## Search found 66 matches

Sat Mar 17, 2018 12:42 am
Forum: Zero Order Reactions
Topic: graph of 0 order
Replies: 10
Views: 800

### Re: graph of 0 order

The graph would be a horizontal line that abruptly drops straight down to zero (once all of the reactants are used up)
Sat Mar 17, 2018 12:41 am
Forum: Limiting Reactant Calculations
Topic: Reactant vs. Reagent [ENDORSED]
Replies: 23
Views: 18476

### Re: Reactant vs. Reagent[ENDORSED]

Used interchangeably
Sat Mar 17, 2018 12:39 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Homework Problem 14.27
Replies: 2
Views: 288

### Re: Homework Problem 14.27

E is not a state function, so you can't simply add them together. G is a state function, so that is why we must convert to G.
Tue Mar 13, 2018 4:26 pm
Forum: Balancing Redox Reactions
Topic: Test 2 #1
Replies: 6
Views: 445

### Re: Test 2 #1

O2 has a charge of 0. For CO2, the O has a charge of -2, and since there are 2 "O"s in CO2 the charge for O is -4. In order to cancel this -4 out, the charge on C must be +4. O2 is reduced since its charge goes from 0 to -4, and thus gained electrons.
Tue Mar 13, 2018 4:23 pm
Forum: Second Order Reactions
Topic: Half life
Replies: 6
Views: 496

### Re: Half life

If you plug it in to the equation, you should get the correct answer. 1/(1/16) is 16.
Tue Mar 13, 2018 4:20 pm
Forum: Zero Order Reactions
Topic: Chart problems [ENDORSED]
Replies: 3
Views: 358

### Re: Chart problems[ENDORSED]

Yes!
Thu Mar 08, 2018 4:23 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Units for rate
Replies: 4
Views: 395

### Re: Units for rate

It is okay to leave your answer in mmol as long as the question doesn't ask for the answer in mol
Thu Mar 08, 2018 4:22 pm
Forum: First Order Reactions
Topic: One of the equations for 1st order rxn
Replies: 3
Views: 247

### Re: One of the equations for 1st order rxn

d[A]/[A] stands for the rate of consumption of [A] during a first order reaction.
Thu Mar 08, 2018 4:20 pm
Forum: Second Order Reactions
Topic: 15.27 vs 15.35
Replies: 3
Views: 383

### Re: 15.27 vs 15.35

This is because in second order reactions, half life depends on initial concentration, whereas half life in first order reactions does not depend on concentration.
Thu Mar 08, 2018 4:19 pm
Forum: First Order Reactions
Topic: Equation variations
Replies: 9
Views: 594

### Re: Equation variations

^ They just rearranged the equation. Both versions should yield the same answer
Thu Mar 08, 2018 4:19 pm
Forum: First Order Reactions
Topic: Equation variations
Replies: 9
Views: 594

### Re: Equation variations

Yes, all they did in the book was switch the ln[A]f to the right side, and moved -kt to the left side. ln[A]o-ln[A]f is the same as ln([A]o/[A]f)
Thu Mar 08, 2018 4:15 pm
Forum: Zero Order Reactions
Topic: zero order rate?
Replies: 14
Views: 817

### Re: zero order rate?

True, in zero order reactions the rate does not depend on concentration. d[A]=-kdt
Thu Mar 08, 2018 4:14 pm
Forum: Second Order Reactions
Topic: 15.35
Replies: 3
Views: 343

### Re: 15.35

For second order half life, the half life depends on the initial concentration, t(1/2)=1/(k[A]o) whereas in first order reactions, half life only depends on k
Thu Mar 08, 2018 4:12 pm
Forum: General Rate Laws
Topic: 15.17 type problems
Replies: 4
Views: 309

### Re: 15.17 type problems

For work, I usually show something like 2^a=2 (the concentration doubled, rate doubled), therefore a=1, and the order of [A] is first order. But you need to show work, at least on the quizzes and tests,
Thu Mar 08, 2018 4:10 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.17
Replies: 6
Views: 534

### Re: 15.17

Yes, once C is determined to be zero order, you can ignore the concentrations for C entirely, since it does not have an effect on the reaction rate.
Wed Feb 28, 2018 10:18 pm
Forum: Administrative Questions and Class Announcements
Topic: Kinetics Test Week 9
Replies: 2
Views: 240

### Re: Kinetics Test Week 9

The test will cover 15.1-15.6, which is up to #39 in the homework problems.
Wed Feb 28, 2018 10:17 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 3
Replies: 6
Views: 440

### Re: Test 3

Up to #39, I checked with a TA!
Wed Feb 28, 2018 10:15 pm
Forum: General Rate Laws
Topic: Overall order [ENDORSED]
Replies: 6
Views: 477

### Re: Overall order[ENDORSED]

After figuring out the order of each reactant, you just add the orders together to get the overall order
Wed Feb 28, 2018 10:13 pm
Forum: Zero Order Reactions
Topic: Units [ENDORSED]
Replies: 7
Views: 1139

### Re: Units[ENDORSED]

Yes! M/s
Mon Feb 26, 2018 4:29 pm
Forum: General Rate Laws
Topic: Negative Sign [ENDORSED]
Replies: 7
Views: 417

### Re: Negative Sign[ENDORSED]

In order to make the rate positive, the negative sign reverses the negative rate of the product being used up in a reaction.
Mon Feb 26, 2018 4:26 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Midterm Question 7 Sig Figs
Replies: 2
Views: 2553

### Re: Midterm Question 7 Sig Figs

Usually you wait until the end to round your answers, but you should definitely ask your TA about it.
Mon Feb 26, 2018 4:25 pm
Forum: Zero Order Reactions
Topic: Zero Order Meaning
Replies: 5
Views: 757

### Re: Zero Order Meaning

Rate is equal to k in a zero order reaction, and therefore plotting the points creates a straight line
Mon Feb 26, 2018 4:24 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Q and K
Replies: 7
Views: 403

### Re: Q and K

Q and K are constant throughout chemistry, having mainly to do with equilibrium.
Mon Feb 26, 2018 4:21 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8039
Views: 1409905

### Re: Post All Chemistry Jokes Here

what kind of dogs do chemists have?

Labratory retrievers
Sun Feb 25, 2018 4:19 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Determining N
Replies: 4
Views: 287

### Re: Determining N

No it does not matter, "n" will be the same no matter what.
Sun Feb 25, 2018 4:17 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8039
Views: 1409905

### Re: Post All Chemistry Jokes Here

I don't trust atoms....

I heard they make up everything
Sun Feb 25, 2018 4:16 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: swapping signs of E values
Replies: 8
Views: 919

### Re: swapping signs of E values

I use Eo(cell) = Eo(cathode) - Eo(anode) so that way I do not need to flip any signs.
Wed Feb 14, 2018 8:39 pm
Forum: Van't Hoff Equation
Topic: Practice Test
Replies: 5
Views: 662

### Re: Practice Test

Nope!
Wed Feb 14, 2018 8:39 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: adibatic [ENDORSED]
Replies: 2
Views: 320

### Re: adibatic[ENDORSED]

Adiabatic only implies that q=0, not delta T
Wed Feb 14, 2018 8:37 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: PV = nRT
Replies: 6
Views: 403

### Re: PV = nRT

For ideal gases when you need to solve for a constant.
Sat Feb 10, 2018 8:47 pm
Forum: Administrative Questions and Class Announcements
Topic: Practice Midterm Winter 2018
Replies: 10
Views: 2324

### Re: Practice Midterm Winter 2018

Where do I find the link?
Fri Feb 09, 2018 4:25 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Question 9.55
Replies: 2
Views: 199

### Re: Question 9.55

You do. It isn't shown in the solution manual because the reactants in these problems have an Hf of 0 (for example, O2, H2, C(S) all have an Hf=0). Therefore you only need to look at the Hf of the product side (in this case).
Fri Feb 09, 2018 4:21 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9. 43
Replies: 5
Views: 323

### Re: 9. 43

You won't have to calculate it, it should be given in the problem. They make you look it up in the book for the homework problems, but on the test it will be given.
Tue Jan 30, 2018 9:00 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Test question [ENDORSED]
Replies: 16
Views: 876

### Re: Test question[ENDORSED]

I stated that energy cannot be created nor destroyed, only transferred. I'm pretty sure that is all they would be looking for, because the First Law of Conservation is primarily concerned with the conservation of energy.
Tue Jan 30, 2018 8:58 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: unit of entropy
Replies: 11
Views: 569

### Re: unit of entropy

Joules per Kelvin (J/K)
Tue Jan 30, 2018 8:58 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: A spontaneous reaction
Replies: 7
Views: 359

### Re: A spontaneous reaction

Spontaneous reactions occur without any type of outside intervention/force. Spontaneous reactions favor the formation of products at the current conditions under which the reaction is occurring.
Tue Jan 23, 2018 6:42 pm
Forum: Phase Changes & Related Calculations
Topic: HW 8.31
Replies: 3
Views: 250

### Re: HW 8.31

For this question, you would use q=mC(delta)T. For part a, where the pressure is held constant (Cp), C would be equal to (5/2)R, where R=8.314. In part b, where the volume is held constant (Cv), C would be equal to (3/2)R, where R is also 8.314. So basically, you would just replace the "C"...
Tue Jan 23, 2018 6:38 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 5
Views: 372

### Re: Hess's Law

The molecules must be on opposite sides and I=equal in quantity to be able to fully cancel them out. For example, if there are 2 modes of CO2 on the reactant side of one equation ands you are adding this equation to one in which there are 2 moles of CO2 on the product side, the CO2's will cancel out.
Tue Jan 23, 2018 6:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess' Law fractions
Replies: 3
Views: 631

### Re: Hess' Law fractions

Since enthalpy is a state function, it does not follow a specific pathway, and thus it it okay to use any coefficients as long as you consistently change the enthalpy along with it.
Wed Jan 17, 2018 5:45 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hw 8.67 part b
Replies: 2
Views: 163

### Re: Hw 8.67 part b

717 kJ/mol would have to be given. It can be found in the appendix at the end of the book.
Wed Jan 17, 2018 5:40 pm
Forum: Phase Changes & Related Calculations
Topic: 8.5
Replies: 5
Views: 240

### Re: 8.5

Yes, because the cylinder is being supplied with energy, this energy (524) will be positive. In addition, because work is being done on the system by the surroundings, 340 will be positive as well.
Wed Jan 17, 2018 5:37 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Q 8.13
Replies: 9
Views: 531

### Re: Q 8.13

If the system is doing work on its surroundings, as in this problem, the work is negative.
Sat Jan 13, 2018 12:21 pm
Forum: Phase Changes & Related Calculations
Topic: Heat and work not state functions
Replies: 7
Views: 525

### Re: Heat and work not state functions

I found this online and found it to be very helpful. "Heat and work, unlike temperature, pressure, and volume, are not intrinsic properties of a system. They have meaning only as they describe the transfer of energy into or out of a system. "Heat & work are the forms of energy in trans...
Sat Jan 13, 2018 12:17 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Specific heat capacity vs molar heat capacity
Replies: 5
Views: 225

### Re: Specific heat capacity vs molar heat capacity

yes!
Sat Jan 13, 2018 12:15 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Not a State Property
Replies: 6
Views: 282

### Re: Heat Not a State Property

Hi, I found this online and found it very helpful. "Heat and work, unlike temperature, pressure, and volume, are not intrinsic properties of a system. They have meaning only as they describe the transfer of energy into or out of a system." "They appear only when there occurs any chang...
Fri Dec 08, 2017 8:12 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: 12.29
Replies: 1
Views: 245

### Re: 12.29

It depends on what is produced. If H3O+ is produced in the reaction, then you can solve for pH. If OH- is produced, then you can solve for pOH.
Fri Dec 08, 2017 8:10 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 12.55/57
Replies: 2
Views: 253

### Re: 12.55/57

You use an ICE table when a weak acid or base is being reacted with water. A strong acid or base completely dissociates in water, so you can go straight to the equilibrium constant expression.
Tue Nov 28, 2017 5:11 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination compounds and complexes
Replies: 2
Views: 172

### Re: Coordination compounds and complexes

A coordination compound is the result of a Lewis acid-base reaction in which ligands (anions) bond to the central metal atom, or ion. Ligands are Lewis bases, meaning they have an extra pair to pairs of electrons to donate to the Lewis acid (the central metal atom).
Tue Nov 28, 2017 5:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: SF6
Replies: 1
Views: 148

### Re: SF6

All of the bonds are 90 degrees. It says 180 for the two atoms directly across from one another.
Tue Nov 21, 2017 5:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.79
Replies: 2
Views: 192

### Re: 11.79

For this problem, we would need to use a graphing calculator in order to solve for "x". We shouldn't get a problem like this on a test unless we are allowed to use a graphing calculator.
Tue Nov 21, 2017 5:20 pm
Forum: Ideal Gases
Topic: Q and K [ENDORSED]
Replies: 35
Views: 1672

### Re: Q and K[ENDORSED]

The two formulas are the same. You compare Q to K in order to determine which way the reaction will shift (sit). If Q<K, it will shift/sit right (toward products), if Q>K, it will shift/sit left (towards reactants).
Sat Nov 18, 2017 6:52 pm
Forum: Bond Lengths & Energies
Topic: Bond length
Replies: 2
Views: 217

### Re: Bond length

I believe the length would be closer to a double bond, but in between the lengths of a single and double bond.
Sat Nov 18, 2017 6:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent or linear?
Replies: 11
Views: 949

### Re: Bent or linear?

The shape depends on the number of lone pairs as well as their placement on the molecule.
Sun Nov 12, 2017 4:10 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polar vs nonpolar vs ionic
Replies: 11
Views: 7909

### Re: Polar vs nonpolar vs ionic

Another thing to note for polarity is in regard to the dipole moments. If the dipole moments are equal and cancel each other out, the molecule is non polar; however, if the dipole moments do not cancel each other out, the molecule is polar.
Sun Nov 12, 2017 4:05 pm
Forum: Dipole Moments
Topic: Dipole moments
Replies: 6
Views: 541

### Re: Dipole moments

In addition to what has already been said, if the dipole moments around a molecule are equal (cancel each other out), the molecule is non polar. If the dipole moments are not equal (do not cancel each other out), the molecule is polar.
Fri Nov 03, 2017 6:06 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 3D shape Lewis Diagrams
Replies: 4
Views: 437

### Re: 3D shape Lewis Diagrams

@Swetha No, I don't believe so.
Fri Nov 03, 2017 6:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Midterm
Replies: 8
Views: 548

### Re: Midterm

On the exam and homework schedule, it says that the midterm covers all material up to November 3, so I think it might be. I can ask Lavelle.
Wed Oct 25, 2017 3:15 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.75
Replies: 2
Views: 190

### Re: 2.75

Since the s-block has lower ionization energies than the p-block, it takes less energy to remove an electron from the s-block than the p-block. Because it can lose electrons easier, the s-block is thus more reactive than the p-block.
Wed Oct 25, 2017 3:12 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: #55 d
Replies: 3
Views: 237

### Re: #55 d

A half filled D-orbital (d^5) or a filled D-orbital (d^10) is more stable than d^4 or d^9, for example, so the electron from the S-orbital will "jump" to the d-orbital in order to make it more stable. In this case, the electron will jump to the d-orbital in order to completely fill it (d^1...
Thu Oct 19, 2017 2:23 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Upcoming Test
Replies: 5
Views: 368

### Re: Upcoming Test

Hey, I've already taken the test and you do not need to know about Heisenberg's uncertainty principle for this test. You are only being tested on Chapter 1 sections 1-5. As for the homework, my TA had us turn in 4 problems that we used to study for the test (so I turned in 4 problems from sections 1...
Tue Oct 17, 2017 1:21 pm
Forum: Properties of Light
Topic: Problem 1.23
Replies: 3
Views: 287

### Re: Problem 1.23

The conversion between KeV and Joules will be given either in the problem or on the conversion/formula sheet. We are not expected to memorize the conversion.

1 eV = 1.6022 x 10^-19 J
Wed Oct 11, 2017 10:20 am
Forum: Photoelectric Effect
Topic: Chapter 1, Question 1.23
Replies: 3
Views: 272

### Re: Chapter 1, Question 1.23

First, you must convert 140.511 eV to Joules. (1eV = 1.6022 x 10^-19 J).

From there, you use the equation E=hc/lambda and solve for lambda (wavelength).

You should get 8.8237 pm for your answer.
Wed Oct 11, 2017 10:16 am
Forum: Properties of Light
Topic: Chapter 1: Exercise 15
Replies: 4
Views: 496

### Re: Chapter 1: Exercise 15

In order to solve the problem, you do use the wavelength. In order to solve for n2, you must first find the frequency (v) so that you can plug the frequency into Rydberg's equation. To find the frequency, you use the equation v=c/lambda. Then you use plug this frequency into Rydberg's equation, v=R(...
Thu Oct 05, 2017 12:04 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E.29 part b HELP
Replies: 3
Views: 284

### Re: E.29 part b HELP

Since you are solving for moles of Cl- ions, you have to convert the 0.0417 mol CuCl2 x 4H2O to moles of Cl-. Since one mole of CuCl2 x 4H2O contains 2 Cl- ions, you take the 0.0417 mol CuCl2 x 4H2O and multiply it by (2 mol Cl- / 1 mol CuCl2 x 4H2O). This is what my work looks like: 0.0417 mol CuCl...
Wed Oct 04, 2017 11:54 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical Coefficients [ENDORSED]
Replies: 12
Views: 1485

### Re: Empirical Coefficients[ENDORSED]

Typically, you will get numbers that are very close to a whole number such as 1.97 or 3.08 which you would round to 2 and 3. In many of the problems I have done so far that I've had to multiply in order to get a whole number, I've gotten numbers like 2.67, 1.33 and 3.75 which can easily be multiplie...
Wed Oct 04, 2017 11:47 pm
Forum: Significant Figures
Topic: Number of sig figs in answer
Replies: 8
Views: 759

### Re: Number of sig figs in answer

As long as the significant figures in your answer match the significant figures given in the problem (or whichever number you are using for calculations), you will be fine. You will get a much more accurate answer if you don't round numbers during your calculations. Just make sure that the significa...

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