## Search found 154 matches

Mon Mar 16, 2020 2:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Delta G of Ionization of water on Final
Replies: 1
Views: 69

### Delta G of Ionization of water on Final

On the final, there was a problem where it asked you to calc the deltaG/deltaH/deltaS of ionization of water of a specific temp. How would you have approached this problem?
Mon Mar 16, 2020 2:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ATP QUESTION ON FINAL
Replies: 9
Views: 211

### Re: ATP QUESTION ON FINAL

Sine it says pi comes from ATP, the two concentrations cancels and K depends on [ADP] only. Maybe I am wrong about how I interpreted this problem, but I assumed that since all the Pi came from ATP, I assumed it meant that it only came from ATP that was broken into ADP...so Pi = ADP concentration......
Sat Mar 14, 2020 3:54 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation "A"
Replies: 3
Views: 22

### Re: Arrhenius Equation "A"

IM pretty sure it stays constant
Sat Mar 14, 2020 3:53 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Determining if a reaction mechanism is feasible
Replies: 3
Views: 95

### Re: Determining if a reaction mechanism is feasible

One way is to see if the slow step rate law matches the overall rate law. Remember that no matter the substitutions u may have to make for intermediates, the rate law will have the same order no matter what.
Sat Mar 14, 2020 3:52 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Endgame Q15
Replies: 2
Views: 70

### Re: Endgame Q15

Yes this is the concept of a pseudo rate law
Sat Mar 14, 2020 2:34 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: UA Practice Final Q4
Replies: 2
Views: 79

### Re: UA Practice Final Q4

First, you would wanna figure out how much H+ there is in solution. You do this by setting up an ice table and solve for H+ (remember is 2H+ in the equation). Then you have the amount of H+ in solution, and in order to neutralize it, you need the same amount of OH- to balance this out. You then use ...
Sat Mar 14, 2020 2:09 pm
Forum: General Rate Laws
Topic: Hw 7A.13
Replies: 8
Views: 130

### Re: Hw 7A.13

So the rate law would be based off of if each reactant is a first, second, or zero order reactant. Based from the info, you can infer that both reactants are first order because as you increase their concentration by a constant, the rate also increases by the same amount. therefore it would be k[CH3...
Thu Mar 12, 2020 8:38 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Lavelle's review slides
Replies: 1
Views: 40

### Re: Lavelle's review slides

He's referencing deltaG overall. He used this equation to see which side (reactants or products) will be favored given the conditions. Since deltaG is positive, it isn't spontaneous but that's for the forward reaction, the reverse reaction will be spontaneous in this case.
Wed Mar 11, 2020 12:48 am
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 282
Views: 134930

### Re: Saying Thank You to Dr. Lavelle

Even with the current situation, Lavelle has been a really great professor for both my 14a and 14b careers. I truly thank him for making my chemistry “good chemistry” :)
Tue Mar 10, 2020 11:07 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Pre-Equil Approach
Replies: 2
Views: 54

### Pre-Equil Approach

Does anyone know any book problem with a situation that we need to use this? The example in the book is the example we did in class. I also dont understand how to do number 14 on the "endgame" worksheet pertaining to this.
Tue Mar 10, 2020 5:00 pm
Forum: Administrative Questions and Class Announcements
Topic: Review Sessions for Final Exam
Replies: 2
Views: 77

### Re: Review Sessions for Final Exam

Will there also still be TA Office Hours?
Mon Mar 09, 2020 7:09 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7.11 part b
Replies: 2
Views: 26

### Re: 7.11 part b

Ok thank you!
Mon Mar 09, 2020 5:28 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7.11 part b
Replies: 2
Views: 26

### 7.11 part b

How do we know, when drawing this reaction profile, where the energies of the products of the first reactants lie energy-wise in relation to the whole profile? I know the whole reaction must be exothermic but where should the middle products/reactants lie? The answer implies they are both the same e...
Sun Mar 08, 2020 6:53 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Example 7C.1
Replies: 1
Views: 18

### Example 7C.1

How should we think of the rate of decomposition vs rate of formation in this type of scenario? Will we have to do this one a test?
Sun Mar 08, 2020 6:33 pm
Forum: General Rate Laws
Topic: Difference b/w General Rate Laws/Elementary
Replies: 2
Views: 49

### Difference b/w General Rate Laws/Elementary

Lavelle states on a worksheet on his website that "2N2O(g) → 2NO(g) + O2(g) • Write the overall rate expression for this first-order reaction. rate= k[N2O] *Note that the exponent does not match the coefficient in front of N2O. By just looking at the overall balanced equation, you cannot tell t...
Sun Mar 08, 2020 6:23 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7.31
Replies: 3
Views: 22

### Re: 7.31

I keep getting 1.12x10^8 M/s =k2 regardless of the order of the equation, but that's incorrect according to the book which has 2.5x10^9M/s as the answer.
Sun Mar 08, 2020 6:19 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: A in the Arrhenius Equation
Replies: 3
Views: 46

### A in the Arrhenius Equation

What does the A stand for in the Ae^(-Ea/RT) equation? I haven't seen this equation directly tested/used on the homework
Sun Mar 08, 2020 6:16 pm
Forum: Zero Order Reactions
Topic: Half life of zero order runs
Replies: 3
Views: 25

### Half life of zero order runs

Why is it when you plot the half-life against [A] for a reaction that is zero order, that the plot is linear?
Also, why is the initial rate of a 1st order rxn vs [A] linear?
Sun Mar 08, 2020 6:11 pm
Forum: Zero Order Reactions
Topic: slope of zero order reaction
Replies: 2
Views: 23

### Re: slope of zero order reaction

Well, when we derived the equation in class, the equation so happened to yield a negative number in front of k resulting in a negative slope. Remember, zero-order reactants don't affect the rate, so it doesn't mean much to the reaction rate, it just speaks to the relationship between [A] vs time.
Sun Mar 08, 2020 6:07 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7E.3A
Replies: 1
Views: 33

### Re: 7E.3A

I found an equation in book which helped. Ea(with catalyst)-Ea(w/o catalyst)/RT= a number. That number you then add a negative sign to and raise it to the e^power. Basically, its putting k2/k1 with the Arrhenius equations both on the top and bottom, respectively. so for part a i got 75000-125000/(8....
Sun Mar 08, 2020 5:22 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7.31
Replies: 3
Views: 22

### 7.31

7.31 The rate constant of the reaction O2(g) + N2(g) --> NO(g) + N(g), which takes place in the stratosphere, is 9.7 x 10^10 M/s at 800 degree C. The activation energy of the reaction is 315 kJ/mol. What is the rate constant at 700 degrees C? I used the equation ln(k2/k1)=Ea/R(1/T2-1/T1) but im gett...
Sun Mar 08, 2020 4:37 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7B.13
Replies: 1
Views: 22

### 7B.13

Half-life of A in a second-order reaction is 50.5 sec when [A]intial=.84 M. Calc the time needed for the conc of A to decrease to (a) one-sixteenth, (b)one-fourth, (c)one-fifth its original value. Can someone explain their thought process and method of doing this problem? I thought all you had to do...
Sun Mar 08, 2020 4:26 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7B.3 part c
Replies: 2
Views: 41

### Re: 7B.3 part c

Thank you!
Sun Mar 08, 2020 1:26 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7B.3 part c
Replies: 2
Views: 41

### 7B.3 part c

c) 2 A --> B + C, given that [A]intial= 0.153 M and that after 115 s the
concentration of B rises to .034 M.
How would I set up this problem? I dont understand how i should use the conc of B since the problem also gave us the initial conc of A.
Sun Mar 08, 2020 1:17 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7E.5
Replies: 1
Views: 43

### 7E.5

7E.5 The hydrolysis of an organic nitrile, a compound containing a OCqN group, in basic solution, is proposed to proceed by the following mechanism. Write a complete balanced equation for the overall reaction, list any intermediates, and identify the catalyst in this reaction. Why is the catalyst fo...
Sun Mar 08, 2020 12:51 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7D.7
Replies: 1
Views: 23

### 7D.7

7D.7 For the reversible, one-step reaction A + a <—>C + D the forward rate constant for the formation B is 265 L/molmin and the rate constant for the reverse reaction is 392 L?mol ?h . The activation energy of the forward reaction was found to be 39.7 kJ?mol21 and 25.4.0 kJ?mol21 for the reverse rea...
Sat Mar 07, 2020 2:40 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7C.7
Replies: 3
Views: 51

### 7C.7

Step 1 NO + Br2 --> NOBr2 slow
Step 2 NOBr2 + NO --> NOBr + NOBr fast
Write the rate law for the formation of NOBr implied by this
mechanism.
I got rate= k[NO2]^2[Br2], but the book has rate= k[NO2][Br2], why is that?
Mon Mar 02, 2020 8:10 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electrolytic Cells
Replies: 1
Views: 23

### Electrolytic Cells

"The potential supplied to an electrolytic cell must be at least as great as that of the cell reaction to be reversed. If there is more than one reducible species in solution, the species with the greater potential for reduction is preferentially reduced. The same principle applies to oxidation...
Mon Mar 02, 2020 7:43 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6.43
Replies: 3
Views: 36

### 6.43

6.43 Indicate for each of the following statements whether it applies to Ecell8, to Ecell, to both, or to neither: (a) decreases as the cell reaction progresses; (b) changes with temperature; (c) doubles when the coefficients of the equation are doubled; (d) can be cal- culated from K; (e) is a meas...
Mon Mar 02, 2020 7:18 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Nerve Cell
Replies: 1
Views: 38

### Nerve Cell

In a neuron (a nerve cell), the concentration of K+ ions inside the cell is about 20–30 times as great as that outside. What potential difference between the inside and the outside of the cell would you expect to measure if the difference is due only to the imbalance of potassium ions? Do we conside...
Mon Mar 02, 2020 7:13 pm
Forum: General Rate Laws
Topic: Homework 7A.17
Replies: 2
Views: 60

### Re: Homework 7A.17

Reactant B is second order. Since you know reactant C is zero order, you can focus on two reactions where reactant A is constant and reactant B is doubling and look at what it does to the rate constant. Hope this helps
Mon Mar 02, 2020 7:10 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Knowing if a Metal will dissolve
Replies: 1
Views: 24

### Knowing if a Metal will dissolve

How do I know if a metal will dissolve in a certain solution? Should it be in a spontaneous way, where the metal will be oxidized by the molecules in the solution?
Mon Mar 02, 2020 7:06 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Review Sessions
Replies: 6
Views: 71

### Final Review Sessions

When will Final Review Sessions start? i need to go to all of them lol
Mon Mar 02, 2020 6:55 pm
Forum: Balancing Redox Reactions
Topic: Basic vs Acidic Conditions.
Replies: 6
Views: 101

### Re: Basic vs Acidic Conditions.

I wouldn't think of it like that just to be sure, I would just make sure I know how to balance them
Mon Mar 02, 2020 6:54 pm
Forum: Student Social/Study Group
Topic: Today's Workshop
Replies: 2
Views: 70

### Re: Today's Workshop

^^^^^
Mon Mar 02, 2020 6:51 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Homework 5.55
Replies: 1
Views: 35

### Re: Homework 5.55

You can use the general equation for Gibbs free energy of formation (products-reactants=rxn total) and then set that equal to deltaG=-RTlnK. For part b its a regular ice table problem.
Mon Mar 02, 2020 6:47 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Week 8 - Wednesday Lecture
Replies: 2
Views: 45

### Re: Week 8 - Wednesday Lecture

I would also suggest reading lesson 7A in the book as a good overview as well. Make sure to understand initial versus average rates
Wed Feb 26, 2020 9:21 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6.63
Replies: 1
Views: 49

### 6.63

When a pH meter was calibrated with a boric acid–borate buffer with a pH of 9.40, the cell potential was +0.060 V. When the buffer was replaced with a solution of unknown hydronium ion concentration, the cell potential was +0.22 V. What is the pH of the solution? How would i begin this problem? I do...
Wed Feb 26, 2020 9:05 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Electrochemical Series
Replies: 2
Views: 43

### Electrochemical Series

The Outline for EChem mentions the electrochemical series, what should we know about this? It seems like its just a ranking of the most likely to get oxidized metal to the most likely to get reduced metal. Am i missing something else?
Wed Feb 26, 2020 7:02 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Free energy dependent on Temp and Pressure
Replies: 1
Views: 51

### Free energy dependent on Temp and Pressure

Thermo outline 4: Understand why reaction free energy depends on pressure and the equilibrium constant
I understand the equations that go along with this statement, but what else should we know about this?
Tue Feb 25, 2020 10:19 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6.57
Replies: 3
Views: 73

### 6.57

6.57 Use the data in Appendix 2B and the fact that, for the half- reaction F2(g) + 2 H+(aq) + 2 e- ---> 2 HF(aq), E(knot)= +3.03 V, to calculate the value of Ka for HF.
How would I do this problem?
Tue Feb 25, 2020 1:37 pm
Forum: Balancing Redox Reactions
Topic: 6K. D
Replies: 3
Views: 104

### Re: 6K. D

Mon Feb 24, 2020 9:08 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.15
Replies: 1
Views: 97

### 6N.15

Calculate the potential of a cell constructed with two nickel electrodes. The electrolyte in one compartment is 1.0 m Ni(NO3)2(aq).In the other compartment, NaOH has been added to a Ni(NO3)2 solution until the pH was 11.0 at 298 K. Ksp=6.5x10^-18 How would I start this problem? I got the concentrati...
Mon Feb 24, 2020 3:59 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.5
Replies: 1
Views: 48

### 6N.5

This question asks for a concentration of one of the species given the cell potential in the problem. However, they give us partial pressures for the other species in the reaction. Do we have to factor this into our Q equation or not at all? How would this work exactly?
Mon Feb 24, 2020 12:40 pm
Forum: Administrative Questions and Class Announcements
Topic: Picking up 14A Finals in Young Hall
Replies: 3
Views: 54

### Picking up 14A Finals in Young Hall

Are we still able to pick up 14A finals? I definitely forgot until now.
Sat Feb 22, 2020 12:41 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7
Replies: 2
Views: 26

### 6L.7

6L.7 Write the half-reactions and devise a galvanic cell (write a cell diagram) to study each of the following reactions: (a) AgBr(s) --> Ag+(aq) + Br2(aq), a solubility equilibrium (b) H+(aq) + OH-(aq)--> H2O(l) How would i write the half reactions for these and the cell diagrams? Its confusing to ...
Sat Feb 22, 2020 12:04 pm
Forum: Phase Changes & Related Calculations
Topic: delta G0 versus delta G
Replies: 15
Views: 359

### Re: delta G0 versus delta G

The difference between the two is that delta G naught is at standard conditions. The reason Professor Lavelle emphasized it is because delta G naught is always the same because it is referring to when the reactants/products are at standard temperature/pressure. As the rxn goes towards equilibrium, ...
Thu Feb 20, 2020 2:51 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 6L.9 Part A
Replies: 1
Views: 52

### 6L.9 Part A

6L.9 (a) Write balanced half-reactions for the redox reaction of an acidified solution of potassium permanganate and iron(II) chloride. (b) Write the balanced equation for the cell reaction and devise a galvanic cell to study the reaction (write its cell diagram). Are we supposed to know that the Fe...
Thu Feb 20, 2020 2:00 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 6L.3 part c
Replies: 1
Views: 32

### 6L.3 part c

How would you write the half-reactions given the cell is :
Pt(s) I O2 (g) I H+(aq) I OH-(aq) I O2 (g) I Pt(s)
Wed Feb 19, 2020 4:32 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox
Replies: 5
Views: 59

### Re: Balancing Redox

Most likely on tests im pretty sure lavelle would give us the charges. If not, just know some common ones like phosphate, sulfate, etc.
Wed Feb 19, 2020 4:30 pm
Forum: Balancing Redox Reactions
Topic: 6K. D
Replies: 3
Views: 104

### Re: 6K. D

The way i start this problem is by balancing the solution in acidic solution and then, at the end, adding OH- to both sides so the H+'s cancel out. The OH- + H+ turns into neutral H2O molecules (which may or may not cancel out. Therefore, Oxidation: 8OH- +P4 --> H2PO2-+4e- Reduction: 12e-+ 12H2O+ P4...
Wed Feb 19, 2020 4:13 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6M. 13
Replies: 1
Views: 38

### Re: 6M. 13

Could you fix the formatting of this question?
Wed Feb 19, 2020 4:11 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Midterm Question 6B
Replies: 3
Views: 74

### Re: Midterm Question 6B

Your logic is correct. Using the equation delta G = delta H - (T)(delta S), it is apparent that the value of delta G will be close to that of delta H when you have a value of delta S close to or equal to 0. Therefore, the answer with the smallest change in entropy, as you mentioned, would be the co...
Wed Feb 19, 2020 4:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Midterm Q3B and Q3D
Replies: 1
Views: 53

### Midterm Q3B and Q3D

Q3B Why is the answer for the question 50ml of 2M HCl and 50ml of 2 M NaOH?
Q3D: How are we supposed to determine the net charge of acetic acid given its at a pH of 6 with pKa = 4.75?
Tue Feb 18, 2020 9:45 pm
Forum: Balancing Redox Reactions
Topic: 6K.3 Part D
Replies: 2
Views: 50

### 6K.3 Part D

Reaction of chlorine in water:
Cl2(g) --> HClO(aq) + Cl2(g)
Can someone help me balance this in an acidic solution?
Tue Feb 18, 2020 9:16 pm
Forum: Balancing Redox Reactions
Topic: Balancing half reactions
Replies: 11
Views: 91

### Re: Balancing half reactions

Make sure that the amount of electrons transferred are all accounted for on the other side of the equation
Tue Feb 18, 2020 9:14 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Replies: 4
Views: 97

### Re: Cubic to quadratic function

If you find yourself with a cubic function you can probably approximate.
Tue Feb 18, 2020 9:13 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concepts
Replies: 3
Views: 38

### Re: Concepts

Cell potential is also equivalent to the max amount of work that the battery can do.
Mon Feb 10, 2020 6:49 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8047
Views: 1412843

### Re: Post All Chemistry Jokes Here

https://www.relatably.com/m/img/light-memes/thumb.jpeg
You won't regret seeing this even though its a Chem14A joke
Mon Feb 10, 2020 11:30 am
Forum: Calculating Work of Expansion
Topic: Reversible and Isobaric
Replies: 4
Views: 68

### Re: Reversible and Isobaric

I would only do the calculation for irreversible reactions if the problem says specifically.
Mon Feb 10, 2020 11:24 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: delta U
Replies: 8
Views: 74

### Re: delta U

805317518 wrote:Conceptually speaking, would an adiabatic system always be an isolated system? Or is there a more specific definition?

It would be an isolated system usually because there is no heat transfer
Sun Feb 09, 2020 2:34 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 4H.1 part B
Replies: 4
Views: 44

### Re: 4H.1 part B

I would look at complexity first. The more orientation it has, the higher the entropy will be. Ne may be heavier but can occupy fewer orientations then NH3.
Sun Feb 09, 2020 2:33 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter and Bomb Calorimeter
Replies: 4
Views: 60

### Re: Calorimeter and Bomb Calorimeter

Calorimeters measure the temperature difference in a reaction. Bomb calorimeter means that the volume is constant. I would review what it means for a system to be isolated, closed, or open.
Sun Feb 09, 2020 2:30 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: delta U
Replies: 8
Views: 74

### Re: delta U

In an adiabatic process, deltaH is equal to 0, so deltaU is equal to work.
Wed Feb 05, 2020 6:12 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Max work
Replies: 2
Views: 29

### Re: Max work

It does more work then an irreversible reaction due to that fact.
Wed Feb 05, 2020 6:11 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: State functions; definition and clarifications
Replies: 3
Views: 48

### Re: State functions; definition and clarifications

I think about it like this, if you and your friend go on a hike and there are two paths, one more difficult and one easier. You take the easier way while your friend goes the long way. Remember, work = pdeltav but also work= force x distance. If your friend goes a farther distance then you but you b...
Fri Jan 31, 2020 11:01 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test 1 #5
Replies: 7
Views: 105

### Re: Test 1 #5

You're given pKb so you can find Kb. However, in the reaction given you need Ka because HF is an acid. Solve for Ka by using Ka*Kb=Kw, K =1*10^-14. Ka is now your equilibrium constant.Then use the given initial concentration of hydrogen fluoride, 0.12M, and complete an ice table using the Ka consta...
Thu Jan 30, 2020 1:52 pm
Forum: Calculating Work of Expansion
Topic: Work equation
Replies: 5
Views: 41

### Re: Work equation

Because when work is being done into the surroundings, the system loses energy and thus the work is negative. If work is being done on the system then there is a positive sign.
Thu Jan 30, 2020 1:15 pm
Forum: Calculating Work of Expansion
Topic: Reversible processes and greatest work
Replies: 3
Views: 34

### Re: Reversible processes and greatest work

It's also easier to think about the amount of work as synonymous with energy or the amount of effort it would take to do something like that.
Thu Jan 30, 2020 1:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test 1 #5
Replies: 7
Views: 105

### Test 1 #5

Hi, can someone explain how they got the answer on test 1 for #5? For reference, "The pkb of fluoride is 10.8. A .12 M solution of hydrogen fluoride was made for silicon water processing. What is the pOH of this solution at equilibrium? HF + H2O -> F- + H3O+"
Mon Jan 27, 2020 12:26 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Extensive vs intensive propeties
Replies: 5
Views: 58

### Extensive vs intensive propeties

Can someone explain the difference between intensive vs extensive properties?
Mon Jan 27, 2020 12:24 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpy of Diatomic Gases
Replies: 4
Views: 38

### Re: Standard Enthalpy of Diatomic Gases

They have the ability to form naturally with very little energy required but a lot of energy released when formed (thus why it is so stable).
Tue Jan 21, 2020 6:50 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Chemical Equilibrium Part 4 Question 13
Replies: 3
Views: 35

### Re: Chemical Equilibrium Part 4 Question 13

I believe part a is correct, treat heat as a product and apply le chatlier.
Tue Jan 21, 2020 6:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Temperature
Replies: 2
Views: 28

### Re: Temperature

The way I understand it is from treating heat as a reactant/product and therefore apply le chatliers principle to it.
Tue Jan 21, 2020 6:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: salt and water reactions
Replies: 2
Views: 45

### Re: salt and water reactions

I would just remove an H from the polyprotic acid and give it the conjugate base a negative charge.
Tue Jan 21, 2020 6:45 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Acids and Bases
Replies: 7
Views: 59

### Re: Acids and Bases

Will we be given equations on test 1 or will we have to infer whether the molecule acts as an acid or a base?
Tue Jan 21, 2020 6:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test #1
Replies: 2
Views: 44

### Re: Test #1

Probably, keep it in mind while doing calculations. Look for the Ka/b value that is lower then 10^-3. If you are unsure you can always calculate it and see that the x is insignificant at the end.
Mon Jan 13, 2020 12:31 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Change in Pressure
Replies: 6
Views: 34

### Re: Change in Pressure

I would just know how to look for a change in pressure in terms of moles on each side to make it easier, but also make sure to understand how the changes in pressure affect the molecules themselves,
Mon Jan 13, 2020 12:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kw calcuation
Replies: 5
Views: 48

### Re: Kw calcuation

I would suggest to just look at it in terms of concentration, activity seems like an advanced topic for gen chem.
Mon Jan 13, 2020 12:28 pm
Forum: General Science Questions
Topic: Salt Dissolving in Water
Replies: 3
Views: 61

### Re: Salt Dissolving in Water

I think its a physical change. But I also think you should see someone about this nightmare.
Mon Jan 13, 2020 12:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Water in Equilibrium Constant
Replies: 2
Views: 21

### Water in Equilibrium Constant

Water is usually implied to be H20(liquid), therefore when do we put it into the Kc equation? Some problems include H20 while others leave it out. Any help would be appreciated
Mon Jan 13, 2020 12:24 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: PV=nRT
Replies: 9
Views: 98

### Re: PV=nRT

Concentration of gases would be one of the only reasons we would use the ideal gas law at this point of the class.
Wed Jan 08, 2020 12:22 pm
Forum: Ideal Gases
Topic: Dynamic Equilibrium
Replies: 10
Views: 116

### Re: Dynamic Equilibrium

It could be disturbed by either taking away/adding products/reactants to the reaction momentarily.
Wed Jan 08, 2020 12:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentration
Replies: 3
Views: 47

### Re: Concentration

When you increase the concentration of a reactant, the reaction must shift left in order to balance out the change in the reaction.
Wed Jan 08, 2020 12:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Comparing Q and K
Replies: 3
Views: 36

### Re: Comparing Q and K

Q is also calculated the same exact way as the K value would be calculated. The only difference is that it's not at equilibrium.
Wed Jan 08, 2020 12:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp of an Aqueous Solution
Replies: 2
Views: 33

### Re: Kp of an Aqueous Solution

I don't think that would work, gases are usual in concentrations relating to the gaseous form, so making the assumption that it's in the liquid form would be incorrect. I think gaseous products/reactants are most likely always going to be in the Kp form.
Wed Jan 08, 2020 12:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Gibs free energy
Replies: 3
Views: 39

### Re: Gibs free energy

Gibbs free energy is energy that is able to do work
Sun Dec 08, 2019 9:29 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: melting point
Replies: 4
Views: 160

### Re: melting point

Determine it by the intermolecular forces of the molecules as compared with another.
Sat Dec 07, 2019 8:06 pm
Forum: Conjugate Acids & Bases
Topic: single arrow vs double arrow
Replies: 2
Views: 139

### Re: single arrow vs double arrow

Yea that works
Sat Dec 07, 2019 8:05 pm
Forum: Amphoteric Compounds
Topic: acid, base, or amphoteric
Replies: 4
Views: 149

### Re: acid, base, or amphoteric

Identify the acid or oxyacid and then determine if it has an electron pair to donate to a proton and therefore maybe also amphoteric.
Fri Dec 06, 2019 11:10 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pKa and Ka
Replies: 9
Views: 179

### Re: pKa and Ka

SGonzales_3L wrote:One thing to know that Dr. Lavelle mentioned in class is that if a pKa value is given it is highly likely that that acid is a weak acid. Strong acids strongly favor the products and, thus, have an astronomically large pKa.

Does that mean strong acids have a high conc of H+?
Fri Dec 06, 2019 11:09 am
Forum: Sigma & Pi Bonds
Topic: test 2 #7a
Replies: 4
Views: 144

### Re: test 2 #7a

i believe it was 11 hydrogen bonding sites if I remember correctly. Count up the number of lone pairs and the number of hydrogens that are bonded to NOF to and add them together to get the number of hbonding sites
Fri Dec 06, 2019 11:07 am
Forum: Bronsted Acids & Bases
Topic: Formic acid strength
Replies: 2
Views: 45

### Re: Formic acid strength

An acid will be stronger if it can easily lose hydrogen to a base. The CH3 in acetic acid donates electrons which makes the O-H bond stronger due to electronegativity therefore the H is harder to remove, which isn't what we want. This makes formic acid the stronger acid. Basically CH3 is electron d...
Fri Dec 06, 2019 11:05 am
Forum: Resonance Structures
Topic: Resonance
Replies: 3
Views: 118

### Re: Resonance

Resonance generally makes a molecule stable, therefore it would be less likely to react if put into water. So I would say in general, resonance doesn't correlate with how strong an acid is.
Fri Dec 06, 2019 11:03 am
Forum: Bronsted Acids & Bases
Topic: Strong Acids and Bases
Replies: 2
Views: 38

### Re: Strong Acids and Bases

Remember when a polyprotic acid gives up a proton (H+), the resulting conjugate base is also able to dissociate more but at a much lower pKa value and is generally not considered a strong acid anymore.
Tue Dec 03, 2019 10:03 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxalate denticity
Replies: 1
Views: 39

### Re: Oxalate denticity

Im pretty sure it always acts a bidentate.
Tue Dec 03, 2019 10:01 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Replies: 2
Views: 54

I am also confused about this. In my notes I have that "pH>Pka: the solution is more alkaline and the acid will give off H+ to form A- and is negatively charged." I'm not completely sure what the application of this means though.
Tue Dec 03, 2019 9:58 am
Forum: Bronsted Acids & Bases
Topic: Stronger Acids and Bases
Replies: 2
Views: 40

### Re: Stronger Acids and Bases

You can use multiple tests. First, check whether each acid/base is a known strong acid or base. For bases, it would be alkaline oxide/hydroxides and for acids, it would be any halogen bonded with hydrogen or an inorganic anion bonded with hydrogen (HNO3). If this isn't the case, I would try to ident...
Mon Dec 02, 2019 6:53 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Test 2 7a
Replies: 6
Views: 80

### Re: Test 2 7a

Jorge Ramirez_4H wrote:Wait, I thought that it was one bonding site. Why do the lone pairs count I thought it explicitly needed to show H bonding to F,O, or N.

Lone pairs count because the resulting shape (trigonal pyramidal, tetrahedral, etc.) may not cancel out the enlarged lone pair thus leaving a delta negative charge
Tue Nov 26, 2019 12:29 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9C.3
Replies: 4
Views: 82

### Re: 9C.3

Always balance the charges using the outside potassium and not the chromate.