Search found 72 matches

by Paula Dowdell 1F
Wed Mar 14, 2018 10:44 pm
Forum: Phase Changes & Related Calculations
Topic: finding q
Replies: 1
Views: 175

finding q

This is from an old midterm. Can someone tell me what equation or relationship was used to find q in part b? Thanks.
by Paula Dowdell 1F
Wed Mar 14, 2018 4:11 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ∆U and ∆H
Replies: 1
Views: 82

∆U and ∆H

How are ∆U and ∆H related?
by Paula Dowdell 1F
Tue Mar 13, 2018 6:34 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Drawing Reaction Profiles
Replies: 3
Views: 150

Re: Drawing Reaction Profiles

How do you know how big the energy barrier is going to be, besides by knowing which step is slow (which makes the energy barrier largest for the slow step).
by Paula Dowdell 1F
Tue Mar 13, 2018 1:32 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Drawing Reaction Profiles
Replies: 3
Views: 150

Drawing Reaction Profiles

How do we draw a reaction profile? (For example the one in problem 15.89)
by Paula Dowdell 1F
Mon Mar 12, 2018 10:10 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Problem 15.61
Replies: 5
Views: 211

Re: Problem 15.61

Does anyone know why they used kilojoules in this problem? When i use regular joules (R= 8.314 J/Kxmol) I get a completely different answer.
by Paula Dowdell 1F
Sun Mar 11, 2018 5:00 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Calculating standard enthalpy [ENDORSED]
Replies: 3
Views: 317

Re: Calculating standard enthalpy [ENDORSED]

Standard formation enthalpy refers to the formation of a compound from elementary compounds, while bond energy is applicable when considering the formation of a molecule from isolated atoms.
by Paula Dowdell 1F
Sun Mar 11, 2018 4:57 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Transferring of Heat
Replies: 4
Views: 293

Re: Transferring of Heat

The balloon expands because the kinetic energy increases due to the warmer temperature, making the molecules move faster and hit the inside of the balloon harder and more frequently.
by Paula Dowdell 1F
Sun Mar 11, 2018 4:53 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Change in Entropy
Replies: 2
Views: 104

Re: Change in Entropy

Reactions with a neg. ∆G release energy (they can proceed without an energy input (are spontaneous)).Reactions with a positive ∆G need an input of energy in order to take place (are non-spontaneous).
by Paula Dowdell 1F
Sun Mar 04, 2018 2:32 pm
Forum: General Rate Laws
Topic: 15.25 part b
Replies: 1
Views: 82

15.25 part b

Hi, In part (b) why is it that 3.5h is used for the value of "t" instead of 2s? I thought we would use 2s because the question asked "(b) If [N2O5]0 = 0.0567 mol L-1, what will be the concentration of N2O5 after 2.0 s? " The work in the solutions manual is as follows: [N2O5]=0.05...
by Paula Dowdell 1F
Sat Mar 03, 2018 3:03 pm
Forum: General Rate Laws
Topic: 15.19 part a
Replies: 1
Views: 87

15.19 part a

Hi! Can someone explain to me how they determined that [B] is second order?
I determined [A] by solving as I have previously seen: 1.25^a/2.5 = 8.7/17/4 => 0.5^a=0.5 (first order)
by Paula Dowdell 1F
Sat Mar 03, 2018 2:48 pm
Forum: First Order Reactions
Topic: Half Lives
Replies: 2
Views: 145

Half Lives

Why is it that half lives of 0-order reactions and 2nd-order reactions are "not used"? (pg. 631 in the book)
by Paula Dowdell 1F
Sat Mar 03, 2018 1:51 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: example 15.4: Measuring a Rate Constant
Replies: 2
Views: 207

example 15.4: Measuring a Rate Constant

For the problem shown in example 15.4 we are supposed to, "Confirm that the reaction is first order in C3H6 and calculate the rate constant". The example then tells us to "Plot the natural logarithm of the reactant concentration as a function of t. If a straight line is obtained, the ...
by Paula Dowdell 1F
Thu Mar 01, 2018 10:47 pm
Forum: General Rate Laws
Topic: Determining Order [ENDORSED]
Replies: 8
Views: 262

Determining Order [ENDORSED]

Can someone explain to me how to determine what kind of order a reaction is? Thanks.
by Paula Dowdell 1F
Mon Feb 19, 2018 11:54 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.17 HW problem
Replies: 1
Views: 64

14.17 HW problem

Can someone explain to me why the H+ is added in this cell diagram?

The answer is: Pt(s)|Fe3+(aq), Fe2+(aq)||H+(aq), MnO4-(aq), Mn2+(aq)|Pt(s)
by Paula Dowdell 1F
Mon Feb 19, 2018 11:26 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.15.c
Replies: 2
Views: 129

Re: 14.15.c

How do we know that this salt bridge is necessary?
by Paula Dowdell 1F
Mon Feb 19, 2018 10:57 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.15 given half reactions?
Replies: 3
Views: 172

14.15 given half reactions?

Write the half-reactions and devise a galvanic cell (write a cell diagram) to study each of the following reactions: (b) H+(aq) + OH-(aq) --> H2O(l), the Brønsted neutralization reaction Are we given the half reactions for this problem or is there some way to figure it out without? I don't know when...
by Paula Dowdell 1F
Mon Feb 19, 2018 10:50 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.15 A cell diagram set-up [ENDORSED]
Replies: 2
Views: 133

14.15 A cell diagram set-up [ENDORSED]

Why is it that the cell diagram is set up like Ag(s)|AgBr(s)|Br-(aq)||Ag+(aq)|Ag(s) ? I thought that it would be set up like Br-(aq)|AgBr(s)|Ag(s)||Ag+(aq)|Ag(s) The cathode shows that Ag+ is reduced to form Ag, which is why they are in the order of Ag+,Ag but how does the order on the anode show th...
by Paula Dowdell 1F
Mon Feb 19, 2018 9:25 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14. 11 (d
Replies: 1
Views: 66

Re: 14. 11 (d

I need help with this too! I do not understand how to get the anode half reaction.
by Paula Dowdell 1F
Sat Feb 17, 2018 12:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic/Voltaic
Replies: 2
Views: 94

Re: Galvanic/Voltaic

A Galvanic cell converts chemical energy into electrical energy. A voltaic cell is an electrochemical cell that uses a chemical reaction to produce electrical energy.
by Paula Dowdell 1F
Sat Feb 17, 2018 12:14 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Work
Replies: 5
Views: 245

Re: Work

It's good to note that work is zero if applied force is zero (W=0 if F=0).
by Paula Dowdell 1F
Sat Feb 17, 2018 12:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Is enthalpy a state function?
Replies: 12
Views: 812

Re: Is enthalpy a state function?

A state function describes the equilibrium state of a system. Internal energy, enthalpy, and entropy are state quantities because they describe quantitatively an equilibrium state of a thermodynamic system, irrespective of how the system arrived in that state.
by Paula Dowdell 1F
Tue Feb 13, 2018 2:44 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: deltaS total spontaneity question 9.73
Replies: 1
Views: 86

deltaS total spontaneity question 9.73

Hi! This relates to question 9.73 in the book: "Under what conditions, if any, does the sign of each of the following quantities provide a criterion for assessing the spontaneity of a reaction? (a) G ; (b) H ; (c) S ; (d) delta S total" I thought that if delta S total was negative the reac...
by Paula Dowdell 1F
Sun Feb 11, 2018 1:10 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Higher Molar Entropy?
Replies: 2
Views: 127

Higher Molar Entropy?

Can someone explain the reasoning behind this to me? "Which substance in each of the following pairs has the higher molar entropy: (a) 1 mol CO2(g) at 25 C and 1 bar or 1 mol CO2(g) at 25 C and 3 bar" A: CO2(g) at 1 bar, because disorder increases with volume. I thought bar corresponded to...
by Paula Dowdell 1F
Fri Feb 09, 2018 11:34 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Homework Question 9.13
Replies: 4
Views: 214

Re: Homework Question 9.13

But how do you know that "for a change in temperature, the energy supplied as heat is related to the increase in temperature by the heat capacity, C". Is that always true?
by Paula Dowdell 1F
Fri Feb 09, 2018 11:21 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: disorder & entropy
Replies: 2
Views: 118

disorder & entropy

What does an increase in disorder correspond to? An increase or decrease in entropy?
And why?
by Paula Dowdell 1F
Fri Feb 09, 2018 10:22 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Homework Question 9.13
Replies: 4
Views: 214

Homework Question 9.13

"During the test of an internal combustion engine, 3.00 L of nitrogen gas at 18.5 C was compressed suddenly (and irreversibly) to 0.500 L by driving in a piston. In the process, the temperature of the gas increased to 28.1 C. Assume ideal behavior. What is the change in entropy of the gas?"...
by Paula Dowdell 1F
Fri Feb 09, 2018 10:08 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Homework Question 9.9
Replies: 1
Views: 152

Homework Question 9.9

Hi!

How come in question 9.9 you use just R instead of 3/2R when determining the change in entropy?
The question is: Calculate the entropy change associated with the isothermal expansion of 5.25 mol of ideal gas atoms from 24.252 L to 34.058 L.

Thanks!
by Paula Dowdell 1F
Fri Feb 02, 2018 11:11 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Entropy [ENDORSED]
Replies: 5
Views: 305

Re: Entropy [ENDORSED]

it's good to note that the entropy of a system decreases only when it interacts with some other system whose entropy increases in the process.
by Paula Dowdell 1F
Fri Feb 02, 2018 11:09 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: entropy
Replies: 4
Views: 187

Re: entropy

It is always good to note that if you increase temperature, you increase entropy.
by Paula Dowdell 1F
Fri Feb 02, 2018 11:07 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7582
Views: 1015282

Re: Post All Chemistry Jokes Here

What Do You Get When You Cut An Avocado Into 6X10^23 Pieces?
Guacamole
by Paula Dowdell 1F
Sun Jan 28, 2018 8:24 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed vs. Isolated
Replies: 8
Views: 355

Re: Closed vs. Isolated

just a fun fact to note: the entire universe is an isolated system!
by Paula Dowdell 1F
Sun Jan 28, 2018 8:23 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Definition of Entropy
Replies: 10
Views: 313

Re: Definition of Entropy

The second law of thermodynamics states that an isolated system's entropy never decreases!
by Paula Dowdell 1F
Sun Jan 28, 2018 8:22 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated vs. Adiabatic system
Replies: 8
Views: 641

Re: Isolated vs. Adiabatic system

Another way of thinking about it is that an adiabatic process is a process where the net heat transfer to the working gas is zero vs an isolated system, which is a system that is completely shut off from the surroundings.
by Paula Dowdell 1F
Mon Jan 22, 2018 10:00 pm
Forum: Phase Changes & Related Calculations
Topic: 8.9 torr conversion
Replies: 1
Views: 79

8.9 torr conversion

Hi!
I'm confused on the work calculation in 8.9!

w= -((750 Torr)/(760 Torr x atm^-1)) ((1846mL - 345mL)/(1000mL x L^-1)) = -1.48 L x atm

where did the 760 Torr & the 1000mL come from in the denominators of this work calculation?

Thanks!
by Paula Dowdell 1F
Mon Jan 22, 2018 3:12 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: heat required in example 8.3 pg 270
Replies: 1
Views: 81

heat required in example 8.3 pg 270

Hi!

I am confused about how they found the heat required (delta T) in example 8.3 from the book on page 270. Can someone walk me through this part?

Thanks!
by Paula Dowdell 1F
Sat Jan 13, 2018 2:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess' Law
Replies: 3
Views: 137

Hess' Law

Can somebody explain Hess' Law and its use to me?
by Paula Dowdell 1F
Sat Jan 13, 2018 2:05 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeters
Replies: 3
Views: 110

Re: Calorimeters

To measure heats of reactions, we enclose reactants in a calorimeter, then we initiate the reaction, and then measure the temperature difference (before and after the reaction). The temperature difference allows us to evaluate the heat released in the reaction.
by Paula Dowdell 1F
Sat Jan 13, 2018 1:48 pm
Forum: Phase Changes & Related Calculations
Topic: Boiling water vs. steam
Replies: 6
Views: 541

Re: Boiling water vs. steam

It would be very helpful to google the "heating curve" graph!
by Paula Dowdell 1F
Sat Dec 09, 2017 2:07 pm
Forum: Conjugate Acids & Bases
Topic: 12.119
Replies: 1
Views: 186

12.119

why is it that in the reaction: "B(OH)2 + 2 H2O(l) ⇌ H3O+(aq) + B(OH)4-(aq)", B(OH)2 serves as a lewis acid. I thought that it was donating electron pairs? Can someone explain this to me in detail?
by Paula Dowdell 1F
Fri Dec 08, 2017 7:33 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 12.33 part c
Replies: 1
Views: 110

12.33 part c

Why is it that in 12.33 the solutions manual says the mass of Na2O is 18mol/L?
I'm confused because the concentration of the original solution is also 18mol/L and i did not think mass and concentration were the same thing.
Thanks!
by Paula Dowdell 1F
Fri Dec 08, 2017 1:04 pm
Forum: Bronsted Acids & Bases
Topic: 12.9 d)
Replies: 1
Views: 136

12.9 d)

Can someone walk me throught the steps (including the net ionic equation) of figuring out whether NH4I(am) + KNH2(am) -> KI(am) + 2NH3(l)
can be classified as a rxn between bronsted acids and bases?
by Paula Dowdell 1F
Wed Dec 06, 2017 10:50 pm
Forum: Bronsted Acids & Bases
Topic: J5 Net Ionic Equations
Replies: 1
Views: 101

J5 Net Ionic Equations

Hello on J5 c) I am very confused!

Why is the net ionic eq of LiOH + HI -> H2O + LiI equal to OH + H -> 2H2O? I thought it would just be OH + H -> H2O.
Thanks!
by Paula Dowdell 1F
Wed Dec 06, 2017 9:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.117
Replies: 2
Views: 288

Re: 11.117

For the same reasons NO is x-0.240
by Paula Dowdell 1F
Tue Dec 05, 2017 11:07 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Equilibria shift with temp. increase 11.77
Replies: 2
Views: 161

Equilibria shift with temp. increase 11.77

Hi! I am having trouble figuring out how to approach this problem. Can someone walk me through their way of going about this problem? What is delta H? Q: Predict whether each of the following equilibria will shift towards products or reactants with a temperature increase: a) N2O4(g) ⇌ 2NO2(g), delta...
by Paula Dowdell 1F
Sun Dec 03, 2017 11:16 am
Forum: Bronsted Acids & Bases
Topic: Lewis Acids and Bases Vs. Bronsted Acids and Bases
Replies: 4
Views: 238

Re: Lewis Acids and Bases Vs. Bronsted Acids and Bases

It is helpful to note that a pH balance of 7 is ideal for neutral water solutions! In this situation, acids and bases neutralize each other's effects and characteristics.
by Paula Dowdell 1F
Sat Dec 02, 2017 6:58 pm
Forum: Administrative Questions and Class Announcements
Topic: 14B Syllabus
Replies: 1
Views: 224

14B Syllabus

Hi! I was wondering when the syllabus would be posted for 14B. I am assuming that the 40minute tests we take in discussion will also be a part of 14B and knowing the dates of those tests would be helpful as I am signing up for my winter quarter work shifts soon! Thank you!
by Paula Dowdell 1F
Sun Nov 26, 2017 5:54 pm
Forum: Naming
Topic: 17.31 part c
Replies: 2
Views: 161

17.31 part c

tetraamminediaquacobalt(III)bromide

How come the answer, "[Co(NH3)4(H20)2]Br3" Bromide has a subscript of 3?
by Paula Dowdell 1F
Sun Nov 26, 2017 5:33 pm
Forum: Naming
Topic: Latin Stems [ENDORSED]
Replies: 1
Views: 134

Latin Stems [ENDORSED]

What are the common Latin Stems of elements we are expected to know?
by Paula Dowdell 1F
Sun Nov 26, 2017 5:17 pm
Forum: Naming
Topic: Latin stems of elements
Replies: 2
Views: 140

Re: Latin stems of elements

Taylor 1F wrote:We have to memorize them, but we only need to know like common ones(i.e numbers 1-8 prefixes)

Where can you find these numbers 1-8 prefixes?
by Paula Dowdell 1F
Sun Nov 26, 2017 3:48 pm
Forum: Naming
Topic: Latin stems of elements
Replies: 2
Views: 140

Latin stems of elements

Are we expected to memorize the latin stems of elements? I know you can find them in appendix 2D but do we need to know all of them? Or are there just a few common ones we should know?
by Paula Dowdell 1F
Fri Nov 24, 2017 7:53 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: determining molecular shape?
Replies: 1
Views: 101

determining molecular shape?

Hi I'm a little confused on when to know if the question is asking for a shape that ignores or includes lone pairs in its answers. 4.11 asks to give the "VSEPR formula and predict its shape" and by judge of it's answers they are taking lone pairs into consideration since the answers are a)...
by Paula Dowdell 1F
Sun Nov 19, 2017 8:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Double bonds vs. single bonds
Replies: 4
Views: 223

Re: Double bonds vs. single bonds

something that might be helpful: Lone pairs of electrons take up more space than bonded pairs!
by Paula Dowdell 1F
Sun Nov 19, 2017 8:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar ve non polar [ENDORSED]
Replies: 7
Views: 375

Re: Polar ve non polar [ENDORSED]

I would note that you need to first determine if the bonds between the atoms are polar! Some shapes will cause dipoles to cancel out.
by Paula Dowdell 1F
Wed Nov 08, 2017 9:32 pm
Forum: Octet Exceptions
Topic: Nonmetals vs. Metalloids
Replies: 2
Views: 169

Re: Nonmetals vs. Metalloids

but are metalloids considered non-metals for periods 3 and on?
by Paula Dowdell 1F
Wed Nov 08, 2017 7:10 pm
Forum: Octet Exceptions
Topic: Nonmetals vs. Metalloids
Replies: 2
Views: 169

Nonmetals vs. Metalloids

Hi,
I read in the textbook that period three and on "non-metal" atoms may expand their valence shells. Are metalloids in this case considered non-metals?
by Paula Dowdell 1F
Tue Nov 07, 2017 10:13 pm
Forum: Molarity, Solutions, Dilutions
Topic: Post Module Assessment Question
Replies: 1
Views: 152

Post Module Assessment Question

Hey! I know the answer to this question is B, but can someone explain to me why A, C, and D are false? 21. When a solution is diluted what is the main concept that one must be aware of? A. The moles of solute change. B. The moles of solute stay the same. C. The volume of solvent stays the same. D. T...
by Paula Dowdell 1F
Tue Nov 07, 2017 6:52 pm
Forum: Empirical & Molecular Formulas
Topic: Test 1 Compound X [ENDORSED]
Replies: 5
Views: 392

Re: Test 1 Compound X [ENDORSED]

I'm confused by this question because when i divide 0.0594mol H/0.16996 I get 2.99 (approximately 3) and then when dividing 0.16996mol C/0.16996 I get 1. This leaves me with CH(sub)3 when I really should be getting C(sub)2 H(sub)6
What am I doing wrong?
by Paula Dowdell 1F
Tue Nov 07, 2017 5:55 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Reactions post-module assessment
Replies: 2
Views: 178

Balancing Chemical Reactions post-module assessment

hi!
What are the coefficients in chemical equations called?
A. Mass-ratio coefficients

B. Stoichiometric coefficients

C. Molar coefficients

D. Reaction coefficients

I thought they were called Molar coefficient but turns out I am wrong! What is the right answer?
by Paula Dowdell 1F
Tue Nov 07, 2017 2:32 am
Forum: Molarity, Solutions, Dilutions
Topic: Test 1 Question Q2B
Replies: 4
Views: 611

Test 1 Question Q2B

Hi! The question is how many milliliters of the stock solution would you need to use to make 250 mL 0.650 M NaOH solution.
How come the answer is 81.2mL? Thanks!
by Paula Dowdell 1F
Sun Nov 05, 2017 8:04 pm
Forum: Octet Exceptions
Topic: Octet Exception Question [ENDORSED]
Replies: 3
Views: 457

Octet Exception Question [ENDORSED]

What does size mean when referring to octet exceptions?
by Paula Dowdell 1F
Sun Nov 05, 2017 8:03 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 8
Views: 450

Formal Charge

When do you know that your lewis structure has a good formal charge?
by Paula Dowdell 1F
Sun Oct 29, 2017 1:23 pm
Forum: Quantum Numbers and The H-Atom
Topic: Calculating the probability of finding an electron at a certain location
Replies: 1
Views: 198

Calculating the probability of finding an electron at a certain location

Hi! I am having some trouble understanding this concept. In the textbook Example 2.1 shows how to calculate the probability of finding an electron, but I am still confused. The question/answer for the problem is as shown below: Can someone walk me through this? Q: Suppose an electron is in a 1s orbi...
by Paula Dowdell 1F
Sat Oct 28, 2017 11:36 pm
Forum: Quantum Numbers and The H-Atom
Topic: Ionization vs. Ionization Energy
Replies: 2
Views: 150

Ionization vs. Ionization Energy

What is the difference between ionization and ionization energy? Is there a limit to ionization energy?
by Paula Dowdell 1F
Sat Oct 28, 2017 8:25 pm
Forum: *Particle in a Box
Topic: Particle in a box
Replies: 1
Views: 419

Particle in a box

Can somebody explain the concept of particle in a box to me?
by Paula Dowdell 1F
Fri Oct 13, 2017 12:47 pm
Forum: Properties of Light
Topic: 1.3 homework [ENDORSED]
Replies: 11
Views: 501

Re: 1.3 homework [ENDORSED]

the extent of change in the electrical field is referring to the amplitude!
by Paula Dowdell 1F
Fri Oct 13, 2017 12:46 pm
Forum: Properties of Light
Topic: 1.3 homework [ENDORSED]
Replies: 11
Views: 501

Re: 1.3 homework [ENDORSED]

It is important to note that all of these instances (a)-(d) can be answered by using E=hv and v(lambda)=c (a) speed does not decrease because it is constant (b) the wavelength does not decrease because frequency is proportional to (lambda)-1 (c) Yes! as frequency decreases the waves get wider and th...
by Paula Dowdell 1F
Thu Oct 12, 2017 11:26 pm
Forum: Properties of Light
Topic: Nuclear Model of the Atom
Replies: 2
Views: 187

Nuclear Model of the Atom

Could somebody explain to me the difference in Thomson and Rutherford's models of the atom?
by Paula Dowdell 1F
Wed Oct 04, 2017 11:54 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E.29 part b HELP
Replies: 3
Views: 232

E.29 part b HELP

Hi I am having trouble with part b of E.29. (a) 0.0417 mol CuCl2 x 4H2O (b) The questions asks how many moles of Cl- ions are present in the sample. The book says to double the amount in part (a) but i don't really understand why. If it is asking specifically how many moles of Cl- ions are present w...
by Paula Dowdell 1F
Wed Oct 04, 2017 4:57 pm
Forum: Molarity, Solutions, Dilutions
Topic: E.15 homework question [ENDORSED]
Replies: 4
Views: 259

Re: E.15 homework question [ENDORSED]

I had the same problem! Just note that the question says "metal hydroxide". You can assume that M=metal and hydroxide= (OH)2.
by Paula Dowdell 1F
Wed Oct 04, 2017 12:33 am
Forum: Significant Figures
Topic: Use of Significant Figures in Self Test E.2A
Replies: 3
Views: 269

Use of Significant Figures in Self Test E.2A

Hi! In question Self-Test E.2A I am trouble figuring out which number of significant figures to use. Question: The mass of a copper coin is 3.20g. Suppose it were pure copper. (a) How many moles of Cu atoms would the coin contain, given a molar mass of Cu of 63.55 g/mol? (b) How many Cu atoms are pr...
by Paula Dowdell 1F
Tue Oct 03, 2017 9:49 am
Forum: SI Units, Unit Conversions
Topic: Exercise E1 [ENDORSED]
Replies: 6
Views: 774

Re: Exercise E1 [ENDORSED]

Is there any reason why you have to change pm to m? Do you typically change to m in most chemistry problems?

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