## Search found 58 matches

Sat Mar 17, 2018 1:03 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: rate and temp in endothermic reaction
Replies: 1
Views: 125

### rate and temp in endothermic reaction

Why is the rate, with regards to k, of the forward reaction of an endothermic reaction more sensitive to temperature, so that an increase in temperature shifts the reaction towards products?
Sat Mar 17, 2018 12:59 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate and equilibrium constants
Replies: 3
Views: 249

### Re: Rate and equilibrium constants

Clarissa Molina 1D wrote:Do we use K=k/k' when there is only one step in a mechanism and K=(k1/k1') x (k2/k2') x ... when there are multiple steps?

Yes that is correct
Sat Mar 17, 2018 12:35 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate and equilibrium constants
Replies: 3
Views: 249

### Rate and equilibrium constants

Do the same conditions change both the equilibrium constant and the rate constant in the same ways? As in if one property affects one, can it be automatically deduced that it affects the other?
Thu Mar 15, 2018 10:25 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Rate determining step
Replies: 2
Views: 213

### Re: Rate determining step

I had this same question - maybe a typo?
Thu Mar 15, 2018 10:23 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.65, part c
Replies: 3
Views: 297

### Re: 15.65, part c

In the problem they give you Ea for the forward and reverse processes, 39.7 kj/mol*min and 25.4 kj/mol*min. You can see that the reaction is endothermic because endothermic reactions have larger activation energies in the forward process than in the reverse process, because it requires more energy t...
Thu Mar 15, 2018 10:00 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.63
Replies: 3
Views: 294

### Re: 15.63

Can someone please explain where the -.59 came from in the solution manual? I'm very confused by this
Thu Mar 15, 2018 8:36 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: What's on the final
Replies: 1
Views: 208

### What's on the final

Do we need to know the math behind the collision theory with the steric requirement, collision rate, and energy requirement for the final? :(
Thu Mar 15, 2018 8:30 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: endothermic reaction.
Replies: 5
Views: 378

### Re: endothermic reaction.

An endothermic reaction will "shift towards products" with an increase in temperature, because the rate of the forward reaction is more sensitive to temperature than the reverse due to its larger activation energy.
Thu Mar 15, 2018 7:56 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: State Functions
Replies: 4
Views: 426

### Re: State Functions

Pressure, volume, temperature, density and internal energy are all state functions.
Thu Mar 15, 2018 7:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Helium-3
Replies: 1
Views: 246

### Helium-3

The book says that all entropies of fusion are positive, which makes sense because melting requires energy for the breaking of bonds. Helium-3 has the only negative entropy of fusion; out of curiosity, why is this?
Thu Mar 15, 2018 7:23 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius eq and integrated rate law
Replies: 1
Views: 160

### Arrhenius eq and integrated rate law

What gives the Arrhenius equation its similar structure to the integrated rate law for a 1st order reaction?
Thu Mar 15, 2018 7:19 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius equation and order of rxn
Replies: 3
Views: 248

### Arrhenius equation and order of rxn

Can the Arrhenius equation be used for all orders of reactions? Or is the order not even relevant to using the equation?
Thu Mar 15, 2018 7:15 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation and constant
Replies: 3
Views: 269

### Re: Arrhenius Equation and constant

Can someone also expand conceptually on what "Exhibiting Arrhenius behavior" entails in regards to rate constants?
Wed Mar 14, 2018 12:07 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Question 15.49
Replies: 1
Views: 159

### Re: Question 15.49

Phases should not be inferred because this would make a difference in reaction rate, so the overall reaction should be left unspecified as the given mechanisms are.
Wed Mar 14, 2018 12:04 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Question 15.51
Replies: 8
Views: 516

### Re: Question 15.51

Another main point to add to this is that the slow step must occur before other elementary steps in order for the overall reaction rate to only depend upon this slowest step; in other words, if there is another elementary step occurring before the slow step, this must be included in the overall rxn ...
Wed Mar 14, 2018 12:00 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Question 15.47
Replies: 4
Views: 262

### Re: Question 15.47

I see what you're saying here, and I originally included them in the overall reaction as well because an atom and an ion of the same element can behave very differently. Maybe they forgot the - for the reactant side Cl?
Tue Mar 13, 2018 11:26 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Steady-State v Pre equilibrium?
Replies: 2
Views: 236

### Re: Steady-State v Pre equilibrium?

^^However, if both overall reaction rates obtained from the above two methods match the experimentally determined rate law, then there should be no difference in which method you use, just that the pre-equilibrium approach is faster and sometimes less accurate in complex reactions.
Tue Mar 13, 2018 11:21 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Steady State Approximation
Replies: 2
Views: 200

### Re: Steady State Approximation

The steady state approach to determining the overall rate law is just a more precise way of ensuring you arrive at the correct overall rate law by eliminating the intermediate concentration in terms of the other elementary-step variables. I guess if its not on the final then it doesn't do much good ...
Mon Mar 12, 2018 9:27 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cp or Cv in temperature change
Replies: 3
Views: 529

### Re: Cp or Cv in temperature change

An easier way to think of it might be that whatever condition is constant is the specific heat used, so if volume is the only variable of the three not changing, you would use Cv in the deltaS equation.
Sat Mar 10, 2018 7:13 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.49
Replies: 2
Views: 228

### 8.49

Question 8.49 asks what the change in internal energy is for 1.00 mol of a reactant where deltaH = -318 KJ. In the solution manual it manipulates the equation deltaU = deltaH - PdeltaV for -PdeltaV = -nRT. However, instead of using the gas constant .08206 as is always used in the ideal gas equation,...
Sat Mar 10, 2018 7:10 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Enthalpy and U
Replies: 1
Views: 178

### Enthalpy and U

Why is the reaction enthalpy less negative than the reaction internal energy for reactions that generate gases?
Sat Mar 10, 2018 7:05 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Reversible Isothermal Expansion [ENDORSED]
Replies: 1
Views: 178

### Reversible Isothermal Expansion[ENDORSED]

Why is work done in reversible isothermal expansion of an ideal gas the maximum expansion work possible?
Wed Mar 07, 2018 10:43 am
Forum: General Rate Laws
Topic: Stoichiometric Coefficients
Replies: 2
Views: 169

### Re: Stoichiometric Coefficients

Unique reaction rates use coefficients because it is specifying the reaction rate in terms of each reactant or product. So if the reaction rate, for example, is .50 L/mol*s and the coefficient in front of one of the reactants is 2, the reaction rate according to this reactant would be different than...
Wed Mar 07, 2018 10:42 am
Forum: General Rate Laws
Topic: Stoichiometric Coefficients
Replies: 2
Views: 169

### Re: Stoichiometric Coefficients

Unique reaction rates use coefficients because it is specifying the reaction rate in terms of each reactant or product. So if the reaction rate, for example, is .50 L/mol*s and the coefficient in front of one of the reactants is 2, the reaction rate according to this reactant would be different than...
Wed Mar 07, 2018 10:38 am
Forum: General Rate Laws
Topic: Problem 15.37
Replies: 3
Views: 260

### Problem 15.37

This problem asks for the time needed for SO2Cl2 concentration to decrease to 10% of the initial concentration. In the answer it says t= ln(SO2Cl2 initial/SO2Cl2 ) / k is equal to ln10/k. Why is this?
Wed Mar 07, 2018 10:35 am
Forum: General Rate Laws
Topic: Table 15.2 in Textbook
Replies: 1
Views: 173

### Table 15.2 in Textbook

Why does table 15.2 in the textbook, which is a list of all the components/equations of 0, 1st, and 2nd order reactions, say that the 1/2-life equations for 0 and 2nd order reactions are not used? Is there a general rule that they do not happen in nature or something?
Wed Mar 07, 2018 10:31 am
Forum: General Rate Laws
Topic: Rate Laws
Replies: 3
Views: 246

### Rate Laws

How do we know when a rate law should depend upon concentrations of products as well as reactants?
Thu Feb 22, 2018 9:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert Electrodes
Replies: 4
Views: 327

### Re: Inert Electrodes

What about for salt bridges too? When do you know to include a salt bridge in the cell diagram and when is it not necessary?
Sun Feb 11, 2018 1:09 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy and compression
Replies: 3
Views: 209

### Re: Entropy and compression

Also I know this is a rather basic and/or unrelated question, but why again are we assuming ideal gas behavior for all of these circumstances? Thanks!
Sun Feb 11, 2018 1:08 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy and compression
Replies: 3
Views: 209

### Entropy and compression

I'm just a little confused conceptually why entropy decreases when a gas is compressed. It seems like it should increase because the space in which the gas is confined is decreased, meaning the molecular collisions would occur more frequently amongst themselves and therefore increase the disorder/en...
Sat Feb 10, 2018 4:20 pm
Forum: Calculating Work of Expansion
Topic: Reversible vs Irreversible
Replies: 4
Views: 286

### Re: Reversible vs Irreversible

Just for clarification, is this why reversible expansion work is always greater in quantity than irreversible expansion? Because it responds to any infinitesimal change in a variable? Makes sense because if work is constantly changing from any variable affecting the system, there would be a greater ...
Tue Jan 23, 2018 10:32 pm
Forum: Calculating Work of Expansion
Topic: 8.55
Replies: 2
Views: 182

### 8.55

This question is a Hess's Law problem that gives the two equations 2Ba+O2--->2BaO with deltaH = -1107 and 2Al+02---->Al2O3 with deltaH = -1676. The equation we want to reach is 3BaO+2Al ---> Al2O3+3Ba. So I flipped the first equation and multiplied by 3/2 in order to get the 3BaO and such, and multi...
Tue Jan 23, 2018 1:44 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.25
Replies: 1
Views: 117

### 8.25

For this question I am just wondering if there is a mistake because in the textbook it uses temperature in 7.32 C and then in the solution's manual it uses 7.32 K without doing the +273.15 K conversion. So it just keeps the value and changes from celsius to kelvin, but this problem is also not liste...
Mon Jan 22, 2018 3:30 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Enthalpy of Fusion
Replies: 1
Views: 131

### Enthalpy of Fusion

Why is melting not endothermic for helium? In other words why is the deltaH(fus) of helium negative? Read this in the book and am just curious.
Mon Jan 15, 2018 6:36 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: State function in relation to heat
Replies: 3
Views: 259

### State function in relation to heat

In the textbook, it says "Because heat is not a state function, we should not speak of a system as possessing a certain amount of heat." (the same claim is said for work). But yet when we describe reactions, we assign it a quantitative value such as +750 kJ or 5 J, etc. Can someone explain...
Sat Dec 09, 2017 10:09 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: What part of ligand attached
Replies: 2
Views: 231

### Re: What part of ligand attached

hey emily ;)
I believe you would attach the C, because O atoms are what allow molecules to form polydentates, and because the other ligands that have more than one atom that is able to bind to the central atom are specified with their variations listed. hope this helps<3
Sat Dec 09, 2017 5:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: SiO2 Polar or Nonpolar
Replies: 2
Views: 6660

### SiO2 Polar or Nonpolar

On the midterm there was a question on the bond type (polar, non polar, or ionic) of some molecules, and SiO2 was one of them. When you draw the structure it looks like it should be the oxygens flanking the silicon atom and both with double bonds connecting them. There are no lone pairs on the Si an...
Sat Dec 09, 2017 11:18 am
Forum: Administrative Questions and Class Announcements
Topic: Practice Test Fall 2017 [ENDORSED]
Replies: 19
Views: 2627

### Re: Practice Test Fall 2017[ENDORSED]

Thank you for this! However I thought LeChatelier's wasn't supposed to be on the test? Now I'm confused
Sat Dec 09, 2017 9:14 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 12.39
Replies: 1
Views: 167

### Re: 12.39

You find the pKb of these bases the same as you do pKa of acids, where you use the Kb values given for them in the book (NH2OH=1.1x10^-8 and (CH3)2NH=5.4x10^-4) and take the negative log of them to get their pKb values, and then subtract that from 14.00 to get the pKa in which to rank them. I think ...
Sat Dec 09, 2017 8:58 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Point of pKa [ENDORSED]
Replies: 1
Views: 269

### Point of pKa[ENDORSED]

What is the point in using pKa/pKb values to describe acidic and basic reactions when we can just use Ka and Kb to relay the same information about its progress? i.e. how strong the solution is, to what degree the acid deprotonated, etc.
Fri Dec 08, 2017 1:24 am
Forum: DeBroglie Equation
Topic: Concept of deBroglie
Replies: 3
Views: 280

### Concept of deBroglie

Why does the deBroglie equation not apply to light? This may be a very general question but I wrote explicitly in my notes “equation works for any particle with momentum, but does not apply to light” and I am unsure as to why that is.
Tue Dec 05, 2017 9:53 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Sig Figs in Calcs
Replies: 1
Views: 189

### Sig Figs in Calcs

What are the rules for significant figures when you're switching between calculations of pH and molar concentrations?
Mon Dec 04, 2017 5:52 pm
Forum: Amphoteric Compounds
Topic: Amphiprotic Character
Replies: 1
Views: 250

### Amphiprotic Character

How do you determine what an amphiprotic molecule will act as? For example the reaction of HCO3- and water obviously shows that HCO3- can act as both an acid and a base, but if this reaction were to take place in a flask, how would you determine which reaction would occur if they are both under the ...
Wed Nov 29, 2017 9:01 am
Forum: Biological Examples
Topic: [Fe(NCS)(OH2)5]2+ name
Replies: 6
Views: 576

### Re: [Fe(NCS)(OH2)5]2+ name

Yes i do believe the corrections you made above are how the name is supposed to be, sometimes the book has small errors like that...
Wed Nov 29, 2017 8:55 am
Forum: Naming
Topic: [CoBr(NH3)5] SO4 name
Replies: 3
Views: 8010

### Re: [CoBr(NH3)5] SO4 name

In the answer posted above they are using the "old" name for bromine as a ligand, but both bromo and bromido work for use in naming ligands. You would know to use either one simply because Br is found within the coordination sphere, or inside the brackets.
Sat Nov 25, 2017 4:14 pm
Forum: Naming
Topic: Textbook Confusion [ENDORSED]
Replies: 1
Views: 171

### Textbook Confusion[ENDORSED]

In section 17.5 of the textbook a sentence says "the terms 'coordination compound' and 'complex' are often used interchangeably." But does this mean these two terms can or can't be used interchangeably? Because complexes are found within coordination compounds so I don't see how they can b...
Sat Nov 25, 2017 3:19 pm
Forum: Hybridization
Topic: HW 4.95
Replies: 1
Views: 209

### HW 4.95

When I did the Lewis structure for CH2 double bonded to CHCHO I got the same result as the book but different formal charges, where the only atom with a formal charge of 0 was oxygen. The book says all the atoms in the molecule have a formal charge of 0, but double bonds only count as 1 regarding fo...
Sat Nov 11, 2017 9:03 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: lewis structure and vsepr
Replies: 3
Views: 255

### Re: lewis structure and vsepr

Drawing the Lewis structure usually helps to visualize what the actually VSEPR shape for the molecule is, but you can otherwise just memorize which shapes have how many bonds and lone pairs or use the notation (A= central atom, X= bonded atom, E= lone pair) to know which model a molecule is.
Sat Nov 11, 2017 8:56 pm
Forum: Lewis Structures
Topic: 3.67 a.
Replies: 2
Views: 191

### 3.67 a.

What is the correct lewis structure for ClO? I used a double bond between the two and put the radical on the chlorine but the book says something otherwise.
Sat Nov 11, 2017 8:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity in Molecular Shape
Replies: 1
Views: 95

### Re: Polarity in Molecular Shape

A molecule's polarity is represented in its VSEPR shape, like how a water molecule is "bent", its polarity is represented by the model having its two paired hydrogens farther from the "top" of the oxygen where its unpaired electrons that repel the hydrogens are. The resulting bon...
Sat Nov 11, 2017 8:43 pm
Forum: Empirical & Molecular Formulas
Topic: Practice Midterm Question
Replies: 4
Views: 369

### Practice Midterm Question

I don't have the exactly worded question, but the problem was asking for the molecular formula of a compound that was 43.2% carbon, 6.35% hydrogen, and 50.4% oxygen. I am just not sure why I don't get the same result, but I think it has something to do with the carbon not resulting in a whole or mul...
Tue Oct 31, 2017 6:00 pm
Forum: Electronegativity
Topic: Electronegativity [ENDORSED]
Replies: 5
Views: 470

### Re: Electronegativity[ENDORSED]

Fluorine is the most electronegative element because it is the most readily available to fill its octet and obtain a noble gas configuration because it has seven valence electrons; or if you will, it is the most "willing" to accept a single electron to fill its octet and the most "unw...
Mon Oct 30, 2017 2:31 pm
Forum: Quantum Numbers and The H-Atom
Topic: Question 2.19 b.
Replies: 5
Views: 301

### Question 2.19 b.

I am still getting the hang of ml terms, but the question asks: "How many values of m(l) are allowed for an electron in a 3p-subshell?" I thought that because ml= l, l-1, -l... the answer would be 3, 2, 1, 0, -1, -2, -3 for a total of seven values but the answer is 5 starting at 2 to -2. W...
Sun Oct 22, 2017 5:25 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Test 3 [ENDORSED]
Replies: 5
Views: 526

### Re: Test 3[ENDORSED]

I am pretty sure Test 3 will have all three of those topics on it, because he says: "Know how to solve problems using Heisenberg’s indeterminacy equation, ∆p ∆x ≥ h " "Understand the relationship between Schrodinger's equation, wave functions, and orbitals." And a bunch of other ...
Sun Oct 22, 2017 5:17 pm
Forum: DeBroglie Equation
Topic: Wavelike Properties
Replies: 3
Views: 485

### Re: Wavelike Properties

Anything with momentum has wavelength properties, including large objects such as cars. It is just a matter of whether or not they are detectable, and we can generally only observe an object's wavelength for measurements of #x10^-15 m.
Sun Oct 22, 2017 5:13 pm
Forum: DeBroglie Equation
Topic: Exercise 1.42 [ENDORSED]
Replies: 2
Views: 240

### Exercise 1.42[ENDORSED]

This is not a required homework problem, but I was trying to do some extra practice with this chapter and I'm not sure how to answer this question:
The average speed of a helium atom at 25 degrees Celsius is 1.23x10^3 m/s. What is the average wavelength of a Helium atom at this temperature?
Thu Oct 05, 2017 11:04 pm
Forum: Limiting Reactant Calculations
Topic: M9
Replies: 4
Views: 440

### M9

For this problem it says to write the net ionic equation for a reaction, but this topic is not listed on the need-to-know basis of the test for tomorrow so I was wondering if anyone knew whether or not we have to know how to do this for the test.
Thu Oct 05, 2017 10:54 pm
Forum: Limiting Reactant Calculations
Topic: M11
Replies: 1
Views: 242

### M11

Hey I am just a little confused on where to start with this problem. It involves two reaction of P4 + 3O2 = P4O6. and if enough oxygen is presentist'll continue to P4O6 + 202 = P4O10. There is 5.77 g of white phosphorus and 5.77 g of oxygen present, and the question first asks for the limiting react...

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