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- University of Wisconsin - Eau Claire
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- Chemistry 104
- King
- Exam 1 Key Equations and Problems

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Equation for Kinetic Energy:

Kinetic Energy = (1/2)mass x velocity^{2 }**OR **E_{KE}=(1/2)mv^{2}

Equation for Work:

Work = force x distance **OR **w=Fd

Equation for Potential Energy:

Potential Energy = mass x (accel. due to gravity) x height **OR **E_{PE}=mgh

Equation to find Change in Enthalpy:

Change in Enthalpy = Enthalpy of the products - Enthalpy of the reactants

Hess's Law: How to use it:

Reverse the first reaction and add it to the 2nd reaction. Cancel out. Write total reaction using remains. Add together enthalpies of the 2 reactions to find the enthalpy of the final reaction.

Equation for specific heat:

c=q/m(Δ**t**) **OR **q=mc(changein**t**)

*note the lowercase c

where:

q=heat

m=mass

t=temp

Equation for heat capacity:

C=q/(Δ**t**)

*note the uppercase C

where

q=heat

t=temp

What are the 2 principal types of heat that can be measured in** calorimetry**?

1. heat changes measured under **constant pressure** conditions in a device **open to the atmosphere**

ΔH= q_{p}

2. heat changes measured under **constant volume** conditions in a **sealed container**

ΔE = q_{v}

*E=internal energy

Formula used to connect enthalpy and interal energy formulas

H = E + p V

(enthalpy = internal energy + (pressure x volume))

What is the most common unit used when measuring reaction rate?

(mol/liter)/second = mol l^{-1}s^{-1} = **Ms ^{-1}**

Equation for the rate of reaction:

Rate of reaction = Δ[reactant] / time interval

**OR **rate = Δ[reactant] / Δt

* note that t in this case stands for time interval, NOT temperature

Include the stoichiometric coefficients of the reactant if the coefficients do not equal unity.

If an equation is: aA + bB --> cC +dD, what is the rate equation for substance A?

Rate of substance A = -(1/a)(Δ[A]/Δt)

*t= time interval

*note that we need a negative sign when finding the rate of a reactant

If an equation is: aA + bB --> cC +dD, what is the rate equation for substance C?

Rate of substance C = (1/c)(Δ[C]/Δt)

*t= time interval

*note that we do NOT need a negative sign when finding the rate of a product

Equation for the rate law:

rate = k[reactant]^{n}

*n=**determined by experiment**

*k=rate constant

If an equation is: aA + bB --> cC + dD, what is the **forward rate law**?

rate = k[A]^{x}[B]^{Y}

*X and Y are determined through experiment

*k = rate constant

If a rate law is: rate = k[A]^{1}[B]^{2} , what order is the reaction in?

The reaction is** first-order** in species A and **second-order** in species B, therefore it is **third-order over all.**

When a zero-order rate law is: -(Δ[A]/Δt) = k , how can we re-write this using [A]_{0}?

[A]_{t} = [A]_{0} - kt

*[A]_{t} = concentration of A at time t

*[A]_{0} = concentration of A at t=0 (initial concentration of A)

*k = rate constant

*t = time

When looking at: [A]_{t} = [A]_{0} - kt , what variable in the rate would be equivilent to the slope(y)? (compare to y=mx + b) What would y, m, and x be?

slope(y) = -k

x = t <-- x-axis

y= [A]_{t }<-- y-axis

b= [A]_{0} <--how far you would move up on the y axis

How would you write a first order rate law for A --> P?

-(Δ[A]/Δt) = k[A] , which can then be re-written as: Δ[A]/Δt = -k[A] , which can then be re-written as: **ln([A]**_{0}/[A]_{t}) = kt , then we use log properties to re-write again as: **[A]**_{t}/[A]_{0} = e^{-kt} , then re-write as **[A]**_{t} = [A]_{0}e^{-kt}

When looking at the equation: ln([A]_{0}/[A]_{t}) = kt , which variables would be equivalent to y, m, x, and b of the straight line equation?

y = ln([A]_{0}/[A]_{t})

m(slope) = k

x = t

If the reaction: A --> P , follows second-order kinetics, what is the rate law?

-Δ[A]/Δt = k[A]^{2} , which can be re-written as **1/[A]**_{t} = 1/[A]_{0 }+ kt

When looking at the equation: 1/[A]_{t} = 1/[A]_{0} + kt , which variables would be equivalent to y, m, x, and b of the straight line equation?

y = 1/[A]_{t}

m(slope) = k

x = t

b = 1/[A]_{0}

What is the half-life equation for a zero-order reaction?

t_{1/2} = [A]_{0}/2k

What is the half-life equation for a first-order reaction?

t_{1/2} = ln(2)/k

According to the collision theory of chemical kinetics, what can we expect rate to be directly proportional to?

(# of collisions) / sec

What is the Arrhenius equation?

k = Ae^{-Ea/RT}

*E_{a} = Activation Energy

*k = rate constant

*R = gas constant

*T = temp (kelvin)

*A = frequency factor (related to collision frequency)

Important Log properties:

ln(e) = 1

ln(XY) = ln(X) + ln(Y)

ln(X/Y) = ln(X) - ln(Y)

ln(X^{m}) = m ln(X)

ln(e^{y}) = Y ln(e) = Y

How can the Arrhenius equation be re-written using natural logs (ln)?

ln*k* = ln(Ae^{-Ea/RT}) , which is then written as: **ln k = lnA - (E_{a}/RT) **

When observing the Arrhenius equation re-written: lnk = lnA - (E_{a}/RT) , which variables are equivalent to y, m, x, and b in the straigh line equation?

y = lnk

m = -(E_{a}/R)

b = lnA

x = T^{-1}

When comparing E_{a} to E_{a+c} (activation energy with catalyst), how would you set up an equation to compare the rate constants?

__k___{c} = __Ae ^{-Ea,c/RT}__

k = Ae ^{-Ea/RT}

^{}

Then re-write it all as **k _{c}/k = e^{(Ea-Ea,c)/(RT)}**

What is the reaction for the **overall** rate constant in the presense of a catalyst?

k_{overall }= k + k_{c}

What is the equation for a reaction quotient?

reaction quotient = (concentration of products)^{product coeff.}/ (concentration of reactants)^{reactant coeff.}

**OR** Q = [products]^{product coeff.}/ [reactants]^{reactant coeff.}

*Q = reaction quotient

What is the reaction quotient for: aA + bB --> cC + dD ?

Q = [C]^{c}[D]^{d}/ [A]^{a}[B]^{b}

When a system is at equilibrium, instead of measuring the reaction quotient (Q), we would measure the __________?

equilibrium constant (K)

*equation is the same as the reaction quotient (Q) equation, but Q is replaced with K

Better way to write K:

K = (([C]/M)^{c}([D]/M)^{d}) / (([A]/M)^{a}([B]/M)^{b})

*K is dimentionless!

When using: A + B --> C , how would you write the equation in terms of the equilibrium constant using concentrations of each species?

K_{c} = [C] / [A][B]

When using: A + B --> 2C , how would you write the equation in terms of the equilibrium constant using partial pressures of each speices?

K_{p} = p^{2}_{C} / (p_{A})(p_{B})

When using: a A <--> b B , how would you relate K_{c} to K_{p}? Hint: Use the ideal gas law! (pv=nrt)

Plug each into the ideal gas law to make:

P_{A} = [A]RT and P_{B} = [B]RT

Then, plug the results into the expression for K_{p}

n_{A}/V_{B}=[A] and n_{B}/V_{B} = [B]

Then, re-write as K_{p} = [B]^{b}/[A]^{A} x (RT)^{Δn}

where Δn = b-a

therefore, **K _{p} = K_{C}(RT)^{Δn}**

T OR F: [Substance] = Density of the substance/ molar mass of the substance

TRUE

What will the final equilibrium constant expression for this equation be? CaCO_{3 }(s) <--> CaO (s) + CO_{2} (g)

K_{c} = [CO2]

*Pure solids and liquids do not appear in the final equilibrium constant expression

K_{p} = p_{CO2}

When adding these 2 reactions: A + B <--> C + D and C + D <--> E + F , what is the reaction and the corresponding equilibrium constant?

A + B <--> E + F

K_{c} = [E][F]/[A][B]

What is the quadratic equation?

ax^{2} + bx + c = 0

**OR**

x = (-b +- (SQ ROOT OF (b^{2} - 4ac)) / 2a

What does an ICE table include?

1. Concentration of molarities

2. Change Line

3. Equilibrium Line (molarity + change line)

* reactants on left, products on right

About this deck

Author: Abbey W.

Created: 2012-02-20

Updated: 2012-02-20

Size: 42 flashcards

Keywords: flash card flashcards digital flashcards note sharing notes textbook wiki college dorm class classroom exam homework test quiz university college education learn student teachers tutors share, study blue studyblue studyblu

Views: 11

Created: 2012-02-20

Updated: 2012-02-20

Size: 42 flashcards

Keywords: flash card flashcards digital flashcards note sharing notes textbook wiki college dorm class classroom exam homework test quiz university college education learn student teachers tutors share, study blue studyblue studyblu

Views: 11

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