## Search found 69 matches

Thu Mar 14, 2019 7:48 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating Equilibrium Composition
Replies: 2
Views: 142

### Re: Calculating Equilibrium Composition

Whichever value that leads to no negative concentrations when plugging back in to the ICE table.
Thu Mar 14, 2019 7:47 am
Forum: General Rate Laws
Topic: Half-life formulas
Replies: 1
Views: 118

### Re: Half-life formulas

They can be found on the Constants and Formulas sheet.

0 order: t1/2 = [A]o/2k

1st order: t1/2 = 0.693/ k

2nd order: t1/2 = 1/k [A]o
Thu Mar 14, 2019 7:45 am
Forum: First Order Reactions
Topic: Writing First Order Reactions
Replies: 4
Views: 386

### Re: Writing First Order Reactions

Either way is fine as they are equivalent.
Thu Mar 07, 2019 5:31 pm
Forum: General Rate Laws
Topic: Average rate vs unique rate vs instantaneous rate
Replies: 2
Views: 188

### Re: Average rate vs unique rate vs instantaneous rate

Average rate: Total Change/Total Time
Instantaneous rate: The rate of change at a particular moment
Unique rate: The rate of change of a species divided by its stoichiometric coefficient. For reactants it's negative, as it is disappearing.
Thu Mar 07, 2019 5:27 pm
Forum: Balancing Redox Reactions
Topic: balancing water
Replies: 8
Views: 371

### Re: balancing water

If there is water on both sides, just cancel them out till there is only water on one side. The solutions manual most likely just wants you to see how much water they added to both sides while trying to find the answer.
Thu Mar 07, 2019 5:25 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating Eºcell
Replies: 2
Views: 164

### Re: Calculating Eºcell

For simplicity, only flip the sign when you have the two reduction equations in front of you and you want to make the anode equation. Like in Hess's Law examples, you just add the two reduction potentials. That is what the equation Eºcell = Eºcathode - Eºanode is basically doing. So make sure to not...
Fri Mar 01, 2019 6:24 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram
Replies: 4
Views: 327

### Re: Cell Diagram

Just to confirm, does order matter when drawing a cell diagram (with regard to on the anode or cathode side, does it matter which species goes first?)
Fri Mar 01, 2019 6:20 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Gas phase products
Replies: 3
Views: 225

### Re: Gas phase products

Why is the reverse reaction very unlikely to occur?
Fri Mar 01, 2019 6:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams (Using Platinum)
Replies: 10
Views: 389

### Re: Cell Diagrams (Using Platinum)

But why in the textbook solutions there occasionally is platinum on both sides of the salt bridge, even though one side has a solid?
Fri Feb 22, 2019 3:33 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibs Free Energy and Enthalpy
Replies: 2
Views: 173

### Re: Gibs Free Energy and Enthalpy

Using the equation Delta G = Delta H - T Delta S, knowing that the reaction is exothermic would increase the chances of Delta G being negative and thus spontaneous.
Fri Feb 22, 2019 3:32 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Change in Gibbs Free Energy
Replies: 3
Views: 275

### Re: Change in Gibbs Free Energy

They are connected by the equation Delta G = Delta G with a degree + RTlnQ.
Fri Feb 22, 2019 3:30 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy
Replies: 2
Views: 124

### Re: Gibbs Free Energy

I believe that Gibbs Free Energy is a term that scientists defined based solely on enthalpy and entropy. For example, a machine cannot directly find the delta G of a reaction on its own. The machine will look at the change in enthalpy and entropy to calculate delta G.
Thu Feb 14, 2019 11:08 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Comparing complex molecules
Replies: 2
Views: 152

### Re: Comparing complex molecules

How large the molecule is. An easy way to do this is by calculating the molar mass. In what state the molecule is in (gaseous has the most entropy). How many unique atoms are within the molecule to allow for more states.
Thu Feb 14, 2019 11:06 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Change Diagram of Water
Replies: 6
Views: 298

### Re: Phase Change Diagram of Water

The best way to understand this is by looking at an energy diagram as water goes from solid to gas. During vaporization, you can see that there is a plateau during 100C as liquid water must convert into water. The energy of water only increases once it gets into the gaseous form.
Thu Feb 14, 2019 10:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp equilibrium constant
Replies: 6
Views: 439

### Re: Kp equilibrium constant

Why do we not add in units when calculating for Kp or Kc? We are plugging in the partial pressures and concentrations, yet we simply ignore the units?
Sun Feb 10, 2019 8:55 pm
Forum: Phase Changes & Related Calculations
Topic: 4.18J or 0.38J
Replies: 8
Views: 632

### Re: 4.18J or 0.38J

Are you referring to the specific heat capacity of water?
Sun Feb 10, 2019 8:54 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Molecular Interlude
Replies: 5
Views: 469

### Re: Molecular Interlude

Don't we need to know that the Cp for a single atom is 5R/2 and the Cv for a single atom is 3R/2?
Sun Feb 10, 2019 8:52 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 3rd Law of Thermodynamics
Replies: 2
Views: 149

### Re: 3rd Law of Thermodynamics

The units always depend on what specific term the question is looking for.
Sun Feb 10, 2019 8:49 pm
Forum: Calculating Work of Expansion
Topic: Work sign convention
Replies: 3
Views: 184

### Re: Work sign convention

W < 0 when work is done by the system
W > 0 when work is done to the system
Sun Feb 10, 2019 8:42 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: complex molecules
Replies: 8
Views: 726

### Re: complex molecules

With a larger molecule, there are more possibilities to where the electrons/atoms position themselves in relation to each other.
Sun Feb 10, 2019 8:26 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U for Reversible and Irreversible
Replies: 3
Views: 329

### Re: Delta U for Reversible and Irreversible

Delta U is equal to 0 when the work done by the system is equally replaced by heat being added into the system.
Fri Jan 25, 2019 12:03 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Test 1
Replies: 9
Views: 366

### Re: Test 1

If pOH and pH always add up to 14, is it possible to have a negative pH? What about a pH higher than 14?
Fri Jan 25, 2019 12:01 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pKa and pH
Replies: 2
Views: 174

### Re: pKa and pH

pH can be used to find the amount of hydronium ions in a certain reaction. pKa allows you to solve for reaction quantities by giving you the equilibrium constant of the reaction.
Thu Jan 24, 2019 11:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units When Calculating Equilibrium Constant
Replies: 4
Views: 199

### Units When Calculating Equilibrium Constant

What happens to the mol/L when calculating K? For example if there are three reactants on the products side and two reactants on the reactants side with stoichiometric coefficients of 1.
Wed Jan 16, 2019 9:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Tricks for ICE tables
Replies: 5
Views: 226

### Re: Tricks for ICE tables

Make sure to always remember that the mole proportion is very important when inserting "x" (the change in molarity). C part of ICE!
Wed Jan 16, 2019 9:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentration
Replies: 4
Views: 208

### Re: Concentration

K is the actual equilibrium constant of a reaction at a certain temperature. Q is called the reaction quotient and is just used as a reference point when the reaction you have at hand is not yet at equilibrium. They both have the same formula, it is just that K uses the formula when the reaction is ...
Wed Jan 16, 2019 9:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentration less than 10^-7
Replies: 4
Views: 172

### Re: Concentration less than 10^-7

He mentioned this detail in order for you to not be confused when you end up with a pH over 7 (basic) while calculating the pH of a solution mixed with a very very weak acid (that means you did it wrong). When calculating for pH, always remember that the hydronium concentration of the water you begi...
Fri Jan 11, 2019 12:34 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Temperature
Replies: 6
Views: 266

### Re: Temperature

Yes, when temperature is increased, it allows for molecules to move around faster and thus interacting with each other more to create new molecules which proceeds the reaction forward.
Fri Jan 11, 2019 12:32 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q and K
Replies: 4
Views: 168

### Re: Q and K

Basically in a question you are given the K value of the reaction when it is at equilibrium. The reaction that you have to work with is not at equilibrium so by finding the reaction quotient, you can figure out which way the reaction will be favored.
Fri Jan 11, 2019 12:25 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th Edition 5H.3
Replies: 3
Views: 216

### Re: 7th Edition 5H.3

As you can see by the reactions Samantha pointed out, when they are added together the Cl2 cancel out, making the reaction asked about in question 5H.3. When you add reactions, the K of the new reaction is the product of the K's of the reactions that were added together.
Fri Dec 07, 2018 7:03 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: How to tell which ligands can be polydentrate
Replies: 4
Views: 208

### Re: How to tell which ligands can be polydentrate

For the 7th edition, it is on page 724.
Fri Dec 07, 2018 6:52 pm
Forum: Bronsted Acids & Bases
Topic: List of strong/weak acids/bases
Replies: 3
Views: 233

### Re: List of strong/weak acids/bases

The ones you should memorize for sure:

Strong Acids: HCl, HBr, HI, H2SO4, HClO4, HNO3, HClO3

Strong Bases: All alkali metals with OH and the larger alkaline metals (Ca,Sr,Ba) with OH
Fri Dec 07, 2018 6:50 pm
Forum: Bronsted Acids & Bases
Topic: Cl- and F-
Replies: 4
Views: 262

### Re: Cl- and F-

As HCl is a strong acid, it will stay dissociated as H+ and Cl- (an acid is stronger the more likely it dissociates and releases a H+). On the other hand, as HF is a weak acid, it will more likely go back into HF as it does not like to be in its dissociated form of H+ and F-.
Tue Dec 04, 2018 11:22 am
Forum: Lewis Acids & Bases
Topic: Electronegativity and strength acids and bases
Replies: 1
Views: 122

### Re: Electronegativity and strength acids and bases

I think it relates to the fact that a greater electronegativity difference would result in more electrons being further away from the hydrogen giving it a stronger positive partial charge. It will then form stronger hydrogen bonds because of the charge difference.
Tue Dec 04, 2018 11:20 am
Forum: Bronsted Acids & Bases
Topic: Distinguishing between acids and bases
Replies: 1
Views: 87

### Re: Distinguishing between acids and bases

Most likely, as it would not make sense otherwise. Perhaps the setting of the problem will hint on whether it is used as an acid or base.
Tue Dec 04, 2018 11:20 am
Forum: Lewis Acids & Bases
Topic: KBr
Replies: 5
Views: 230

### Re: KBr

It may be because bromine is a bigger element than fluorine.
Sun Nov 25, 2018 11:08 pm
Forum: Hybridization
Topic: hybridization of BeCl2
Replies: 4
Views: 172

### Re: hybridization of BeCl2

First draw the lewis structure. You see that BeCl2 only has two regions of electron density around it. Thus, its hybrid orbital will be sp. If it had three regions of electron density around it, the hybrid orbital would be sp2. Regions of electron density is equal to the number of hybrid orbitals.
Sun Nov 25, 2018 11:03 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sigma and Pi Bonds
Replies: 2
Views: 141

### Re: Sigma and Pi Bonds

Just try to remember the demonstration that Dr. Lavelle did during class. He put two sticks between his two index fingers and tried to turn his index fingers. From rotating his fingers, the sticks fell out of their formation.
Sun Nov 25, 2018 11:01 pm
Forum: Hybridization
Topic: Questions in Chapter
Replies: 5
Views: 263

### Re: Questions in Chapter

I believe that knowing the name of molecules is not necessary for our course. If you are really worried, just ask your TA for the basic molecules that someone should always know like water and carbon dioxide.
Sat Nov 17, 2018 1:12 pm
Forum: Photoelectric Effect
Topic: Calculate the Ionization energy... midterm Q3B
Replies: 1
Views: 484

### Re: Calculate the Ionization energy... midterm Q3B

You need to use the conversation of energy equation expressed during the photoelectric effect: Energy of photon = Work Function + Kinetic Energy of released electron. You were able to find the energy of the photon correctly, you just forgot to find the KE of the electron through using the equation K...
Sat Nov 17, 2018 1:00 pm
Forum: Hybridization
Topic: Hybridization for VSPER model
Replies: 2
Views: 124

### Re: Hybridization for VSPER model

Yes, they do. They are considered to simply count as one of the total number of electron densities surrounding a central atom.
Sat Nov 17, 2018 12:59 pm
Forum: Dipole Moments
Topic: Polarity and dipole moment
Replies: 4
Views: 244

### Re: Polarity and dipole moment

Yes, symmetric molecules tend to be nonpolar. For instance, carbon dioxide (linear shape) is nonpolar as the dipole moments cancel each other out.
Tue Nov 13, 2018 10:03 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lowest Energy Lewis Structures
Replies: 3
Views: 194

### Re: Lowest Energy Lewis Structures

Just always make sure to first have all the atoms have an octet. After all the atoms have an octet, check the formal charges of each atom and adjust accordingly (usually by adding double bonds).
Tue Nov 13, 2018 10:01 pm
Forum: Dipole Moments
Topic: Determining Intermolecular Forces
Replies: 5
Views: 355

### Re: Determining Intermolecular Forces

You can also look where the particular element is on the periodic table. Metals and nonmetals tend to form ionic bonds and two nonmetals tend to form covalent bonds.
Tue Nov 13, 2018 9:58 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework Focus 2A
Replies: 3
Views: 237

### Re: Homework Focus 2A

If it did ask for Cu 2+ then it is most likely a textbook error.
Fri Nov 09, 2018 12:19 am
Forum: Ionic & Covalent Bonds
Topic: Electronegativity values
Replies: 4
Views: 206

### Re: Electronegativity values

Most likely, as we do not need to memorize each element's value, but rather the trend across a group and period.
Fri Nov 09, 2018 12:17 am
Forum: Bond Lengths & Energies
Topic: Dispersion Force/State of Matter Correlation
Replies: 2
Views: 152

### Re: Dispersion Force/State of Matter Correlation

With more dispersion forces, there is more attraction between atoms meaning they will be less likely to move freely. States of matter are based on the movement of atoms/molecules.
Fri Nov 09, 2018 12:11 am
Forum: Trends in The Periodic Table
Replies: 3
Views: 282

The atomic radius increases down a group as another shell of electrons is being added (energy level). Once the second period hits 8 electrons, its shell becomes full and a new shell (the n=3 shell) begins. Across a period the radius decreases because as the shell remains the same, the number of prot...
Sun Nov 04, 2018 6:46 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Post-Module Q#17
Replies: 1
Views: 195

### Re: Post-Module Q#17

No, you do not multiply by 2. Uncertainty is what becomes delta v.
Sun Nov 04, 2018 6:45 pm
Forum: Properties of Electrons
Topic: Frequency of an electron equation
Replies: 2
Views: 364

### Re: Frequency of an electron equation

For an electron, you would most likely be given info to complete the equation E - work function = KE to find the frequency.
Sun Nov 04, 2018 6:40 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Which electron disappears for ion configurations
Replies: 2
Views: 205

### Re: Which electron disappears for ion configurations

I do not believe so. Just remember to take away the 4s electrons before the 3d electrons.
Wed Oct 31, 2018 1:28 pm
Forum: Ionic & Covalent Bonds
Topic: 2A.17 7th edition
Replies: 2
Views: 188

### Re: 2A.17 7th edition

I am not exactly sure about a and c, but for d, a +3 charge means the element is losing 3 electrons. Knowing this, phosphorus if it lost 3 electrons would have the configuration of magnesium which has 2 valence electrons.
Wed Oct 31, 2018 1:17 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge and correct numbers
Replies: 2
Views: 170

### Re: Formal Charge and correct numbers

Whichever one has a higher electronegativity (a want for electrons), that element will gain the negative charge.
Fri Oct 26, 2018 1:38 pm
Forum: Lewis Structures
Topic: Periodic Table Trends
Replies: 3
Views: 152

### Re: Periodic Table Trends

I am pretty sure there is one exception dealing with half filled sub-shells but he has not gone over them specifically. At least I believe so.
Fri Oct 26, 2018 1:36 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Replies: 5
Views: 270

For nodal planes I am pretty sure p has 1, and then as you go up each subshell it increases by 2. So d has 3 nodal planes and f has 5 and so on. Is there a difference between nodal and radial planes?
Fri Oct 26, 2018 1:34 pm
Forum: Lewis Structures
Topic: octets
Replies: 13
Views: 530

### Re: octets

An element has an octet if it has 8 valence electrons. Yes, an orbital does need a full octet before moving to the next orbital (at least for the level we are learning).
Mon Oct 22, 2018 8:39 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework 2.55 part c
Replies: 3
Views: 221

### Re: Homework 2.55 part c

Where do you find the corrections to the textbook problems? I only see the solution manual corrections.
Mon Oct 22, 2018 6:20 pm
Forum: DeBroglie Equation
Topic: 1B 15 7th edition
Replies: 6
Views: 328

### Re: 1B 15 7th edition

For part c I keep getting 12nm and not 8.8nm (the answer). What am I doing wrong as I am plugging in the exact formula for speed of light?
Mon Oct 22, 2018 5:59 pm
Forum: Trends in The Periodic Table
Topic: 1 F 11
Replies: 2
Views: 88

### 1 F 11

Which element of each of the following pairs has the higher electron affinity: a) tellurium or iodine; b) beryllium or magnesium; c) oxygen or sulfur; d) gallium or indium? So why is the answer for c) sulfur and for b) and d) the answer is that they are equal. All these scenarios show one element on...
Mon Oct 22, 2018 5:56 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: 1 A 15 7th Edition [ENDORSED]
Replies: 1
Views: 194

### 1 A 15 7th Edition[ENDORSED]

In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that leads to this spectral line. I understand how to solve this question it is just that I am confused why ...
Mon Oct 22, 2018 4:10 pm
Forum: Octet Exceptions
Topic: Specific formula
Replies: 3
Views: 249

### Re: Specific formula

By octet exceptions are you referring to the half d block and full d block exceptions we learned in class today?
Mon Oct 22, 2018 4:09 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron configuration for elements > Z = 56
Replies: 3
Views: 275

### Re: Electron configuration for elements > Z = 56

I am unsure to your question (I assume you would include the f orbitals), but I wanted to make sure that all we need to know for electron configurations are the s-block, p-block, and 1st row of d-block.
Mon Oct 22, 2018 4:06 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Uncertainty Question
Replies: 3
Views: 268

### Re: Heisenberg Uncertainty Question

All you have to know conceptually is that at the atomic level, one can never exactly determine the position and velocity of a particle because when they are that small, they exhibit both wavelike and particle like properties. It becomes uncertain whether to find their features through formulas we us...
Fri Oct 12, 2018 1:53 am
Forum: SI Units, Unit Conversions
Topic: Rounding Off of 5
Replies: 7
Views: 491

### Re: Rounding Off of 5

Sorry I am still confused about this rule. For single problems is it not fine to just round up at 5 as it is in the upper half of 0-9?
Fri Oct 12, 2018 1:47 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Wavelike properties
Replies: 7
Views: 211

### Re: Wavelike properties

I think it always depends on the situation you put it in. For example, with the photoelectric effect it will act as a particle but when testing for interference it will act as a wave.
Fri Oct 12, 2018 1:43 am
Forum: Properties of Electrons
Topic: Electron Energy Levels
Replies: 2
Views: 153

### Re: Electron Energy Levels

I believe that with very small particles such as electrons, it is just a natural occurrence that they must be quantized (for electrons being between energy levels).
Thu Oct 04, 2018 12:12 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Fundamentals E.17
Replies: 4
Views: 905

### Re: Fundamentals E.17

When asked questions about comparing atoms, grams, or moles in this case, just always take the time to use Avogadro's number and the molar mass to get the unit that you want. Using dimensional analysis can help you cross out units and see if the unit that is remaining is the one you want (such as th...
Wed Oct 03, 2018 11:26 pm
Forum: SI Units, Unit Conversions
Topic: Naming Compounds
Replies: 9
Views: 535

### Re: Naming Compounds

So is the molecular formula for magnesium sulfate heptahydrate MgS7H2O? I am not even sure if that is how the formula is written, for example is the 7 supposed to be distributed like so: MgSH14O7?
Wed Oct 03, 2018 6:16 pm
Forum: Limiting Reactant Calculations
Topic: This question from the post assessment
Replies: 2
Views: 193

### Re: This question from the post assessment

It is not possible due to the Law of Conservation of Matter/Mass. In a reaction, mass does not suddenly disappear or appear such as when liquid water evaporates, the water is still there just in a gaseous form. Thus, reactants totaling a mass of 12 grams will form products that total 12 grams - no l...