * atm/ K * mol
T = absolute temperature


Gas constant

0.0821 L * atm/K * mol


How to convert Celsius to Kelvin

C + 273.15


How to convert mmHg to atm

1 atm = 760 mmHg
Ex: 100 mmHg * (1 atm / 760 mmHg)


van't Hoff factor

count number of particles from chemical formula
Ex: What is van't Hoff factor of Fe2(SO4)3?
i = 5
2 Fe and 3 SO4


Boiling point of water

100 degrees C


Freezing point of water

0 degrees C


Rate of a Reaction

Change in the concentration of a reactant or a product with time.

A -> B
rate = (change in concentration of B)/(change in time)
rate = -(change in concentration of A)/(change in time)

units of mol/L * s


Rate Law

rate = k[A]^x[B]^y
Reaction is xth order with respect to A, yth order with respect to B, and (x + y)th order overall


Steps for determining rate order, rate constant and, rate of reaction given information.

1.) Using the experimental data, place rate law over rate law, i.e., rate y/rate x, where
rate x = k[A]^x[B]^x
rate y = k[A]^y[B]^y
2.) Simplify the expression until the order of the reaction with respect to the reactant is determined.
3.) Perform steps 1 and 2 for each reactant in the experiment.
4.) Now that order with respect to each reactant is known, Use any experiment to determine k, i.e.,
rate = k[A]^x[B]^y, where
rate = rate of any experiment
x and y are known from steps 1 - 3
5.) Using the k that was found in step 4, determine any requested information using provided data from the question.


0th order reaction

Rate Law:
rate = k

k Units:
M/s or mol/L * s

Concentration-Time Equation
[A]t = -kt + [A]o

Half-life Equation:

[A]t vs time = straight line with slope of -k


1st order reaction

Rate Law:
rate = k[A]

k Units:
1/s or s^-1

Concentration-Time Equation:
[A]t = [A]o * e^-kt

Half-life Equation:

ln[A]t vs time = straight line with slope of -k


2nd order reaction

Rate Law:
rate = k[A]^2

k Units:
1/M * s or M^-1 * s^-1 or mol/L * s or mol * L^-1 * s^-1

Concentration-Time Equation:
(1/[A]t) = kt + (1/[A]o)

Half-life Equation:

1/[A]t vs time = straight line with slope of k


Arrhenius Equation

k = Ae^-(Ea/RT)
k = rate constant
A = frequency factor
Ea = activation energy
R = 8.314 J/K * mol
T = absolute temperature in Kelvin

ln(k1/k2) = (Ea/R)((T1 - T2)/(T1 * T2))
k1 and k2 = rate constants (at least one given)
Ea = activation energy of the reaction (kJ/mol)
R = 8.314 J/K * mol
T1 and T2 = temperature in Kelvin (at least one given)

ln(k) vs 1/T = straight line with slope of (-Ea/R)



A substance that increases the rate of a chemical reaction without being consumed.


Units for k when rate = k[A][B]

M^-1 * s^-1


Units for k when rate = k[A]^2[B]

M^-2 * s^-1