Search found 60 matches

Thu Mar 14, 2019 2:08 pm
Forum: *Enzyme Kinetics
Topic: Catalysts
Replies: 7
Views: 289

Re: Catalysts

It should, when looking at the graph of potential energy and progress of reaction it shows that the catalysts lower the activation energy or Ea. This applies to both ways, forward and reverse.
Mon Mar 11, 2019 5:56 pm
Forum: Second Order Reactions
Topic: 15.29 6th Edition
Replies: 1
Views: 58

Re: 15.29 6th Edition

a) We need to find the rate constant first which requires us using [A]=[A]0 e^-kt. But first, we need to find the value of [A]. To do so we need to use the reaction they gave us and [B](which will show us the [A] produced through the reaction). As shown in the reaction, for every mole of A there are...
Mon Mar 11, 2019 5:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Finding heat(q)
Replies: 3
Views: 80

Re: Finding heat(q)

I think in our situation it is based upon the information presented to us in the question.
Sun Mar 10, 2019 2:51 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Homework 6th edition, 15.17
Replies: 3
Views: 76

Re: Homework 6th edition, 15.17

It means that C is zero order, it doesn't affect the rate law like A and B does. You can show this by finding the order for C by comparing experiments 1 and 4.
Sun Mar 10, 2019 2:49 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.17 6th Ed
Replies: 2
Views: 64

Re: 15.17 6th Ed

To clarify along further, C is zero order and you will see that in the rate law, it doesn't seem to be represented- which is due to its zero order turning its concentration to 1.
Sun Mar 10, 2019 2:33 pm
Forum: Zero Order Reactions
Topic: 15.17 6th edition
Replies: 1
Views: 39

15.17 6th edition

For this problem, the reaction had 3 different reactants. One of the reactants was shown to be zero order. When figuring out the other two reactant's order of reactions would it be ok to just ignore the concentration of the zero order reactant?
Sat Mar 09, 2019 4:23 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating E naught
Replies: 5
Views: 95

Re: Calculating E naught

You would have to determine which of the reactions is more easily reduced and that will be your cathode. You will have to compare the absolute values of the cell potentials. A helpful tip to remember is that you don't want a negative E naught.
Tue Mar 05, 2019 9:59 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: K
Replies: 2
Views: 87

Re: K

Yes, you determine k by comparing the experimental data containing the initial molar concentration and rate. It is important to compare only one of the reactant's initial molar concentrations if you have more than one reactant. By comparing the two, you will be able to find the order of each reactan...
Sun Mar 03, 2019 2:31 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.3
Replies: 1
Views: 80

15.3

In 20. s, the concentration of nitrogen dioxide, NO2, decreases from 450 (mmol)(L) to 320 (mmol)(L) in the reaction 2 NO2(g) => 2 NO(g) + O2(g). (a) Determine the rate of reaction of NO2. (b) Determine the rate of formation of O2. (c) What is the unique rate of the reaction? I'm confused about how t...
Sun Mar 03, 2019 2:10 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Determining n and the order
Replies: 2
Views: 55

Re: Determining n and the order

The order of the reaction gives insight into the rxn mechanism- an essential part of finding the rate of a reaction (Rate= k[Reactant]^n, where n is the order of the reaction). You can find the order of the reaction by comparing at the experimental data of several different experiments.
Sun Feb 24, 2019 4:10 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Practice exercise 9.2B 6th edition
Replies: 1
Views: 57

Re: Practice exercise 9.2B 6th edition

It doesn't seem like this question requires the molar quantity. It gave you the mass in grams, as well as a specific heat capacity that is capable of canceling out the grams of the mass.
Sun Feb 24, 2019 4:03 pm
Forum: Balancing Redox Reactions
Topic: salt bridge?
Replies: 3
Views: 83

Re: salt bridge?

The salt bridge allows for neutral balance for anion transport to counter electron build-up, or otherwise it balances the charge between the two solutions.
Sun Feb 24, 2019 3:35 pm
Forum: Balancing Redox Reactions
Topic: 6th edition 14.5a
Replies: 1
Views: 44

Re: 6th edition 14.5a

O3 on the reactant side is 0 while it goes to -2 on the product side in BO3-, which makes it the oxidizing agent. Br- goes from -1 on the reactant side to +5 in BrO3- on the product side. O3 and O2 are not the same species. O2 still has 0 oxidation number. Otherwise, oxygen usually is -2. Exceptions...
Sun Feb 24, 2019 3:22 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Not at Equilibrium
Replies: 3
Views: 79

Re: Not at Equilibrium

Also when at equilibrium, delta G =0.
Sun Feb 24, 2019 3:17 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.67 6th edition
Replies: 1
Views: 55

9.67 6th edition

Assume that H and S are independent of temperature and use data in Appendix 2A to calculate G for each of the following reactions at 80 degrees C. Over what temperature range will each reaction be spontaneous under standard conditions? a) B2O3(s) +6 HF (g) => 2BF3(g) +3H2O(l) b)CaC2(s) + 2HCl(aq)=> ...
Fri Feb 08, 2019 7:18 pm
Forum: Calculating Work of Expansion
Topic: Conversions to joules?
Replies: 4
Views: 111

Re: Conversions to joules?

I think you were supposed to change the units earlier in the calculation to avoid this problem. It would be much easier to change the area of the cylinder, -141.37 cm ^, to L by dividing by 1000 ( since 1000 cm^3 make 1 L). Then when you found the work, it would be in L x atm, which can be changed i...
Fri Feb 08, 2019 7:13 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 6th edition 8.25 Calorimeter problem
Replies: 1
Views: 61

Re: 6th edition 8.25 Calorimeter problem

Normally, it wouldn't matter because celsius and kelvin use the same scale. The difference in temperatures between celsius and kelvin would the same. However, in this case it is probably a typo because 2.49 is given in celsius. Both temperatures have to be using the same temperature scale for the ca...
Fri Feb 08, 2019 7:02 pm
Forum: Phase Changes & Related Calculations
Topic: Homework Problem 8.21
Replies: 6
Views: 2098

Re: Homework Problem 8.21

No it would actually be (100-Tf). This is due to the temperature of the copper being 100 degrees celsius, which would result in the change in temperature for the copper to be negative. This would result in a negative answer when (Tf -100) or (100-Tf) to make it easier in the equation.
Sun Feb 03, 2019 12:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.113a 6th edition
Replies: 2
Views: 57

Re: 8.113a 6th edition

I think because only H2O and CO2 are in a gaseous state while carbon is a solid.
Sat Feb 02, 2019 6:06 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Compression of Gas
Replies: 4
Views: 97

Re: Compression of Gas

When a gas is compressed, work is done and the internal energy is changed. This means that heat is added. When the gas is decompressed, work/energy is lost and heat is lost.
Sat Feb 02, 2019 6:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: The Relationship Between ΔH and ΔU
Replies: 2
Views: 82

Re: The Relationship Between ΔH and ΔU

ΔU is considered heat transfer at constant volume because no work is done, which means the volume doesn't change. ΔU then only equals q, or heating/cooling. At that point,ΔU= ΔH since its only the heat transfer that happens.
Sun Jan 27, 2019 11:45 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Work, state property
Replies: 3
Views: 76

Work, state property

I understand that enthalpy is a state property and it is not dependent on the path taken to obtain that state. My notes also says that work is the opposite and is pathway dependent. What does this entail in terms of calculating it?
Sun Jan 27, 2019 11:42 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 6th edition 8.11
Replies: 2
Views: 69

6th edition 8.11

8.11 A piston confines 0.200 mol Ne(g) in 1.20 L at 25 C. Two experiments are performed. (a) The gas is allowed to expand through an additional 1.20 L against a constant pressure of 1.00 atm. (b) The gas is allowed to expand reversibly and isothermally to the same final volume. Which process does mo...
Sun Jan 27, 2019 11:38 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: The 3 methods
Replies: 5
Views: 106

The 3 methods

We learned that there were 3 methods to calculate the enthalpy. Does this mean we can use whatever method interchangeably, or is based upon the question??
Sun Jan 20, 2019 2:41 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Removing products
Replies: 10
Views: 187

Re: Removing products

I think it would just affect Q, since K shouldn't really change. WIth the change of the concentration of products, the Q will tell us which way the equation will shift to reestablish equilibrium.
Sun Jan 20, 2019 2:37 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: pKa vs pH?
Replies: 3
Views: 112

Re: pKa vs pH?

pKa and pH are not really the same thing, however, they work very similarly. The p in front of the Ka and [H+] just means to take the negative log of whatever comes after. So its the negative log of Ka and [H]. The method to turn pKa and pH are just about the same, you would just do 10^neg of either...
Sun Jan 20, 2019 2:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When x is small
Replies: 4
Views: 78

Re: When x is small

Conceptually wise, its just seen that x is so insignificant compared to whatever it is being subtracted from. The example we used in class was that if you had one million dollars and you gave away one thousand dollars, you had essentially barely lost anything from the million dollars.
Sun Jan 20, 2019 2:26 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5% rule
Replies: 4
Views: 95

Re: 5% rule

It wouldn't hurt to expect that when you see that the Ka is that low, but I wouldn't count on it every single time. It would still be good to go through the entire process.
Tue Jan 08, 2019 4:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc vs Kp
Replies: 4
Views: 59

Re: Kc vs Kp

It important also to take note of the states of the reactants and products. For example, if you have only gases you are probably using partial pressures and therefore Kp.
Tue Jan 08, 2019 3:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Question 5G.5 (7th Edition) Part C)
Replies: 2
Views: 65

Re: Question 5G.5 (7th Edition) Part C)

First we need to find the K expression, which is K=(Px)^2/(Px2). Then we have to find the partial pressures of both X and X2, which can be found by Mole fraction of A = # of molecules of A / total # of separate molecules. For X, Px=(12 molecules/17 molecules)0.10 bar. Px=0.071 For X2, Px2=(5 molecul...
Wed Dec 05, 2018 4:52 pm
Forum: Naming
Topic: Polyatomic ions and naming
Replies: 7
Views: 163

Re: Polyatomic ions and naming

It would also be helpful if you could figure out the other polyatomic charges through the ones you already know. For example in [Co(NH3)4(OH2)2]Br3, if you knew that the charge of NH3 and OH2 (or H20) was 0, you could figure out that the charge of Co is +3.
Wed Dec 05, 2018 4:46 pm
Forum: Naming
Topic: Writing chemical formulas
Replies: 2
Views: 51

Re: Writing chemical formulas

Also good to note when naming a coordination compound with water in it, use aqua.
Wed Dec 05, 2018 4:36 pm
Forum: Naming
Topic: Formula
Replies: 1
Views: 64

Re: Formula

(C2H4(NH2)2)(C2H3O2)4
Wed Dec 05, 2018 4:34 pm
Forum: Naming
Topic: Poly v Mono
Replies: 2
Views: 31

Re: Poly v Mono

The difference is in the number of ligands bonded to the transition metal. Mono- means one and poly- just means more than one. It affects the naming if it has bi- or tri-dentate(where there is more than one ligand bonded to the transition metal), which would then add a bis- or tris-, respectively to...
Fri Nov 30, 2018 3:15 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Amines and strength of acid
Replies: 4
Views: 80

Amines and strength of acid

I remember learning that any amine were classified as weak acids back in highschool. Can anybody clarify if this is true and if so why?
Fri Nov 30, 2018 3:06 pm
Forum: Dipole Moments
Topic: Molecular Geometry and polarity
Replies: 5
Views: 112

Molecular Geometry and polarity

If a molecule's molecular geometry is linear, is it a good indicator of the molecule being nonpolar?
Sat Nov 24, 2018 2:13 pm
Forum: Hybridization
Topic: hybridization problems
Replies: 4
Views: 103

Re: hybridization problems

Also good to note that single bonds, double bonds, and triple bonds all equal one region of electron density.
Sat Nov 24, 2018 2:11 pm
Forum: Hybridization
Topic: 4.43 6th Edition
Replies: 1
Views: 56

Re: 4.43 6th Edition

The s-character is the percentage of the "s" in the hybridization. For example sp3, its s-character is 25%. In sp2, the s-character is 33%. When it says the s-character is increasing, it means that the percentage of "s" in the hybridization is increasing. As s-character increases...
Sat Nov 24, 2018 1:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Slightly less than bond angles
Replies: 4
Views: 84

Slightly less than bond angles

If a vsepr model has lone pairs resulting in the bond angle being slightly less than whatever it is usually, would we have to know the exact angle or can we just answer slightly less than?
Fri Nov 16, 2018 4:10 pm
Forum: Ionic & Covalent Bonds
Topic: Fluorine bonds
Replies: 3
Views: 141

Fluorine bonds

Dr. Lavelle mentioned today that fluorine can only form single bonds. Can someone explain why?
Tue Nov 13, 2018 6:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 7th Edition 2E #21 part d
Replies: 1
Views: 51

7th Edition 2E #21 part d

Part D requires you to draw the lewis structure and give the approximate bond angle of the molecule N2H4.
I drew the correct lewis structure but I could not figure out how the bond angle would be 107 degrees and have the molecular geometry of a trigonal pyramidal.
Can someone please explain.
Mon Nov 12, 2018 12:30 pm
Forum: Lewis Structures
Topic: 7th edition 2E #5
Replies: 2
Views: 101

7th edition 2E #5

A)What is the shape of a ClO2+ ion?
B)What is the expected OCLO bond angle?

I know the bond angle would not be 180 degrees since the shape is not linear, but the answer says it is slightly less than 120 degrees. How did they arrive at this answer?
Mon Nov 12, 2018 12:19 pm
Forum: Formal Charge and Oxidation Numbers
Topic: 3.39b 6th edition
Replies: 2
Views: 119

Re: 3.39b 6th edition

For the lewis structure, you would need to draw three individual potassium atoms.
Sun Nov 04, 2018 3:18 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron configuration when 4s and 3d
Replies: 3
Views: 87

Re: Electron configuration when 4s and 3d

It also should be noted that after the 4s shell is filled, it switches the order of 3d and 4s. For example, Sc:[Ar]3d14s2.
Fri Nov 02, 2018 6:11 pm
Forum: Photoelectric Effect
Topic: Chem Test 2, #5 b
Replies: 4
Views: 216

Chem Test 2, #5 b

IN a neon lamp, the electrons moving in the current transfer their kinetic energy to Ne atoms resulting in the excitation of an electron in the Ne atom. At the threshold voltage, the current decreases and light is emitted. b)Light is only emitted at certain voltages. What does this tell us about the...
Fri Nov 02, 2018 6:07 pm
Forum: Photoelectric Effect
Topic: Photoelectric Experiment - Chem Test 2
Replies: 3
Views: 204

Re: Photoelectric Experiment - Chem Test 2

You would use the mass of the electron in the Ek equation since it is an electron being ejected, not a lead atom.
Sat Oct 27, 2018 5:28 pm
Forum: Trends in The Periodic Table
Topic: Homework 2.59
Replies: 3
Views: 113

Re: Homework 2.59

I think the exponents are just based on the trends on the periodic table. For group 15, their charges are -3 which explains P^-3. For group 16 and 17, it's -2 and -1 respectively. That explains S^-2 and Cl^-1.
Sat Oct 27, 2018 5:22 pm
Forum: Trends in The Periodic Table
Topic: 7th edition 1F.3
Replies: 2
Views: 102

Re: 7th edition 1F.3

Based on ionic radii trends, the ionic radius increase down a group and decrease across a period. Since P^-3 is the leftmost option is has the largest ionic radius. The rightmost option is Cl^-1, which would have the smallest ionic radius. SInce S^-2 is between them on the periodic table, its ionic ...
Sat Oct 27, 2018 3:25 pm
Forum: Ionic & Covalent Bonds
Topic: formal charges
Replies: 4
Views: 101

Re: formal charges

They should write it out for you to see. Example Copper (II) sulfate, which tells you the charge of copper is +2.
Sat Oct 27, 2018 1:24 pm
Forum: Ionic & Covalent Bonds
Topic: Ground State
Replies: 6
Views: 192

Re: Ground State

It also means configurations follow principles like building-up principle(Aufbau), where the electrons don't jump energy levels.
Thu Oct 25, 2018 3:57 pm
Forum: Trends in The Periodic Table
Topic: Homework
Replies: 10
Views: 238

Re: Homework

We will probably start homework from chapter 2 after week 4, seeing how the topic after is related to bonding.
Tue Oct 23, 2018 9:54 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: HW Question Regarding 1B.27
Replies: 6
Views: 171

Re: HW Question Regarding 1B.27

It would be 10 m/s instead of 5 m/s because you take the (highest value - lowest value) of 5 plus or minus 5 m/s. The highest value would be 5+5= 10 m/s and the lowest value would be 5-5=0 m/s. If you subtract 10 - 0, you would get 10 m/s which you would use as delta v.
Sat Oct 20, 2018 5:14 pm
Forum: *Shrodinger Equation
Topic: Book Example 1.8:
Replies: 4
Views: 148

Re: Book Example 1.8:

The test material should conclude with the material gone over this Friday, with Shrodinger's equation. The website's announcements specifies that the test will be based up onto the end of week 3.
Mon Oct 15, 2018 5:43 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 7th Edition, 1B.27
Replies: 3
Views: 94

Re: 7th Edition, 1B.27

The solution manual is incorrect and the error is posted on the class website under "Solution Manual Errors".
You were correct to use 10 m/s for delta v and the correct answer is 6.7*10-37 m.
Mon Oct 15, 2018 12:22 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Incorrect Atomic Model
Replies: 6
Views: 160

Re: Incorrect Atomic Model

The first thing to note is that he showed us this example to demonstrate that the Heisenberg equation can be used to prove some models impossible. The example gives you the diameter of the atom, which is 1.7 * 10^-15 and is looking for the uncertainty of the electron's uncertainty of position, dv. H...
Sat Oct 13, 2018 10:34 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 1.25
Replies: 1
Views: 97

1.25

What is the minimum uncertainty in the position of a hydrogen atom in a particle accelerator given that its speed is known to within _+ 5.0 ms^-1? Not sure how to apply the equation in the textbook to this question.
Mon Oct 08, 2018 1:09 pm
Forum: Einstein Equation
Topic: Homework, 1.15 a
Replies: 2
Views: 66

Homework, 1.15 a

The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 x 10^3 km/s.
a)What is the wavelength of the ejected electron?
Not even sure where to begin.
Thu Oct 04, 2018 3:01 pm
Forum: Balancing Chemical Reactions
Topic: H21
Replies: 1
Views: 159

H21

The psychoactive drug methamphetamine ("speed"), which is sold as the prescription medication Desoxyn, C10H15N, undergoes a series of reactions in the body; the net result of these reactions is the oxidation of solid methamphetamine by oxygen gas to produce carbon dioxide gas, liquid water...
Thu Oct 04, 2018 2:14 pm
Forum: Balancing Chemical Reactions
Topic: H3, coefficients
Replies: 7
Views: 217

H3, coefficients

For this question, there was a diagram that demonstrated that the answer would be 2SiH4 + 4H20 -> 2SiO2 +8H2. I got that answer but I went a step further and divided all the coefficients by 2 and got SiH4 + 2H2O -> SiO2 +4H2. However, the answer in the textbook says it is 2SiH4 + 4H20 -> 2SiO2 +8H2....
Wed Oct 03, 2018 7:12 pm
Forum: Molarity, Solutions, Dilutions
Topic: Concentration Calculations
Replies: 3
Views: 1982

Re: Concentration Calculations

You should use M1V1=M2V2 when you have both the initial molarity and volume and you are trying to figure out the molarity or volume of the final solution, depending on whether they give you the M2 or V2. When the question gives you M2, you solve for V2 and vice versa. Although this question is askin...

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