Search found 65 matches
- Fri Mar 15, 2019 6:00 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 7th edition 6N.1
- Replies: 5
- Views: 804
7th edition 6N.1
calculate the equilibrium constants for the following reactions: a. Mn(s) + Ti^2+(aq) <--> Mn^2+(aq) + Ti(s) b. In^3+(aq) + U^3+(aq) <--> In^2+(aq) + U^4+(aq) for part a, I split the equation into two reactions, Mn(s) --> Mn^2+(aq) +2e- Ti^2+(aq) + 2e- --> Ti(s) then I found the E for each one, -1.1...
- Wed Mar 13, 2019 9:03 pm
- Forum: General Rate Laws
- Topic: 7th edition 7B.17
- Replies: 1
- Views: 294
7th edition 7B.17
the second part of this question gives [A]0 = 0.15 mol/L and [B] = 0.19 mol/L for the equation A --> 2B + C
how do I turn the 0.19 mol/L of B into the [A]t I need to be able to calculate the time it takes for the reaction to take place?
how do I turn the 0.19 mol/L of B into the [A]t I need to be able to calculate the time it takes for the reaction to take place?
- Wed Mar 13, 2019 2:28 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding an Inert Gas
- Replies: 4
- Views: 605
Re: Adding an Inert Gas
The reaction won't shift because the partial pressures of the reactants and the products are not altered when the gas is added. an inert gas is basically a noble gas, so it does not undergo chemical reactions because it is so stable. it is unreactive so it does not impact the chemical equation/react...
- Wed Mar 13, 2019 2:25 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Adding Pt in 6L5 b)
- Replies: 2
- Views: 335
Re: Adding Pt in 6L5 b)
if there is no solid/conductor on either your cathode or anode side of the cell diagram, you need to add platinum
- Wed Mar 13, 2019 2:24 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Platinum in Cell Diagram
- Replies: 7
- Views: 1902
Re: Platinum in Cell Diagram
basically if you notice in your cell diagram that there is no solid/conducting component, you add platinum to either the cathode, anode, to both depending on which is missing a conductor.
in general, if there is no solid in the cell diagram you need to add platinum
in general, if there is no solid in the cell diagram you need to add platinum
- Wed Mar 13, 2019 2:22 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activation Energies
- Replies: 3
- Views: 452
Re: Activation Energies
they are both the same and will give the same value. it is up to you which is easier to visualize and use in the equation
- Wed Mar 13, 2019 2:21 pm
- Forum: General Rate Laws
- Topic: Rate equations to know
- Replies: 5
- Views: 553
Re: Rate equations to know
you also need to know how to derive the rate laws for zero, first, and second order reactions
- Wed Mar 13, 2019 2:20 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: What is an intermediate?
- Replies: 3
- Views: 410
Re: What is an intermediate?
an intermediate appears in multi-step reactions and is basically something that is formed during the first step of the reaction and is then subsequently used in the following step of the reaction. So, it goes from being a product to being a reactant and will be canceled out from your final equation.
- Wed Mar 13, 2019 2:18 pm
- Forum: First Order Reactions
- Topic: First Order Reactions
- Replies: 3
- Views: 442
Re: First Order Reactions
reaction orders can only be determined experimentally, so it could be a first order but is not necessarily
- Wed Mar 13, 2019 2:17 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Catalyst vs. Intermediate
- Replies: 8
- Views: 813
Re: Catalyst vs. Intermediate
an intermediate is formed and then used up in the reaction
a catalyst is there the whole time and is not used up in the reaction
a catalyst is there the whole time and is not used up in the reaction
- Wed Mar 13, 2019 12:04 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3592835
Re: Post All Chemistry Jokes Here
What should you do if no one laughs at your chemistry jokes?
Keep telling them until you get a reaction.
Keep telling them until you get a reaction.
- Wed Mar 13, 2019 12:03 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3592835
Re: Post All Chemistry Jokes Here
Two chemists walk into a bar.
One says, “I’ll have an H2O.” The other says, “I’ll have an H2O, too.”
The second chemist dies.
One says, “I’ll have an H2O.” The other says, “I’ll have an H2O, too.”
The second chemist dies.
- Wed Mar 13, 2019 12:02 am
- Forum: First Order Reactions
- Topic: finding the concentration of a reactant
- Replies: 1
- Views: 318
finding the concentration of a reactant
When you are given a chemical reaction and the final concentration of one of the products, how do you translate that to the final concentration of the reactant over your given time interval? For example, if A --> 3B and we know reactant A began with .012 moles and then over the time period the conce...
- Mon Feb 25, 2019 11:52 pm
- Forum: Balancing Redox Reactions
- Topic: Homework problem 6L.9 - 7th edition
- Replies: 1
- Views: 225
Re: Homework problem 6L.9 - 7th edition
never mind--I just made a mistake.
the Mn actually starts as 7+ so it makes sense now
the Mn actually starts as 7+ so it makes sense now
- Mon Feb 25, 2019 11:38 pm
- Forum: Balancing Redox Reactions
- Topic: Homework problem 6L.9 - 7th edition
- Replies: 1
- Views: 225
Homework problem 6L.9 - 7th edition
(a) write the balanced half-reactions for the redox reaction of an acidified solution of potassium permanganate and iron (II) chloride. (b) write the balanced equation for the cell reaction and devise a galvanic cell to study the reaction (write its cell diagram). so the reaction itself would be MnO...
- Mon Feb 25, 2019 5:24 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: HW problem 5G.17 (7th edition)
- Replies: 1
- Views: 196
HW problem 5G.17 (7th edition)
this question asks you to depict the process of the reaction in question 5G.13 graphically. In the back of the book, it indicates a decrease in the partial pressure of I (reactant) and an increase in the partial pressure of I2 (product) over time until they reach equilibrium. In question 13, however...
- Fri Feb 15, 2019 1:47 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy equations
- Replies: 8
- Views: 1070
Re: Entropy equations
you use the different equations depending on which initial conditions you are given and what variables are changing/remain constant in the system
- Fri Feb 15, 2019 1:45 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: n in degeneracy
- Replies: 8
- Views: 2563
Re: n in degeneracy
n is the number of molecules, not individual atoms
- Fri Feb 15, 2019 1:43 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: How to calculate W
- Replies: 9
- Views: 1463
Re: How to calculate W
W=(# of micro states)^(# of molecules)
or using s=kb(ln(W))
or using s=kb(ln(W))
- Fri Feb 15, 2019 1:41 pm
- Forum: Calculating Work of Expansion
- Topic: S=0
- Replies: 12
- Views: 1774
Re: S=0
delta S is zero when there is no change in the disorder of the system between the initial and final values
S itself I think can be zero if you have a perfect system, but I'm not 100%
S itself I think can be zero if you have a perfect system, but I'm not 100%
- Fri Feb 15, 2019 1:38 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3592835
Re: Post All Chemistry Jokes Here
Did you know that you can cool yourself to -273.15 degrees Celsius and still be 0K?
- Fri Feb 15, 2019 1:36 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isobaric
- Replies: 12
- Views: 1704
Re: Isobaric
it means that you can use the equation w=-PdeltaV
- Fri Feb 15, 2019 1:29 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy graph
- Replies: 2
- Views: 263
Re: Gibbs Free Energy graph
^ yes I think that is correct. the system will spontaneously approach equilibrium, but will not be spontaneous when at equilibrium exactly because it does not want to leave equilibrium
- Fri Feb 15, 2019 1:27 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Ideal gases
- Replies: 4
- Views: 494
Re: Ideal gases
5/2 is for when pressure is constant and 3/2 is for when volume is constant
- Fri Feb 15, 2019 1:25 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Liquid and moles
- Replies: 8
- Views: 1148
Re: Liquid and moles
only is the H2O is a gas it will be used. if it is a liquid then it will not be in the keq or in the ICE table
- Fri Feb 15, 2019 1:24 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Quick Conceptual question
- Replies: 7
- Views: 952
Re: Quick Conceptual question
enthalpy is the heat released from the system and entropy is the amount of disorder of the system
- Fri Feb 15, 2019 1:23 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Microstate
- Replies: 7
- Views: 820
Re: Microstate
it is a specific arrangement of the molecules. different micro states have different energy levels and having multiple micro states increases the entropy of a system
- Mon Jan 21, 2019 2:34 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Homework
- Replies: 1
- Views: 139
Re: Homework
Cl2 is the more stable one.
The ratio for Cl2:Cl is greater than F2:F. This shows that Cl2 is more stable because at equilibrium, chlorine favors the reactants more. So basically, whichever K is smaller is the reaction that is more stable.
The ratio for Cl2:Cl is greater than F2:F. This shows that Cl2 is more stable because at equilibrium, chlorine favors the reactants more. So basically, whichever K is smaller is the reaction that is more stable.
- Mon Jan 21, 2019 1:54 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: HW problem 5H.3 in 7th ed
- Replies: 2
- Views: 249
HW problem 5H.3 in 7th ed
Use the information in table 5G.2 to determine the value of K at 300 K for the reaction 2BrCl(g) + H2(g) --> <-- Br2(g) + 2HCl(g) How do you use the table to determine this? I'm a bit stuck because I'm not sure which reaction to use in the table since none match the one given. Would I use the first ...
- Fri Jan 11, 2019 10:08 am
- Forum: Ideal Gases
- Topic: use
- Replies: 8
- Views: 267
Re: use
In regards to the question above, when is Kp used? Kp is the same as Kc, but it just represents the equilibrium constant as a value of partial pressures rather than molar concentrations. You can use the equation mentioned in the responses above to convert between the two. You just must make sure th...
- Fri Jan 11, 2019 10:04 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc of the Forward/Reverse Reaction
- Replies: 6
- Views: 10378
Re: Kc of the Forward/Reverse Reaction
Think about when you reverse a reaction. The reactants and products will get flipped, so similarly, you just have to flip your value of Kc (take the inverse) and you will get the Kc of the reverse reaction since Kc is just a ratio.
- Fri Jan 11, 2019 10:03 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Liquids and Solids in Equilibrium Constants
- Replies: 5
- Views: 393
Re: Liquids and Solids in Equilibrium Constants
the change in concentration is too small and can be omitted--only worry about non-pure substances that are aqueous or gaseous
- Fri Dec 07, 2018 11:39 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs
- Replies: 5
- Views: 548
Re: Lone Pairs
yes. shape depends entirely on what is connected to the central atom. AlCl3, for example, is trigonal planar even though each of the chlorines has 3 pairs of lone electrons
- Fri Dec 07, 2018 11:28 am
- Forum: Lewis Acids & Bases
- Topic: Ligands
- Replies: 7
- Views: 921
Re: Ligands
a neutral ligand has no affect on the charge of the compound. like H2O for example
- Fri Dec 07, 2018 11:27 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Total Charge
- Replies: 5
- Views: 715
Re: Total Charge
just add up all of the charges of the transition metal and ligands
- Fri Dec 07, 2018 11:25 am
- Forum: Naming
- Topic: Final Exam
- Replies: 9
- Views: 901
Re: Final Exam
I'd say memorize. better safe than sorry-plus some of the practice problems use those
- Fri Nov 30, 2018 5:23 pm
- Forum: Dipole Moments
- Topic: Molecular Geometry and polarity
- Replies: 5
- Views: 442
Re: Molecular Geometry and polarity
if the two atoms attached are the same, then yes. But if they are different, then the dipoles may not cancel and you could have a polar molecule.
- Fri Nov 30, 2018 5:22 pm
- Forum: Sigma & Pi Bonds
- Topic: Triple bond?
- Replies: 18
- Views: 1752
Re: Triple bond?
one sigma and two pi bonds
a single has just one sigma
a double has one sigma and one pi
a single has just one sigma
a double has one sigma and one pi
- Mon Nov 26, 2018 5:37 pm
- Forum: Dipole Moments
- Topic: Homework Question 3F.1
- Replies: 1
- Views: 334
Homework Question 3F.1
Question 3F.1 in 7th Edition asks to identify the types of attractive intermolecular interactions that might arise between molecules of each of the following substances: a) NH2OH b) CBr4 c) H2SeO4 d) SO2 I am a bit confused on how to do this. For part a, for example, I can tell that there are hydrog...
- Fri Nov 16, 2018 1:25 am
- Forum: Electronegativity
- Topic: Electronegativity
- Replies: 8
- Views: 923
Re: Electronegativity
fluorine is the most electronegative atom since it is in the top right corner of the periodic table. just remember that electronegativity is how badly an atom wants another electron, so those closest to a full octet will be more electronegative. In addition, the smaller the atom is (the higher up in...
- Fri Nov 16, 2018 1:21 am
- Forum: Lewis Structures
- Topic: Picking Central Atom Special Cases
- Replies: 2
- Views: 322
Re: Picking Central Atom Special Cases
The idea about the "unique" atom being the central atom does typically hold true and is a good starting point. Another way to help distinguish which atom goes where is that the central atom will typically have a positive formal charge while the surrounding atoms will take a negative formal...
- Fri Nov 16, 2018 1:12 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Vsepr Formula
- Replies: 7
- Views: 445
Re: Vsepr Formula
VSEPR just helps us visualize the 3-D structure of a molecule while a lewis structure is a 2-D drawing. While lewis structures are useful in showing where bonds and lone pairs are, the VSEPR model helps us understand more about how a molecule will act in an environment and what 3-D structure it will...
- Fri Nov 16, 2018 1:07 am
- Forum: Lewis Structures
- Topic: Axial Bond Angles
- Replies: 3
- Views: 692
Re: Axial Bond Angles
axial bond angles are angles between atoms that reside on the axis of a molecule
- Thu Nov 08, 2018 9:06 pm
- Forum: Electronegativity
- Topic: Hydrogen electronegativity
- Replies: 3
- Views: 321
Re: Hydrogen electronegativity
and to answer the second part of your question, yes hydrogen has relatively high electronegativity due to only having one electron in its 1s shell. Atoms are more stable with a full shell, so hydrogen has a high electronegativity, (or in other words a high want to attract an electron) since it only ...
- Thu Nov 08, 2018 9:04 pm
- Forum: Electronegativity
- Topic: Hydrogen electronegativity
- Replies: 3
- Views: 321
Re: Hydrogen electronegativity
The positive charge on fluorine is +9, but on hydrogen it is +1, so the magnitude positive charge (which is responsible for high electronegativity because it contributes to the pull on the electrons by the nucleus) is very high on fluorine.
- Thu Nov 08, 2018 5:46 pm
- Forum: Bond Lengths & Energies
- Topic: Tests
- Replies: 5
- Views: 637
Re: Tests
Yep. Our test number 3 is the week of November 19th and our final is December 9th
- Thu Nov 08, 2018 5:39 pm
- Forum: Bond Lengths & Energies
- Topic: Formula/ Memorization of Bond lengths?
- Replies: 3
- Views: 390
Re: Formula/ Memorization of Bond lengths?
I do not believe that we have to memorize bond lengths--just know how to use them and know what they tell us about a molecule.
- Fri Nov 02, 2018 12:03 pm
- Forum: Electronegativity
- Topic: Units for EN
- Replies: 3
- Views: 523
Re: Units for EN
electronegativity is more of a concept than anything. It simply helps us understand the pull between atoms due to periodic trends and so it doesn't really require a unit
- Fri Nov 02, 2018 12:01 pm
- Forum: Lewis Structures
- Topic: Formal Charge Tricks
- Replies: 5
- Views: 3598
Re: Formal Charge Tricks
the 1/2 shared portion of formal charge has to do with the shared bonds between electrons. Each bond represents 2 electrons, but since they are being shared, we only calculate with half of this number. (I.e. if two atoms share 2 bonds you take 4(electrons)/2(bonds) to get two. An easier way to think...
- Fri Nov 02, 2018 11:55 am
- Forum: Ionic & Covalent Bonds
- Topic: Dipole
- Replies: 4
- Views: 352
Re: Dipole
Dipole has to do with polar covalent bonds! This means that one of the atoms will always be more electronegative, and in turn you will be able to draw the arrow without worrying about the atoms being too close in electronegativity.
- Fri Oct 26, 2018 12:49 pm
- Forum: Properties of Light
- Topic: measuring wavelength
- Replies: 5
- Views: 546
Re: measuring wavelength
Lavelle's rule of thumb is that anything smaller than 10^-18 will be too small to measure. Conceptually, though, if you are working on the atomic scale wavelength will normally be detected and if you are working with objects that can be seen by the human eye, wavelength will not be able to be detect...
- Fri Oct 26, 2018 12:46 pm
- Forum: Ionic & Covalent Bonds
- Topic: Valence Electrons
- Replies: 2
- Views: 292
Re: Valence Electrons
The number comes from the octet rule. The octet rule is a chemical rule of thumb that states that atoms of main-group elements tend to combine in a way that each atom has eight electrons in its valence shell, giving it the same electron configuration as a noble gas.
- Fri Oct 26, 2018 12:44 pm
- Forum: Lewis Structures
- Topic: Lewis Dot Order
- Replies: 10
- Views: 1249
Re: Lewis Dot Order
No, there is not a particular order that you need to follow. As long as there are no more than two dots on each side you should be fine.
- Sun Oct 21, 2018 10:45 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: HW problem 1E.1
- Replies: 1
- Views: 247
HW problem 1E.1
Problem 1E.1 goes as follows: Which of the following increase when an electron in a lithium atom undergoes a transition from the 1s-orbital to a 2p-orbital? (a) energy of the electron. (b) value of n. (c) value of l. (d) radius of the atom. Which answers would be different for a hydrogen atom and in...
- Sun Oct 21, 2018 10:22 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test On Tuesday
- Replies: 10
- Views: 1072
Re: Test On Tuesday
Professor Lavelle stated that only the material covered in lecture up until last Friday (10/19/18) will be on the test. Since we did not cover periodic trends in lecture, it will not be on the test. If you know everything up until multi-electron atoms, which I believe is section 1E in the seventh ed...
- Thu Oct 18, 2018 9:59 pm
- Forum: *Shrodinger Equation
- Topic: Shrodinger Equation
- Replies: 2
- Views: 216
Shrodinger Equation
I understand the basis of the shrodinger equation, but Lavelle mentioned that we won't be using it. So what about shrodinger do we need to know, if anything, for our test/for the class in general? Is it just background knowledge, or will it be something we are tested on?
- Mon Oct 15, 2018 11:10 pm
- Forum: Student Social/Study Group
- Topic: Note Taking
- Replies: 145
- Views: 16473
Re: Note Taking
Personally, I prefer hand written. It helps me retain the information better. Also, I find it best not to just copy exactly what your professor has on their slides--making yourself write it in your own words/summarize it deepens your understanding and makes you think about the material.
- Mon Oct 15, 2018 9:09 pm
- Forum: Properties of Light
- Topic: Mass
- Replies: 4
- Views: 265
Re: Mass
light cannot physically exist in a stationary state, so there cannot be a mass for it stationary
- Thu Oct 11, 2018 7:33 pm
- Forum: Properties of Light
- Topic: Light
- Replies: 9
- Views: 911
Re: Light
Amplitude and frequency are related in that they are inversely proportional to one another. So, if the amplitude increases, the frequency decreases, or if the amplitude decreases, the frequency increases. This relationship is derived from the equation v = c/(lamda). Actually, amplitude and frequenc...
- Thu Oct 11, 2018 7:25 pm
- Forum: Properties of Light
- Topic: Wavelength
- Replies: 10
- Views: 498
Re: Wavelength
Units in an equation must ALWAYS be the same! You can't multiply nanometers by meters, because then what would be the units of your answer? Once you get your answer, however, it can sometimes be easier to convert to nanometers or maybe kilometers if you are giving a really large or really small numb...
- Thu Oct 11, 2018 7:20 pm
- Forum: Empirical & Molecular Formulas
- Topic: Rounding for limiting reactants
- Replies: 5
- Views: 842
Re: Rounding for limiting reactants
Typically you don't want to round by more than 0.05, so I recommend rounding something like 7.30 to 7.33 and then multiply by 3 to get 22. When working with the empirical formula in particular, if you get numbers that are 0.1 or less off from a whole number then usually you are in the clear, but it ...
- Fri Oct 05, 2018 11:34 am
- Forum: General Science Questions
- Topic: Nomenclature
- Replies: 1
- Views: 229
Nomenclature
Hi! So on the outline for our first test next week, one of the topics to know is to write the symbols of the elements given their name and vice versa. I haven't taken chem in a while, so I am still reviewing nomenclature, and I know Dr. Lavelle mentioned that we will learn names as we go, but I was ...
- Wed Oct 03, 2018 4:42 pm
- Forum: Limiting Reactant Calculations
- Topic: Limiting Reactant Step 5
- Replies: 1
- Views: 177
Re: Limiting Reactant Step 5
Hi! so in step 5, it asks to compare the calculated moles (step 4) to the required moles (step 2) to determine in there is a limiting reactant. This basically means that you take the moles you calculated in step 4 of each of the reactants and look back to the balanced chemical equation in step 2 to ...
- Mon Oct 01, 2018 1:31 am
- Forum: SI Units, Unit Conversions
- Topic: Grams/mole
- Replies: 12
- Views: 1199
Re: Grams/mole
Both notations are the same! It is more of a personal preference on which to use. I, for example, prefer g/mol because I am used to writing units that way. In g.mol^-1, the -1 just means that the mole is raised to the negative first power, meaning it is in the denominator of the fraction just like y...
- Mon Oct 01, 2018 1:26 am
- Forum: SI Units, Unit Conversions
- Topic: Unit Conversions
- Replies: 4
- Views: 508
Re: Unit Conversions
Here are a couple mnemonic devices that list the order from largest to smallest: King Henry Doesn't Usually Drink Chocolate Milk (kilo, hecto, deka, unit, deci, centi, milli) Kittens Hate Dogs But Do Chase Mice (kilo, hecto, deca, base, deci, centi, milli) Good Models Know How Dunkin Donuts Can Make...