## Search found 60 matches

Tue Mar 12, 2019 4:55 pm
Forum: Zero Order Reactions
Topic: zero order in rate law
Replies: 7
Views: 413

### Re: zero order in rate law

If a reactant is a zero order reactant, it would not be included in the overall rate law since anything to the 0th power as an exponent would be one. Also since it is a 0th order, changes to the concentration of that reactant would have no effect on the rate and therefore, it make sense that it woul...
Tue Mar 12, 2019 4:47 pm
Forum: Experimental Details
Topic: Pre Equilibruim Approach
Replies: 6
Views: 983

### Re: Pre Equilibruim Approach

The pre-equilibrium approach starts with has a fast elementary step followed by a slow elementary step. With the pre-equilibrium approach, we can't have intermediates between the fast and slow in the rate law. This approach also doesn't factor in account the reverse reaction that is occurring in the...
Tue Mar 12, 2019 4:42 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: order of a cell diagram
Replies: 4
Views: 175

### Re: order of a cell diagram

The order of a cell diagram would have a structure of: anode|gas, liquid| aq. molecule || aq. molecule|gas, liquid|cathode. Everything to the left of the || is the oxidation reaction while everything to the right of the || is the reduction reaction. H+ if it is in aqueous state would be in the secti...
Tue Mar 05, 2019 5:05 pm
Forum: General Rate Laws
Topic: Order of Reaction
Replies: 6
Views: 261

### Re: Order of Reaction

The order of the reaction is determined by the sum of the orders of the reactants. If the rate=k[A][B]^2, A is first order and B is second order, therefore the overall reaction order is third order.
Tue Mar 05, 2019 5:02 pm
Forum: Balancing Redox Reactions
Topic: Strength of reducing agent
Replies: 10
Views: 411

### Re: Strength of reducing agent

Reducing agents are most spontaneous when in oxidation half reactions and therefore they want to lose e-. In order to rank, we can compare the E⁰. The most negative value should be the strongest reducing agent.
Tue Mar 05, 2019 4:57 pm
Forum: Phase Changes & Related Calculations
Topic: Steam vs Boiling Water
Replies: 8
Views: 525

### Re: Steam vs Boiling Water

Steam has a greater amount of energy, and therefore heat, as it has both the heat energy of boiling water and latent heat of vaporization in comparison to just boiling water which is just the energy required to boil water.
Tue Feb 26, 2019 3:16 pm
Forum: Balancing Redox Reactions
Topic: Cell Diagram
Replies: 4
Views: 151

### Re: Cell Diagram

We would use an inert electrode in the cell diagram when the oxidization or reduction side do not have a solid metal. In Fe^3(aq) + e- --> Fe^2+(aq), we would use Pt(s) or C(graphite) to act as the filler metal since the oxidation/reduction side don't have a metal.
Tue Feb 26, 2019 3:01 pm
Forum: Balancing Redox Reactions
Topic: oxidized vs oxidizing agent
Replies: 3
Views: 68

### Re: oxidized vs oxidizing agent

Being oxidized mean that one of the reacting molecules loses its electrons. An oxidizing agent however is referring to molecules that accepts electrons to switch to be their reduced form.
Tue Feb 26, 2019 2:53 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E˚ vs E
Replies: 13
Views: 1716

### Re: E˚ vs E

E˚ means that it is under standard condition which is T=298K and P=1 atm. E would then be the cell potential at a different temperature and or pressure. We can assume standard condition unless stated otherwise.
Tue Feb 19, 2019 7:54 pm
Forum: Phase Changes & Related Calculations
Topic: Specific Heat of Ice
Replies: 3
Views: 1335

### Re: Specific Heat of Ice

Specific heat capacity of ice, 2.03 J/g*C, would be used when trying to find the heat needed to bring up the temperature of the ice before it melts. This specific heat capacity would be used in q=mCdeltaT which is a temperature change and not a phase change.
Tue Feb 19, 2019 5:23 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isobaric
Replies: 11
Views: 696

### Re: Isobaric

If there is no change in pressure, as stated as ΔP=0, then there is value for the pressure to be plugged in the equation of w =-PΔV. If the value of pressure or the change in volume are not given, then you can use -Δn*R*T to find work. At a constant pressure,qp equal to ΔH. You can also find q with ...
Tue Feb 19, 2019 5:08 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: What to do when temperature isn't given
Replies: 8
Views: 233

### Re: What to do when temperature isn't given

If your problem is at standard conditions, the temperature is 298K or 25C. Otherwise, it will give you a temperature value to calculate with. Pay attention to units as that can help determine if the temperature would be calculated in K or C.
Wed Feb 13, 2019 1:29 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Heating water + cooling
Replies: 2
Views: 127

### Re: Heating water + cooling

If we start out with qtotal = qsystem + qsurrounding, you can get qsystem=-qsurrounding if no energy can be lost to the surrounding. Therefore, if you pick ice to be your system and water to the be surrounding, qice=-qwater. which means that heat gained by ice will be from the heat of water, (making...
Wed Feb 13, 2019 1:23 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: state function
Replies: 4
Views: 149

### Re: state function

Work is not a state function along with heat and cell potential. Internal energy is a state function as at equilibrium, there is a set amount as delta Utotal = deltaU system + deltaU surrounding. Work and heat are path functions, so you can't find its value based on final - initial.
Wed Feb 13, 2019 1:17 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Finding W (degeneracy)
Replies: 4
Views: 365

### Re: Finding W (degeneracy)

If you are given mols of a substance, Avogadro's number (NA) will appear in the the raised power, times the number of amount of identical molecules/particles.
For example, when calculating the residual entropy of 1 mol of C6H5Br, w = 6 ^ 1*NA, therefore S = Kb*ln (6^1NA) = NA*Kb*ln6.
Tue Feb 05, 2019 10:58 pm
Forum: Calculating Work of Expansion
Topic: work done by system or on system
Replies: 3
Views: 173

### Re: work done by system or on system

q (heat) is positive when its has key words such as absorbed/gain energy and is negative when it released/emitted/loses energy. w (work) is positive when work is done on the system and negative when the system does or is doing the work.
Tue Feb 05, 2019 8:32 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Quick Conceptual question
Replies: 7
Views: 306

### Re: Quick Conceptual question

Enthalpy (H) refers to the heat in the system while entropy (S) can be thought of as the disorder of the system. They are connected by delta G = delta H - T*delta S. For enthalpy, use the 3 methods: Standard Enthalpy of Formation, Bond Enthalpy, and Hess's Law. In Entropy, changes in volume would us...
Tue Feb 05, 2019 7:27 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Reversible Processes
Replies: 2
Views: 132

### Re: Reversible Processes

A reversible process is a process whose direction can be "reversed" by inducing very very small changes to a system via its surroundings. Most of the time it occurs with a constant temperature/isothermic.
Mon Jan 28, 2019 10:53 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 2
Views: 105

### Re: Bond Enthalpies

To add, this is why bond enthalpy is the least accurate of the three methods since its value is made up from the average of data of many different molecules of different reactions.
Mon Jan 28, 2019 10:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Breaking Bonds
Replies: 4
Views: 167

### Re: Breaking Bonds

It is best to draw out the Lewis structures of all the reactants and the products in order to tell which bonds are broken/formed. From there, look for the difference in the reactants to the products of each atom to atom bond in order to tell what the net difference is. From the net difference, you w...
Mon Jan 28, 2019 10:30 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law (Method 1)
Replies: 4
Views: 203

### Re: Hess's Law (Method 1)

Since we do not know the delta H of the net reaction, we have to rely on the delta Hs of the intermediate reactions that can lead us to the net reaction. It is not necessarily adding the two delta H as we have to make sure first the you use the intermediate reactions correctly that would lead you th...
Thu Jan 24, 2019 12:08 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Specific Notation
Replies: 5
Views: 265

### Re: Specific Notation

Notation does matter when calculating K. Use brackets when dealing with concentration such as [PCl5]. Brackets are not require if you write out the value of the concentration of PCl5. As for the gaseous states, you don't not use brackets. If you want, you can use parentheses around P PCl5 like so (P...
Wed Jan 23, 2019 11:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reactions at Equilibrium
Replies: 1
Views: 83

### Re: Reactions at Equilibrium

I believe that the question will inform the reaction's reactant and/or products. And to know which way the reaction will run, compare Q and K. If Q>K, then the reaction will favor the reactant while if Q<K, then the reaction will favor the product.
Wed Jan 23, 2019 11:50 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Problem 12.45 (6th edition)
Replies: 2
Views: 307

### Re: Problem 12.45 (6th edition)

The trend is that the a smaller pKa/larger the Ka, the stronger the acid and the larger the pKb/smaller the Kb, the stronger the acid. Likewise, the smaller the pKb/larger the Kb, the stronger the base and the larger the pKA/smaller Ka, the stronger the base.
Wed Jan 16, 2019 11:32 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert Gases
Replies: 5
Views: 211

### Re: Inert Gases

Adding an inert gas won't have an effect on the equilibrium composition as inert gases do not want to interact/react as they are already stable.
Wed Jan 16, 2019 11:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Conjugates
Replies: 5
Views: 208

### Re: Conjugates

The conjugate seesaw describes the relationship between an acid and its conjugate base and also a base with tis conjugate acid. The acid or base and their conjugate are inversely proportionate in terms of strength. This is a seesaw as when the acid or base is stronger, the weaker the conjugate acid ...
Wed Jan 16, 2019 11:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentration
Replies: 4
Views: 180

### Re: Concentration

K stands for Equilibrium Constant which describes the reaction at equilibrium. Q is the reaction quotient which describes the reaction at any point in time. We compare K and Q as it will tell us whether the reaction is favoring the reactant, products, or neither. If Q>K, then he reaction favors the ...
Thu Jan 10, 2019 10:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q and K
Replies: 13
Views: 316

### Re: Q and K

The difference between Q and K is that Q is an expression that can be used to describe the composition of the reaction mixture at any time of the reaction. And also between Q and K, the reaction quotient Q at equilibrium is equal to the equilibrium constant K.
Thu Jan 10, 2019 10:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K vs Kp [ENDORSED]
Replies: 4
Views: 357

### Re: K vs Kp[ENDORSED]

K in general is an expression to describe the composition of the reaction at equilibrium. Kp is for concentration of partial pressure of the reactants/products while Kc is used in concentration of the reactants/products. Solid and liquids aren't included in the equilibrium constant expression, only ...
Tue Jan 08, 2019 10:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Leaning to the left/right
Replies: 4
Views: 184

### Re: Leaning to the left/right

I believe this phrase is talking about which side the equilibrium will move/shift, to the left or right side of the reaction. It is talking about moving back and forth between the forward and backward reaction.
Mon Dec 03, 2018 10:57 pm
Forum: Naming
Topic: Order of Ligand Naming
Replies: 6
Views: 209

### Re: Order of Ligand Naming

If there are multiple ligands, the order the ligands are named should follow alphabetical order. If the coordinate compound is PtCl2(NO2)2, then the Cl would be named before the NO2.
Mon Dec 03, 2018 10:54 pm
Forum: Naming
Topic: Prefix bis, tris, tetrakis, etc. [ENDORSED]
Replies: 5
Views: 309

### Re: Prefix bis, tris, tetrakis, etc.[ENDORSED]

Di-, tri-, and tetra- should be used for multiple monodentate ligands while bis-, tris-, tetrakis- would be used for for multiple polydentate ligands.
Mon Dec 03, 2018 10:39 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted Acids and Bases?
Replies: 2
Views: 130

### Re: Bronsted Acids and Bases?

Lewis Acid accepts e- pair and Lewis Base donates e- pairs. Bronsted Acid donates H+ and Bronsted Base accepts H+. Bronsted Acid and Base only involve Hydrogen while Lewis Acid and Base deals with all atoms/molecules. All Bronsted Acids/Bases are Lewis Acids/Bases are Lewis Acids/Bases for this reas...
Tue Nov 27, 2018 10:51 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: ion-ion bond vs. H-bond
Replies: 4
Views: 383

### Re: ion-ion bond vs. H-bond

Ion-ion bonds are stronger than hydrogen bond. Ion-ion bonds result in solids as seen in an example with Na+ and Cl-. Together Na+ and Cl- will form an ordered lattice. Hydrogen bonding comes second as this is still the strongest type of intermolecular forces since the difference in electronegativit...
Tue Nov 27, 2018 10:44 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw Shape Bond Angles
Replies: 8
Views: 351

### Re: Seesaw Shape Bond Angles

The bond angles in a see saw shape molecule are less than 120 in equatorial and less than 90 in axial.
Tue Nov 27, 2018 10:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Angle Distorted
Replies: 4
Views: 159

### Re: Angle Distorted

Angle distortion means that the angles in the bond has been changed from the typical bond angle arrangement. This is most likely the result of lone pair repulsion which allows electrons in the lone pair to push the other regions of electron density in the molecule away, making the bond angles now di...
Sat Nov 24, 2018 12:53 am
Forum: Ionic & Covalent Bonds
Topic: Bond Lengths
Replies: 10
Views: 547

### Re: Bond Lengths

Due to resonance, the most stable structure of the nitrate will be an average of the bonds nitrate holds which is both a single and double bond. As an overall molecule, nitrate's structure will even out and be an inbetween version of a single and double bond. Therefore, the average of 120 and 140 is...
Sat Nov 24, 2018 12:49 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR RULE 3
Replies: 4
Views: 186

### Re: VSEPR RULE 3

If would make sense if single, double, triple bonds are considered the same as each of these bond still has the same purpose of linking atoms to the other atoms. Each atom holds electrons and therefore each bond is linked to one region of electron density.
Sat Nov 24, 2018 12:40 am
Forum: Bond Lengths & Energies
Topic: H bonding
Replies: 14
Views: 706

### Re: H bonding

As hydrogen bonding is on the stronger side of intermolecular forces, it requires more energy to break this bond. This results in high boiling points since it requires more energy to separate the molecules.
Thu Nov 15, 2018 9:28 pm
Forum: Octet Exceptions
Topic: The center atom
Replies: 20
Views: 1013

### Re: The center atom

O would be the central atom since it is the least ionization energy and can form more bond than the H and Cl. It would not H since H can only have one bond and it would not be Cl either since can normally only form one bond.
Thu Nov 15, 2018 9:21 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 10
Views: 790

### Re: Formal Charge

It is better to follow and determine molecular structures base on the formal charger as there are exceptions to the octet rule. Formal charge is the best way to make sure the Lewis structure is in the most stable state it can be as well as writing out the right Lewis structure since the formal charg...
Thu Nov 15, 2018 9:18 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Vespr Formula
Replies: 6
Views: 228

### Re: Vespr Formula

The VSEPR formula is simply the letter A follow by X with a subscript of how many atoms are attached to the central atom you pick and E with the subscript of the number of lone pairs of electrons attached to the central atom as well.
Thu Nov 08, 2018 9:08 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: Van Der Waal forces
Replies: 3
Views: 622

### Re: Van Der Waal forces

Dipoles have intermolecular forces that are between two or more different molecules. Dipole-dipole forces are between opposite partial charges on two different polar molecules that wants to attract each other. In an induced dipole-dipole, it is a coercive force in which the one causes the other to b...
Thu Nov 08, 2018 8:58 pm
Forum: Octet Exceptions
Topic: Octet vs formal charge
Replies: 16
Views: 1048

### Re: Octet vs formal charge

I believe having the correct formal charge is more important than having a full octet. As seen in some examples with radicals and expanded octets, it is alright if the atom does not have an entire octet, however, your formal charges between the atoms should be equal to the formal charge of the molec...
Mon Nov 05, 2018 3:29 pm
Forum: Octet Exceptions
Topic: Expanded Octet [ENDORSED]
Replies: 5
Views: 143

### Re: Expanded Octet[ENDORSED]

Elements are allowed an expanded octet if they are n=3 and after. They are able to do so as there is a d orbital where they can be electrons in. Since n=3, l can be 0, 1, or 2 and therefore corresponds with s, p, and d orbitals.
Wed Oct 31, 2018 10:49 pm
Forum: Lewis Structures
Topic: Central Atom
Replies: 13
Views: 350

### Re: Central Atom

The central atom is normally determined by the element with the lowest ionization energy, in your case with the example, CH3OH, carbon. However, if its finding the Lewis structure for HOCO for example, then you would write it straight out like that (H-O-C-O) since it is written in that manner.
Wed Oct 31, 2018 10:41 pm
Forum: Ionic & Covalent Bonds
Topic: p block atoms
Replies: 4
Views: 169

### Re: p block atoms

Atoms from n=3 and on, such as P, S, and Cl can have more than 8 valence electrons as they had a d-orbital to put electrons there. They are able to have an expanded octet since there is an empty orbital (d) that is not used. Atoms on row 2 can't have expanded octets.
Wed Oct 31, 2018 10:34 pm
Forum: Ionic & Covalent Bonds
Topic: octet rule
Replies: 11
Views: 373

### Re: octet rule

The octet rule concerns atoms wanting to share their electrons in order to complete their valence shell and be the most stable they can. To do this, atom want to either complete their last orbital shell or get rids of some on the last and share/lend it to another atom. They would want to share and h...
Tue Oct 23, 2018 11:03 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Bohr Frequency Condition
Replies: 2
Views: 156

### Re: Bohr Frequency Condition

En is actually the energy of an electron in a energy level which is denoted by n. If it is a problem dealing with atomic spectra and the Rydberg Equation, such as asking to find the frequency of a proton that was emitted as it transitioned from the 5th or 3rd energy level, then you have 2 n and ther...
Tue Oct 23, 2018 10:43 pm
Forum: Quantum Numbers and The H-Atom
Topic: Principle Quantum #
Replies: 5
Views: 319

### Re: Principle Quantum #

n is the energy level. It describes the type of orbital the electron will be located in. If n=1, then it is at the ground state/first energy level where energy is the lowest. The higher the n, the more energy there are at those energy levels.
Tue Oct 23, 2018 10:31 pm
Forum: Student Social/Study Group
Replies: 5
Views: 308

For uncertainty questions, delta v depends on the part after the ±. So in the case of your example, 23 ± 0.1 m/s, just multiple the uncertainty part (± 0.1 m/s) by two as the possible values is up and down at 22.9 m/s and 23.1 m/s.
Thu Oct 18, 2018 9:16 pm
Forum: Properties of Light
Topic: calculating wavelength
Replies: 10
Views: 576

### Re: calculating wavelength

You should use De Broglie to solve for the wavelength of a mass. Atoms and objects have mass but light does not. The p (momentum) of De Broglie can be split into (mass*velocity) and that is where mass can be seen. Between the two formula, it is best to just list all the given values and put question...
Thu Oct 18, 2018 9:04 pm
Forum: Properties of Light
Topic: color of light
Replies: 11
Views: 451

### Re: color of light

Both can be used to determine the color of visible light. You can identity the specific color of light by mainly by wavelength but if you know the wavelength you find the frequency of light and compare it to what color that would be as well, by the equation speed of light = frequency x wavelength. T...
Thu Oct 18, 2018 8:44 pm
Forum: *Shrodinger Equation
Topic: Using the Equation
Replies: 2
Views: 127

### Re: Using the Equation

The Schrodinger's Wave Question is meant to describe where electrons are in an atom and basically the physical changes of the quantum state of an atom that occurs over time. It's just important to know that Ψ represent the height of the wave at position x,y,z and Ψ^2 is the probability of finding an...
Thu Oct 11, 2018 10:24 pm
Forum: Empirical & Molecular Formulas
Topic: Is it possible for the Empirical and Molecular formula to be the same? [ENDORSED]
Replies: 8
Views: 438

### Re: Is it possible for the Empirical and Molecular formula to be the same?[ENDORSED]

Empirical and molecular formula can be the exact same as each other. The empirical formula is the simplest ratio of elements in that molecule, however, the molecular formula is merely the exact/actual ratio of elements. It could be that a molecule is in both its empirical and molecular formula alrea...
Thu Oct 11, 2018 10:02 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Mass percent composition [ENDORSED]
Replies: 4
Views: 365

### Re: Mass percent composition[ENDORSED]

Mass percent composition is the proportion of an element of that whole molecule. It would be the mass of that element divided by the entire molar mass of a compound.
Thu Oct 11, 2018 9:57 pm
Forum: Significant Figures
Topic: sig figs in periodic table
Replies: 6
Views: 363

### Re: sig figs in periodic table

It is best to use the all the significant figures from the periodic table as well as solving your way through a problem with multiplication, division, addition, etc. This way the calculation will be as exact as possible for the final answer. Only by the very end do you round the answers according to...
Mon Oct 01, 2018 10:17 pm
Forum: SI Units, Unit Conversions
Topic: Naming Compounds
Replies: 8
Views: 337

### Re: Naming Compounds

There is no trick to memorizing and knowing how to write in molecular terms for cases such as Calcium Sulfide. It is something to either study or pick up. I was say the best way to know the name of compounds would be to learn the common polyatomic ions in groups according to the patterns in their na...
Mon Oct 01, 2018 10:08 pm
Forum: SI Units, Unit Conversions
Topic: Grams/mole
Replies: 12
Views: 531

### Re: Grams/mole

g/mol and g.mol^-1 are two different notation but they mean the same things. the ^-1 denotes that mol will be in the denominator. I like to use g/mol to see it fully written out and for it to already be in that form when I use it to solve problems.
Mon Oct 01, 2018 9:44 pm
Forum: General Science Questions
Topic: Periodic Table
Replies: 16
Views: 888

### Re: Periodic Table

I tend to use the entirety of the atomic weight listed for that element on the periodic table. I only round at the very end for the final answer and that depends on how many significant figures are used in the given values that is stated at the very beginning from the question.