## Search found 57 matches

Sat Mar 17, 2018 9:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Writing Cell Diagrams
Replies: 3
Views: 318

### Re: Writing Cell Diagrams

You need two half reactions in order to write a cell diagram. The example you provided is a whole cell and it can be broken up into two half-cells. With the half reactions from this, you write the anode on the left side of the salt bridge and the cathode on the right side.
Sat Mar 17, 2018 9:29 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: Final 2011 1C
Replies: 1
Views: 199

### Re: Final 2011 1C

NO has greater residual entropy because its two atoms can result in the arrangement of two different molecules. It can either be NO or ON. However, the BF3 molecule only has one way it can be arranged. This is related to Boltzmann's formula for calculating residual entropy.
Sat Mar 17, 2018 9:26 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: internal energy
Replies: 2
Views: 300

### Re: internal energy

If the problem asks for you to find the total increase in the internal energy and then states that the internal energy returns to its original state, you see how much the internal energy increases by in the first step and then make it negative. However, the overall change in internal energy will be 0.
Sat Mar 17, 2018 9:25 pm
Forum: Calculating Work of Expansion
Topic: Spontaneity and Work
Replies: 1
Views: 254

### Re: Spontaneity and Work

I don't think so. I think that you must put energy into the system in order to get it to react, and therefore it cannot produce energy that can be used as work.
Thu Mar 15, 2018 9:58 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: HW 14.15
Replies: 1
Views: 134

### HW 14.15

For the cell diagram in HW 14.15 a, why is there a line instead of a comma between Ag(s) and AgBr(s)?
Mon Mar 12, 2018 4:36 pm
Forum: *Enzyme Kinetics
Topic: Michaelis-Menten Mechanism [ENDORSED]
Replies: 1
Views: 412

### Michaelis-Menten Mechanism[ENDORSED]

Will we need to know about the Michaelis-Menten Mechanism for the final?
Sun Mar 11, 2018 6:41 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Molar Entropy
Replies: 9
Views: 657

### Re: Molar Entropy

Things that often lead to higher molar entropy are more complex structures (the bonds can absorb more vibration energy), heavier atoms, and formation of gas particles. Therefore, size and complexity are helpful to determine the molar entropy.
Sun Mar 11, 2018 6:40 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-Equilibrium
Replies: 4
Views: 209

### Re: Pre-Equilibrium

I think the processes are the same for both rate of formation and rate of decomposition. Just make sure that the equilibrium constant is correct.
Sun Mar 11, 2018 6:38 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: A relationship to K
Replies: 2
Views: 135

### Re: A relationship to K

When the molecules in a reaction collide with each other more, or if there is a higher frequency, then there is a greater chance that a reaction will occur. The molecules need to collide in order for the reaction to occur, and the having a high frequency increases collisions. Therefore, because more...
Sun Mar 04, 2018 11:20 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.55 a
Replies: 3
Views: 209

### Re: 15.55 a

As said before, the rate constant is always proportional to K. Therefore, when K is very large, meaning the products are favored, you will have a large rate constant.
Sun Mar 04, 2018 11:18 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 0 order
Replies: 6
Views: 2177

### Re: 0 order

The graph of Zero order has time on the x axis and concentration on the y axis. Since the reaction rate is independent of the concentration, this graph will just be linear with a slope of -k.
Sun Mar 04, 2018 11:16 am
Forum: First Order Reactions
Topic: 15.23
Replies: 4
Views: 266

### Re: 15.23

You start with the initial concentration of A, and you need to find how much b is produced to see how much the concentration of A decreases. Therefore, you would subtract 2*b from the initial concentration of A
Sun Feb 25, 2018 6:39 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: reducing power?
Replies: 5
Views: 824

### Re: reducing power?

Something with a high reducing power will have a large negative potential difference. Something with a high oxidizing power will have a high positive potential difference.
Sun Feb 25, 2018 6:31 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Positive Slope???
Replies: 4
Views: 305

### Re: Positive Slope???

Like said before, the tangent can be negative if the reverse reaction is occurring. In this case, the products will be decreasing in their concentration, meaning that they have a negative rate of change.
Sun Feb 25, 2018 6:30 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: activation energy
Replies: 4
Views: 258

### Re: activation energy

When you have a high activation energy, that means you will need a significant amount of energy in order for the reaction to occur. Often times, because you need more energy for the reaction, this will result in the time needed for the reaction to be completed being longer.
Sun Feb 18, 2018 3:37 pm
Forum: Balancing Redox Reactions
Topic: 14.9
Replies: 1
Views: 143

### Re: 14.9

When you balance the half reactions, you will get the number of electrons that are either lost or gained depending on whether it is a reduction or oxidation reaction. When you add the two half reactions together, you will need to multiply the half reactions by a coefficient in order to end up with t...
Sun Feb 18, 2018 3:35 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: "Molar" form/ Pure number
Replies: 2
Views: 197

### Re: "Molar" form/ Pure number

I think it is used to change the units of deltaG. If n was not "pure", then the units of deltaG would be Joules, but if n was pure, then the units of deltaG would be Joules/mol. I'm not completely sure though
Sun Feb 18, 2018 3:32 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Standard Cell Potentials
Replies: 5
Views: 218

### Re: Standard Cell Potentials

The standard cell potential is not changed because it is equal to deltaG/(n*F). Therefore, if you would double the reaction, you would end up doubling both deltaG and n, which would cancel out.
Sun Feb 11, 2018 4:33 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Understand equation
Replies: 2
Views: 296

### Re: Understand equation

You multiply the standard reaction entropy for the molecule by the stoichiometric coefficient given to you by the reaction. It does not matter if it is a solid, liquid, or gas. you multiply the standard reaction enthalpy of each substance by the amount of moles of that substance that are used during...
Sun Feb 11, 2018 4:31 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Stable vs Unstable
Replies: 4
Views: 610

### Re: Stable vs Unstable

It helps to think about the compound in terms of its gibbs free energy of formation. If the free energy of formation of a compound is negative, this means that in the reaction for the formation of the compound, the elements (reactants) will tend to combine to form the compound (products). On the oth...
Wed Jan 31, 2018 6:29 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.13
Replies: 5
Views: 335

### Re: 9.13

For ideal gases, it is 5/2R at constant volume and 3/2R at constant pressure
Wed Jan 31, 2018 6:26 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.43
Replies: 5
Views: 200

### Re: 9.43

It is a constant that the book provides you or that Dr. Lavelle will give to us before a test.
Wed Jan 31, 2018 6:23 pm
Forum: Phase Changes & Related Calculations
Topic: Example in Lecture
Replies: 4
Views: 266

### Re: Example in Lecture

When deltG is negative, this means that a reaction is spontaneous. In this problem, when deltaG is zero, neither the forward nor reverse reaction are favored. However, even a slight increase in temperature above the temperature value that makes the deltaG zero will result in the favorability of the ...
Sun Jan 28, 2018 11:45 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bondy Enthalpy Accuracy
Replies: 3
Views: 278

### Re: Bondy Enthalpy Accuracy

The bond enthalpy method actually takes into account mean bond enthalpy. In different molecules, the amount of atoms attached to the central molecule, lone pair electrons, and etc. affect the strength of bonds. As a result, the same bond between two atoms in different molecules will have a different...
Sun Jan 28, 2018 11:43 am
Forum: Phase Changes & Related Calculations
Topic: Calculating the Change in Enthalpy
Replies: 4
Views: 283

### Re: Calculating the Change in Enthalpy

The enthalpy will be given to you often times in kJ/mole and often times you will be given the mass of the substance, so for these problems it is important that you change the mass of the substance into moles and then multiply it to the given enthalpy.
Sun Jan 28, 2018 11:40 am
Forum: Phase Changes & Related Calculations
Topic: 8.40
Replies: 4
Views: 262

### Re: 8.40

I think the answer is right. What you need to do is calculate the heat needed to first change the water's temperature using q=m*C*deltaT. After you add the amount of energy times the moles of water needed for the phase change.
Tue Jan 16, 2018 8:07 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat Capacities
Replies: 6
Views: 204

### Re: Heat Capacities

Molar heat capacity is the heat required to raise the temperature of a mol of the substance, while the specific heat capacity is the heat required to raise hte temperature of a gram of the substance.
Tue Jan 16, 2018 7:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Work function
Replies: 4
Views: 181

### Re: Work function

When the system is gaining energy through work, or when work is being done on the system from the surroundings, W is positive. when the system releases energy by doing work on the surroundings, W is negative.
Tue Jan 16, 2018 7:56 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.77
Replies: 2
Views: 205

### Re: 8.77

In order to do this problem, you would first calculate the energies to break the bonds of 3 double bonded carbons and 3 single bonded carbons. You would then compare this value to 6 resonance carbon bonds, and see that the resonance structure requires more energy to break the bonds, and it is theref...
Fri Jan 12, 2018 9:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess Law
Replies: 4
Views: 185

### Re: Hess Law

Hess' law states that a specific reaction is equal to the sum of the enthalpies of any set of reactions equal to the specific reaction. This means that if you have the enthalpies for reactions that can be added together to make another reaction, you can add the enthalpies together to find the net en...
Fri Jan 12, 2018 9:34 pm
Forum: Phase Changes & Related Calculations
Topic: Methods of Enthalpy
Replies: 8
Views: 449

### Re: Methods of Enthalpy

I think that he will give you a problem and based on the information he gives you, you will have to use a certain method to find the enthalpy. So I would make sure to know the various methods to calculate the enthalpy.
Fri Jan 12, 2018 9:26 pm
Forum: Phase Changes & Related Calculations
Topic: Heating Curve
Replies: 3
Views: 205

### Re: Heating Curve

As other people explained, the plateaus occur because energy is needed to break the bonds between the atoms in order for a phase change to occur. The molecules absorb the heat, even though the temperature is not increasing. This is the reason that steam burns are worse than boiling water burns.
Sat Dec 09, 2017 9:46 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Compression effect on a system
Replies: 2
Views: 251

### Re: Compression effect on a system

Compressing a system will decrease the volume, which will increase the pressure. For equilibriums, when the pressure is increased, the equilibrium will shift towards the side with less moles of gas.
Sat Dec 09, 2017 9:44 pm
Forum: Naming
Topic: Memorizing all the names???
Replies: 4
Views: 491

### Re: Memorizing all the names???

I think you have to know the whole name incase the test gives you the formula of a complex and you have to name the whole complex. I think you only use the abbreviation when writing the formula, not the full name.
Sat Dec 09, 2017 9:43 pm
Forum: Conjugate Acids & Bases
Topic: Protanation
Replies: 2
Views: 307

### Re: Protanation

Protonation is when a base receives a proton. Deprotonation is when an acid donates a proton.
Sat Dec 09, 2017 9:42 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Conjugate seesaw
Replies: 3
Views: 380

### Re: Conjugate seesaw

The conjugate seesaw is where if you have a strong base, its conjugate will be a weak acid or if you have a strong acid, its conjugate base will be a weak base. It works the opposite way too, where weak acids will have stronger conjugate bases and weak bases will have stronger conjugate acids.
Sat Dec 09, 2017 9:40 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Lewis Structures of Compounds with Ligands
Replies: 1
Views: 166

### Re: Lewis Structures of Compounds with Ligands

I don't think you do. All you have to do is show what the central atom is and which atom is bonding with the central atom.
Sat Dec 09, 2017 9:37 pm
Forum: Ideal Gases
Topic: Kc and shifting of reaction
Replies: 3
Views: 473

### Re: Kc and shifting of reaction

With just Kc, you can only determine if the reaction favors the products or reactants. You need to find Q in order to see which direction the reaction will shift.
Fri Dec 08, 2017 7:56 am
Forum: Hybridization
Topic: Sigma/Pi bond notation
Replies: 1
Views: 300

### Re: Sigma/Pi bond notation

For bond notation, you first list the time of bond (pi or sigma), then you list one of the atoms and which orbital the electron is coming from (hybrid, p, or s), and then you list the second atom and which orbital the electron is coming from. For example, if you have an atom such as H2CO, the notati...
Thu Dec 07, 2017 10:10 pm
Forum: Hybridization
Topic: Hybridization/Hybrid Orbitals of Pi Bonds
Replies: 2
Views: 250

### Re: Hybridization/Hybrid Orbitals of Pi Bonds

I believe so. I don't think you can use hybrid orbitals for pi bonds, and it would therefore have to come from the p orbital.
Thu Dec 07, 2017 10:05 pm
Forum: Bronsted Acids & Bases
Topic: "Do you expect the pH of pure water to increase or decrease with increasing temperature?"
Replies: 1
Views: 218

### Re: "Do you expect the pH of pure water to increase or decrease with increasing temperature?"

pH decreases as temperature increases. This is because at higher temperatures, ionization increases. This means water will dissociate more and form more H+ ions.
Thu Dec 07, 2017 10:03 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Equilibrium Shift
Replies: 2
Views: 176

### Equilibrium Shift

In module 4, the question asks: The photosynthesis reaction, 6 CO2(g) + 6 H2O(l) ⇌ C6H12O6(aq) + 6 O2(g), is endothermic. What effect will the following changes have on the equilibrium composition. a) Water is added. b) The partial pressure of CO2 is decreased. The answer was a) Increase [C6H12O6] a...
Thu Dec 07, 2017 9:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Different Shapes
Replies: 4
Views: 694

### Re: Different Shapes

I think you got all the shapes we learned.
The formula for seesaw is AX4E and the formula for T-shaped is AX3E2
Sun Dec 03, 2017 7:04 pm
Forum: Lewis Acids & Bases
Topic: Problem 12.51 Part (a)
Replies: 3
Views: 493

### Re: Problem 12.51 Part (a)

The weaker the bond strength of an Acid, the stronger it will be because it will be able to dissociate quickly and therefore create more H30. When measuring pH, since it is weaker and more easily dissociated, there will be a higher molarity in H+ ions and the pH will show that it is a stronger acid.
Sun Dec 03, 2017 6:59 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Concept Q// Change in Temp
Replies: 3
Views: 232

### Re: Concept Q// Change in Temp

When I do these problems, I like to think of heat as one of the reactants or products. For an endothermic reaction, I think of the energy as a reactant because the reaction requires energy, and when a reaction is exothermic, I think of the energy as a product because it releases energy. With this in...
Sun Nov 26, 2017 9:25 pm
Forum: Hybridization
Topic: HMK 4.91
Replies: 3
Views: 275

### Re: HMK 4.91

I believe it is because the triple bond in Benzyne results in a linear shape for that carbon, which in turn makes it highly reactive because the molecule typically is not linear. The triple bond will break because of this and form a double bond with a more stable shape.
Sun Nov 26, 2017 9:16 pm
Forum: Hybridization
Topic: Hybridization
Replies: 5
Views: 374

### Re: Hybridization

The goal is to create a molecule with overall lower energy. Although it takes energy to bring an electron from the s sub shell to the hybrid orbital, the molecule that forms bonds will typically have a lower overall energy because of how hybridization allows for more bonds to form.
Mon Nov 13, 2017 9:50 pm
Forum: Lewis Structures
Topic: HW Problem 4.13c
Replies: 2
Views: 211

### Re: HW Problem 4.13c

I believe that this is just one of the resonance structures, and typically the Lewis structure for iodate has iodine double bonded to 2 of the oxygens and single bonded to a third with a lone electron pair.
Mon Nov 13, 2017 9:46 pm
Forum: Octet Exceptions
Topic: Expanded Octets
Replies: 3
Views: 274

### Re: Expanded Octets

I’ve noticed that typically elements form a maximum of six bonds when they have an expanded octet. However, I’m not sure if this is the maximum or just what is common.
Sat Nov 04, 2017 7:59 pm
Forum: Bond Lengths & Energies
Topic: Bond Order
Replies: 6
Views: 612

### Re: Bond Order

The bond order is determined by the number of valence electrons between the atoms as well as the formal charge. This will help you determine whether you need to form a single, double, or triple bond. The bond order is then just 1,2 or 3 corresponding to single, double, and triple bond.
Sat Nov 04, 2017 7:48 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic and Covalent Bonds
Replies: 9
Views: 632

### Re: Ionic and Covalent Bonds

The best way to tell is that the electro negativity is <1.5 for covalent bonds and is >2 for ionic bonds. It is also important to realize that some ionic bonds have covalent bond characteristics, and some covalent bonds have ionic bond characteristics. This depends on the extent of attraction of an ...
Thu Oct 26, 2017 2:50 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Exceptions to Electron Configuration [ENDORSED]
Replies: 5
Views: 1107

### Re: Exceptions to Electron Configuration[ENDORSED]

I also have a follow up question to this. Is there a way to tell which of the electron configurations in groups 6 and 11 will be exceptions? and why are some exceptions but others not?
Thu Oct 26, 2017 2:47 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuraiton
Replies: 2
Views: 247

### Electron Configuraiton

When you write an Electron configuration that is abbreviated, such as the electron configuration for Magnesium which is [Ne] 3s2, can you use can element for the abbreviation or does it have to be a noble gas? For example, could I use Beryllium when writing the electron configuration for Magnesium s...
Wed Oct 11, 2017 3:20 pm
Forum: Properties of Light
Topic: Speed of Light [ENDORSED]
Replies: 8
Views: 657

### Re: Speed of Light[ENDORSED]

Typically, I use the more precise number because I try to limit the possible rounding errors that could affect my answer. I also try doing this by keeping the whole numbers in my calculator and try as little to possible to round until I get my final answer. However, as other people are saying, there...
Wed Oct 11, 2017 2:57 pm
Forum: Einstein Equation
Topic: E=hv and ΔE=hv
Replies: 3
Views: 576

### Re: E=hv and ΔE=hv

ΔE is the change in energy and can have either a positive or negative value. You usually use the equation when an electron absorbs energy to move to a different energy level.
E is the energy of a given wavelength. It typically shows you how much energy a photon has.
Thu Oct 05, 2017 10:04 am
Forum: Molarity, Solutions, Dilutions
Topic: G13 Homework Problem
Replies: 2
Views: 344

### Re: G13 Homework Problem

For this problem you first determine the concentration of the NH4NO3 with it's new volume: .20M(1.0L) = .20mol .20mol/(3.0L+1.0L) = .05M After finding the concentration of the solution, it doesn't matter how many plants there are. It is asking how many moles one of the plants receives, so you just n...
Wed Oct 04, 2017 3:38 pm
Forum: Empirical & Molecular Formulas
Topic: Identifying Empirical and Molecular Formulas [ENDORSED]
Replies: 13
Views: 5450

### Re: Identifying Empirical and Molecular Formulas[ENDORSED]

What are the differences between the Molecular and Empirical formulas? More specifically, how do you identify one from the other? I have a similar additional question to add to this post. When doing a problem, what is the best way to realize if I have found the molecular or empirical formula? Somet...