Search found 20 matches

by DAllaf
Mon Dec 11, 2017 12:02 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pKa & pKb [ENDORSED]
Replies: 1
Views: 542

pKa & pKb [ENDORSED]

What is the relationship between pKa & pKb? Also, what's the significance of pKa & pKb?
by DAllaf
Mon Dec 11, 2017 12:00 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: HW Question [ENDORSED]
Replies: 1
Views: 330

HW Question [ENDORSED]

For problem 33 in chapter 12, why is the original solution in part b have volume of 5 mL and not 200mL?
by DAllaf
Sat Dec 02, 2017 10:12 pm
Forum: Sigma & Pi Bonds
Topic: Sigma and pi
Replies: 12
Views: 645

Re: Sigma and pi

Yes, every double bond has 1 sigma and 1 pi bond. The first bond is always sigma and then subsequently they are pi bonds. So single bonds have 1 sigma bond, double bonds have 1 sigma and 1 pi, and tripe bonds have 1 sigma and 2 pi bonds.
by DAllaf
Sat Dec 02, 2017 10:04 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Weaks vs. Strong acids
Replies: 3
Views: 232

Re: Weaks vs. Strong acids

A way to test the difference in weak acids vs strong acids is by comparing how they react in water. Weak acids tend to partially ionize in water, while strong acids tend to completely dissociate. Essentially we are comparing how much H+ is ionized. Another method is just memorizing which acids are w...
by DAllaf
Tue Nov 28, 2017 10:43 pm
Forum: Lewis Structures
Topic: Best way to start Lewis Structures
Replies: 12
Views: 511

Re: Best way to start Lewis Structures

In the first step it's essential to total up how many valence electrons you are working with, because without it you're answer will be off. Next, try looking at the name of the molecule and analyze the elements within it to figure out what the central atom will be. From there try piecing it together...
by DAllaf
Tue Nov 28, 2017 10:38 pm
Forum: SI Units, Unit Conversions
Topic: Significant Figures in relation to molar mass [ENDORSED]
Replies: 4
Views: 4042

Re: Significant Figures in relation to molar mass [ENDORSED]

While solving the problem try to keep the molar mass as precise as possible by rounding as little as possible. And then when you reach the final answer round to till you get the proper sig figs.
by DAllaf
Tue Nov 28, 2017 10:35 pm
Forum: Ideal Gases
Topic: R in PV=nRT [ENDORSED]
Replies: 7
Views: 396

Re: R in PV=nRT [ENDORSED]

R is the ideal gas constant (not to be confused with the Rydberg constant) and its value is dependent on other units of measure (P, V, n, T) within the equation.

Hope this helps!
by DAllaf
Tue Nov 28, 2017 10:31 pm
Forum: Ideal Gases
Topic: Pascal vs Atmosphere
Replies: 3
Views: 341

Pascal vs Atmosphere

When solving for partial pressure is it better to use pascal or atmosphere? Are there situations in which one is better than the other? Does Lavelle prefer one over the other?
by DAllaf
Sun Nov 19, 2017 9:55 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 3.5 b) [ENDORSED]
Replies: 5
Views: 309

Re: 3.5 b) [ENDORSED]

In regards to solving it, it is just important to keep in mind that when electrons are taken away they are taken from the outermost shell. And in regards to writing out your answer, it is important to write them out in increasing energy levels. Hope this helps!
by DAllaf
Sun Nov 19, 2017 9:51 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: electron configuration for Fe2+
Replies: 3
Views: 14431

Re: electron configuration for Fe2+

So I also got this question wrong on the midterm but my TA helped explain it to me. Basically since the electron configuration of Fe is [Ar] 3d^6 4s^2, it is important to start by looking at this first rather than looking straight at Chromium which has an electron configuration of [Ar] 3d^5 4s^1. Si...
by DAllaf
Sat Nov 11, 2017 2:32 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polar vs nonpolar vs ionic
Replies: 11
Views: 1930

Re: Polar vs nonpolar vs ionic

Hi Jason, The difference in electronegativity is our best tool to guess what type of bond the elements will form. An ionic bond is when there is a transfer of one or more electrons from a metal onto a non-metal. The general rule of thumb is that if the difference in electronegativity is greater than...
by DAllaf
Sat Nov 11, 2017 2:28 am
Forum: Electronegativity
Topic: Polar or non polar [ENDORSED]
Replies: 4
Views: 297

Re: Polar or non polar [ENDORSED]

Hi Fenared, The difference in electronegativity is our best tool to guess what type of bond the elements will form. The general rule of thumb is that if the difference in electronegativity is greater than 2, then it is ionic. If it is less than 1.5, then it is covalent. The area between 1.5 and 2 is...
by DAllaf
Mon Oct 30, 2017 3:26 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 3d and 4s
Replies: 5
Views: 328

Re: 3d and 4s

Hi Mike,
Cr (Chromium) and Cu (Copper) are the two 2 exceptions that you need to know for electron configurations. Essentially what will happen is that the 3d subshell will take one of the electrons that is the 4s so that it is more stable.
Hope this helps
by DAllaf
Mon Oct 30, 2017 3:18 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Difference Between Orbitals and Subshells [ENDORSED]
Replies: 7
Views: 667

Re: Difference Between Orbitals and Subshells [ENDORSED]

So a subshell is a group of orbitals with particular properties like shape and angular momentum (E.g. s, p, d, f, g etc.) While an orbital can contain up to two electrons and has a particular shape and orientation.

Hope this helps!
by DAllaf
Sun Oct 22, 2017 2:43 am
Forum: Properties of Light
Topic: Color of visible light
Replies: 11
Views: 574

Re: Color of visible light

Hi Charolette, I would say that it probably not expected of us to memorize the exact wavelength for each color, but it would be good to know that visible light region ranges from 400 nm (violet) to 700 nm (red). It may also be a good idea to have a general idea about the order of the light spectrum ...
by DAllaf
Sun Oct 22, 2017 2:36 am
Forum: Photoelectric Effect
Topic: Post Module #29 (KJ*mol^-1 problem)
Replies: 4
Views: 222

Re: Post Module #29 (KJ*mol^-1 problem)

Hi Jenny,

Yes, you should divide by Avogrado's constant (6.02214 x 10^23 mol^-1) so that you can get rid of the mol-1. Then be sure to notice that it gives you kJ, so you need to multiple 150.6 by 10^3, so that you get J only.

Hope this helps
by DAllaf
Sun Oct 15, 2017 2:37 pm
Forum: Properties of Electrons
Topic: Converting Between keV and Joules
Replies: 3
Views: 643

Re: Converting Between keV and Joules

HI Remi, In lecture Dr. Lavelle mentioned how we do not need to memorize unit conversions like that, because we would be provided a sheet full of equations and conversation during exams. So just try to practice problem solving and making the equations work together and you'll be fine. Hope this helps
by DAllaf
Sun Oct 15, 2017 2:31 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Rounding Rule for 5
Replies: 5
Views: 438

Re: Rounding Rule for 5

Hi Michelle, I was also initially confused about this weird rounding rule, but I found it the reason that rule exists is because some people are taught to round down and some people are taught to round up when the number ends in 5. My advice would be to wait to rounding till the end of your problem ...
by DAllaf
Thu Oct 05, 2017 11:08 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical equations too slow... any advice? [ENDORSED]
Replies: 18
Views: 1540

Re: Balancing Chemical equations too slow... any advice? [ENDORSED]

Hi Priscilla, First off, I would just recommend by saying that there is no definitive way to approach these types of problems the 'right' way. But my rule of thumb is to look for the atom that occurs the least and build from there. It helps because you would likely have to go back and fix the coeffi...
by DAllaf
Thu Oct 05, 2017 10:54 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E.15 [ENDORSED]
Replies: 10
Views: 694

Re: E.15 [ENDORSED]

Hey Michael, You should begin by treating 'M' as an unknown variable. Then find the molar mass of (OH)2. Oxygen's molar mass is 15.99 g.mol^-1 and Hydrogen's molar mass is 1.008 g.mol^1. So multiply each by two since it has a subscript of two and then add them together to get a total molar mass of 3...

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