Search found 74 matches
- Thu Mar 14, 2019 1:34 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Catalyst vs. Intermediate
- Replies: 8
- Views: 822
Re: Catalyst vs. Intermediate
A catalyst can be found in the beginning of the reaction, while an intermediate is found in the later steps.
- Thu Mar 14, 2019 1:30 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Units for K
- Replies: 4
- Views: 848
Re: Units for K
The units for k change depending on the order so that it can produce the correct units for the rate which is always in molarity per second.
- Thu Mar 14, 2019 1:23 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: comparing forward and reverse rates
- Replies: 4
- Views: 472
Re: comparing forward and reverse rates
The rate constants are different from the actual rate of the forward and reverse reaction. Also, the rate constant does not necessarily correspond to the rate of the reaction as it also depends on the concentrations and the order of the species.
- Sat Mar 09, 2019 11:21 pm
- Forum: Zero Order Reactions
- Topic: Half-life
- Replies: 6
- Views: 941
Half-life
What exactly is a half-life? I do not understand the concept behind this.
- Sat Mar 09, 2019 11:19 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Microscopic reversibility
- Replies: 4
- Views: 495
Re: Microscopic reversibility
Microscopic reversibility basically says that the reaction has the same path for both the forward and reverse directions.
- Sat Mar 09, 2019 11:14 pm
- Forum: First Order Reactions
- Topic: Half-Life 1st Order Reaction
- Replies: 6
- Views: 694
Re: Half-Life 1st Order Reaction
Yes, it is applicable to all first order rate reactions.
- Sat Mar 09, 2019 11:10 pm
- Forum: General Rate Laws
- Topic: integrals
- Replies: 8
- Views: 1010
Re: integrals
You can find help in the class resources section. Also, you just need to understand the concepts behind it and how to use the final equations that are produced by calculus.
- Fri Mar 01, 2019 5:03 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams (Using Platinum)
- Replies: 10
- Views: 1006
Cell Diagrams (Using Platinum)
When do we use platinum metal in the cell diagram, and why do we use platinum as the metal?
- Fri Mar 01, 2019 5:01 pm
- Forum: Balancing Redox Reactions
- Topic: Adding H+ and H2O
- Replies: 13
- Views: 2962
Re: Adding H+ and H2O
You must balance the elements other than oxygen and hydrogen first. Thus, you can do both.
- Fri Mar 01, 2019 4:57 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Finding n
- Replies: 12
- Views: 1150
Re: Finding n
Yes, n is the number of moles of electrons transferred and can be found through the oxidation or reduction half reactions.
- Sat Feb 23, 2019 1:45 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Favor ability of Cell portential
- Replies: 5
- Views: 646
Re: Favor ability of Cell portential
A positive cell potential means that the reaction is spontaneous, while a negative cell potential means that the reaction is not spontaneous.
- Sat Feb 23, 2019 1:39 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cathode vs. Anode
- Replies: 9
- Views: 831
Re: Cathode vs. Anode
The cathode is the reduction half reaction, while the anode is the oxidation half reaction. Basically, whichever chemical species being reduced will be the cathode and whichever chemical species being oxidized will be the anode.
- Sat Feb 23, 2019 1:36 am
- Forum: Balancing Redox Reactions
- Topic: Galcanic cell
- Replies: 3
- Views: 397
Re: Galcanic cell
A galvanic cell and voltaic cell are essentially the same and are interchangeable.
- Fri Feb 15, 2019 2:34 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: 758
Re: Finding W (degeneracy)
Yes, you raise it to the number of Avogadro's constant if they ask you to use one mole of a substance.
- Fri Feb 15, 2019 2:31 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Cv vs. Cp
- Replies: 6
- Views: 1053
Re: Cv vs. Cp
You use the value for Cv when the volume in the problem is constant, and you use the value for Cp when the pressure in the problem is constant.
- Fri Feb 15, 2019 2:28 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: ΔS=q/t
- Replies: 8
- Views: 938
Re: ΔS=q/t
Yes, you can use this when pressure is constant since the change in enthalpy is equal to q when pressure is constant.
- Fri Feb 08, 2019 9:08 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: closed systems
- Replies: 6
- Views: 637
Re: closed systems
Closed systems can have constant or changing pressure or volumes.
- Fri Feb 08, 2019 9:06 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: w=-PdeltaV
- Replies: 6
- Views: 603
Re: w=-PdeltaV
The first equation would only be used for questions that deal with reversible expansion, while the second equation of w=-PdeltaV would only be used for irreversible expansion.
- Fri Feb 08, 2019 9:04 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated System
- Replies: 4
- Views: 421
Re: Isolated System
Delta U would be 0 due to the fact that it is an isolated system. Since it is isolated, the internal energy will remain the same.
- Fri Feb 01, 2019 10:40 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Internal Energy of Isolated Systems
- Replies: 6
- Views: 2553
Re: Internal Energy of Isolated Systems
Yes, the change in internal energy of an isolated system is 0.
- Fri Feb 01, 2019 10:34 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Thermo Test/Midterm
- Replies: 9
- Views: 806
Re: Thermo Test/Midterm
Most likely not as we will be expected to already know how to draw Lewis structures from chem 14A.
- Fri Feb 01, 2019 10:33 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: closed vs isolated
- Replies: 14
- Views: 1106
Re: closed vs isolated
A closed system can only exchange energy with its surroundings, while the isolated system cannot exchange anything with its surroundings.
- Fri Feb 01, 2019 10:28 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Surroundings
- Replies: 11
- Views: 968
Re: Surroundings
When referring to surroundings in chemistry, we usually mean everything outside the system that we are looking at. This means there really is not a boundary that exists for how far the surroundings can go.
- Sat Jan 26, 2019 6:17 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Changes and Temperature
- Replies: 3
- Views: 381
Phase Changes and Temperature
Why does the temperature not change during a phase change even though more heat energy is being added?
- Sat Jan 26, 2019 6:14 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: heat capacity
- Replies: 7
- Views: 804
Re: heat capacity
Heat capacity is the amount of heat needed to increase the temperature of one gram of a substance by one degree. It has a state property because it is independent of how the substance was prepared.
- Sat Jan 26, 2019 6:08 pm
- Forum: Phase Changes & Related Calculations
- Topic: Why steam causes severe burns
- Replies: 9
- Views: 2003
Re: Why steam causes severe burns
Steam causes a more severe burn than that of boiling water even when they are at the same temperature due to the fact that steam holds more heat energy as becoming a vapor from a liquid requires a large amount of heat before it can change phases.
- Sat Jan 19, 2019 9:15 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: "Shifting"
- Replies: 15
- Views: 1811
Re: "Shifting"
Sitting to the left just means that the reactants are being favored over the products. Thus, if it is shifting left, the reactants are being favored to reach equilibrium.
- Sat Jan 19, 2019 9:11 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium constant in different temperatures
- Replies: 3
- Views: 305
Equilibrium constant in different temperatures
Why does the equilibrium constant change when the temperature changes?
- Sat Jan 19, 2019 9:07 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ignoring solids
- Replies: 6
- Views: 793
Re: ignoring solids
We leave out solids and liquids because they do not affect the equilibrium. We only account for species in the aqueous and gas phases when calculating equilibrium.
- Sat Jan 12, 2019 9:28 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE table and cubic expressions
- Replies: 1
- Views: 661
ICE table and cubic expressions
If an expression for an ice table becomes cubic and is no longer quadratic, how exactly would we solve for the x value to find the concentrations of the species?
- Sat Jan 12, 2019 9:25 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Tables
- Replies: 3
- Views: 261
Re: ICE Tables
You can calculate the C expression by combining the initial and change together. Then to find the value of the variable x in the C expression, you set all the expressions in the C category into the equilibrium constant form where products is over reactants and set it equal to the equilibrium constan...
- Sat Jan 12, 2019 9:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc and Kp
- Replies: 4
- Views: 428
Re: Kc and Kp
Both Kc and Kp are both equilibrium constants except that Kc is for molar concentrations while Kp is for partial pressures.
- Sat Dec 08, 2018 10:07 pm
- Forum: Lewis Acids & Bases
- Topic: Lewis Acid
- Replies: 6
- Views: 648
Lewis Acid
Why is HBr a stronger acid than HF?
- Sat Dec 08, 2018 10:05 pm
- Forum: Conjugate Acids & Bases
- Topic: NH3, acid or base?
- Replies: 12
- Views: 8283
Re: NH3, acid or base?
Yes, in most cases in which we work with NH3, it is considered in the terms of bronsted base.
- Sat Dec 08, 2018 10:02 pm
- Forum: Bronsted Acids & Bases
- Topic: KOH
- Replies: 1
- Views: 775
Re: KOH
You would draw the lewis structure in terms of ionic compounds as it is not covalent, so thus you would draw K with a plus charge next to OH with a negative charge while showing the paired shared and lone electrons on and between the O and H. KOH is considered a strong lewis base and is usually not ...
- Sat Dec 08, 2018 9:55 pm
- Forum: Bronsted Acids & Bases
- Topic: Strong acid
- Replies: 6
- Views: 846
Re: Strong acid
HCl is a strong acid as the most of the halogens in group 7 except flourine form strong acids due to the fact that they pull the electron density from hydrogen, and as it goes down the group the bond gets weaker and thus increases the strength of the acidity.
- Sat Dec 08, 2018 9:50 pm
- Forum: Bronsted Acids & Bases
- Topic: Strong base
- Replies: 5
- Views: 766
Re: Strong base
NaOH is a strong base because any hydroxides bonded to group 1 elements are considered strong bases.
- Sat Dec 01, 2018 8:50 pm
- Forum: Naming
- Topic: Water as a ligand
- Replies: 4
- Views: 190
Re: Water as a ligand
It should be written as OH2 when you want to demonstrate that the oxygen is bonding to the central transition metal.
- Sat Dec 01, 2018 8:48 pm
- Forum: Lewis Acids & Bases
- Topic: Lewis vs Bronsted
- Replies: 2
- Views: 303
Lewis vs Bronsted
Can someone explain to me the difference between Lewis(acids and bases) and Bronsted(acids and bases)?
- Sat Dec 01, 2018 8:43 pm
- Forum: Naming
- Topic: Spaces in naming
- Replies: 2
- Views: 298
Re: Spaces in naming
You should write it without spaces just to be safe and yes you add an O to anionic ligands.
- Sat Dec 01, 2018 8:36 pm
- Forum: Naming
- Topic: Oxidation State
- Replies: 4
- Views: 369
Re: Oxidation State
You calculate the oxidation state of the transition metal by first finding the overall charge of the ligands attached to it. After you have found that, you will want to look at the overall charge of the whole compound. You should then be able to find the oxidation state of the transition metal as it...
- Sat Nov 24, 2018 11:23 pm
- Forum: Hybridization
- Topic: Hybridization when dealing with pi and sigma bonds
- Replies: 1
- Views: 191
Hybridization when dealing with pi and sigma bonds
How come hybridization does not occur when forming pi bonds, but it does occur when forming sigma bonds?
- Sat Nov 24, 2018 11:21 pm
- Forum: Sigma & Pi Bonds
- Topic: Double Bonds
- Replies: 9
- Views: 1053
Re: Double Bonds
Yes, double bonds consist of one sigma bond and one pi bond.
- Sat Nov 24, 2018 11:20 pm
- Forum: Sigma & Pi Bonds
- Topic: Sigma and Pi Bonds
- Replies: 2
- Views: 174
Re: Sigma and Pi Bonds
Yes, sigma bonds are longer than pi bonds since pi bonds have a larger electron density and thus have greater attraction between the electrons and the nucleus's protons. Thus, pi bonds are shorter than sigma bonds.
- Sat Nov 24, 2018 4:23 pm
- Forum: Hybridization
- Topic: Test 3
- Replies: 13
- Views: 1209
Re: Test 3
The test will be on everything after the midterm to now. Essentially, you must understand the last concepts in chemical bonding, intermolecular forces, and both VSEPR and valence bond theory.
- Sat Nov 17, 2018 1:48 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Drawings of Molecular Shape
- Replies: 2
- Views: 291
Drawings of Molecular Shape
Do we need to understand how to draw the molecular shape in which it shows how the atoms are in different dimensions using techniques, such as dotted lines?
- Sat Nov 17, 2018 1:42 pm
- Forum: Hybridization
- Topic: Hybridization for VSPER model
- Replies: 2
- Views: 227
Re: Hybridization for VSPER model
Yes, they are just considered one electron density.
- Sat Nov 17, 2018 1:39 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: CH4 HW 4.43 6TH EDITION
- Replies: 1
- Views: 153
Re: CH4 HW 4.43 6TH EDITION
As the s-character of a hybrid orbital increases, the bond angle increases.
- Sat Nov 17, 2018 1:32 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Seesaw Shape
- Replies: 2
- Views: 250
Re: Seesaw Shape
Yes, you are correct the angle is actually less than 90 degrees due to the electron repulsion from the electron lone pair.
- Fri Nov 09, 2018 9:48 am
- Forum: Dipole Moments
- Topic: Dipole induced dipole
- Replies: 3
- Views: 361
Dipole induced dipole
How exactly does a dipole induce another dipole onto a neutral atom if the neutral atom only has London dispersion forces?
- Fri Nov 09, 2018 9:45 am
- Forum: Bond Lengths & Energies
- Topic: MIDTERM Bond Length Question
- Replies: 15
- Views: 1620
Re: MIDTERM Bond Length Question
Since they actually exist as a hybridization resonance structure, the true bond lengths exist between 120 and 140. We need further experimental data to get a more accurate answer of the true bond length.
- Fri Nov 09, 2018 9:23 am
- Forum: Bond Lengths & Energies
- Topic: Larger to weaker bond correlation
- Replies: 3
- Views: 369
Re: Larger to weaker bond correlation
A larger bond results in a weaker bond due to the fact that there is more distance the bond is covering. Using coulomb's law, F=(K(q1*q2))/r^2, as distance, r, increases, the force becomes weaker as it is inversely proportional to force.
- Fri Nov 09, 2018 9:15 am
- Forum: Bond Lengths & Energies
- Topic: Dispersion Force/State of Matter Correlation
- Replies: 2
- Views: 257
Re: Dispersion Force/State of Matter Correlation
Dispersion forces increased as we go down the periodic table due to increased electrons which lead to more London dispersion forces as there is more temporary interactions between electrons. As these forces increased, atoms are held more tightly together, which leads to states, such as liquids and s...
- Fri Nov 02, 2018 4:57 pm
- Forum: Lewis Structures
- Topic: How to decide central atom?
- Replies: 6
- Views: 973
How to decide central atom?
Is the central atom in the Lewis structures based off of which atom has the lowest electronegativity or which atom has the lowest ionization energy?
- Fri Nov 02, 2018 4:54 pm
- Forum: Lewis Structures
- Topic: 6th edition 3.35b Lewis Structure of BrO-
- Replies: 1
- Views: 173
Re: 6th edition 3.35b Lewis Structure of BrO-
Yes, the oxygen carries the formal charge due to the fact that it is the most electronegative. Also, because bromine can only have one shared bond pair, which forces oxygen to hold the negative charge.
- Fri Nov 02, 2018 4:47 pm
- Forum: Lewis Structures
- Topic: Lewis Structure Shortcuts
- Replies: 1
- Views: 429
Re: Lewis Structure Shortcuts
A shortcut you can use when dealing with larger molecules, such as CH3NH2, is that you split up the molecule by the different compounds within it. In this case, you place the carbon with the three hydrogen atoms and the nitrogen with the 2 hydrogen atoms as there are two separate compounds within it...
- Fri Nov 02, 2018 4:42 pm
- Forum: Lewis Structures
- Topic: H Element
- Replies: 2
- Views: 264
Re: H Element
Hydrogen atoms can only form one bond known as a duet as it cannot form an octet. In covalent bonding, a central atom must have enough available electrons to form at least two bonds.
- Sun Oct 28, 2018 12:00 pm
- Forum: Ionic & Covalent Bonds
- Topic: Second ionization of alkali metals
- Replies: 3
- Views: 781
Second ionization of alkali metals
Why does the second ionization energy of the alkali metals increase so dramatically after the first ionization energy?
- Sun Oct 28, 2018 11:47 am
- Forum: Ionic & Covalent Bonds
- Topic: Ground State Electron Configurations
- Replies: 7
- Views: 694
Re: Ground State Electron Configurations
An element like Argon is used as it is the closest noble gas that can be used for writing short-hand ground state electron configurations based off of noble gases.
- Sun Oct 28, 2018 11:44 am
- Forum: Ionic & Covalent Bonds
- Topic: Valence electrons
- Replies: 8
- Views: 1519
Re: Valence electrons
Valence electrons can be determined by looking at their group number at the top. For, example chlorine is in group 7, so thus it has 7 electrons. In cases of ions like Ag+, one should write out the ground state electron configuration to figure out the valance electrons as they differ from the regula...
- Sun Oct 28, 2018 11:34 am
- Forum: Ionic & Covalent Bonds
- Topic: ionization energy [ENDORSED]
- Replies: 4
- Views: 242
Re: ionization energy [ENDORSED]
Removing the second electron from an atom is more difficult due to the higher ionization energy required to remove it. This is due to the fact that the nuclear charge has a stronger pull on the remaining electrons as there is now one less electron. Thus, with a stronger attraction due to a positive ...
- Fri Oct 19, 2018 1:37 pm
- Forum: Trends in The Periodic Table
- Topic: Atomic Radius [ENDORSED]
- Replies: 4
- Views: 712
Re: Atomic Radius [ENDORSED]
The atomic radius would not increase across a period due to the fact that the quantum number stays the same and that there are now more protons, which essentially produces a larger effective nuclear charge on the electrons.
- Fri Oct 19, 2018 1:31 pm
- Forum: *Shrodinger Equation
- Topic: Schrodinger Equation
- Replies: 2
- Views: 314
Schrodinger Equation
To what extent of the Shrodinger Equation will we have to understand for the upcoming test on quantum? Do we just need to understand the concepts behind it or must we understand how to calculate solutions using the equation as well?
- Fri Oct 19, 2018 1:29 pm
- Forum: Properties of Electrons
- Topic: Rydberg formula
- Replies: 5
- Views: 474
Re: Rydberg formula
Adding on, you can use the formula E=hR(1/n^2(final)-1/n^2(initial)) to find the energy difference in one step. Then plugging it back into the equation E=hv to find frequency and then using C=wavelength(frequency) to find wavelength.
- Fri Oct 19, 2018 1:25 pm
- Forum: Properties of Electrons
- Topic: Nodal Plane
- Replies: 5
- Views: 907
Re: Nodal Plane
A nodal plane is a plane in space where the electron probability reaches zero. Usually, there exists nodal planes at the nucleus. The s subshell is the only subshell that is symmetrical and thus does not have a nodal plane.
- Sun Oct 14, 2018 6:27 pm
- Forum: Trends in The Periodic Table
- Topic: 6th Edition Ch.2 Number 93
- Replies: 2
- Views: 165
6th Edition Ch.2 Number 93
The solutions manual suggests that A=Na B=Cl C=Na ion and D=Cl ion based off the diagram given, but chlorine should have a smaller atomic radius than that of sodium at ground state. So is this a typo and if not can someone explain to me how they got that answer?
- Sun Oct 14, 2018 10:16 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: G and H orbitals
- Replies: 1
- Views: 308
G and H orbitals
Is there any element that actually incorporates g and h orbitals and is it even under the scope of our class that we must learn this?
- Sun Oct 14, 2018 10:10 am
- Forum: Properties of Light
- Topic: C=Wavelength*Frequency
- Replies: 11
- Views: 3287
Re: C=Wavelength*Frequency
C is a constant value for the speed of light which is 3.00X10^8 meters/second.
- Sun Oct 14, 2018 10:09 am
- Forum: Properties of Light
- Topic: Measuring Wavelength
- Replies: 5
- Views: 588
Re: Measuring Wavelength
Most likely there is not a maximum for the length of a wavelength. We most likely will not have to deal with this as it is probably outside the scope of which this class teaches as it was not mentioned in lecture.
- Sun Oct 14, 2018 9:57 am
- Forum: Properties of Electrons
- Topic: photoelectric effect question
- Replies: 2
- Views: 256
Re: photoelectric effect question
Adding on to the earlier response before me, the formula, Ke=1/2mv^2, is just a physics formula we used to find the kinetic energy of a system. In this case, we are trying to find the kinetic energy held by the released electron that is left over after subtracting the energy given by the light sourc...
- Sun Oct 07, 2018 11:18 pm
- Forum: SI Units, Unit Conversions
- Topic: Dilutions Equations
- Replies: 2
- Views: 370
Dilutions Equations
I was confused when to use the equation M1V1=M2V2 vs the equation molarity=moles/volume when doing dilution problems?
- Thu Oct 04, 2018 1:42 am
- Forum: Limiting Reactant Calculations
- Topic: Significant figures in textbook 7th edition [ENDORSED]
- Replies: 5
- Views: 383
Significant figures in textbook 7th edition [ENDORSED]
Some of the solutions in the back of the textbook have different significant figures in their answers than what was given. An example would be that the given has three significant figures, while the solution in the back has four significant figures. Why is that if anyone knows?
- Thu Oct 04, 2018 1:39 am
- Forum: Limiting Reactant Calculations
- Topic: Combustion Analysis? [ENDORSED]
- Replies: 7
- Views: 453
Re: Combustion Analysis? [ENDORSED]
It might appear on the test just as an equation to be used for another topic like limiting reagents.
- Thu Oct 04, 2018 1:37 am
- Forum: Limiting Reactant Calculations
- Topic: Homework Questions [ENDORSED]
- Replies: 4
- Views: 389
Re: Homework Questions [ENDORSED]
You can do any seven questions out of all the categories as long as it is on the topics that we have already covered in class.