## Search found 20 matches

Sat Dec 09, 2017 4:11 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration of Br-
Replies: 6
Views: 7540

### Electron Configuration of Br-

The electron configuration of Br- is [Ar] 3d10 4s2 4p6. However, would it also be correct to write it as just [Kr]?
Sun Dec 03, 2017 4:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.89
Replies: 4
Views: 337

### Re: 11.89

I'm still not sure why the 5, 10, and 18 are over 100 in the equilibrium concentration calculation. A kPa equals 1000 Pa, so it would make sense if it were over 1000, not 100??
Thu Nov 30, 2017 12:32 pm
Forum: Sigma & Pi Bonds
Topic: Localization
Replies: 3
Views: 384

### Re: Localization

I know that pi bonds in a Carbon ring like benzene are delocalized because the electrons that make up those pi bonds and equally distributed between all 6 of the Carbon atoms in that benzene ring.
Tue Nov 28, 2017 11:15 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Bar vs. atm [ENDORSED]
Replies: 2
Views: 298

### Bar vs. atm[ENDORSED]

When calculating equilibrium constants for equations using partial pressure, does the partial pressure need to be in bar? In other words, if the problem gives the partial pressure in atm, do we first need to convert it to bar?
Tue Nov 21, 2017 4:42 pm
Forum: Ideal Gases
Topic: Q and K [ENDORSED]
Replies: 35
Views: 1665

### Re: Q and K[ENDORSED]

No difference in the formulas, just the fact that K is the constant at chemical equilibrium and Q refers to the initial concentrations of the reactants and products.
Tue Nov 21, 2017 4:39 pm
Forum: Naming
Topic: 17.31d
Replies: 4
Views: 400

### Re: 17.31d

Julia Meno 1D wrote:Why is water written as OH2 instead of H2O?

I talked to my TA today and he said water is usually written with the oxygen first because the oxygen is what is donating its electrons in bonding, not the hydrogen. Technically, either way of writing the formula for water is correct.
Tue Nov 21, 2017 3:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.13
Replies: 2
Views: 238

### Re: 11.13

K is the equilibrium constant; Q is the concentration at the "initial stage" of the reaction, before equilibrium.
Mon Nov 13, 2017 2:00 pm
Forum: Dipole Moments
Topic: Dipole for cis-dichloroethene
Replies: 2
Views: 264

### Re: Dipole for cis-dichloroethene

The dipole "arrow" you are referring to is called a vector because it has direction. As far as including the C-H bond in the analysis, the C-Cl bond has a much greater difference in electronegativity. The C-Cl bond is going to contribute much more to the polarity of the molecule. Once you ...
Mon Nov 13, 2017 1:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Question 4.13 a
Replies: 2
Views: 199

### Question 4.13 a

Determine the VSEPR formula and molecular shape of I₃- I understand why the VSEPR formula would be: AX₂E₃ But why would the molecular shape be linear if there is an odd number of lone pairs? I would imagine that the two lone pairs above the central I atom would be more "powerful" than the ...
Sun Nov 05, 2017 5:37 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge For Element In The Middle [ENDORSED]
Replies: 3
Views: 435

### Re: Formal Charge For Element In The Middle[ENDORSED]

To clarify, the best structure is when the entire molecule's overall charge is 0. It does not necessarily matter if it is the central atom or not.
Sun Nov 05, 2017 5:23 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8037
Views: 1408904

### Re: Post All Chemistry Jokes Here

Are you made of Copper and Tellurium?

Because you're CuTe
Thu Oct 26, 2017 5:24 pm
Forum: Trends in The Periodic Table
Replies: 4
Views: 368

### Re: Trends of ionic radius

Hannah is correct, the atom doesn't necessarily lose or gain an entire shell when it loses or gains electrons. When e- are lost, the atom is a cation and has more protons than e-. Therefore, the positive charge of the protons can pull more on each e- than it could in the atom's neutral state. The e-...
Tue Oct 24, 2017 12:25 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8037
Views: 1408904

### Re: Post All Chemistry Jokes Here

Why is Polonium the grumpiest element?

Because it's always Po'ed!
Fri Oct 20, 2017 12:26 pm
Forum: Quantum Numbers and The H-Atom
Topic: Electron configurations
Replies: 3
Views: 418

### Re: Electron configurations

To add on, the reason the noble gas from the previous row is used is because that element satisfies the configuration of all the electrons in the lower energy states. In other words, the configuration of the element you are working with will be the same up to that noble gas. After that, you drop dow...
Mon Oct 16, 2017 3:06 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty in Kinetic Energy
Replies: 2
Views: 240

### Re: Uncertainty in Kinetic Energy

Yes. To further explain, the velocity is the only variable in the kinetic energy equation (1/2mv²) that can be uncertain. Mass is an observable number, and will almost always be an exact number. Plugging in the uncertainty value for velocity will give you the uncertainty value for kinetic energy.
Mon Oct 16, 2017 9:37 am
Forum: Photoelectric Effect
Topic: Photoelectric Effect Post-Module Assessment 32B, 33 [ENDORSED]
Replies: 2
Views: 448

### Re: Photoelectric Effect Post-Module Assessment 32B, 33[ENDORSED]

For 33B, you can use the equation Energy(photon)- Energy(remove electron) = E(kinetic). To find the energy of the photon, use the wavelength given and convert it to meters: 194nm = 194 x 10^-9 m. Then, using c=ƛv, solve for the frequency of the photon (v), and then use the E=hv equation to solve for...
Mon Oct 16, 2017 9:20 am
Forum: DeBroglie Equation
Topic: De Broglie Wavelength
Replies: 23
Views: 1878

### Re: De Broglie Wavelength

The wavelength of an object directly relates to how energetic the wave is. Being able to calculate and knowing the wavelength is helping in determining how "powerful" the wave is and if it is safe (radio, microwave, visible light, etc.) or dangerous (gamma rays, x-rays, UV radiation).
Fri Oct 13, 2017 10:07 am
Forum: Einstein Equation
Topic: Chapter 1 #23
Replies: 6
Views: 638

### Re: Chapter 1 #23

1.60218e-19 J is not necessarily a constant, but just a conversion factor. You can use (1 eV/1.60218e-19 J) to convert between eV and J in any problem.
Wed Oct 04, 2017 5:23 pm
Forum: Balancing Chemical Reactions
Topic: Order of molecules balanced
Replies: 6
Views: 757

### Re: Order of molecules balanced

For me, I first like to balance the elements that do not appear in several of the reactants or products. Balancing those elements first allows me to then move on to the more challenging ones that have elements in several molecules within the reaction. Oxygen always seems to be one of the last elemen...
Wed Oct 04, 2017 4:31 pm
Forum: Significant Figures
Topic: All students read this sig fig post [ENDORSED]
Replies: 131
Views: 17115

### Re: All students read this sig fig post[ENDORSED]

Do you know if the problems will specifically tell us how many significant figures to use? No. With the numbers that are given, you should know how many sig figs to use. But when using molecular mass, the best number is 3-4 sig figs. When in doubt, use 3 sig figs. Other than that, always apply the ...