Search found 49 matches

Tue Mar 17, 2020 12:32 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pH of acids
Replies: 11
Views: 355

Re: pH of acids

pH=-log[H+] and strong acids cause there to be a high [H+] than weak acids this strong acids have a pH closer to 0 while weak acids are closer to 7 on the scale of 0-7
Tue Mar 17, 2020 12:27 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Kelvin or Celsius?
Replies: 47
Views: 1068

Re: Kelvin or Celsius?

kelvin so it cancels out with the units of R
Tue Mar 17, 2020 12:26 pm
Forum: Zero Order Reactions
Topic: 0 order
Replies: 7
Views: 151

Re: 0 order

zero-order rate isn't dependent on the reactant concentrations and has a linear graph when [A] is graphed vs time
Tue Mar 17, 2020 12:24 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Redox from cell diagram
Replies: 6
Views: 100

Re: Redox from cell diagram

the left of the double line is being oxidized while the right is being reduced (you can remember this because of the two r's)
Tue Mar 17, 2020 12:21 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: k
Replies: 7
Views: 162

Re: k

a large k means a faster reaction rate
Tue Mar 17, 2020 12:17 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Slowest step
Replies: 9
Views: 142

Re: Slowest step

the slow step takes the most time and the reaction cannot be completed before this step is completed, it determines the reaction rate therefore
Tue Mar 17, 2020 12:15 pm
Forum: Calculating Work of Expansion
Topic: Ideal gas
Replies: 4
Views: 212

Re: Ideal gas

that indicates that PV=nRT is applicable
Tue Mar 17, 2020 12:13 pm
Forum: Zero Order Reactions
Topic: Equations for 0, 1st, and 2nd order reactions
Replies: 4
Views: 94

Re: Equations for 0, 1st, and 2nd order reactions

to get a linear graph for each type of order do the following:
0th- [A] vs time
1st- ln[A] vs time
2nd- 1/[A] vs time
Tue Mar 17, 2020 11:49 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G of ionization
Replies: 3
Views: 336

Re: Delta G of ionization

yes
Tue Mar 17, 2020 11:48 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Doubling the amount of reducer/oxidizer
Replies: 2
Views: 111

Re: Doubling the amount of reducer/oxidizer

yes
Tue Mar 17, 2020 11:47 am
Forum: General Rate Laws
Topic: Axes labels
Replies: 6
Views: 123

Re: Axes labels

y-axis: 1/[A]
x-axis: time
Tue Mar 17, 2020 11:45 am
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 291
Views: 136083

Re: Saying Thank You to Dr. Lavelle

Dear Dr. Lavelle, Thank you so much for your positive energy this year. Your lecture is very clear and productive however, it is your evident love for teaching that makes it so amazing. Thank you for all of your resources and the quick and smooth transition to an online final, I cannot imagine how s...
Tue Mar 17, 2020 11:38 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Increasing voltage of a cell
Replies: 3
Views: 125

Re: Increasing voltage of a cell

changing the size of the anode doesn't affect the voltage
Tue Mar 17, 2020 11:38 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Increasing voltage of a cell
Replies: 3
Views: 125

Re: Increasing voltage of a cell

you can change the concentration to affect the voltage
Tue Mar 17, 2020 11:36 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: n of concentration cell
Replies: 3
Views: 98

n of concentration cell

How do we know the value of 'n' for concentration cells
Tue Mar 17, 2020 11:31 am
Forum: Student Social/Study Group
Topic: Coronavirus Joke
Replies: 14
Views: 794

Re: Coronavirus Joke

thanks
Tue Mar 17, 2020 11:28 am
Forum: Balancing Redox Reactions
Topic: Reversing the anode
Replies: 10
Views: 154

Re: Reversing the anode

the anode is being oxidized so you must flip the equation since all cell potentials are given in the reduction form
Tue Mar 17, 2020 10:18 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Units for delta G
Replies: 14
Views: 258

Re: Units for delta G

Tue Mar 17, 2020 10:17 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration Cells
Replies: 8
Views: 184

Re: Concentration Cells

concentration cells always have a smaller delta E than galvanic cells because the difference in the standard potential=0
Tue Mar 17, 2020 10:16 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration Cells
Replies: 8
Views: 184

Re: Concentration Cells

the difference in the standard potentials is zero because they have the same standard potential, they're the same solution
Sun Mar 01, 2020 8:50 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Finding N
Replies: 6
Views: 122

Re: Finding N

to find n you must either balance the half equations to get the number or you can look at the standard enthalpy table to find number of electrons needed in both equations and set those equal to each other
Sun Mar 01, 2020 8:48 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Units for delta G
Replies: 14
Views: 258

Re: Units for delta G

delta G is given in kJ
Sun Mar 01, 2020 8:46 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Rules for Writing Cell Diagrams
Replies: 2
Views: 54

Re: Rules for Writing Cell Diagrams

you shouldn't write the stoichiometric coefficients
Thu Feb 27, 2020 9:14 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: homework 6N.1
Replies: 1
Views: 40

homework 6N.1

For part b what is the standard potential for In 3+ -> In2+? This value would be different than the transition from In3+ to In (s) right?
Thu Feb 27, 2020 8:33 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cells
Replies: 5
Views: 43

Re: cells

galvanic cells are positive while electrolysis is negative a helpful way to remember this is by knowing that electrolysis requires electricity to occur
Thu Feb 27, 2020 8:31 pm
Forum: Balancing Redox Reactions
Topic: homework 6K.3
Replies: 1
Views: 29

homework 6K.3

what is the half-reaction in part d for Cl2 -> Cl2?
Thu Feb 27, 2020 3:34 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Coefficients in Calculating Cell Potential?
Replies: 3
Views: 37

Re: Coefficients in Calculating Cell Potential?

the coefficients don't affect the standard potential but make sure to change the sign if you need to flip the equation given in the table
Thu Feb 27, 2020 3:32 pm
Forum: General Science Questions
Topic: Test 2
Replies: 16
Views: 352

Re: Test 2

the last lecture it will cover is the start of class this Wednesday, it won't include kinetics
Thu Feb 27, 2020 3:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Drawing Cell Diagram
Replies: 7
Views: 112

Re: Drawing Cell Diagram

make sure to write the state of the compound but you don't need to include the coefficient which means you don't need to find the balanced equation unless asked for separately
Wed Feb 26, 2020 8:53 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Calculating Standard Potentials
Replies: 4
Views: 137

Re: Calculating Standard Potentials

the cell diagram should always have the cathode on the right so your method should be correct but to avoid getting the wrong answer due to an error in the set up of the cell diagram remember that it is E cathode - E anode
Tue Feb 11, 2020 5:28 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Delta H and Delta U
Replies: 2
Views: 36

Re: Delta H and Delta U

For an ideal gas, in an isothermal process, ΔU=0=Q−W, so Q=W. delta H is zero for isothermal reactions with ideal gases.
Tue Feb 11, 2020 5:22 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 4H.7 partc c
Replies: 1
Views: 51

Re: 4H.7 partc c

you can guess that the entropy would be decreasing based on the state change of SO2 and BR2 from gas to aq, we know gas has a much larger entropy.
Tue Feb 11, 2020 5:11 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Pizza Rolls 3b
Replies: 1
Views: 46

Pizza Rolls 3b

what formula is used to find the enthalpy of fusion in question 3b
Tue Feb 11, 2020 4:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Pizza Rolls 4
Replies: 1
Views: 53

Re: Pizza Rolls 4

the easiest way to solve problems like these is to find chemicals that you want in your final equation that only appear once in the other equations. In 4a ginger ale only appears in the first equation so you know you must multiple that equation x2 to get the 2gingerale you see in the final equation....
Sat Feb 08, 2020 6:50 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hf and Hc
Replies: 3
Views: 46

Re: Hf and Hc

you can use Hc the same way you would use Hf mathematically but Hc stands for enthalpy of combustion
Sat Feb 08, 2020 6:47 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneous vs Nonspontaneous
Replies: 4
Views: 46

Re: Spontaneous vs Nonspontaneous

I don't think that we've had a practice problem in which we weren't told if a reaction was reversible vs irreversible if that information was needed but an example of a irreversible reaction would be combustion. If a reaction is spontaneous the gibbs free energy value would be negative
Fri Feb 07, 2020 6:06 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: negative Delta U
Replies: 5
Views: 59

negative Delta U

if you burn fuel what does it mean conceptually for the Delta U to be negative? can the system then not do work?
Fri Feb 07, 2020 5:59 am
Forum: Calculating Work of Expansion
Topic: units
Replies: 3
Views: 57

units

if you can use equation -P deltaV to find work done from expansion how do you convert this to joules? my answer is in ATM x L
Wed Feb 05, 2020 9:05 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Thermodynamically stable/unstable
Replies: 2
Views: 51

Re: Thermodynamically stable/unstable

It can but it is not a given that all thermodynamically unstable compounds will decompose. There are three types of decomposition reactions: Thermal, electrolytic, and catalytic.
Wed Feb 05, 2020 8:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard State of Compounds
Replies: 2
Views: 37

Re: Standard State of Compounds

these compounds are not in their standard state, for example- C(s, graphite) + O2(g) → CO2(g)
C(s) and O2(g) are their standard states with standard enthalpies of formation=0
Wed Feb 05, 2020 8:56 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: q/T=H/T
Replies: 1
Views: 38

Re: q/T=H/T

This equation is used to find delta S of melting ice, delta H is the heat required to melt 1 mol of ice at 1atm divided by the melting point in Kelvin
Wed Feb 05, 2020 8:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy
Replies: 2
Views: 35

Re: Enthalpy

This can be shown from:
deltaH = (qp + w) + PdeltaV -> deltaH = (qp - PdeltaV) + PdeltaV -> deltaH= qp
Wed Feb 05, 2020 8:49 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy
Replies: 2
Views: 35

Re: Enthalpy

Assuming that the only work done by the reaction is work of expansion gives an equation in which the P deltaV terms cancel.
Thu Jan 30, 2020 2:56 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter q
Replies: 2
Views: 30

Re: Calorimeter q

q is negative if the reaction is exothermic a bomb this will be indicated by an increase in the thermometer of the bomb calorimeter
Thu Jan 30, 2020 1:10 pm
Forum: Calculating Work of Expansion
Topic: 4B.5
Replies: 1
Views: 27

Re: 4B.5

The cylinder for the problem is in an environment that has 750 Torr. The conversion for Torr to atm is 760Torr/1atm so the environment we are working with would have a pressure slightly less than 1atm
Thu Jan 30, 2020 12:45 pm
Forum: Calculating Work of Expansion
Topic: Reversible processes and greatest work
Replies: 3
Views: 40

Re: Reversible processes and greatest work

Reversible processes do the most work, because they have to push against more external pressure
Sat Jan 25, 2020 5:39 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: standard enthalpy
Replies: 3
Views: 41

Re: standard enthalpy

the standard enthalpy is 0 because it takes no energy to form a naturally-occurring compound
Thu Jan 23, 2020 9:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: homework 6A.23
Replies: 2
Views: 37

homework 6A.23

How are we supposed to find the concentrations of Ba2+, OH−, and H3O+ if we aren't given the Ka or pH?
Thu Jan 23, 2020 2:05 pm
Forum: Phase Changes & Related Calculations
Topic: Phase change of water
Replies: 2
Views: 33

Re: Phase change of water

This happens for more than just water, you can google the phase change of other compounds to find examples.