## Search found 70 matches

Fri Mar 16, 2018 7:13 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Work and derivations
Replies: 2
Views: 316

### Work and derivations

So I know for a reaction that produces a net number of moles, w=-(delta n)RT, is this in anyway related to Delta H=\Delta U+\Delta nRT (which is found in the book)? If so, how come we can use this equation under constant volume. I thought that work is zero for constant volume. However, this is the p...
Fri Mar 16, 2018 12:31 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Book Thinking Point
Replies: 1
Views: 281

### Book Thinking Point

I saw this in the book and don't understand. "Potential energy is related to position. Therefore, in an isothermal expansion, why is there no potential energy change as the molecules move further apart?" Is this because temperature is related to the heat energy of the particles, and so the...
Fri Mar 16, 2018 12:29 am
Forum: Phase Changes & Related Calculations
Topic: Constant Volume
Replies: 3
Views: 272

### Constant Volume

Is this correct? So I know that when volume is constant, work is zero. However, for a reaction with changing pressure and moles, but constant volume, that is behaving ideally, we can relate deltaPV=delta nRT, in which there would be work, right?
Mon Mar 12, 2018 11:24 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Distinguishing a Catalyst
Replies: 4
Views: 291

### Re: Distinguishing a Catalyst

A reactant does not show up on the product sides. It is consumed in the reaction. A catalyst, on the other hand, will show up on both sides.
Mon Mar 12, 2018 11:23 pm
Forum: General Rate Laws
Topic: graphs
Replies: 8
Views: 426

### Re: graphs

I would assume so, as they will aid in finding the y intercepts, and the overall shape of the graph, based on the order.
Mon Mar 12, 2018 11:22 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Mechanism Steps
Replies: 4
Views: 257

### Re: Reaction Mechanism Steps

I think so because the rate law is just determined by that one step, so that is the only step that could be the rate determining step.
Mon Mar 12, 2018 11:21 pm
Forum: Administrative Questions and Class Announcements
Topic: Discussion Sections
Replies: 2
Views: 273

### Re: Discussion Sections

Yes. Discussion sessions meet this week. However, next week, there are no classes.
Fri Mar 09, 2018 12:03 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: What is Molecularity?
Replies: 9
Views: 1236

### Re: What is Molecularity?

I don't think that molecularity isn't involved in intermediates. Molecularity only applies to the reactants in the rate determining step. If there are intermediates in the slow step, you have to solve for correct pre-equilibrium rate law, I believe.
Fri Mar 09, 2018 12:01 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 5
Views: 411

### Re: Catalysts

The activation energy determines the rate of reaction. To increase the rate of reaction, the activation energy or energy barrier must be lowered. For example, when rolling a ball up a hill and then letting it roll down, the get up the hill is the activation energy. A catalyst just builds a tunnel th...
Fri Mar 09, 2018 12:00 pm
Forum: Second Order Reactions
Topic: Units of k for orders above 2nd
Replies: 6
Views: 478

### Re: Units of k for orders above 2nd

Yes this trend should continue. Just remember that for zero order, it is actually mol/l*s, not inverted.
Sat Mar 03, 2018 3:20 pm
Forum: General Rate Laws
Topic: 15.39a
Replies: 3
Views: 245

### 15.39a

For a, because the reaction is 2A-->B + C, why isn't there a 2 in the reaction. If we are solving the differential rate law -1/2 d[A]/dt=k[A]^2, we get -1/2 d[A]/[A]^2= kdt. If we multiply the 2 to the other side, we are left with -d[A]/[A]^2=2kdt. If we integrate both sides, we get 1/[A]=2kt + 1/[A...
Wed Feb 28, 2018 10:39 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Determining order
Replies: 1
Views: 176

### Re: Determining order

They determined the concentration of H3O+ from steps 2 and 4. In these steps, both BrO3- and Br- are staying the same initial concentration. However, only H3O+ is changing. Therefore, by using these two steps, find the exponent of H3O+. And fc and ln is just another way of finding the exponent. They...
Wed Feb 28, 2018 10:37 pm
Forum: First Order Reactions
Topic: Derivation
Replies: 8
Views: 454

### Re: Derivation

No. My TA stated that this won't be necessary. However, Dr. Lavelle has spoken on how it helps to know how to derive each formula, as it demonstrates a deeper understanding of the concepts.
Wed Feb 28, 2018 10:36 pm
Forum: General Rate Laws
Topic: Overall order [ENDORSED]
Replies: 6
Views: 481

### Re: Overall order[ENDORSED]

We will need to know the overall order, if given experimental data (in order to right a rate law). However, for integrated rate laws, as of right now, we are only are dealing with zero, first, and second orders, and only one reactant.
Wed Feb 21, 2018 10:57 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Notation
Replies: 2
Views: 183

### Re: Notation

And remember, each side is usually written (anode reactant, anode product) and (cathode reactant, cathode product).
Wed Feb 21, 2018 10:55 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: E and Eo
Replies: 2
Views: 424

### Re: E and Eo

E depends on the concentrations of the products and reactants. However, Eo is at standard state, and with respect to a hydrogen electrode.
Tue Feb 20, 2018 3:09 pm
Forum: Balancing Redox Reactions
Topic: 14.115
Replies: 2
Views: 275

### 14.115

This problem states that "the aluminum air fuel cell is used as a reserve battery in remote location. In this cell , aluminum reacts with the oxygen in air in basic solution. It asks for the oxidation/reduction half reactions. However, for the oxidation, the answer key shows Al-->Al(OH)3. How w...
Wed Feb 14, 2018 2:32 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Constant Pressure
Replies: 2
Views: 212

### Re: Constant Pressure

Lucian1F wrote:For a constant volume, not pressure, the work is 0 so U=q=H. The example you stated says U=q at constant volume

According to the example 8.6b, it is at constant pressure.
Wed Feb 14, 2018 2:19 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Constant Pressure
Replies: 2
Views: 212

### Constant Pressure

How come at constant pressure, for the first law, delta U=q=delta H? Why is there no work being done? An example of this is on pages 281-282 for example 8.6 where it asks for the change in internal energy at constant pressure.
Tue Feb 13, 2018 2:52 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: First Law
Replies: 5
Views: 659

### First Law

So delta U is 0 when it is an isothermal, reversible expansion. However, what if the expansion is irreversible? Is it still zero? Also, when is q in the first law zero?
Tue Feb 13, 2018 2:50 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible but not-isothermal expansion?
Replies: 3
Views: 259

### Re: Reversible but not-isothermal expansion?

That could work. However, delta U would have to be given. But we do have an equation for a reversible reaction that is not isothermal for work.
Tue Feb 13, 2018 2:49 pm
Forum: Phase Changes & Related Calculations
Topic: Reversible
Replies: 5
Views: 625

### Re: Reversible

Reversible is when there is an infinitesimally small change, the reaction can be "reversed" and is not greatly affected. On the other hand, a irreversible reaction is a large change that is can be specifically pinpointed.
Tue Feb 13, 2018 2:48 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: deltaS total spontaneity question 9.73
Replies: 1
Views: 140

### Re: 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 rea...
Wed Feb 07, 2018 10:59 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.103
Replies: 4
Views: 286

### Re: 9.103

Minie 1G wrote:So how would you tell whether the equations, A and B, are spontaneous or not?

If the ΔG is negative for the reaction, it is spontaneous. If it is positive, it is non spontaneous. Another way you could do it is by calculating the total ΔS. If ΔS total is greater than 0, the reaction is spontaneous.
Wed Feb 07, 2018 10:56 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.51 [ENDORSED]
Replies: 3
Views: 353

### Re: 9.51[ENDORSED]

Exothermic reactions transfer heat from the system to the surroundings. One of the common formulations of the 2nd Law of Thermodynamics is that the entropy of the universe always increases. This means that exothermic reactions are more likely to be spontaneous. If you consider the relationship ΔG =...
Wed Feb 07, 2018 10:53 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.89 [ENDORSED]
Replies: 1
Views: 121

### 9.89[ENDORSED]

I don't understand the explanation of the book. In previous examples, it has said that entropy of dissolving decreases for the surroundings (thermally) and increases for the system (positionally) (positive overall). Therefore, why are some still negative? The answer speaks of errors in reference poi...
Thu Feb 01, 2018 2:12 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: sign of entropy
Replies: 11
Views: 675

### Re: sign of entropy

How do I know whether the entropy has a "+" or a "-"? It depends on the the ratio of final to initial temperature, volume, and/or pressure. You can logically think about by analyzing whether the number of microstates is increasing or decreasing, which can give an indication to w...
Thu Feb 01, 2018 2:11 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Regarding the equation deltaS=nCln(Tf/Ti)
Replies: 3
Views: 468

### Re: Regarding the equation deltaS=nCln(Tf/Ti)

melissa carey 1f wrote:Also, when do we need to include n, the number of moles, as I see it omitted in some forms of the equations? Thanks!

You pretty much always include them for entropy calculations. Because the units have to cancel out to leave you with J/K.
Thu Feb 01, 2018 2:09 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.11 [ENDORSED]
Replies: 3
Views: 250

### Re: 9.11[ENDORSED]

We are not given values for V or T in this problem. Only n and P . Thus, two of the unknowns in the ideal gas equation of state PV = nRT are left unknown. The information that the change occurs isothermally is enough for us to use the formula \Delta S = nRln\frac{V_{f}}{V_{i}} but since we are give...
Thu Jan 25, 2018 10:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Internal Energy
Replies: 5
Views: 273

### Re: Internal Energy

William Lan 2l wrote:If delta P = 0 (constant pressure), why is delta U = q + w? I thought that w = -PdeltaV. If P is 0, there would be no work then right?

That is a variation of the original equation. It all depends on what the environment/surrounding/situation is and whether the reaction is reversible or not.
Thu Jan 25, 2018 10:41 pm
Forum: Calculating Work of Expansion
Topic: Expanding VS Compressing
Replies: 2
Views: 174

### Re: Expanding VS Compressing

Cristian Carrasco 1F wrote:If a system is expanding would that be the system doing work? and would Delta U be positive or negative

Delta U would depend on both q and w, not just q. If a system is expanding, it is doing work. If it is being compressed, work is being done on the system, and thus is a positive value.
Tue Jan 23, 2018 8:40 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8047
Views: 1412824

### Re: Post All Chemistry Jokes Here

Organic chemistry is difficult. Those who study it have alkynes of trouble.
Tue Jan 23, 2018 8:39 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat vs. Enthalpy
Replies: 5
Views: 236

### Re: Heat vs. Enthalpy

so when using delta H, is it wrong for someone to refer to that as heat? delta H is enthalpy right? Heat and enthalpy are only equal when pressure is constant and volume is constant. That is why Dr. Lavelle wrote the equation qp=delta H. If these are not constant, you have to assume that Delta U=De...
Tue Jan 23, 2018 8:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Units
Replies: 2
Views: 138

### Units

When is delta H in kJ/mol or just kJ? (because the book uses both units)
Thu Jan 18, 2018 6:29 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Energy and matter?
Replies: 6
Views: 389

### Re: Energy and matter?

Yes. That is correct. Isolated let’s nothing in or out.
Thu Jan 18, 2018 6:27 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat vs. Enthalpy
Replies: 5
Views: 236

### Re: Heat vs. Enthalpy

Enthalpy is heat but not heat is enthalpy.
Thu Jan 18, 2018 6:26 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Specific Heat Capacity vs Heat Capacity
Replies: 5
Views: 351

### Re: Specific Heat Capacity vs Heat Capacity

Heat capacity doesn’t take into account how much of a substance is there. It doesn’t include grams or moles
Wed Jan 10, 2018 6:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 5
Views: 224

### Re: Bond Enthalpies

Yes and no. You are just adding the values together. The values of energy required are always positive and the values of energy released are negative. So just add the positive and negative values.
Wed Jan 10, 2018 6:47 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity vs. Specific Heat Capacity
Replies: 6
Views: 318

### Re: Heat Capacity vs. Specific Heat Capacity

It's basically just about the units. It depends whether you are using grams or moles.
Wed Jan 10, 2018 6:46 pm
Forum: Phase Changes & Related Calculations
Topic: Why can state properties be added?
Replies: 11
Views: 684

### Re: Why can state properties be added?

They cannot be changed by intrinsically. That allows for them to be added. For example, work cannot be added together because of how "it is prepared." Either force or distance can be changed. But energy "preparation" is the same, and likewise for all state properties, allowing th...
Sat Dec 09, 2017 9:35 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Replies: 2
Views: 269

The book specifies that adding water will only shift an equilibrium if the other products or reactants are not dilute. However, if they are dilute, it says that we can assume that the concentration is unchanged. Will this be specified, whether the products or reactants are dilute in solution or not,...
Sat Dec 09, 2017 9:19 am
Forum: Octet Exceptions
Replies: 3
Views: 287

I've heard many conflicting arguments whether when assigning a radical, formal charge or electronegativity is more important. Some say that the electron is assigned to the atom of the lower electronegativity. However, in the book, there is a homework problem of CL-O where chlorine has a full octet w...
Fri Dec 08, 2017 1:54 pm
Forum: Conjugate Acids & Bases
Topic: Acid Strength Comparison. 12.115A [ENDORSED]
Replies: 1
Views: 218

### Acid Strength Comparison. 12.115A[ENDORSED]

If we are given only the structures of two conjugate bases from weak acids and are asked to compare which acid is stronger, how would we tell from the molecular structure? For example, in 12.115A, it asked whether carbonic acid would act as an acid or base in an acetate solution, without looking at ...
Wed Dec 06, 2017 9:09 pm
Forum: Lewis Acids & Bases
Topic: Strength [ENDORSED]
Replies: 1
Views: 208

### Strength[ENDORSED]

When we were talking about bond character and polarizability and polarizing power, we said that those with higher polarizing power and higher polarizability express more covalent character than ionic character and becomes less soluble. However, does this only apply to salts? Because, this seems to b...
Wed Dec 06, 2017 9:48 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Reason for not including water
Replies: 6
Views: 418

### Re: Reason for not including water

Both your reasons that you stated are equally correct. Remember though than in Le Chatelier's Principle, the concentration of everything can be affected by the addition or subtraction of water.
Wed Dec 06, 2017 9:46 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: ICE Chart [ENDORSED]
Replies: 9
Views: 569

### Re: ICE Chart[ENDORSED]

It's okay to use an ICE chart whenever there is a reaction. It just depends what you put for the starting and change values. For a strong base/acid, the change will cause the reactant base/acid to go to 0 while for weak base/acid, there will be some reactant still left over.
Mon Dec 04, 2017 10:57 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Acid Strength
Replies: 1
Views: 150

### Acid Strength

When determining acid strength comparisons, which is more important: bond length or polarity of the bond? It seems to differ between oxoacids/carboxylic acids and acids like HF, HBr, HI, and HCl.
Fri Dec 01, 2017 9:18 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8047
Views: 1412824

### Re: Post All Chemistry Jokes Here

I'm out of chemistry jokes. I should zinc of a new one.
Mon Nov 27, 2017 2:34 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Chem Equilibrium Module 4 #15 [ENDORSED]
Replies: 6
Views: 760

### Re: Chem Equilibrium Module 4 #15[ENDORSED]

In this situation, liquid water is a part of the reaction. According to Le Chatelier's Principle, if more reactant is added then more CO2 will react and more product will be made. If the reaction did not include water however, then the addition of water will not affect the amount of product that is...
Mon Nov 27, 2017 2:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Homework 4.13
Replies: 3
Views: 314

### Re: Homework 4.13

P can have an expanded octet. You want to achieve the lowest normal charge possible. That is when O has two bonds and two lone pairs. This gives it a formal charge of 0. If it only had one bond, it would have a formal charge of -1.
Mon Nov 27, 2017 1:24 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Bidentates
Replies: 1
Views: 174

### Bidentates

If a compound is a tridentate for example, will it only act as a tridentate, or could it be a bidentate or monodentate?
Wed Nov 22, 2017 3:55 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Using the ICE Box
Replies: 2
Views: 215

### Re: Using the ICE Box

The bars are another way of writing molarity or concentration. []=molarity
Wed Nov 22, 2017 3:54 pm
Forum: Lewis Structures
Topic: Extended Octets
Replies: 1
Views: 137

### Re: Extended Octets

Look at their hybridization and how many orbitals are half filled as well as their location in the periodic table.
Wed Nov 15, 2017 10:23 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Difference Between Orbitals and Subshells [ENDORSED]
Replies: 7
Views: 1148

### Re: Difference Between Orbitals and Subshells[ENDORSED]

Remember when it asks for sub shell designation, it means both n and l as well (e.g. 4s, 2p, etc...).
Wed Nov 15, 2017 10:22 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Bond Angles
Replies: 8
Views: 653

### Re: Bond Angles

Usually with bond angles and molecular/electron shape, it is pure memorization and nothing more. However, most of the bond angles are relatively easy to figure out by using logic and working through the lewis structure.
Tue Nov 07, 2017 5:12 pm
Forum: Octet Exceptions
Replies: 4
Views: 1307

If a molecule has an unpaired electron, where does this electron go? Should the Lewis structure be made so that the lowest formal charge is achieved and that determines the placement of this electron?
Tue Nov 07, 2017 4:37 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration of Ions
Replies: 2
Views: 184

### Re: Electron Configuration of Ions

Remember, atoms want to be in the lowest energy and most stable state. This is either when all the orbitals are filled or none are filled. For group 13, they lose 3 electrons so that they reach noble gas configuration. Noble gasses are in the most stable state. They neither accept nor donate electro...
Tue Nov 07, 2017 4:32 pm
Forum: Octet Exceptions
Topic: Resonance Structures and Isomers
Replies: 2
Views: 323

### Re: Resonance Structures and Isomers

A resonance structure means that the molecule is the same but the bonds can be interchanged. The bonds blur together in (dotted line). In isomers, this is referring to only organic compounds. The bonds do not blur with one another. Resonance structures can refer to both organic and inorganic molecul...
Mon Nov 06, 2017 6:12 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8047
Views: 1412824

### Re: Post All Chemistry Jokes Here

Chemists never die. They just reach equilibrium.
Wed Nov 01, 2017 10:30 am
Forum: Trends in The Periodic Table
Topic: Chapter 2, #93
Replies: 3
Views: 254

### Re: Chapter 2, #93

When in ground state and having lost or gained no electrons, atomic radius increases from right to left and down. However, when ions come into play, because those on the right of the periodic table gain electrons, they have an expanded shell and thus have a larger radius than cations. But, in all, a...
Wed Nov 01, 2017 10:28 am
Forum: Octet Exceptions
Topic: Octet Rule [ENDORSED]
Replies: 1
Views: 257

### Octet Rule[ENDORSED]

Which takes priority? Should you have a lower formal charge with an expanded octet or higher formal charge with the 8 valence e-? And should you try to the central atom to have the lowest formal charge in all?
Thanks!
Wed Oct 25, 2017 9:44 am
Forum: Quantum Numbers and The H-Atom
Topic: 4s before 3d
Replies: 3
Views: 2324

### Re: 4s before 3d

Why exactly do electrons fill up the 4s orbital before filling up the 3d? And why when writing out the configuration must we write 3d before 4s? It all depends on the where the atom is on the periodic table. If d is 4/5, or 9/10, then d fills up first (goes to the higher number). If not these scena...
Wed Oct 25, 2017 9:41 am
Forum: Properties of Electrons
Topic: Rydberg Equation [ENDORSED]
Replies: 6
Views: 566

### Re: Rydberg Equation[ENDORSED]

Rydberg's Equation describes the change in energy. Change is always final-initial, except in very few specific cases.
Tue Oct 17, 2017 7:49 pm
Forum: Properties of Electrons
Topic: Rydberg's formula
Replies: 6
Views: 725

### Re: Reinberg's formula

It's easier to think about in terms of E=-hR/n^2. Then, calculated the change of final-initial. Or use energy to get wavelength or frequency. Hope this helps!
Tue Oct 17, 2017 7:46 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: ch1 question 43
Replies: 8
Views: 730

### Re: ch1 question 43

Set up the equation like this. The change in momentum times the change in position has to be greater than or equal to h/4pi. Momentum is mv of an electron. v is the unknown but you do know the position. So, plug in these numbers (9.110x10^-31 kg)(x m/s)(350.x10^-12 m)>/(6.626x10^-34 Js)/4pi. Solve t...
Tue Oct 10, 2017 10:32 pm
Forum: Properties of Light
Topic: Chapter 1 #3
Replies: 9
Views: 567

### Re: Chapter 1 #3

EM radiation can be seen through the particle lens. If the frequency is decreasing, the energy of the field/wave is decreasing as well. With relation to an electric field, if the frequency, hence the energy decreases.
Tue Oct 10, 2017 10:29 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Chapter 1 question 15
Replies: 4
Views: 665

### Re: Chapter 1 question 15

Laura Riccardelli wrote:How often will be asked to apply Rydberg's equation in this class?

Usually, you can assume to apply the Rydberg equation whenever there is a change in energy level, say from n=2 to n=1, etc... Other than that scenario, the Rydberg equation is not that useful.
Wed Oct 04, 2017 11:02 am
Forum: Balancing Chemical Reactions
Topic: Combustion Reaction Water Phase
Replies: 2
Views: 379

### Re: Combustion Reaction Water Phase

joshuaxian wrote:During a combustion reaction of an organic compound, is water vapor usually produced, or are there situations in which liquid water is produced instead?

usually water vapor unless otherwise stated.
Wed Oct 04, 2017 10:42 am
Forum: Molarity, Solutions, Dilutions
Topic: HW Problem E35
Replies: 5
Views: 621

### Re: HW Problem E35

As a follow-up question for Problem E35, I was wondering how you know the conversion of 1 mol Ca5((PO4)3)OH is exactly 1 mol Ca5((PO4)3)F ? Is it assumed since the problem doesn't state otherwise? That was the whole point of the percent increase problem. If you have a certain number of grams of Ca5...
Tue Oct 03, 2017 10:49 pm
Forum: Significant Figures
Topic: All students read this sig fig post [ENDORSED]
Replies: 131
Views: 17185

### Re: All students read this sig fig post[ENDORSED]

Do you know if the problems will specifically tell us how many significant figures to use? No. With the numbers that are given, you should know how many sig figs to use. But when using molecular mass, the best number is 3-4 sig figs. When in doubt, use 3 sig figs. Other than that, always apply the ...