Search found 48 matches

by Te Jung Yang 4K
Sun Feb 10, 2019 9:39 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: DeltaU=q+w
Replies: 5
Views: 17

DeltaU=q+w

I don't understand why the equation is change in U is equal to q + w. Why is it not change in U is equal to the change in q + the change in w?
by Te Jung Yang 4K
Sun Feb 10, 2019 9:32 pm
Forum: Ideal Gases
Topic: How do I know what is an Ideal Gas
Replies: 3
Views: 16

Re: How do I know what is an Ideal Gas

An ideal gas is a man-made notion about a "perfect" gas to simplify calculations. It refers to a gas in which the molecules don't have any volume and don't interact with one another, which of course does not exist in real life. All our equations are assuming that the gas is ideal, and in q...
by Te Jung Yang 4K
Sun Feb 10, 2019 9:26 pm
Forum: Calculating Work of Expansion
Topic: Reversible Expansion
Replies: 3
Views: 15

Re: Reversible Expansion

It depends on the system at hand. If the system is isolated, heat cannot come into the reversible expansion and replace the additional energy loss, so the first law of thermodynamics tells us that in the case that both systems (reversible and irreversible) are isolated, the irreversible one would in...
by Te Jung Yang 4K
Sun Feb 03, 2019 11:17 pm
Forum: Calculating Work of Expansion
Topic: Different ways to derive work
Replies: 3
Views: 11

Re: Different ways to derive work

W= F*d is the more general definition of work which is good to know, but I don't think we will ever need to calculate anything using that definition. It would lean more toward physics.
by Te Jung Yang 4K
Sun Feb 03, 2019 11:10 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: intensive vs extensive properties
Replies: 2
Views: 12

Re: intensive vs extensive properties

An intensive property is does not depend on the system size or the amount of material in the system.
An extensive property does depend on the system size or the amount of material in the system.
by Te Jung Yang 4K
Sun Feb 03, 2019 10:57 pm
Forum: Phase Changes & Related Calculations
Topic: Heating Curve
Replies: 4
Views: 24

Re: Heating Curve

Basically if you look at the phase change curve, you can see that it takes energy to heat up the liquid to a gas at the same temperature. So that additional energy goes into burning your hand if it's steam that's hitting your hand.
by Te Jung Yang 4K
Sun Jan 27, 2019 5:24 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: State Properties
Replies: 3
Views: 11

Re: State Properties

If you're referring to heat energy (which is enthalpy) then yes.
If you're referring to temperature, then also yes.
by Te Jung Yang 4K
Sun Jan 27, 2019 5:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Solving for a reaction's enthalpy
Replies: 2
Views: 11

Re: Solving for a reaction's enthalpy

In lecture, Dr. Lavelle said that bond enthalpies were the least accurate way of finding a reaction's change of enthalpy as they are average values.

Having said that, I would assume that the other two are preferable as they are more specific to the reaction you are trying to solve.
by Te Jung Yang 4K
Sun Jan 27, 2019 5:01 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat capacity & enthalpy
Replies: 1
Views: 10

Re: Heat capacity & enthalpy

They are not the same thing.

Heat capacity is the number of heat units needed to raise the temperature of a body by one degree, while enthalpy is heat energy.
by Te Jung Yang 4K
Sun Jan 20, 2019 11:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Post Assessment
Replies: 1
Views: 33

Re: Post Assessment

If the answer is 0.25, then here is what I did. You figure out how much BrCl at eq by 3.312 * 10^-5 * 0.18. Set up your eq constant equation (with concentrations). Subtract the initial amount of BrCl with eq amount of BrCl and divide that difference by 2 to get the amount of both Cl2 and Br2 at eq a...
by Te Jung Yang 4K
Sun Jan 20, 2019 11:33 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure
Replies: 7
Views: 31

Re: Pressure

I'm assuming you are using the equation PV=nRT, which is the ideal gas law. As the name implies, the equation is only for gases.
by Te Jung Yang 4K
Sun Jan 20, 2019 11:31 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Common Strong/Weak Acids and Bases
Replies: 2
Views: 23

Re: Common Strong/Weak Acids and Bases

Strong Acids: Group 17 Acids: HCl - hydrochloric acid. HBr - hydrobromic acid. HI - hydroiodic acid. Others: HNO3 - nitric acid. H2SO4 - sulfuric acid (HSO4- is a weak acid) HClO4 - perchloric acid. HClO3 - chloric acid. Weak Acids (usually organic): Formic HCOOH Acetic CH3COOH Hydrocyanic HCN Hydro...
by Te Jung Yang 4K
Sat Jan 12, 2019 10:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.7 6th Edition
Replies: 1
Views: 35

11.7 6th Edition

Would it be possible for someone to help me on 11.7 part c. I got the answer but I'm not quite sure if my reasoning is right. Thanks!
by Te Jung Yang 4K
Sat Jan 12, 2019 11:29 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle: Change in temperature
Replies: 2
Views: 17

Re: Le Chatelier's Principle: Change in temperature

To answer this question, there needs to be an understanding of the thermodynamics behind it. G = H – T*S, where G is the change in Gibb's Free Energy, H is the change in enthalpy, T is the temperature, and S is the entropy. Before dissecting this equation and using it to explain why an increase in t...
by Te Jung Yang 4K
Sat Jan 12, 2019 11:11 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 6th Edition Hw#11.29
Replies: 2
Views: 28

Re: 6th Edition Hw#11.29

You are correct when you say you need to find K so that you can compare it with Q.

You need Gibbs Free Energy (G) as K and G are linked with the following equation (which we didn't see in class yet):
G = - R*T*ln(K)

You use this equation to find K, which you can use to answer the question.
by Te Jung Yang 4K
Sun Dec 09, 2018 10:41 pm
Forum: Conjugate Acids & Bases
Topic: Definition of conjugate base
Replies: 2
Views: 30

Re: Definition of conjugate base

A conjugate base is the compound that is formed when an acid loses its hydrogen.

For example, Cl- would be the conjugate base of HCl.
by Te Jung Yang 4K
Sun Dec 09, 2018 10:40 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Acid Rain
Replies: 2
Views: 26

Re: Acid Rain

I'm pretty sure it was S02 (g) + H20 (l) -> H2S04 (aq).
by Te Jung Yang 4K
Sun Dec 09, 2018 10:39 pm
Forum: Naming
Topic: Cations
Replies: 1
Views: 21

Re: Cations

I don't think it matters.
by Te Jung Yang 4K
Wed Nov 28, 2018 11:02 pm
Forum: Bond Lengths & Energies
Topic: Interaction Potential Energy and Polarizability
Replies: 1
Views: 26

Re: Interaction Potential Energy and Polarizability

Interactive potential energy is the energy required to break the interactive forces between molecules/atoms. Polarizability is the how easily electrons from an atom is distorted (displaced away from the nucleus of the atom). Interactive potential energy is always negative as it is always attractive ...
by Te Jung Yang 4K
Wed Nov 28, 2018 10:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: SnCl2
Replies: 2
Views: 22

Re: SnCl2

It really depends on what Sn is bonding with. In your case, Cl can only accept 1 lone pair. Putting a double bond onto the Sn is not good as the formal charge of Cl will become +1 and Sn will become -1. Usually, it comes down to formal charge.
by Te Jung Yang 4K
Wed Nov 28, 2018 10:50 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing power and polarizability
Replies: 4
Views: 55

Re: Polarizing power and polarizability

Polarizability is the how easily the electrons in an atom can be distorted (moved away from the nucleus) with higher polarizability being electrons more easily displaced from the nucleus.
Polarizing power is how good an atom is at polarizing another atom.
by Te Jung Yang 4K
Wed Nov 28, 2018 10:43 pm
Forum: Electronegativity
Topic: Ionic character
Replies: 2
Views: 28

Re: Ionic character

I would think it is just the electronegativity. In your example, the bonds in H2S are the same, namely H - S bond. Since they are the same, they do not add to the ionic character.
by Te Jung Yang 4K
Wed Nov 28, 2018 10:40 pm
Forum: Hybridization
Topic: s-character
Replies: 1
Views: 21

Re: s-character

S-character refers to how prevalent the s-orbital is in the hybrid orbital.
For example, sp3 is made up of 4 different atomic orbitals, one of which is the s-orbital. So the s-orbital can be seen as 25% of the hybrid orbital.
sp2 = 33%
sp = 50%

sp3>sp2>sp: increasing s-character.
by Te Jung Yang 4K
Wed Nov 28, 2018 10:35 pm
Forum: Biological Examples
Topic: acids
Replies: 5
Views: 42

Re: acids

Some parts of our body are more flexible in terms of pH levels. The digestive tract can handle varying levels of pH, while the inside of the skin cannot.
by Te Jung Yang 4K
Wed Nov 28, 2018 8:41 pm
Forum: Lewis Structures
Topic: Lewis structure of I3-
Replies: 1
Views: 23

Lewis structure of I3-

I don't understand how to make the I3- lewis structure. The correct lewis structure puts the formal charge -1 on the center I, while I put the formal charge -1 on the side I (via a double bond, creating a resonance structure). I did this because I figured that the formal charge would be the best fur...
by Te Jung Yang 4K
Wed Nov 14, 2018 5:19 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: IMFs [ENDORSED]
Replies: 2
Views: 71

Re: IMFs [ENDORSED]

If there are no questions in the HW or past midterms about those properties, I would guess not. It would be safer to make sure with Professor Lavelle himself though.
by Te Jung Yang 4K
Wed Nov 14, 2018 5:17 pm
Forum: Ionic & Covalent Bonds
Topic: Contribution to the resonance structure?
Replies: 3
Views: 54

Re: Contribution to the resonance structure?

The ionic structures are the models of Cl2 on the far left and right (with - and + charges assigned to a Cl, right above your quoted sentence). Resonance describes delocalization of electrons. From these notes, the sentence seems to be implying that, since in the Cl2 molecule the electrons in the co...
by Te Jung Yang 4K
Wed Nov 14, 2018 5:05 pm
Forum: Lewis Structures
Topic: Question 4.19b in 6th edition
Replies: 1
Views: 26

Re: Question 4.19b in 6th edition

You would have 3 hydrogens on each carbon. But, the carbons are not attached to each other. Instead, the Be is bonded to each C.

H3CBeCH3
by Te Jung Yang 4K
Sun Nov 11, 2018 5:49 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Graphical Representation of Orbitals
Replies: 2
Views: 39

Graphical Representation of Orbitals

In class, professor Lavelle said that orbitals are wave functions, but when he pointed to the graphical representation of the orbitals, he kept using the term probability density/distribution. I know that the probability density is the square of the wave function, but I just wanted a clarification o...
by Te Jung Yang 4K
Sun Nov 11, 2018 5:30 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angles and lone pairs
Replies: 4
Views: 40

Re: bond angles and lone pairs

Usually you would first make a Lewis structure and see if there are lone pairs that way, but I'm assuming that you want to know to tell if there are lone pairs solely given the bond angles of a molecule. But, in this case, you would not even know the elements comprising the molecule in question as i...
by Te Jung Yang 4K
Sun Nov 11, 2018 5:18 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Different States of Matter based on Polarizability
Replies: 1
Views: 25

Re: Different States of Matter based on Polarizability

Differences in strength polarizability mean that the intermolecular (molecule to molecule interactions) forces differ in strength. Intermolecular forces determine the state of matter. Gaseous state means that the intermolecular forces between molecules have been broken, usually by temperature/heat. ...
by Te Jung Yang 4K
Wed Oct 31, 2018 11:28 am
Forum: Octet Exceptions
Topic: Octet rule
Replies: 2
Views: 41

Re: Octet rule

The octet rule is basically a guideline for bonding which says that elements (with atomic number below 20) should have 4 bonding pairs of electrons (8 e- total - the noble gas configuration). The first 4 elements do not follow this guideline as they do not need 8 e- to reach a noble gas configuratio...
by Te Jung Yang 4K
Wed Oct 31, 2018 11:04 am
Forum: Bond Lengths & Energies
Topic: Bond Strength and Resonance
Replies: 2
Views: 80

Re: Bond Strength and Resonance

Resonance gives the single bonds partial multiple bond properties by delocalization. Multiple bonds are stronger than single bonds, so the single bonds are strengthened.
by Te Jung Yang 4K
Wed Oct 31, 2018 10:22 am
Forum: Trends in The Periodic Table
Topic: Electron Affinity equation/definition
Replies: 2
Views: 53

Re: Electron Affinity equation/definition

The first equation is simply an example of a species gaining an electron, which relates to electron affinity as it is defined as the energy difference between the energy of a gaseous atom and the energy of the anion of the gaseous atom. X(g)+ e- -> X- (g) This second equation is the definition of el...
by Te Jung Yang 4K
Wed Oct 24, 2018 8:26 pm
Forum: Trends in The Periodic Table
Topic: Sizes of ions and neutral atoms
Replies: 4
Views: 86

Sizes of ions and neutral atoms

Can someone please explain to me why anions are larger than their neutral atoms? Thank you!
by Te Jung Yang 4K
Wed Oct 24, 2018 4:01 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum numbers for the "exception" cases
Replies: 15
Views: 162

Re: Understanding a textbook problem

Hey there, there was a problem that I didn't understand the concept behind. A particle (6.644 * 10^-34 kg) and textbook (2.18 kg) travel the same speed. Which will have a smaller wavelength? I know it is the textbook, but what is the concept behind it? Is it that the larger the mass, the smaller th...
by Te Jung Yang 4K
Wed Oct 24, 2018 3:58 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum numbers for the "exception" cases
Replies: 15
Views: 162

Re: Quantum numbers for the "exception" cases

I think you have a misconception here. Firstly, the quantum numbers do not describe atoms. They describe individual electrons within an atom. So when you say atoms have quantum numbers, you are actually talking about the outermost electron, in your case 4s1. Now, to answer your question, the electro...
by Te Jung Yang 4K
Wed Oct 24, 2018 3:42 pm
Forum: Einstein Equation
Topic: 6th Edition, Question 1.55
Replies: 2
Views: 68

Re: 6th Edition, Question 1.55

It means to use the energy you got from part b of the exercise.
So, on the previous exercise, you would have for one absorbtion 7.2 * 10^-20J.
For the answer to part c, you would need to multiply that energy by Avogadro's constant.
by Te Jung Yang 4K
Wed Oct 17, 2018 5:18 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Conflict with lecture and solution manual
Replies: 1
Views: 26

Conflict with lecture and solution manual

In lecture, Dr. Lavelle told us that when given a measurement of a length (ie 10m +-1m), the uncertainty would be 2m in this measurement as the range of values can be 9m - 11m. However, in the solution manual 6th edition for problem 1.45, it uses the value immediately after the +- for a calculation ...
by Te Jung Yang 4K
Wed Oct 17, 2018 4:55 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg equation hw problem
Replies: 1
Views: 30

Re: Heisenberg equation hw problem

I think you might have misread the manual. It uses the h with a dash on top (ħ), this is not Planck's Constant, which does not have the additional stroke. ħ = h / 2pi So, the solution manual is correct, if you simply used the substitution on top for the formula used in the manual, you would get the ...
by Te Jung Yang 4K
Wed Oct 17, 2018 4:38 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework Question 1.57 (6th Ed.)
Replies: 1
Views: 29

Re: Homework Question 1.57 (6th Ed.)

It's possible. First, recall that the Balmer series corresponds to the transitions of electrons in higher quantum levels to the 2nd quantum level. Knowing this, you need to find out which transition corresponds to 410.2nm, the shortest wavelength given to us by the question. We want to use this one ...
by Te Jung Yang 4K
Wed Oct 17, 2018 12:36 pm
Forum: Properties of Light
Topic: Atomic Spectrum and Series
Replies: 4
Views: 40

Re: Atomic Spectrum and Series

The common aspect of each of these series is that the energized (excited electron) falls down to the same quantum level (n=X). For example, the Balmer series is the result of electron transitions from higher levels down to the energy level with principal quantum number 2. This definition causes the ...
by Te Jung Yang 4K
Thu Oct 11, 2018 11:07 pm
Forum: Einstein Equation
Topic: Symbol for frequency
Replies: 12
Views: 117

Symbol for frequency

What symbol for frequency should we use in homework assignments and exams? The letter f or the greek letter nu? Or perhaps it doesn't matter at all and the correcter will allow both? I know that we've only used nu so far, but I'm used to the letter f from high school.
by Te Jung Yang 4K
Thu Oct 11, 2018 10:50 pm
Forum: Molarity, Solutions, Dilutions
Topic: memorizing [ENDORSED]
Replies: 4
Views: 121

Re: memorizing [ENDORSED]

If this is for tests and what not, I'm fairly certain that a formula and constants sheet will be included for every test so we won't need to rote memorize anything (at least here was one for this week's test). If this is for general use, I'd suggest just understanding the formulas rather than memori...
by Te Jung Yang 4K
Thu Oct 11, 2018 10:45 pm
Forum: Identifying Acidic & Basic Salts
Topic: Title for sub-forum
Replies: 1
Views: 218

Title for sub-forum

I just can't help but notice that the title is misspelt.
by Te Jung Yang 4K
Thu Oct 04, 2018 10:51 pm
Forum: SI Units, Unit Conversions
Topic: 6th Edition E27, First Part
Replies: 5
Views: 36

Re: 6th Edition E27, First Part

Oh hey, quick reply guys! Thanks. To catch you guys here, is the reason why it is 1 / (6.022 x 10^23) moles because of the need to cancel out the units via dimensional analysis?
by Te Jung Yang 4K
Thu Oct 04, 2018 10:43 pm
Forum: SI Units, Unit Conversions
Topic: 6th Edition E27, First Part
Replies: 5
Views: 36

6th Edition E27, First Part

I'm stuck on the first part of the question in title. How do you convert 1 H20 molecule to moles?
by Te Jung Yang 4K
Wed Oct 03, 2018 4:36 pm
Forum: SI Units, Unit Conversions
Topic: Fundamental Exercises E27
Replies: 3
Views: 63

Re: Fundamental Exercises E27

To find the number of water molecules in 1.00 kg of water, you would have to convert the 1.00 kg of water to moles of water (using the molecular mass of water and the relevant equation - don't forget to convert kg to g when using the equation!). Then, once you have the moles of water in 1.00 kg of w...

Go to advanced search