Search found 64 matches
- Sat Mar 16, 2019 6:58 pm
- Forum: *Electrophilic Addition
- Topic: nucleophile and electrophile reactions
- Replies: 6
- Views: 3283
Re: nucleophile and electrophile reactions
You only draw the curved arrows when asked for the mechanism.
- Sat Mar 16, 2019 6:56 pm
- Forum: *Organic Reaction Mechanisms in General
- Topic: Functional Groups
- Replies: 7
- Views: 2080
Re: Functional Groups
Should we remember all of the functional groups mentioned in the slide in lecture?
Re: Final
Try to remember the structures and how to identify them.
- Fri Mar 08, 2019 5:56 pm
- Forum: Balancing Redox Reactions
- Topic: Test #2
- Replies: 6
- Views: 826
Re: Test #2
Alyssa Wilson 2A wrote:I believe one of the TA's will be holding a review session next week where they will be going through the entire test.
Where and when is this review session being held?
- Fri Mar 08, 2019 5:55 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Pt
- Replies: 14
- Views: 1365
Re: Pt
You add Pt when there are no conducting solids in the cell diagram. Also, you can use graphite as well but Pt is more common in the textbook.
- Fri Mar 08, 2019 5:52 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Changes
- Replies: 11
- Views: 1445
Re: Phase Changes
Yes, understanding phase changes is beneficial and it is important to note that temperature is constant during a phase change.
- Sat Mar 02, 2019 3:19 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Cell Potential Spontaneity
- Replies: 7
- Views: 858
Re: Cell Potential Spontaneity
When cell potential is positive then the forward reaction is spontaneous. When the cell potential is negative then the forward reaction is nonspontaneous.
- Sat Mar 02, 2019 3:17 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams (Using Platinum)
- Replies: 10
- Views: 998
Re: Cell Diagrams (Using Platinum)
Platinum is used when there is no conducting metal on either or both sides of the redox reaction. Another used electrode can be graphite, but platinum is most common in the textbooks.
- Sat Mar 02, 2019 3:14 pm
- Forum: Balancing Redox Reactions
- Topic: Strength of reducing agent
- Replies: 10
- Views: 1963
Re: Strength of reducing agent
The more negative the E cell, then the stronger the reducing agent.
- Sun Feb 24, 2019 1:00 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: q=mCdeltaT
- Replies: 15
- Views: 8196
Re: q=mCdeltaT
Use whichever the question is asking for, but if you are not given the molar heat capacity then convert the moles into grams and use specific heat capacity.
- Sun Feb 24, 2019 12:58 am
- Forum: Phase Changes & Related Calculations
- Topic: Phase Changes
- Replies: 3
- Views: 372
Re: Phase Changes
You can use mass x delta H of phase change or number of moles x delta H of phase change depending on what you are given.
- Sun Feb 24, 2019 12:48 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Internal energy (U) of an isolated system
- Replies: 17
- Views: 2715
Re: Internal energy (U) of an isolated system
There would not be change because matter and energy is not exchanged between an isolated system and its surroundings.
- Mon Feb 18, 2019 2:25 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: When does delta U equal zero?
- Replies: 17
- Views: 8328
Re: When does delta U equal zero?
In an isothermal reaction then delta U is zero.
- Mon Feb 18, 2019 2:22 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q VS. K
- Replies: 13
- Views: 1647
Re: Q VS. K
Q and K are calculated in the same way. Q is calculated at any point of the reaction, but K is calculated only at equilibrium. If Q is less than K then the products are favored. If Q is less than K then the reactants are favored.
- Mon Feb 18, 2019 2:20 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: K constant
- Replies: 5
- Views: 955
Re: K constant
Brackets means that the K is Kc and should be in terms of concentration. P means that K is Kp and should be in terms of partial pressure.
- Mon Feb 18, 2019 2:18 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Reversible vs. Irreversible
- Replies: 5
- Views: 1050
Re: Reversible vs. Irreversible
For a reversible reaction, you use w=-nRT ln (v2/v1) and for an irreversible reaction, you use w=-Pex times delta V.
- Sun Feb 17, 2019 11:08 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Residual Entropy
- Replies: 2
- Views: 339
Residual Entropy
I know boltzman equation is S= k ln W, but when am I supposed to use S= R Ln W ( k times avogadro's number is R)?
- Mon Feb 11, 2019 5:05 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: closed systems
- Replies: 6
- Views: 628
Re: closed systems
They can have both be constant or changing.
- Mon Feb 11, 2019 3:04 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 7.71 [ENDORSED]
- Replies: 5
- Views: 5162
Re: 7.71 [ENDORSED]
The question is asking what is the standard enthalpy formation of N2O5, not the overall reaction. From the chemical equation, O2 is in its natural state, so the enthalpy for O2 is 0. We are also given the standard enthalpy of formation for NO which is 90.25 KJ. With this information we know that del...
- Sun Feb 10, 2019 3:23 pm
- Forum: Ideal Gases
- Topic: The Difference between Q and Kc [ENDORSED]
- Replies: 18
- Views: 8796
Re: The Difference between Q and Kc [ENDORSED]
Q and K are calculated the same way (products/reactants), but Q can be measured at any point of the reaction and K is only measured at equilibrium. If Q < K then the forward reaction is favored. If Q > K then the reverse reaction is favored.
- Thu Feb 07, 2019 3:23 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 11
- Views: 1557
Re: Le Chatelier's Principle
If you shift the partial pressure of the product, then equilibrium will shift to the reactants. If you shift partial pressure of a reactant, then equilibrium will shift towards the products. If you introduce an inert gas that is not involved in the chemical reaction then equilibrium will remain unch...
- Thu Feb 07, 2019 3:18 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Le Chateliers Priniciple
- Replies: 9
- Views: 938
Re: Le Chateliers Priniciple
An increase in pressure means a decrease in volume, so equilibrium will shift to the side where there are less moles of gas.
- Thu Feb 07, 2019 3:13 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding Inert Gas
- Replies: 10
- Views: 4599
Re: Adding Inert Gas
When a reaction vessel has an inert gas pumped into it at a constant volume to increase the total pressure, then the total pressure will increase but the partial pressures of the reactants and products are unchanged and therefore the K value will not be affected.
- Sat Feb 02, 2019 10:16 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert Gas
- Replies: 6
- Views: 598
Re: Inert Gas
As long as there is no change in volume, then equilibrium will not be shifted because the inert gas is not included in the chemical reaction.
- Sat Feb 02, 2019 10:14 pm
- Forum: Phase Changes & Related Calculations
- Topic: PΔV of Solids and Liquids
- Replies: 4
- Views: 475
Re: PΔV of Solids and Liquids
Solids and liquids do not compress or expand, so their volume does not change.
- Sat Feb 02, 2019 10:12 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: delta H vs q
- Replies: 9
- Views: 937
Re: delta H vs q
Delta H is the change in enthalpy and q represents heat.
- Wed Jan 23, 2019 11:46 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Module 2
- Replies: 3
- Views: 1905
Re: Module 2
I did the same thing as explained above and I get Kc=[BrCl]^2/[Br2][Cl2]=[3.37 x 10^-5]^2/[7.52 x 10^-5][7.52 x 10^-5]. My answer: 0.199637845, however, is not an answer choice can someone please explain what I did wrong? Thank you! I made this mistake as well. The question should be answered in te...
- Sun Jan 20, 2019 11:26 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pressure
- Replies: 7
- Views: 674
Pressure
When determining the moles of the reaction in terms of pressure, do we include the number of moles of solids and liquids in the reaction or just the gases?
- Sun Jan 20, 2019 11:22 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Removing products
- Replies: 10
- Views: 3935
Re: Removing products
Removing products would only affect Q because only temperature causes the K value to change.
- Sun Jan 20, 2019 11:21 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Changing partial pressure of components vs changing pressure of system
- Replies: 2
- Views: 254
Re: Changing partial pressure of components vs changing pressure of system
If pressure increases then that means volume decreases, so reaction will shift toward the side with less gas moles.
If pressure decreases then that means volume increases, so reaction will shift toward the side with more gas moles.
If pressure decreases then that means volume increases, so reaction will shift toward the side with more gas moles.
- Sun Jan 20, 2019 11:16 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5%
- Replies: 5
- Views: 530
Re: 5%
5% refers to the x value and if it is less than 5% then x will be insignificant to calculations, so the quadratic formula would not have to be used and you can simply plug in the values that are given.
- Sun Jan 20, 2019 11:14 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Changes in Temperature
- Replies: 8
- Views: 1139
Re: Changes in Temperature
For endothermic reactions: If temperature increases, then the forward reaction is favored. If temperature decreases, then the reverse reaction is favored. For exothermic reactions: If temperature increases, then the reverse reaction is favored. If temperature decreases, then the forward reaction is ...
- Sun Jan 20, 2019 11:06 pm
- Forum: Ideal Gases
- Topic: K value
- Replies: 8
- Views: 865
Re: K value
K=1 is rare because there is a 1:1 ratio of reactants to products and that is usually never seen in real life applications.
- Sun Jan 20, 2019 11:04 pm
- Forum: Ideal Gases
- Topic: kc vs kp
- Replies: 19
- Views: 3507
Re: kc vs kp
Kp cannot be used in place for Kc, but you can convert one into the other by using the formula: Kp= Kc(RT)^delta n. Delta n is equal to the moles of the products minus the moles of the reactants. This formula relates Kp to Kc, so you can convert one to the other.
- Sun Jan 20, 2019 11:00 pm
- Forum: Ideal Gases
- Topic: PV=nRT
- Replies: 8
- Views: 1156
Re: PV=nRT
For most problems R and T are constants and will be given in the problem. This formula is generally used to find pressure or concentration.
- Sat Dec 01, 2018 6:15 pm
- Forum: Ionic & Covalent Bonds
- Topic: Bond Lengths
- Replies: 10
- Views: 1091
Re: Bond Lengths
You can add the bond lengths together and divide by the total amount of resonance structures to find the average bond length.
- Sat Dec 01, 2018 1:31 am
- Forum: Hybridization
- Topic: Difference between hybridization and hybrid orbitals
- Replies: 4
- Views: 750
Re: Difference between hybridization and hybrid orbitals
These are the same.
- Sat Dec 01, 2018 1:28 am
- Forum: Hybridization
- Topic: S character
- Replies: 3
- Views: 433
Re: S character
s-character is the contribution of the sigma type bond in hybridization So, if you have sp, it is a 50-50 percent s-p character ratio, while sp2 has a ratio of 33-66 and sp3 has a ratio of 25 to 75 s character to p character. It's simply the percent that the s takes up in hybridization. This is cor...
- Sat Dec 01, 2018 1:22 am
- Forum: Hybridization
- Topic: Bond Strengths
- Replies: 4
- Views: 436
Re: Bond Strengths
A C=C double bond is stronger than a single bond but it is weaker than the sum of 2 single C-C bonds. Sigma bonds are harder to break than pi bonds because sigma bonds have their overlap closer to both of the atom's nuclei and the electrons are more attracted to the nuclei because of the positive ch...
- Wed Nov 28, 2018 4:02 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: linear vs bent question
- Replies: 7
- Views: 1195
Re: linear vs bent question
The bent shape comes from the lone electron pair because that region counts as an area of electron density. That lone pair causes a repulsion for the other electrons which push the other bond angles closer together.
- Wed Nov 28, 2018 3:08 pm
- Forum: Lewis Structures
- Topic: Lewis structures vs VSEPR
- Replies: 2
- Views: 209
Lewis structures vs VSEPR
Just to be clear, when we draw lewis structures we draw the electrons of the atoms, but when we draw the VSEPR model we do not include the electrons? We only include the shared electrons?
- Wed Nov 28, 2018 1:20 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Week 8 Worksheet (3A3I3K)
- Replies: 5
- Views: 976
Re: Week 8 Worksheet (3A3I3K)
Thanks Joyce!
- Tue Nov 27, 2018 3:24 pm
- Forum: Coordinate Covalent Bonds
- Topic: Difference between coordinate covalent and covalent bond
- Replies: 6
- Views: 10031
Difference between coordinate covalent and covalent bond
What is the difference between a coordinate covalent bond and covalent bond? How can you identify if a molecule has a coordinate covalent bond or a covalent bond?
- Tue Nov 27, 2018 3:20 pm
- Forum: Significant Figures
- Topic: Calculating process
- Replies: 5
- Views: 867
Re: Calculating process
Round your answer at the end to avoid errors in your calculations beforehand.
- Tue Nov 27, 2018 3:13 pm
- Forum: Empirical & Molecular Formulas
- Topic: Limiting Reactants
- Replies: 3
- Views: 609
Re: Limiting Reactants
You can use either of the products to find the limiting reactant. Just make sure that you use the same product (does not matter which you choose) when comparing the reactants. However, on a test the next subquestion might ask about a specific product, so it may be more beneficial to choose that one ...
- Tue Nov 27, 2018 3:10 pm
- Forum: Sigma & Pi Bonds
- Topic: Why are sigma bonds stronger than pi bonds?
- Replies: 10
- Views: 4710
Re: Why are sigma bonds stronger than pi bonds?
Sigma bonds head-on overlap puts the electron closer to the other atom's nucleus. The pi bonds overlap does not put the electron as close in comparison to the sigma bond, so the sigma bond is stronger.
- Tue Nov 27, 2018 2:00 pm
- Forum: Empirical & Molecular Formulas
- Topic: Empirical & Molecular Formulas
- Replies: 11
- Views: 1569
Re: Empirical & Molecular Formulas
Yes they can, if the combined mass of the empirical formula is the same as the molecular mass given then they are the same.
- Tue Nov 27, 2018 1:56 pm
- Forum: Sigma & Pi Bonds
- Topic: Which bond would break first.
- Replies: 15
- Views: 2729
Re: Which bond would break first.
Pi bonds would break first because their electrons are more spread out than those of sigma bonds. The electrons in a sigma bond are directly between the two nuclei and are harder to break.
- Tue Nov 27, 2018 1:52 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond lengths
- Replies: 1
- Views: 181
Bond lengths
How can you tell what atom has a shorter or longer bond length when comparing atoms and ions? For example, rank the molecules from smallest to largest N-O bond length.
NO2-, NO3-, NO+, NO
NO2-, NO3-, NO+, NO
- Mon Nov 05, 2018 4:49 pm
- Forum: Trends in The Periodic Table
- Topic: Periodic Trends in Relation
- Replies: 3
- Views: 772
Re: Periodic Trends in Relation
Can someone explain the reasons behind the trends we see in the periodic table? - Atomic radius - Ionization energy - Electronegativity How do they relate to shielding effect and number of electrons or protons? Atomic radius increases going down the periodic table because a valence electron is adde...
- Sat Nov 03, 2018 1:38 am
- Forum: Trends in The Periodic Table
- Topic: Ionization energy and electronegativity
- Replies: 1
- Views: 228
Ionization energy and electronegativity
Since both ionization energy and electronegativity are the energies to remove an electron, then what is the difference between them? Does ionization energy refer only to ionic bonds and electronegativity refers to covalent bonds?
- Sat Nov 03, 2018 1:35 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Cu and Cr electron configuration exceptions
- Replies: 1
- Views: 9832
Cu and Cr electron configuration exceptions
Why do Cu and Cr not follow the same trend of writing the electron configuration as other atoms?
- Fri Oct 26, 2018 9:39 pm
- Forum: General Science Questions
- Topic: Midterm studying
- Replies: 10
- Views: 1464
Midterm studying
What are some methods for studying for the midterm that people have found helpful?
- Fri Oct 26, 2018 9:33 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Degeneracy
- Replies: 4
- Views: 463
Re: Degeneracy
I do not understand the importance of degeneracy.
- Thu Oct 25, 2018 9:08 pm
- Forum: DeBroglie Equation
- Topic: Given the energy, calculate the wavelength of y-rays
- Replies: 12
- Views: 3360
Re: Given the energy, calculate the wavelength of y-rays
Ahhh thank you for the explanation.
- Tue Oct 16, 2018 4:02 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: G7
- Replies: 7
- Views: 2542
Re: G7
Ok so to start off we have to find out how much grams of KNO3 are in the sample of 510 g The first step is to to get 5.45 from a percentage to a decimal so we divide it by 100 and it becomes .0545. Then we multiply .0545 by the 510 g to get how much grams of KNO3 were in this aqueous solution which...
- Thu Oct 11, 2018 3:58 pm
- Forum: Properties of Light
- Topic: HW 1.7 6th Edition Part B
- Replies: 2
- Views: 324
HW 1.7 6th Edition Part B
1.7 (a) The frequency of violet light is 7.1 " 1014 Hz. What is the wavelength (in nanometers) of violet light? (b) When an electron beam strikes a block of copper, x-rays with a frequency of 2.0 " 1018 Hz are emitted. What is the wavelength (in picometers) of these x-rays. The answer for ...
- Thu Oct 11, 2018 3:01 pm
- Forum: Properties of Light
- Topic: Chapter 1 Homework Question [ENDORSED]
- Replies: 7
- Views: 4814
Re: Chapter 1 Homework Question [ENDORSED]
Electromagnetic radiation is another word for energy propagated through free space or through a material medium in the form of electromagnetic waves. Therefore, we can think of this as light since it is a type of electromagnetic wave. Looking at the equation for energy per photon of light, E = h\nu...
- Thu Oct 11, 2018 11:35 am
- Forum: Student Social/Study Group
- Topic: Studying techniques
- Replies: 12
- Views: 845
Studying techniques
What are some effective ways to study for chemistry?
- Sat Oct 06, 2018 7:41 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 3I 3K Discussion Notes
- Replies: 1
- Views: 276
Re: 3I 3K Discussion Notes
These are very helpful! Thank you!
- Thu Oct 04, 2018 12:18 pm
- Forum: Empirical & Molecular Formulas
- Topic: L35
- Replies: 5
- Views: 3499
Re: L35
First, you must convert the 2.50 t of NaBr to grams using the conversion factor 1.0 x 10^6 grams = 1 ton. Then you find the molar mass of NaBr (102.89g) and divide the grams of NaBr by NaBr's molar mass. Next, find the mole ratio between Fe and NaBr which is 3 mol Fe: 8 mol NaBr (don't forget to ma...
- Mon Oct 01, 2018 12:17 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3654570
Re: Post All Chemistry Jokes Here
I asked the guy sitting next to me if he had any Sodium Hypobromite
He said NaBrO
He said NaBrO
- Mon Oct 01, 2018 12:14 am
- Forum: General Science Questions
- Topic: Rusty on High School Chem [ENDORSED]
- Replies: 347
- Views: 442777
Re: Rusty on High School Chem [ENDORSED]
Adding on from other people's suggestions, look up Tyler Dewitt on Youtube. He is really good at teaching chemistry and helped me get through my AP chemistry class in high school.
- Sat Sep 29, 2018 1:18 pm
- Forum: Significant Figures
- Topic: Significant Figures
- Replies: 10
- Views: 2886
Significant Figures
When using significant figures, do you use significant figures throughout your whole calculation (for example if the given significant figures is 2, but I am using molar mass and the molar mass contains 4 significant figures then do I change the molar mass to 2 significant figures or leave as is) or...