Search found 52 matches

by chris_tsai_4H
Sun Mar 10, 2019 10:01 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox
Replies: 4
Views: 70

Re: Balancing Redox

Electrons are an intensive property and therefore do not become affected by the other changing concentrations in the redox reaction.
by chris_tsai_4H
Sun Feb 24, 2019 3:59 pm
Forum: Balancing Redox Reactions
Topic: TEST
Replies: 7
Views: 128

Re: TEST

The test includes everything we've learned up until Friday's (2/22) lecture, which does include Gibb's Free Energy.
by chris_tsai_4H
Sun Feb 24, 2019 3:31 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox
Replies: 4
Views: 70

Re: Balancing Redox

The E value given is dependent on the reaction itself. Therefore, the concentration of the compounds involved in the reaction does not affect this value.
by chris_tsai_4H
Sun Feb 24, 2019 3:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Oxidation and Reduction
Replies: 3
Views: 57

Re: Oxidation and Reduction

Yes it will always be like that because when something is reduced, it gains electrons and when it is oxidized, it gains electrons.
by chris_tsai_4H
Sat Feb 16, 2019 12:04 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Adding reaction entropies
Replies: 8
Views: 150

Re: Adding reaction entropies

Since entropy is a state function and is dependent on other situations occurring in the reaction, we have to calculate each change in entropy separately and then add all of them together to find total entropy.
by chris_tsai_4H
Sat Feb 16, 2019 12:03 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 3 Step Entropy Change Calculations
Replies: 2
Views: 69

Re: 3 Step Entropy Change Calculations

The middle step accounts for the change in volume while the other steps only account for change in temperature which is why you have to add all the changes in entropy together in order to find the total deltaS.
by chris_tsai_4H
Sat Feb 16, 2019 12:02 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Monatomic VS Diatomic Gases and their C
Replies: 3
Views: 215

Re: Monatomic VS Diatomic Gases and their C

When calculating C, you have to use different R values, depending on whether the gas is monatomic or diatomic. The R value you should use is given on the equations sheet.
by chris_tsai_4H
Sat Feb 16, 2019 12:01 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: gibbs free energy
Replies: 10
Views: 146

Re: gibbs free energy

When delta G is negative, the system(reaction) is spontaneous.
by chris_tsai_4H
Sat Feb 16, 2019 11:59 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: When does delta U equal zero?
Replies: 17
Views: 346

Re: When does delta U equal zero?

When a reaction is isothermal, delta U (internal energy) equals zero.
by chris_tsai_4H
Sat Feb 16, 2019 11:58 am
Forum: Calculating Work of Expansion
Topic: Reversible Expansion
Replies: 2
Views: 82

Re: Reversible Expansion

Reversible expansion does the most amount of work because the gas is pushing against the maximum possible external pressure and less of the energy is lost to heat.
by chris_tsai_4H
Sun Feb 03, 2019 9:11 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: PV=nRT
Replies: 5
Views: 131

Re: PV=nRT

This equation is given for the ideal gas law so you'd only us it when you have a problem where the volume and moles of a gas are changing.
by chris_tsai_4H
Sun Feb 03, 2019 8:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of Formation
Replies: 2
Views: 52

Re: Enthalpy of Formation

Yes, bond enthalpy can be either positive or negative since the value is based on whether the formation of the bond requires or produces heat.
by chris_tsai_4H
Sun Feb 03, 2019 8:47 pm
Forum: Calculating Work of Expansion
Topic: Isolated System
Replies: 5
Views: 120

Re: Isolated System

In an isolated system, you assume that there are no interactions with the outside. Therefore, the heat in the system should not be considered.
by chris_tsai_4H
Sun Jan 27, 2019 4:17 pm
Forum: Ideal Gases
Topic: Approximations for ICE
Replies: 20
Views: 242

Re: Approximations for ICE

If the value of K is less than 10^-3, then we can assume that the value is too small to have any impact and therefore we can assume that X minus any number becomes just x.
by chris_tsai_4H
Sun Jan 27, 2019 4:15 pm
Forum: Phase Changes & Related Calculations
Topic: Why are phase changes endothermic?
Replies: 11
Views: 159

Re: Why are phase changes endothermic?

Phase changes are endothermic because, in order to go from one state of matter to another, the bonds have to be broken, which requires heat.
by chris_tsai_4H
Wed Jan 23, 2019 11:50 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Strong Acids and Bases
Replies: 5
Views: 120

Re: Strong Acids and Bases

A good way to memorize strong acids and bases is understanding the relationships between the two elements in terms of electronegativity. Usually, when they have very opposite electronegativities, the two elements form a strong acid/base.
by chris_tsai_4H
Wed Jan 23, 2019 11:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Rounding concentration
Replies: 2
Views: 46

Re: Rounding concentration

To be safe, it would be best to do all the calculations without rounding first, and then rounding to the correct number of significant figures once you have the final answer.
by chris_tsai_4H
Wed Jan 23, 2019 11:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K for gaseous equations
Replies: 2
Views: 53

Re: K for gaseous equations

Usually for equilibrium reactions that involve only gases, we use Kp to determine partial pressures.
by chris_tsai_4H
Sun Jan 20, 2019 10:39 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Equilibrium Conditions
Replies: 2
Views: 68

Re: Equilibrium Conditions

For the equilibrium constant K, it is not affected by any changes in pressure, temperature, or concentration.
by chris_tsai_4H
Sun Jan 20, 2019 10:39 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constant
Replies: 2
Views: 40

Re: Equilibrium Constant

If the equilibrium constant K is larger than 10^3, then the equilibrium favors the product. And, if the equilibrium constant K is smaller than 10^-3, then the equilibrium favors the reactants.
by chris_tsai_4H
Sun Jan 13, 2019 1:03 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constant Eq.
Replies: 4
Views: 78

Equilibrium Constant Eq.

Are solids and liquids included in the equilibrium constant equation?
by chris_tsai_4H
Sun Jan 13, 2019 12:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: (aq) in calculating K
Replies: 9
Views: 110

Re: (aq) in calculating K

Aqueous and gaseous products and reactants are included in the equilibrium constant but solids and liquids are excluded.
by chris_tsai_4H
Sun Jan 13, 2019 12:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Heterogeneous and homogeneous equilibria [ENDORSED]
Replies: 8
Views: 142

Re: Heterogeneous and homogeneous equilibria [ENDORSED]

Heterogeneous equilibrium is when there are different states of matter present in the reaction and homogeneous equilibrium is when all the states are the same.
by chris_tsai_4H
Sat Dec 08, 2018 10:12 pm
Forum: Bronsted Acids & Bases
Topic: Lewis vs Bronsted
Replies: 10
Views: 424

Lewis vs Bronsted

What is the difference between Bronsted acids and bases and Lewis acids and bases?
by chris_tsai_4H
Sat Dec 08, 2018 10:09 pm
Forum: Lewis Acids & Bases
Topic: Lewis Acid
Replies: 6
Views: 95

Re: Lewis Acid

HF has a stronger bond due to the higher difference in electronegativity therefore the bond is harder to break, meaning the proton is harder to donate. Therefore, HBr is a stronger acid since it has a weaker bond and can more easily donate a proton.
by chris_tsai_4H
Sun Dec 02, 2018 7:53 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 12
Views: 277

Re: Bond Angles

Determine the VSEPR model for each individual atom and then determine what the bond angle would be based off of the model.
by chris_tsai_4H
Sun Dec 02, 2018 7:23 pm
Forum: Hybridization
Topic: pi vs sigma
Replies: 12
Views: 265

Re: pi vs sigma

Pi bonds are side side while sigma bonds are end to end. Therefore sigma bonds are inherently stronger. Also, when pi bonds rotate, they break, so they are weak.
by chris_tsai_4H
Sun Dec 02, 2018 7:21 pm
Forum: Hybridization
Topic: hybridization
Replies: 13
Views: 408

Re: hybridization

Count the number of electron densities that are surrounding the central atom. For example, if there are 4, then the hybridization is sp3. If there are 5, then it is sp3d, since the p orbital can only contain three, and s can only have one, the 5th electron goes to the d orbital.
by chris_tsai_4H
Sun Nov 25, 2018 10:55 am
Forum: Hybridization
Topic: Carbon rotation in C2H4
Replies: 2
Views: 47

Re: Carbon rotation in C2H4

The rotation does not affect the strength of the pi bond. The pi bond simply is not capable of rotating, since it is a side-by-side bond, unlike sigma bonds, which are capable of rotating, since they are end-to-end bonds. Therefore, if the two carbon atoms in the compound were to rotate, this would ...
by chris_tsai_4H
Sun Nov 25, 2018 10:02 am
Forum: Bond Lengths & Energies
Topic: Single, Double, Triple Bond Lengths
Replies: 5
Views: 123

Re: Single, Double, Triple Bond Lengths

Triple bonds are the shortest and single bonds are the longest because as more bonds between atoms occur, it brings the two atoms closer together.
by chris_tsai_4H
Sun Nov 25, 2018 9:30 am
Forum: Hybridization
Topic: Figuring out the number of sigma and pi bonds in a molecule
Replies: 2
Views: 51

Re: Figuring out the number of sigma and pi bonds in a molecule

First, you should draw the lewis structures for both molecules. Then, you can see the types of bonds between each atom. Single bonds have one sigma bond, double bonds have one sigma bond and one pi bond, and triple bonds have one sigma bond and two pi bonds.
by chris_tsai_4H
Sun Nov 18, 2018 8:49 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sigma/Pi bonds
Replies: 7
Views: 134

Sigma/Pi bonds

How do you determine the difference between sigma and pi bonds?
by chris_tsai_4H
Sun Nov 18, 2018 8:45 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Question 6.5 (Sixth Edition)
Replies: 1
Views: 98

Re: Question 6.5 (Sixth Edition)

In order to compare melting points, you have to look at the different intermolecular forces that are found within each compound. For example, hydrogen bonds are much higher to break (melt) than dipole-dipole bonds. Therefore, if one compound has a hydrogen bond and another does not, the compound wit...
by chris_tsai_4H
Sun Nov 18, 2018 8:42 pm
Forum: Hybridization
Topic: Hybridization
Replies: 2
Views: 65

Re: Hybridization

Hybridization is the concept of mixing atomic orbitals into new hybrid ones.
by chris_tsai_4H
Sat Nov 10, 2018 9:31 pm
Forum: Dipole Moments
Topic: Melting points
Replies: 5
Views: 100

Re: Melting points

Hydrogen bonds occur between hydrogen and elements such as oxygen, nitrogen, and fluorine. Hydrogen bonds require a lot more energy to break apart. Since H2S does not have any hydrogen bonds, and H2O does, the melting point of H2O is much higher since it requires more heat to break the bonds apart.
by chris_tsai_4H
Sat Nov 10, 2018 9:29 pm
Forum: Dipole Moments
Topic: Hydrogen Bonds
Replies: 20
Views: 286

Re: Hydrogen Bonds

Hydrogen bonds are the strongest among the intra molecular bonds but are weaker than the intermolecular bonds (covalent and ionic)
by chris_tsai_4H
Sat Nov 10, 2018 9:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: how to know which shape it is
Replies: 6
Views: 132

Re: how to know which shape it is

The VSEPR model for Lewis structures is based on electron pairs so you have to count them to determine which one they correspond to.
by chris_tsai_4H
Sun Nov 04, 2018 3:56 pm
Forum: Photoelectric Effect
Topic: intensity
Replies: 4
Views: 115

Re: intensity

Intensity does not affect the energy of the ejected electron. The intensity will only affect the amount of electrons ejected
by chris_tsai_4H
Sun Nov 04, 2018 3:50 pm
Forum: Quantum Numbers and The H-Atom
Topic: degeneracy in quantum numbers
Replies: 3
Views: 94

Re: degeneracy in quantum numbers

Degenerate orbitals mean that the electrons within the orbital contain the same energy level.
by chris_tsai_4H
Sun Nov 04, 2018 3:47 pm
Forum: Student Social/Study Group
Topic: Radicals
Replies: 3
Views: 89

Re: Radicals

To be safe, you should know what they are. Radicals occur when there is a single unpaired electron, making it highly reactive.
by chris_tsai_4H
Sat Oct 27, 2018 1:17 pm
Forum: DeBroglie Equation
Topic: Nodal Planes
Replies: 4
Views: 181

Re: Nodal Planes

There are no electrons in nodal planes because they are theoretical areas in between the lobes of orbitals that have zero probability of having electron density.
by chris_tsai_4H
Sat Oct 27, 2018 1:14 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: D-block Question
Replies: 2
Views: 60

Re: D-block Question

For multielectron atoms after the atomic number 20, the 4s state is higher energy than the 3d state, which is why it is written first in electron configurations. Also, the first electron to be removed is the lower energy levels so, 4s.
by chris_tsai_4H
Sat Oct 27, 2018 1:09 pm
Forum: Trends in The Periodic Table
Topic: Atomic Radius
Replies: 7
Views: 162

Re: Atomic Radius

Since one electron has already been removed, the remaining electrons are now experiencing a greater attraction to the nucleus. The subsequent electrons being removed will have a higher ionization energy since they are less easy to remove.
by chris_tsai_4H
Sun Oct 21, 2018 11:15 pm
Forum: Quantum Numbers and The H-Atom
Topic: Difference between ground and excited state of electrons
Replies: 4
Views: 113

Re: Difference between ground and excited state of electrons

Excited states of electrons have higher energy levels and the higher level energy electrons naturally want to move to the ground level of electrons.
by chris_tsai_4H
Sun Oct 21, 2018 11:01 pm
Forum: Administrative Questions and Class Announcements
Topic: Exam 2
Replies: 4
Views: 143

Re: Exam 2

The equation sheet has all the equations that we need but they aren't labeled so you need to be able to know which equation is which and when to use each one.
by chris_tsai_4H
Sun Oct 21, 2018 10:53 pm
Forum: Properties of Light
Topic: Test 2 Equations
Replies: 14
Views: 291

Re: Test 2 Equations

Most of the equations that we need to know for Test 2 are on the equations sheet in the front page of the test. But you should probably know what they are used for, what the variables represent, and how to manipulate them.
by chris_tsai_4H
Sun Oct 14, 2018 11:09 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: G and H orbitals
Replies: 1
Views: 38

Re: G and H orbitals

There are some elements that have g and h orbitals, but only in their respective excited states. There are no discovered ground elements with g or h orbitals... and I don't think we'll need those concepts for this class.
by chris_tsai_4H
Sat Oct 13, 2018 5:46 pm
Forum: Einstein Equation
Topic: Energy of a Photon
Replies: 2
Views: 71

Re: Energy of a Photon

The energy "E" from the equation is the initial energy of the photon that is responsible for removing the electron. The energy "released by the photon" is most likely referring to the small amount of energy that the electron emits when it is removed and moves with some velocity.
by chris_tsai_4H
Sat Oct 13, 2018 5:38 pm
Forum: DeBroglie Equation
Topic: DeBroglie Equation
Replies: 5
Views: 115

Re: DeBroglie Equation

The DeBroglie equation is used in determining if the object being observed is showing wave-like properties. If the wavelength of the observed object is higher than a certain threshold, then the object is showing wavelike properties. So, you would use this equation when finding the wavelength of a mo...
by chris_tsai_4H
Thu Oct 04, 2018 6:47 pm
Forum: Significant Figures
Topic: M11 Sig Figs
Replies: 4
Views: 122

Re: M11 Sig Figs

You should answer each part with the amount of sig figs that correspond to that part. For example, if in Part A, the problem gives values with 2 sig figs, then answer Part A in 2 sig figs.
by chris_tsai_4H
Thu Oct 04, 2018 6:31 pm
Forum: Limiting Reactant Calculations
Topic: Actual yield [ENDORSED]
Replies: 4
Views: 116

Re: Actual yield [ENDORSED]

The actual yield refers to the amount of product that is produced from a chemical reaction after taking the limiting reactant in an equation into account. This differs from the theoretical yield, which would be the amount of product produced assuming no limitations.
by chris_tsai_4H
Thu Oct 04, 2018 2:02 pm
Forum: Limiting Reactant Calculations
Topic: Significant figures in textbook 7th edition [ENDORSED]
Replies: 5
Views: 144

Re: Significant figures in textbook 7th edition [ENDORSED]

For the final answer, you should use the same amount of significant figures that are given in the problem. Also, make sure not to use significant figures while showing your work; you should only round to significant figures when you are producing your final answer.

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