## Search found 60 matches

Mon Mar 18, 2019 11:59 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Profiles
Replies: 3
Views: 374

### Re: Reaction Profiles

Basically the slower the step the higher the peak
Mon Mar 18, 2019 11:58 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre Equilibrium Approach
Replies: 3
Views: 389

### Re: Pre Equilibrium Approach

We use the preequilibrium approach in order to get rid of intermediates in the final rate law
Mon Mar 18, 2019 11:57 am
Forum: Reaction Mechanisms, Reaction Profiles
Replies: 3
Views: 342

The steady state is a much more complicated method compared to preequilibrium and therefore we won’t be required to know if for the class, preequilibrium gives us sufficient accuracy for the scope of the class
Sat Mar 09, 2019 9:38 pm
Forum: Second Order Reactions
Topic: Determining the Order of a Reaction
Replies: 3
Views: 153

### Re: Determining the Order of a Reaction

You find the order of the individual reactants, which can be found based on the information given, then adding up all the orders tells you the order of the overall reactant.
Sat Mar 09, 2019 9:35 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Fast Step vs Slow Step
Replies: 3
Views: 125

### Re: Fast Step vs Slow Step

The slow step has the same rate law as the reaction, this is because the rate of the reaction is determined by the slowest step, all other steps go at a higher rate, therefore, the reaction can only proceed as fast as its slowest step can produce the necessary products
Sat Mar 09, 2019 9:30 pm
Forum: Zero Order Reactions
Topic: Zero order
Replies: 10
Views: 683

### Re: Zero order

A zero-order reaction is one in which the rate is independent of the concentration, we use artificial zero-order reactions to determine the order of reactants in a reaction. By supplying an excess amount of all reactants except one and then varying the concentration of the non-excess reactant to fin...
Sun Mar 03, 2019 9:42 pm
Forum: General Rate Laws
Topic: Overall sum
Replies: 7
Views: 254

### Re: Overall sum

The Overall reaction order is the sum of the exponents and provides insight as to the complexity of the reaction.
Sun Mar 03, 2019 9:35 pm
Forum: General Rate Laws
Topic: Calculus Review
Replies: 8
Views: 280

### Re: Calculus Review

I think we only need to know some of the basic topics covered in Calculus AB (or equivalent)
Sun Mar 03, 2019 9:32 pm
Forum: General Rate Laws
Topic: Reaction Order
Replies: 2
Views: 101

### Re: Reaction Order

The reaction order is all the exponents of the reactants added together
Sun Feb 24, 2019 8:47 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: ions
Replies: 2
Views: 84

### Re: ions

yes, an ion is alway aqueous. Ions can only exist in solution therefor if there is an ion it must be in solution or it can't exist.
Sun Feb 24, 2019 8:45 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: SHE
Replies: 3
Views: 104

### Re: SHE

The standard hydrogen electrode is essentially a null electrode. The electrode itself is an inert metal (such as platinum) and while we don't know the exact cell potential we set it to be zero so it serves as a reference point. So every electrode's cell potential is calculated with reference to the ...
Sun Feb 24, 2019 8:42 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagram
Replies: 3
Views: 109

### Re: Cell diagram

essentially one line between means there is simply a porous disk which allows the solutions to mix, a double line means that the solutions are in different containers & are separated by solid walls that don't allow mixing but are connected by a wire that allows the transfer of electrons.
Sun Feb 24, 2019 8:39 pm
Forum: Balancing Redox Reactions
Topic: How do you balance a redox reaction
Replies: 4
Views: 140

### Re: How do you balance a redox reaction

while you balance it like any other equation the way you go about it is different. You add water because sometimes there are oxygens that appear on one side of the equation and not the other. To show the actual reaction we add water because that is where those oxygens came from. We then add protons,...
Sun Feb 24, 2019 8:33 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox
Replies: 4
Views: 151

### Re: Balancing Redox

Despite what the previous posts say E is not an independent of concentration. The standard cell potential is independent of concentration but that is because it assumes that everything is at standard conditions. However just cell potential is dependant on concentration because as a battery proceeds ...
Sun Feb 24, 2019 8:30 pm
Forum: Balancing Redox Reactions
Topic: Oxidation
Replies: 4
Views: 221

### Re: Oxidation

It is helpful to to think of it in terms of charges, when something is reduced it's charge is "reduced" to a lower number and if it is oxidized it looses electrons
Sun Feb 24, 2019 8:28 pm
Forum: Balancing Redox Reactions
Topic: salt bridge?
Replies: 3
Views: 118

### Re: salt bridge?

The salt bridge allows the two electrolytes to be separated. Originally in a Daniel cell the electrolytes & electrodes canceled out charges so in order to separate the electrolytes & electrodes a salt bridge needed to be added in order to have two solutions at relatively neutral charge. It d...
Sun Feb 24, 2019 8:24 pm
Forum: Balancing Redox Reactions
Topic: Which Equation to Flip?
Replies: 9
Views: 478

### Re: Which Equation to Flip?

You flip the oxidation reaction. The reason Ecell is supposed to be positive is that is has an inverse relationship with delta G so when it is positive delta G is negative and the reaction is spontaneous, when it is negative delta G is positive and the reverse reaction is spontaneous.
Sun Feb 24, 2019 8:22 pm
Forum: Balancing Redox Reactions
Topic: platinum
Replies: 7
Views: 189

### Re: platinum

Platinum is added to the cell diagram whenever it is present, it is added into cells when we need a inert metal (non reacting metal) and we want water to be included in the reaction such as in a Standard Hydrogen Electrode. It isnt included in the reaction due to the fact that it doesn't react.
Sun Feb 24, 2019 8:18 pm
Forum: Balancing Redox Reactions
Topic: Oxygen Oxidation Number
Replies: 3
Views: 162

### Re: Oxygen Oxidation Number

Oxygen will tend to have a -2 charge due to the face that it wants an octet and due to its high electronegativity it will usually have the octet at the cost of having a formal charge of -2
Sun Feb 24, 2019 8:14 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox equations in Basic conditions
Replies: 3
Views: 124

### Re: Balancing Redox equations in Basic conditions

You have to add water to balance out the oxygens once you balance all other elements, so in this case it would be on the left. Then you add OH^- to balance the hydrogens and oxygens. Then lastly you balance the charges. Since you can't raise the charge of one side, you can only lower it you add elec...
Sun Feb 24, 2019 7:22 pm
Forum: Balancing Redox Reactions
Topic: Order to balance
Replies: 6
Views: 197

### Re: Order to balance

You follow the order in the previous posts but you don't balance electrons. Electrons are used to balance the charge of the reaction. Electrons are then balanced (by multiplying either the reduction or oxidation reaction) so that they cancel out in the redox reaction to show the transfer of electron...
Sun Feb 24, 2019 7:20 pm
Forum: Balancing Redox Reactions
Topic: 1/2 Rxns: Elements vs. Compounds
Replies: 3
Views: 111

### Re: 1/2 Rxns: Elements vs. Compounds

You only include reacting elements/molecules, spectator ions aren't important in chemical reactions and because of such aren't included. Water is used to balance out the oxygens and hydrogen ions(protons) are used to cancel out the hydrogens from other molecules. If the molecule doesn't react then i...
Sun Feb 24, 2019 7:16 pm
Forum: Balancing Redox Reactions
Topic: Balancing Half Reactions
Replies: 3
Views: 65

### Re: Balancing Half Reactions

The reason the charge isn't multiplied is due to the equation Ecell=-nR/DeltaG, Delta G is doubled when concentrations are doubled but so is n (the coefficient for moles), therefor the Ecell stays the same regardless of coefficient change
Mon Jan 21, 2019 3:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pure substances
Replies: 3
Views: 121

### Re: Pure substances

This is because solids don't change in concentration because they don't have a concentration and liquids don't change because it is usually in excess and would cancel out on both sides.
Mon Jan 21, 2019 3:26 pm
Forum: Ideal Gases
Topic: PV=nRT
Replies: 8
Views: 592

### Re: PV=nRT

The ideal gas law is used in order to convert from molarity to partial pressure, with K and R being given
Mon Jan 21, 2019 3:23 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 4
Views: 162

### Re: Le Chatelier's Principle

Amy Dinh 1A wrote:Adding on to that, his principle applies to changing physical parameters Pressure and Temperature.

When pressure increases, the reaction favors the side with the least moles of gas.

It isn't that when pressure changes it will favor one side, it is when molarity is affected.
Mon Jan 21, 2019 3:21 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q and K
Replies: 10
Views: 392

### Re: Q and K

Q and K are very similar, at equilibrium Q = K but any other time than that Q won't equal K but it will tell us which side will be favored in order to get to K.
Mon Jan 21, 2019 3:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Salt
Replies: 4
Views: 170

### Re: Salt

Knowing strong/weak acids and bases help to determine if the reaction is with salt. It isn't too different than an acid/base reaction you just have to write out the reations that affect ph and do the necessary calculations.
Mon Jan 21, 2019 3:16 pm
Forum: Ideal Gases
Topic: 5% rule
Replies: 12
Views: 1679

### Re: 5% rule

You use the 5% rule to determine if X is negligible, if it is over 5% then you just need to include (#-x) in your calculations when trying to find the value of X.
Thu Dec 06, 2018 4:33 pm
Forum: Conjugate Acids & Bases
Topic: Ion concentration
Replies: 2
Views: 122

### Re: Ion concentration

to find the concentration of (H30) you put e to the -pH and you can use stoichiometry to find concentrations of other molecules in the reaction.
Thu Dec 06, 2018 4:27 pm
Forum: Lewis Acids & Bases
Topic: HCl vs. HI
Replies: 7
Views: 231

### Re: HCl vs. HI

electronegativity only matters for molecules, not single atom ions, because the higher electronegativity will help spread the negative charge over a higher area and thus will make it more stable but electronegativity doesn't matter for single atom ions because regardless of the electronegativity the...
Thu Dec 06, 2018 4:23 pm
Forum: Lewis Acids & Bases
Topic: Determining which H^+ ions are given off
Replies: 4
Views: 138

### Determining which H^+ ions are given off

When trying to see how many H^+ ions can be given off by an acid, which ones are usually given off? Like I know those attached to nitrogen usually are given off but what if it is bonded to an O or another element?
Thu Nov 29, 2018 11:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AX2E2
Replies: 14
Views: 971

### Re: AX2E2

a molecule with formula AX2E2 will have a bond angle >>109.5 as the lone pairs repulse the atoms more that atoms repulse atoms, however a molecule with formula AX4E2 will have bond angles at exactly 90 degrees as the lone pair-atom repulsion will cancel out.
Thu Nov 29, 2018 11:03 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Electron density
Replies: 3
Views: 347

### Re: Electron density

yes the hybridization is the same as electron densities around the central atom as double and triple bonds require unhybridized p orbitals, single, double, and triple bonds as well as lone pairs each count as one electron density
Thu Nov 29, 2018 11:00 pm
Forum: Hybridization
Topic: Delocalized Pi Bonding
Replies: 3
Views: 121

### Re: Delocalized Pi Bonding

this is the cloud of electrons over a molecule it an have three pi bonds on every other bond, and due to resonance there are characteristics of double bonding at every bond at the same time, resulting in a delocalized pi bond over the entire molecule.
Thu Nov 29, 2018 10:57 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: sigma and pi bonds
Replies: 4
Views: 188

### Re: sigma and pi bonds

a sigma bond can rotate because it is connected at one point so the atoms can rotate freely, in a double or triple bond (containing a sigma and pi bonds) there are connections at either 3 or 5 points and so if it was to rotate, it would need to break the bonds at those points and reform them at the ...
Thu Nov 29, 2018 10:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: trans/cis
Replies: 4
Views: 224

### Re: trans/cis

yes because the formula for a cis/trans molecule is the exact same, the difference comes in how the atoms are positions which is where the cis/trans part comes in it tells you is the same elements are on the same side or on the opposite side
Thu Nov 29, 2018 10:46 pm
Forum: Hybridization
Topic: Bond Strengths
Replies: 4
Views: 160

### Re: Bond Strengths

a pi bond is weaker than a sigma bond because it is higher energy than a sigma bond, remember everything wants to be in the lowest energy state possible, pi bonds have a nodal plane between the nuclei which is where the electrons would like to be therefor it is weaker than a sigma bond as the electr...
Thu Nov 29, 2018 10:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polar or not polar
Replies: 4
Views: 232

### Re: polar or not polar

it helps to visualize the molecule in your head, on paper the Lewis model of CH2Cl2 may look symmetrical but in reality, no matter how it is positioned the 2 Cls will be opposite the 2 Hs which explains the polarity, the molecule needs to be symmetrical in 3D in order for it to be non-polar.
Thu Nov 29, 2018 10:35 pm
Forum: Hybridization
Topic: hybridization notation
Replies: 3
Views: 147

### Re: hybridization notation

The 2 in 2sp^2 is the energy level of the hybridized orbital it is simply the period of the element.
Thu Nov 29, 2018 10:29 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polarity
Replies: 11
Views: 292

### Re: polarity

yes going off of the previous post, molecules that are symmetric are non-polar, for example, a square planar molecule is non-polar despite having two lone pairs due to it being symmetric, usually larger molecules with different elements that isn't symmetrical are non-polar. To help determine if it i...
Thu Nov 29, 2018 10:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipole moment
Replies: 7
Views: 335

### Re: Dipole moment

The Dipole Moment has a direct correlation with polarity so the more polar the larger the dipole moment.
Sun Nov 11, 2018 8:12 pm
Forum: Hybridization
Topic: Composition of a bond (Sigma and Pi Bonds)
Replies: 3
Views: 289

### Re: Composition of a bond (Sigma and Pi Bonds)

the 1 and 2 simply refer to the energy level of the orbital that is participating in the bond, so it is also the period number of the atom as that is the energy level of valence orbitals.
Sun Nov 11, 2018 8:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: molecular shapes
Replies: 13
Views: 388

### Re: molecular shapes

I think we have to be able to name the different shapes but its important to note that shape is different than the electron arrangement, the shape is named after the how the molecule looks (excluding lone pairs) so its possible for some vsepr models to have the same angles as there can be a lone pai...
Sun Nov 11, 2018 8:05 pm
Forum: Hybridization
Topic: Energy levels
Replies: 6
Views: 373

### Re: Energy levels

degeneracy relates to all energy levels, orbitals and subshells, it simply states subshells are the same exact energy, however, degeneracy is broken in the D orbital due to some subshells being lower energy then others
Sun Nov 11, 2018 8:03 pm
Forum: Sigma & Pi Bonds
Topic: Difference between Bonds [ENDORSED]
Replies: 7
Views: 644

### Re: Difference between Bonds[ENDORSED]

A sigma bond is always first due to the fact that it is lower energy, so if the molecule always picks a lower energy state, it makes sense that a sigma bond is first, it is only after then that any other bond formed are pi because they require more energy then a sigma bond but less energy than the i...
Sun Nov 11, 2018 7:57 pm
Forum: Sigma & Pi Bonds
Topic: Pi bonds
Replies: 3
Views: 379

### Re: Pi bonds

yes, such as in benzene carbon has 3sp^2 orbitals, with two being bonded to other c-atoms and one being bonded to a hydrogen, the leftover unhybridized pz bond is what forms the molecular orbital above and below the ring structure of the benzene
Sun Nov 11, 2018 7:54 pm
Forum: Sigma & Pi Bonds
Topic: Sigma v. Pi
Replies: 6
Views: 388

### Re: Sigma v. Pi

A sigma bond has increased electron probability between nuclei whereas a pi bond has a nodal plane between nuclei making it higher energy than a sigma bond.
Mon Oct 29, 2018 1:34 am
Forum: Quantum Numbers and The H-Atom
Topic: Nodal Planes and test 2
Replies: 3
Views: 155

### Re: Nodal Planes and test 2

It's pretty easy to remember how many nodal planes are in an orbital by looking at the L value in quantum numbers, it is the same as how many nodal planes there are.
Mon Oct 29, 2018 1:30 am
Forum: Dipole Moments
Topic: London Forces
Replies: 7
Views: 430

### Re: London Forces

They are the weakest of any type of attractive force as they are the weakest intermolecular and intramolecular are stronger than intermolecular, but basically, since electrons can randomly gravitate towards one side it creates a temporary dipole where a weak negative side is created with the electro...
Mon Oct 29, 2018 1:21 am
Forum: Quantum Numbers and The H-Atom
Topic: s,p,d,f
Replies: 8
Views: 405

### Re: s,p,d,f

It is because, in terms of energy level, 3D is closer in energy to 4S orbital, than 4D thus when being filled with electrons it is written where it is
Mon Oct 29, 2018 1:16 am
Forum: Sigma & Pi Bonds
Topic: Detail of Bonds
Replies: 3
Views: 323

### Re: Detail of Bonds

What exactly are sigma and pi bonds? Are they a type of covalent bond or are they the same as a covalent bond? I went over them briefly in AP Chem but not too much for me to understand them.
Sun Oct 28, 2018 8:35 pm
Forum: Octet Exceptions
Topic: He, Li and Be
Replies: 3
Views: 291

### Re: He, Li and Be

The rule is that below the third period the octet rule is followed (except for the first 4 elements), but after is when extended orbitals come into play
Sun Oct 28, 2018 8:22 pm
Forum: Ionic & Covalent Bonds
Topic: Polyatomic Ions [ENDORSED]
Replies: 4
Views: 196

### Re: Polyatomic Ions[ENDORSED]

Is there a list of common polyatomic ions we should memorize?
Thu Oct 25, 2018 5:51 pm
Forum: Trends in The Periodic Table
Topic: Atomic, Covalent, and Ionic Radius
Replies: 5
Views: 277

### Re: Atomic, Covalent, and Ionic Radius

I think Covalent and Ionic Radii is the distance between the center of two atoms halved so if you look at the distance between the center of two atoms bonded together and halve it, it should be the covalent or ionic radii (depending on the bond between the atoms.
Thu Oct 25, 2018 5:48 pm
Forum: Trends in The Periodic Table
Topic: Isoeletronic
Replies: 3
Views: 169

### Re: Isoeletronic

While Atoms and ions may have the same amount of electrons it is important to remember they still have different properties, due the the difference in protons in the nucleus, so while ions may be isoelectronic, they can have different sizes and so forth.
Thu Oct 25, 2018 5:46 pm
Forum: Trends in The Periodic Table
Topic: Removing 2nd Electron
Replies: 9
Views: 327

### Re: Removing 2nd Electron

Removing the second electron is harder because as stated in class the atom becomes a cation (which normally attract electrons from other atoms) so it pulls on the electron more than before through a high Zeffective.
Sun Oct 21, 2018 11:37 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electron Spin States?
Replies: 4
Views: 87

### Re: Electron Spin States?

My assumption is that the spin affected the photon by centrifugal force if the electron is spinning up then the spectral line will be sent upwards and if it spinning downward then the spectral line will be sent lower, which can be seen in the figure drawn by Lavelle in class as the two spectral line...
Sun Oct 21, 2018 11:31 pm
Forum: Trends in The Periodic Table
Topic: electron affinity [ENDORSED]
Replies: 15
Views: 773

### Re: electron affinity[ENDORSED]

Florine is the most electronegative atom, using that fact you can establish a variety of periodic trends from the table, as you move from left to right on a period all subshells become smaller ever so slightly due to the increase in protons, and as you move from top to bottom the radius increases by...
Sun Oct 21, 2018 11:20 pm
Forum: Properties of Electrons
Topic: Atomic Spectra
Replies: 4
Views: 214

### Re: Atomic Spectra

The difference between the Ballmer Series and the Lyman series is only the region because that is by definition what makes it in the series. The wavelength of any photon that is emitted from an electron dropping energy levels in the UV spectrum belongs to the Lyman Series and if it falls in the visi...