## Search found 63 matches

Sun Mar 17, 2019 2:22 am
Forum: General Science Questions
Topic: Midterm Q3D
Replies: 1
Views: 328

### Midterm Q3D

Can someone help me figure out how to think through this questions. Thnx
Sun Mar 17, 2019 1:38 am
Forum: Balancing Redox Reactions
Topic: Reducing power
Replies: 1
Views: 276

### Reducing power

How do I compare reducing power? Which values have greater or lesser reducing power?
Sun Mar 17, 2019 1:36 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Midterm Q3-C
Replies: 4
Views: 366

### Re: Midterm Q3-C

If you write the equation out you get

HA +H2O -> A- +H3O+

you know that A- and H3O+ concentrations are equal to x and [HA] was 0.1-x so it can't be

[HA]=[H3O+] or [HA]=[A-]

so the answer is [HA] can't equal [H3O+]
Sun Mar 17, 2019 1:33 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Midterm Q3-C
Replies: 4
Views: 366

### Re: Midterm Q3-C

[HA] = 0
can't be true because they gave you [HA] in the problem already
[HA] = Ka
can't be true because of the relationship between pKa and Ka (pKa = -logKa)
Sun Mar 17, 2019 1:24 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Final
Replies: 2
Views: 367

### Final

For the final if we are asked to find internal energy but are not given conditions for change in temperature, do we just ignore the fact that internal energy is only when there is no constant temperature?
Sat Mar 16, 2019 11:34 pm
Forum: General Science Questions
Topic: Easy ways to remember
Replies: 5
Views: 401

### Re: Easy ways to remember

This is from my PLF
Sat Mar 16, 2019 4:37 pm
Forum: General Rate Laws
Topic: H.W. Problem 15.17
Replies: 5
Views: 421

### Re: H.W. Problem 15.17

If you look at experiments 1 and 4, you see that concentrations for C change but the initial rates are both 2. This means that C is independent of the rate.
Sat Mar 16, 2019 4:31 pm
Forum: General Rate Laws
Topic: H.W. Problem 15.17
Replies: 5
Views: 421

### Re: H.W. Problem 15.17

Experiments 1 and 2 would help you get the order for [A] but not for [B] because the concentrations are the same in both equations.
Sat Mar 16, 2019 12:33 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Equation
Replies: 9
Views: 575

### Equation

With ln k2/k1 =Ea/R (1/T - 1/T2) is it assumed that A is 1?
Sat Mar 16, 2019 12:32 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Units
Replies: 1
Views: 81

### Units

What are the units for Activation Energy?
Fri Mar 15, 2019 8:45 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: exercise 14.13 (d)
Replies: 2
Views: 97

### Re: exercise 14.13 (d)

You're supposed to refer to Appendix 2B.
Fri Mar 15, 2019 8:39 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration Q
Replies: 2
Views: 134

### Re: Concentration Q

The reaction quotient Q is set up the same as the equilibrium constant K.
Fri Mar 15, 2019 8:36 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: state functions?
Replies: 6
Views: 367

### Re: state functions?

Work would not be considered a stat function because the we need the information in between. Work is a path function.
Fri Mar 15, 2019 8:35 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Q6 on the midterm
Replies: 3
Views: 291

### Re: Q6 on the midterm

I think it's because there was a change in moles from 30 to 36.
Fri Mar 15, 2019 8:27 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Midterm
Replies: 4
Views: 386

### Re: Midterm

Don't forget to check midterm solutions on the course website!
Fri Mar 15, 2019 8:22 pm
Forum: Student Social/Study Group
Topic: Studying for the Final
Replies: 25
Views: 1332

### Re: Studying for the Final

Make sure you have a good grasp on the conceptual things as well. Lecture notes would be most helpful for this but the book explains a lot as well. The concepts will help putting a lot of things together during the final.
Fri Mar 15, 2019 8:19 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Which cell potential?
Replies: 1
Views: 254

### Re: Which cell potential?

I believe that in the example that you provided you would look at Cu to Cu+ etc. The question should help you determine which one to use. Just like in test 2.
Fri Mar 15, 2019 8:13 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Temperature Change
Replies: 1
Views: 259

### Temperature Change

Why does the shift of a reaction due to a temperature change depend on if the reaction is exothermic or endothermic?
Mon Feb 25, 2019 11:26 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: HW Q
Replies: 1
Views: 82

### HW Q

For 14.13 part c

After balancing :

the cathode is Cl2 + 2e --> 2Cl-

the anode is H2 --> 2H+ +2e

The book adds these and gets Cl2+H2 --> 2Cl-

I don't understand what happens to 2H+ once this is added or if I am missing some conceptual step.
Sun Feb 24, 2019 1:52 am
Forum: Balancing Redox Reactions
Topic: Test 2 Material
Replies: 13
Views: 500

### Test 2 Material

Do we have to know how to balance redox reactions in a basic solution for Test 2?
Sun Feb 24, 2019 1:50 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Plugging in
Replies: 2
Views: 122

### Plugging in

How do we know which value to plug in for n when finding the reaction Gibbs free energy?
Sat Feb 09, 2019 3:45 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Equations
Replies: 1
Views: 72

### Equations

When should I use deltaS=nRln(t2/t1) as opposed to deltaS=nCvln(t2/t1) in a 2 step problem that had a volume change?

I am comparing example 9.5 from the book and 9.13 in the HW (6th edition).
Tue Jan 29, 2019 5:56 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: HW Q
Replies: 2
Views: 122

### HW Q

I'm doing 8.31 of the sixth edition and to calculate the Cp and Cv, the solutions manual uses R=8.314 J·K^-1·mol^-1 but writes the Cv and Cp in J·C^-1·mol^-1. How does that work???
Tue Jan 29, 2019 5:52 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cp and Cv in calculating
Replies: 2
Views: 97

### Re: Cp and Cv in calculating

In 8.31 of the sixth edition they used q=n*Cv*deltaT for calculating at a constant volume.
Tue Jan 29, 2019 5:23 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Signs for Bond Enthalpies
Replies: 4
Views: 156

### Re: Signs for Bond Enthalpies

Bond breaking is an endothermic process while bond forming is an exothermic process!
Tue Jan 29, 2019 5:15 pm
Forum: Phase Changes & Related Calculations
Topic: 6th edition problem
Replies: 2
Views: 147

### Re: 6th edition problem

We haven't covered work in lecture yet. The answer is actually 28J for a. First, they based the calculations off of w=-P*deltaV To find the volume they used deltaV=-pi(r^2)(d)=-pi(1.5^2cm)(20cm)(1L/10^3cm^3)= -0.14L Volume is negative because it was compressed to a smaller volume. They plug in the d...
Tue Jan 29, 2019 5:08 pm
Forum: Calculating Work of Expansion
Topic: Work
Replies: 2
Views: 120

### Work

How do we know which expansion equations to use?
Tue Jan 29, 2019 5:06 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Lecture
Replies: 5
Views: 199

### Lecture

Can someone summarize the explanation of the heating curve. I didn't exactly follow everything that was said.
Sun Jan 20, 2019 6:46 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Replies: 1
Views: 105

How do I test and confirm any approximations from acid and base equilibria pH?
Sun Jan 20, 2019 4:35 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strength and Weakness
Replies: 12
Views: 498

### Strength and Weakness

How do I compare the strength of two acids?
Sun Jan 20, 2019 4:34 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strength and Weakness
Replies: 2
Views: 110

### Strength and Weakness

How do I compare the strength of two acids?
Sun Jan 20, 2019 1:37 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: HW Q
Replies: 2
Views: 72

### HW Q

HW Question: A careless laboratory technician wants to prepare 200.0 mL of a 0.025 m HCl(aq) solution, but uses a 250.0-mL volumetric fl ask by mistake. (a) What would the pH of the desired solution have been? (b) What will be the actual pH of the solution as prepared? For part a I simply calculated...
Sun Jun 10, 2018 8:23 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelating complex
Replies: 7
Views: 289

### Re: Chelating complex

You also have to consider the geometry. You have to visually tell if the molecule will bend to make a chelating structure
Sun Jun 10, 2018 8:20 pm
Forum: Lewis Acids & Bases
Topic: Strong Acids
Replies: 4
Views: 305

### Re: Strong Acids

I have HCl, HBr, and HI in my notes

I also have HF which is considered a weak acid
Sun Jun 10, 2018 7:57 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Homework Problem 17.33.)
Replies: 4
Views: 359

### Re: Homework Problem 17.33.)

a) tridentate, you can see that there are three nitrogens meaning there are three lone pairs. b) bidentate, usually if there is a charge on an oxygen, a metal will be able to bind. There is a minus 2 charge. c) monodentate, honestly I've asked around and no one has been able to give a good explanati...
Sat Jun 09, 2018 1:20 pm
Forum: Electron Configurations for Multi-Electron Atoms
Replies: 1
Views: 166

Does anyone know why the electron configuration of Palladium is [Kr] 4d^10 and not [Kr] 4d^8 5s^2?
Fri Jun 08, 2018 4:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.23, confusing LS
Replies: 1
Views: 127

### Re: 4.23, confusing LS

The book mentions that other structures are possible and more stable. They could've just wanted the easiest to draw on there or soemthing. There is no real reason why they did that.
Fri Jun 08, 2018 3:15 pm
Forum: Photoelectric Effect
Topic: Visible or measurable light
Replies: 4
Views: 201

### Visible or measurable light

What is the cutoff of visible ot measurable light?
Fri Jun 08, 2018 2:46 pm
Forum: Calculating the pH of Salt Solutions
Topic: Dissociating
Replies: 1
Views: 167

### Dissociating

How do we know when a salt dissocociates in a reaction? And what exactly does that mean?
Fri Jun 08, 2018 2:43 pm
Forum: Molarity, Solutions, Dilutions
Topic: Theoretical Yield, Actual Yield
Replies: 1
Views: 140

### Theoretical Yield, Actual Yield

Which yield are we usually given? And which do we use to make further calculations?
Sat Jun 02, 2018 5:14 pm
Forum: Bond Lengths & Energies
Topic: Test 3 Q 8 [ENDORSED]
Replies: 9
Views: 675

### Test 3 Q 8[ENDORSED]

I was asked to identify the shortest boxed bond and indicate whether it is stronger. I didn't know how to answer this because they look the same to me. Pls help
Sat Jun 02, 2018 4:59 pm
Forum: Electronegativity
Topic: Test 3. Question 7.
Replies: 6
Views: 438

### Re: Test 3. Question 7.

The difference in electronegativity determines ionic character. If you remember the trend of electronegativity, it increases going up and increases going across. With that in mind, you notice that Mg is higher in the periodic table than Ca so you can assume that Mg is more electronegative than Ca wh...
Sat Jun 02, 2018 4:52 pm
Forum: Hybridization
Topic: List of the different shapes
Replies: 6
Views: 401

### Re: List of the different shapes

Here is a helpful image I've been using to memorize the names
Sun May 27, 2018 12:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AXE Notation and Shape
Replies: 4
Views: 379

### Re: AXE Notation and Shape

Yes, the AXE notation will tell you the molecular structures.
Sun May 27, 2018 12:06 pm
Forum: Bond Lengths & Energies
Topic: Bond Strength
Replies: 5
Views: 433

### Bond Strength

Is the bond strength affected when the overall charge of the molecule is negative?
Thu May 24, 2018 12:05 am
Forum: Formal Charge and Oxidation Numbers
Replies: 2
Views: 884

How do you calculate formal charge when considering radicals?
Wed May 16, 2018 10:28 pm
Forum: Dipole Moments
Topic: Dipoles
Replies: 2
Views: 178

### Re: Dipoles

Drawing the structure might help

Ex:
Wed May 16, 2018 10:23 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formula Provided
Replies: 6
Views: 453

### Re: Formula Provided

There is also an easier way to tell. If you get the number of valence electrons and subtract the electrons "directly surrounding it", you will find the formal charge.

Ex: CH4
C: 4 valence electrons - 4 electrons around it = 0
H: 1 valence electron - 1 electron around it = 0
Wed May 16, 2018 10:08 pm
Forum: Ionic & Covalent Bonds
Replies: 9
Views: 525

They are electrons that are not used while making bonds I don’t think that is totally true. Lone pairs also are electrons that are not used “while making bonds.” But radicals are more specific, like what Emily said above, that radicals involve a single , unpaired valence electron. What I meant was ...
Sun May 13, 2018 12:13 am
Forum: Ionic & Covalent Bonds
Topic: Lewis Structure vs Resonance Structure
Replies: 6
Views: 262

### Re: Lewis Structure vs Resonance Structure

A resonance structure is a version of a lewis structure.
Sun May 13, 2018 12:11 am
Forum: Properties of Light
Topic: Keywords for Work Function or E_photon?
Replies: 4
Views: 287

### Re: Keywords for Work Function or E_photon?

You should know what the work function means exactly. It is the threshold energy. So when they ask for a minimum amount of energy of the photon to meet the threshold energy, there will be no kinetic energy. The threshold energy will not cause any electrons to bounce off. Any value greater than the t...
Sun May 13, 2018 12:01 am
Forum: Ionic & Covalent Bonds
Replies: 9
Views: 525

They are electrons that are not used while making bonds
Sun May 06, 2018 6:55 pm
Forum: Properties of Light
Topic: Sig Figs [ENDORSED]
Replies: 3
Views: 277

### Re: Sig Figs[ENDORSED]

Yes, you can lose a maximum of one point for each page where you don't use the correct sig figs.
Sun May 06, 2018 6:49 pm
Forum: Trends in The Periodic Table
Topic: electronegativity
Replies: 4
Views: 270

### Re: electronegativity

The trend on the periodic table is a positive slope so as you go across and up the periodic table, the electronegativities are greater.
Sun Apr 29, 2018 9:26 pm
Forum: Properties of Light
Topic: Memorizing formulas test 2
Replies: 16
Views: 879

### Re: Memorizing formulas test 2

Memorizing the units will be helpful. Dimensional analysis helps a lot when figuring out what units each answers should be in.
Wed Apr 25, 2018 10:37 pm
Forum: Properties of Light
Topic: HW Q
Replies: 3
Views: 278

### HW Q

In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that leads to this spectral line? For this question I would think that the final energy level is n=1 since t...
Wed Apr 25, 2018 4:37 pm
Forum: DeBroglie Equation
Topic: Module Question [ENDORSED]
Replies: 3
Views: 314

### Module Question[ENDORSED]

What does it mean when the peak of one wave interacts with the trough of another wave?
Sun Apr 15, 2018 9:43 pm
Forum: SI Units, Unit Conversions
Topic: Quiz 1
Replies: 6
Views: 423

### Re: Quiz 1

It's easier if you find the molecular formula first. Once you find it, you can try to divide it by the least common denominator that will make it the empirical formula. Sometimes the molecular and empirical formulas are the same. Remember that the molecular formula gives the actual number and the em...
Sun Apr 15, 2018 9:41 pm
Forum: Balancing Chemical Reactions
Topic: Trick to balance?
Replies: 5
Views: 441

### Re: Trick to balance?

Look for which elements are least present and begin placing those coefficients. If there is an odd number of elements for one, multiply by the fraction then cancel that out by multiplying the whole thing by the denominator. Remember that the stoichiometric coefficients should be whole numbers
Sun Apr 15, 2018 9:37 pm
Forum: Properties of Light
Topic: Photoelectric Effect
Replies: 1
Views: 94

### Photoelectric Effect

Why was it important for scientists to undergo this experiment? What questions led to their conclusion and what real contribution did they expect to make with their initial hypothesis?
Sun Apr 08, 2018 7:08 pm
Forum: Molarity, Solutions, Dilutions
Topic: Variables
Replies: 5
Views: 296

### Variables

Just to confirm,

n is amount in moles
m is mass of a sample which comes in the form of grams
M is mass per mole (g/mol)
N is number of objects, (not quite clear on this)

Are there any other important variables?
Sun Apr 08, 2018 7:01 pm
Forum: Balancing Chemical Reactions
Topic: H3 Image [ENDORSED]
Replies: 2
Views: 156

### H3 Image[ENDORSED]

The first box below represents the reactants for a chemical reaction and the second box the products that form if all the reactant molecules shown react. Use the following key to write a balanced equation for the reaction. Assume that if two atoms are touching, they are bonded together. Key: ● oxyge...
Fri Apr 06, 2018 11:53 am
Forum: Empirical & Molecular Formulas
Topic: Homework Question
Replies: 4
Views: 336

### Homework Question

Question: Vanillin is found in vanilla extracted from Mexican orchids. A report on the analysis of vanillin listed the mass percentage composition as 63.15% C, 5.30% H, and 31.55% O. In what atom ratios are the atoms present in vanillin? I started by converting each mass to an amount of atoms and ge...