Search found 39 matches

by Andre-1H
Sun Jun 10, 2018 11:00 am
Forum: Hybridization
Topic: sigma vs pi bonds
Replies: 4
Views: 187

Re: sigma vs pi bonds

I hope this comparison table helps! Sigma bonds have a head on overlap compared to pi bonds which overlap sideways. Pi bonds also restrict rotation while sigma bonds allow free rotation around the bond. Could you talk about how to understand sp2 and sp3 hybridization? I'm still confused on this sub...
by Andre-1H
Sun Jun 10, 2018 10:57 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Molar Mass
Replies: 5
Views: 196

Re: Molar Mass

It's always the molar mass multiplied by the subscript attached to that element and/or compound. for example (PO2)2 would require you to find the molar mass of PO2 and then multiply it by two because in whatever molecule there are two PO2 molecules bound.
by Andre-1H
Sun Jun 10, 2018 10:55 am
Forum: Naming
Topic: Naming on Final
Replies: 8
Views: 270

Re: Naming on Final

I think something we are expected to do is understand what the molecular formula is based on a more simple type of name. for example compounds in the form YtetraX, where that molecule would be the element Y surrounded by four X elements.
by Andre-1H
Tue Jun 05, 2018 8:18 pm
Forum: Bronsted Acids & Bases
Topic: How to identify a Bronsted acid or base
Replies: 11
Views: 368

Re: How to identify a Bronsted acid or base

Jade Corpus-Sapida 1G wrote:I would imagine from our lecture notes, that Bronsted refers to protons either being donated (acid) or accepted (base). While lewis refers to electrons.


I think bronsted comes from the name of the guy who came up with the idea. kind of like schrodinger's equation. I could be mistaken though
by Andre-1H
Tue Jun 05, 2018 8:15 pm
Forum: Lewis Structures
Topic: Test 3 Question 2
Replies: 5
Views: 160

Re: Test 3 Question 2

The answer is titanium connected to 4 chlorines by a single bond. The question tells you that the molecule must be neutral (sum of formal charges is 0), which means that it is highly likely that all chlorine atoms have 3 lone pairs and one bond. 4 chlorines with 7 valence electrons and 1 titanium wi...
by Andre-1H
Sat Jun 02, 2018 8:54 pm
Forum: Electronegativity
Topic: Test 3. Question 7.
Replies: 6
Views: 198

Re: Test 3. Question 7.

I think about ionic and covalent character as how much they share electrons or how much they keep them to themselves. Bonds where elements share electrons more (less difference in electronegativity) have more covalent character, whereas a higher difference in electronegativity yields a bond with mor...
by Andre-1H
Sat Jun 02, 2018 8:44 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: homework problem 4.17 [ENDORSED]
Replies: 4
Views: 153

Re: homework problem 4.17 [ENDORSED]

If you're ever confused about shape I think the best way is to start by drawing the lewis structure. For N3- the lewis structure has only 2 regions of electron density and no lone pairs, so it is linear. (Using this website : https://chemstuff.co.uk/academic-work/a-level/unit-1/shapes-of-molecules/ ...
by Andre-1H
Sat Jun 02, 2018 8:40 pm
Forum: Hybridization
Topic: σ vs π bond tips thread
Replies: 5
Views: 105

Re: σ vs π bond tips thread

What do we need to know about the properties of sigma and pi bonds? I remember in class it had something to do with rotation, and that would break the pi bond, why would the rotation then not affect the sigma bond?
by Andre-1H
Sun May 27, 2018 11:47 am
Forum: Ionic & Covalent Bonds
Topic: ionic and covalent character
Replies: 7
Views: 154

Re: ionic and covalent character

I'm pretty sure determining this revolves around electronegativity. For ionic bonds the covalent character can be determined by polarizing power and polarizability but even then those originate from the atom's electronegativity in the first place so I'm not too sure if there is anything but knowing ...
by Andre-1H
Sun May 27, 2018 11:44 am
Forum: Electronegativity
Topic: Calculating electronegativity
Replies: 10
Views: 314

Re: Calculating electronegativity

I don't think there will be a question where there is a need to know the exact value to get the answer, just the trend is important. And we don't need to know how to calculate it.
by Andre-1H
Sun May 27, 2018 11:32 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing power
Replies: 10
Views: 393

Re: Polarizing power

Im having trouble understanding this topic so I was wondering if anyone can explain the difference between polarizing power and polarizability and provide a quick example. Polarizing power and polarizability refer to cations and anions respectively and helps determine the covalent character of ioni...
by Andre-1H
Tue May 22, 2018 9:04 pm
Forum: Lewis Structures
Topic: 3.51
Replies: 2
Views: 55

Re: 3.51

I think this is just an exercise to help understand why the one with oxygen in the middle is the correct one. The question asks to select the more likely structure based on formal charges etc. So it's likely that the lewis structure drawn with oxygen in the middle will minimize formal charges more e...
by Andre-1H
Tue May 22, 2018 4:54 pm
Forum: Lewis Structures
Topic: confusion about # of bonds in a Lewis structure
Replies: 2
Views: 83

Re: confusion about # of bonds in a Lewis structure

I'm pretty sure the answer relates to formal charge. The correct lewis structure is the one that minimizes formal charge while at the same time maintaining the octet rule for elements that cannot break it. Using your example of oxygen, if we calculate the formal charge for an oxygen with 3 lone pair...
by Andre-1H
Tue May 22, 2018 4:44 pm
Forum: Lewis Structures
Topic: 3.53 Lower energy by lewis structures
Replies: 1
Views: 42

3.53 Lower energy by lewis structures

In 3.53 the question asks us to find the formal charges of the two different lewis structures and then asks which structure has lower energy. The answer is that the lewis structure with a minimized formal charge distribution has a lower energy. Can someone explain conceptually why this is true?
by Andre-1H
Sun May 20, 2018 3:47 pm
Forum: Lewis Structures
Topic: 3.49 part c
Replies: 2
Views: 47

Re: 3.49 part c

When you do the lewis structure for CO with 2 double bonds you end up not having enough electrons to satisfy carbon's octet. Carbon has 4 valence electrons and oxygen has 6. So we have 10 valence electrons to work with. a double bonded CO has 6 electrons left but oxygen and carbon both need 4 more e...
by Andre-1H
Sun May 20, 2018 3:42 pm
Forum: Bond Lengths & Energies
Topic: Test 3
Replies: 8
Views: 167

Re: Test 3

No, I think we will just need to know general trends about how atoms interact during bonding (ionic and covalent) and how this interaction correlates to the strength of the bond.
by Andre-1H
Sun May 20, 2018 3:39 pm
Forum: Octet Exceptions
Topic: Question 3.63 part b
Replies: 2
Views: 105

Re: Question 3.63 part b

I think that just because an element has a complete octet does not make bonding impossible. You're right in the sense that it makes it a lot harder and an element like Xenon won't want to bond with anything. I looked it up and it said that when Xenon and Fluorine are heated at 400 degrees celsius, t...
by Andre-1H
Mon May 14, 2018 8:27 pm
Forum: Ionic & Covalent Bonds
Topic: 3.23 (meaning of oxidation)
Replies: 7
Views: 202

Re: 3.23 (meaning of oxidation)

The question says that chlorine can exist in both positive and negative oxidation states. You're probably right in that most chlorine is in an oxidation state of -1.
by Andre-1H
Mon May 14, 2018 8:07 pm
Forum: Resonance Structures
Topic: Number of Resonance Strucutres
Replies: 3
Views: 119

Re: Number of Resonance Strucutres

Even though drawing them can be painstaking, I'm pretty sure it's a solid way to figure it out. Maybe it wouldn't necessarily be the best way to do it on a test but I think getting comfortable with drawing structures is good practice to save time on tests.
by Andre-1H
Mon May 14, 2018 8:04 pm
Forum: Significant Figures
Topic: how many place numbers to round to
Replies: 3
Views: 162

Re: how many place numbers to round to

I'm guessing you're talking about on a test/midterm where time is an issue. An easy way to do it is to look at the question and first, determine how many sig figs your answer will have. Let's say for instance your answer has 2 sig figs. When doing a calculation, there really is no need to multiply 1...
by Andre-1H
Mon May 14, 2018 8:00 pm
Forum: Ionic & Covalent Bonds
Topic: 3.23 (meaning of oxidation)
Replies: 7
Views: 202

Re: 3.23 (meaning of oxidation)

I believe oxidation state refers to the number of electrons gained or lost. So that seems to line up with the answer you gave, meaning that chlorine at most would lose 7 electrons because it has 7 valence electrons. At most chlorine is going to gain 1 electron. Both of these numbers take the element...
by Andre-1H
Tue May 08, 2018 8:41 pm
Forum: Properties of Light
Topic: Test 2 Q1B
Replies: 2
Views: 106

Re: Test 2 Q1B

You're correct, higher frequency corresponds to greater energy. In this case 10^-8 is smaller than10^-7 so that would correspond to a larger frequency for the photon with wavelength 1*10^-8 m, therefore greater energy.
by Andre-1H
Sun May 06, 2018 5:27 pm
Forum: Trends in The Periodic Table
Topic: Decrease across a period
Replies: 3
Views: 112

Re: Decrease across a period

I think also that because as you go across a period there are more valence electrons, this also attracts it towards the increasing amount of protons. More negative particles on the outermost part of the atom become attracted with a stronger force to the increased amount of positive protons in the nu...
by Andre-1H
Sun May 06, 2018 5:22 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s and 3d
Replies: 4
Views: 107

Re: 4s and 3d

So, even though we are not responsible for the elements that occupy these orbitals, could we then apply this to the next row and say that 4d is lower in energy than 5s? Or would that be the only exception for this line of thinking?
by Andre-1H
Sun May 06, 2018 5:19 pm
Forum: Quantum Numbers and The H-Atom
Topic: valence electrons question
Replies: 2
Views: 100

Re: valence electrons question

A way that makes it a lot easier for me is thinking about certain orbitals as a multiple of n and p. For example you said n=2 and l =1. From class we know that when l=1 we are talking about p orbitals. n*p in this case would give us the 2p orbital. from the periodic table there are six elements that...
by Andre-1H
Sun May 06, 2018 4:26 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Ions in terms of molar mass
Replies: 2
Views: 107

Ions in terms of molar mass

Hello, I have a question about the concept of an ion which is a topic that has come up on our tests but I guess I don't have the best understanding of it. When calculating the molar mass of an ion would you for example (Na+) get the molar mass of sodium (periodic table) and then subtract the mass of...
by Andre-1H
Sun Apr 29, 2018 6:14 pm
Forum: Quantum Numbers and The H-Atom
Topic: HW Problem 2.2 [ENDORSED]
Replies: 3
Views: 85

Re: HW Problem 2.2 [ENDORSED]

I think another way to think about this is from the equation E(n)= -hR/n^2 As n increases the electron has more energy which means that if an electron were to drop down to a lower level it would emit energy. This would mean an input of energy is required to elevate an electrons level.
by Andre-1H
Sun Apr 29, 2018 6:10 pm
Forum: DeBroglie Equation
Topic: Calculating velocity
Replies: 5
Views: 181

Re: Calculating velocity

I'm pretty sure that the only way to calculate it would be if the mass of the object with that wavelength is given because otherwise with the DeBroglie equation there would be two unknown variables.
by Andre-1H
Sun Apr 29, 2018 6:07 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Example 1.7a in the Textbook [ENDORSED]
Replies: 4
Views: 120

Re: Example 1.7a in the Textbook [ENDORSED]

Yep just to add on it makes sense that the second equation is like that because for an object like a marble its speed can change, meaning that its momentum can change, leading to the delta symbol. However, its mass is constant, and cannot change.
by Andre-1H
Sun Apr 22, 2018 12:08 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Calculating energy [ENDORSED]
Replies: 3
Views: 96

Re: Calculating energy [ENDORSED]

Like everyone has said, just because there is not a given equation for energy in terms of what is given doesn't mean that you can't rearrange two equations to obtain what you want. Combine the equations E=h(frequency) and c=v (frequency)
by Andre-1H
Sun Apr 22, 2018 12:01 pm
Forum: DeBroglie Equation
Topic: DeBrogile Module
Replies: 6
Views: 154

Re: DeBrogile Module

Are you getting the wrong answer or is it because a car's mass influences its wavelength to be negligible that there is confusion. The unit for velocity in the equation is m/s so you did the right thing by converting it.
by Andre-1H
Sun Apr 22, 2018 11:56 am
Forum: Properties of Light
Topic: Memorizing Wavelengths [ENDORSED]
Replies: 4
Views: 146

Re: Memorizing Wavelengths [ENDORSED]

It definitely wouldn't be a waste of time, it could even save some time on tests/midterms. Also by memorizing wavelengths you can easily find the frequency with the speed of light equation so memorizing one is like memorizing both.
by Andre-1H
Sat Apr 14, 2018 7:30 pm
Forum: Limiting Reactant Calculations
Topic: Q.22 on Audio-Visual Focus-Topic [ENDORSED]
Replies: 2
Views: 79

Re: Q.22 on Audio-Visual Focus-Topic [ENDORSED]

C6H9Cl3 + 3AgNO3 ---> AgCl + C6H9(NO3)3 You just use the reaction and the stoichiometric coefficients to determine how many moles can be produced. So you said you found C6H9Cl3 was the limiting reactant and by doing that you did the hardest part of the problem, now you use how many moles of that to ...
by Andre-1H
Sat Apr 14, 2018 7:23 pm
Forum: Significant Figures
Topic: Sig fifs in 750 [ENDORSED]
Replies: 6
Views: 292

Re: Sig fifs in 750 [ENDORSED]

I'm pretty sure the zero after the decimal point is not significant. So, for example the number 0.0000023 has two sig figs. (Sourcehttp://www.rpi.edu/dept/phys/Dept ... ode12.html)
by Andre-1H
Sat Apr 14, 2018 7:20 pm
Forum: Significant Figures
Topic: Expected mastery of Significant Figures
Replies: 6
Views: 233

Re: Expected mastery of Significant Figures

There's also a part on his website along the lines of "everything you need to know about sig figs" I'd recommend that (it helped me).
by Andre-1H
Wed Apr 11, 2018 6:02 pm
Forum: Molarity, Solutions, Dilutions
Topic: Molarity formula
Replies: 6
Views: 168

Re: Molarity formula

That equation basically comes from the fact that in a dilution the amount of moles does not change. It's just a rewritten form of C(molarity)= moles/vol. There could be other questions asking to reorganize the formula to find a different unknown. But for most dilution problems the formula you gave i...
by Andre-1H
Wed Apr 11, 2018 5:58 pm
Forum: SI Units, Unit Conversions
Topic: Sig Figs
Replies: 9
Views: 299

Re: Sig Figs

I'm pretty sure the periodic table is used 99% of the time, you would only really use 1 for hydrogen if you did not have/were not allowed to use a calculator.
by Andre-1H
Tue Apr 10, 2018 4:55 pm
Forum: Empirical & Molecular Formulas
Topic: f11
Replies: 3
Views: 130

Re: f11

Hey just to add on when it gives you a mass percentage the easiest way to interpret that is to assume that there is a 100g sample of whatever you are trying to analyze. So for this example you basically just find the molar ratios using a 100g sample. Let me know if you need anything else!

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