Search found 60 matches
- Sun Mar 17, 2019 8:59 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Effects of Compression
- Replies: 5
- Views: 620
Re: Effects of Compression
Yes, any molecules in the gas phase would be affected.
- Sun Mar 17, 2019 8:33 am
- Forum: First Order Reactions
- Topic: First Order Equation
- Replies: 3
- Views: 594
First Order Equation
How is ln[R]=-kt+ln[R]0 useful? What does it tell us?
- Sun Mar 17, 2019 8:28 am
- Forum: Zero Order Reactions
- Topic: Zero Order Reaction Example
- Replies: 6
- Views: 1361
Zero Order Reaction Example
I don't really understand what a zero order reaction is. Can someone explain what it is and give an example of one?
- Thu Mar 07, 2019 9:38 am
- Forum: Second Order Reactions
- Topic: pseudo-first-order reaction
- Replies: 4
- Views: 516
pseudo-first-order reaction
What is a pseudo-first-order reaction and how do you get one from a second-order reaction?
- Thu Mar 07, 2019 9:35 am
- Forum: General Rate Laws
- Topic: 7A.1 7th edition
- Replies: 1
- Views: 193
7A.1 7th edition
Can someone explain to me why and how to solve 7A.1 from the 7th edition textbook? I looked at the solutions manual but I didn't understand where these formulas and units came from.
- Thu Mar 07, 2019 9:34 am
- Forum: Zero Order Reactions
- Topic: zero vs. first vs. second reactions
- Replies: 3
- Views: 338
zero vs. first vs. second reactions
Does anyone know how to tell which order a reaction is, and what are the differences between the different orders?
- Sun Mar 03, 2019 9:57 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Entropy and Enthalpy
- Replies: 2
- Views: 306
Re: Entropy and Enthalpy
A greater enthalpy can cause greater entropy.
- Sun Mar 03, 2019 9:48 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: the phases in a cell diagram
- Replies: 4
- Views: 455
the phases in a cell diagram
During a discussion session, our TA listed the order that substances in different phases should be written in a cell diagram. Does anyone know the order? (I think it was solids on the outer sides and aqueous on the inner sides of the cell diagram, but I'm not sure.) For reference: I think it was som...
- Sun Mar 03, 2019 9:36 pm
- Forum: Balancing Redox Reactions
- Topic: Adding H+ and H2O
- Replies: 13
- Views: 2900
Re: Adding H+ and H2O
For an acidic solution, balance oxygen with water molecules and balance hydrogen with H+. For a basic solution, balance oxygen with water molecules, and balance the hydrogen from those water molecules with water molecules on the other side of the equation. Then, balance oxygen with OH- on the first ...
- Sat Feb 23, 2019 11:45 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: electrochemical vs. electrolytic
- Replies: 2
- Views: 318
electrochemical vs. electrolytic
What's the difference between an electrochemical cell and an electrolytic cell?
- Sat Feb 23, 2019 11:38 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: cell diagram order
- Replies: 2
- Views: 318
cell diagram order
When writing out a cell diagram, is there a specific order the ions should be listed in?
- Sat Feb 23, 2019 11:37 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Daniell cell
- Replies: 1
- Views: 251
Daniell cell
Can someone explain what the Daniell cell mentioned in the book is?
- Fri Feb 15, 2019 4:27 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Why do we care about ΔG
- Replies: 3
- Views: 384
Re: Why do we care about ΔG
You can figure out the spontaneity of a reaction simply from whether or not delta G is positive or negative.
- Fri Feb 15, 2019 4:21 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Clausius inequality
- Replies: 1
- Views: 199
Clausius inequality
The book mentions the Clausius inequality, which states that deltaS is greater than or equal to q/T for a reversible process, but then why is there another equation that states that deltaS is only equal to q/T?
- Fri Feb 15, 2019 4:18 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: deltaS=nRln(V2/V1) vs. deltaS=Cln(T2/T1)
- Replies: 1
- Views: 1251
deltaS=nRln(V2/V1) vs. deltaS=Cln(T2/T1)
So I know that you can derive deltaS=nRln(P2/P1) from deltaS=nRln(V2/V1) due to Boyle's law, but how do you get deltaS=Cln(T2/T1)? Where does the C come from?
- Sat Feb 09, 2019 10:02 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta H and q
- Replies: 3
- Views: 523
Re: Delta H and q
q represents the heat supplied to a system. Delta H represents the change in enthalpy, which is the change in energy as expansion work during heat transfer. When the pressure is constant, the heat supplied to a system is equal to the change in energy, so delta H and q are equal.
- Sat Feb 09, 2019 9:55 am
- Forum: Calculating Work of Expansion
- Topic: when to use each equation
- Replies: 2
- Views: 396
when to use each equation
When do you use w = -Pex(deltaV) vs. w = -nRTln(V2/V1)?
- Sat Feb 09, 2019 9:50 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Examples
- Replies: 1
- Views: 228
Examples
Can someone give an example of each of the types of thermodynamic systems? (For example, in discussion, we talked about how a closed thermos is an example of an isolated system)
- Sun Feb 03, 2019 8:16 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 2
- Views: 288
Bond Enthalpies
In class, Professor Lavelle talked about how we would only need to know the enthalpies of the bonds involved in the reaction, not the other bonds in the molecules uninvolved in the reaction itself. How do we know which bonds are involved in the reaction? Would we just have to draw the Lewis structur...
- Sun Feb 03, 2019 8:09 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: U vs. H
- Replies: 2
- Views: 769
U vs. H
What's the difference between delta U and delta H? The textbook states that heat transfer at constant volume is delta U and that heat transfer at constant pressure is delta H, but can someone give more detail as to why that is?
- Sun Feb 03, 2019 8:06 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Equipartition Theorem
- Replies: 2
- Views: 336
Equipartition Theorem
Do we have to know the equipartition theorem? We haven't gone over it in class, but it's on the syllabus.
- Sat Jan 26, 2019 1:10 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond enthalpies to calculate change in enthalpy
- Replies: 3
- Views: 543
Re: Bond enthalpies to calculate change in enthalpy
You would need the enthalpy of each bond in the reaction broken and each bond in the reaction formed. Add these values together to get the total change in enthalpy.
- Sat Jan 26, 2019 1:09 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy Definition Clarification
- Replies: 2
- Views: 249
Re: Enthalpy Definition Clarification
Volume would also need to be constant, as pressure and volume are dependent on each other.
- Sat Jan 26, 2019 12:57 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Changing sign of enthalpy
- Replies: 3
- Views: 420
Re: Changing sign of enthalpy
Since reversing the equation would reverse the chemical process taking place, the sign of the enthalpy would change. For example, if you start with an exothermic reaction, the enthalpy would be negative because the reactants are releasing/losing heat to form the products. If you reverse this reactio...
- Sun Jan 20, 2019 5:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Water in the Equilibrium Constant.
- Replies: 4
- Views: 420
Re: Water in the Equilibrium Constant.
Water isn't included because it's usually the solvent for the equation.
- Sun Jan 20, 2019 5:27 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Temperature
- Replies: 2
- Views: 248
Temperature
For exothermic/endothermic reactions, in which directions do the reactions shift when temperature is changed, and why?
- Sun Jan 20, 2019 4:42 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: The Conjugate Seesaw
- Replies: 13
- Views: 998
Re: The Conjugate Seesaw
The conjugate seesaw states that the stronger the acid, the weaker its conjugate base. The stronger the base, the weaker its conjugate acid.
- Sun Jan 13, 2019 11:16 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Change in concentration
- Replies: 3
- Views: 128
Re: Change in concentration
The value of Kc is always constant for a given reaction at a constant temperature. A change in concentration of the reactants or the products will just shift the direction of the reaction.
- Sun Jan 13, 2019 10:56 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Replies: 3
- Views: 498
Re: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
A homogeneous reaction is a reaction with reactants and products that are all in the same phase. In contrast, heterogeneous reactions are reactions with two or more different phases.
- Sun Jan 13, 2019 9:52 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Solids and Liquids with the Reaction Quotient
- Replies: 3
- Views: 412
Solids and Liquids with the Reaction Quotient
I know that solids and liquids are not included when considering the equilibrium constant, but are they also not included when calculating the reaction quotient?
- Fri Dec 07, 2018 1:29 am
- Forum: Lewis Acids & Bases
- Topic: Determining which H^+ ions are given off
- Replies: 4
- Views: 337
Re: Determining which H^+ ions are given off
Protons that are attached farther away on the molecule from the central atom/ion are more likely to be given.
- Fri Dec 07, 2018 1:27 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: equilibrium table [ENDORSED]
- Replies: 1
- Views: 926
equilibrium table [ENDORSED]
When using an equilibrium table to calculate the pH of a salt solution, can we use it for any type of reaction?
- Fri Dec 07, 2018 1:17 am
- Forum: Conjugate Acids & Bases
- Topic: Conjugate Bases
- Replies: 7
- Views: 2602
Re: Conjugate Bases
The conjugate base of an acid would be the product of that acid losing a proton (H+). The conjugate acid of a base would be the product of that base gaining a proton (H+).
- Fri Nov 30, 2018 9:23 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR (lone pairs taking axial vs equatorial positions)
- Replies: 2
- Views: 476
Re: VSEPR (lone pairs taking axial vs equatorial positions)
In addition, say we replace the lone pairs in AX4E2 with bonded atoms, making it AX6. This molecule is square bipyramidal, which has 90-degree bond angles all around. The atoms replaced with the lone pairs aren't necessarily the axial atoms because the molecule is symmetrical in all directions.
- Fri Nov 30, 2018 9:14 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Trigonal Bipyramidal
- Replies: 6
- Views: 738
Re: Trigonal Bipyramidal
The axial bonds have a 90-degree bond angle with the equatorial bonds, while the equatorial bonds have a 120-degree bond angle with each other. Since the bond angles of the equatorial bonds are greater than those of the axial bonds, these atoms are replaced with the lone pairs because it gives the l...
- Fri Nov 30, 2018 9:10 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs
- Replies: 11
- Views: 957
Re: Lone Pairs
Lone pairs repulse bonds even more than other bonds do because they belong to the respective atom alone instead of being shared. Because of this, they push on the existing bonds more, resulting in an even more distorted shape. They are not considered when identifying the shape, but they contribute t...
- Sat Nov 24, 2018 11:58 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone pairs determining shape?
- Replies: 5
- Views: 1702
Re: Lone pairs determining shape?
Lone pairs affect bond angles and molecular shape since they also have a charge. However, the molecular shape has to do with the shape of the actual molecule, not the electrons, so they are not accounted for in that sense.
- Sat Nov 24, 2018 11:56 pm
- Forum: Hybridization
- Topic: pi and sigma bonds
- Replies: 3
- Views: 326
pi and sigma bonds
I've been reading everywhere, and I don't think I really understand what pi and sigma bonds are and what the difference between them is. Can someone please explain?
- Sat Nov 24, 2018 11:37 pm
- Forum: Octet Exceptions
- Topic: list of exceptions and why?
- Replies: 1
- Views: 407
list of exceptions and why?
Can someone list some octet exceptions and explain why they're exceptions (if there are reasons)?
- Thu Nov 15, 2018 4:12 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Electron Density
- Replies: 2
- Views: 232
Re: Electron Density
Though the bonds themselves are what you should consider in terms of what to call the shape of the molecule, lone pairs should also be taken into account as they can change the measurement of the angles in between bonds.
- Thu Nov 15, 2018 4:06 pm
- Forum: Bond Lengths & Energies
- Topic: 2D.13 7th edition
- Replies: 3
- Views: 444
Re: 2D.13 7th edition
The more bonds that are shared in between two atoms, the shorter the bond between them will be. Multiple bonds cause the atoms to have stronger pulls on each other and bring them closer. Therefore, more bonds = less distance.
- Thu Nov 15, 2018 3:56 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge
- Replies: 10
- Views: 1676
Re: Formal Charge
Having zero as the formal charge on an atom is more important, as some elements don't completely follow the octet rule and can have more than eight valence electrons.
- Tue Nov 06, 2018 10:18 am
- Forum: Bond Lengths & Energies
- Topic: Resonance Structures
- Replies: 4
- Views: 402
Resonance Structures
How do resonance structures affect bond length?
- Tue Nov 06, 2018 10:08 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge of a compound
- Replies: 3
- Views: 461
Re: Formal Charge of a compound
The overall charge can be zero, but it doesn't have to be.
- Tue Nov 06, 2018 10:03 am
- Forum: Lewis Structures
- Topic: Double Bonds
- Replies: 7
- Views: 570
Re: Double Bonds
You can use a double bond to change the formal charge on an atom (if it's not zero/stable) or if there are not enough electrons in the molecule.
- Fri Nov 02, 2018 9:49 am
- Forum: Einstein Equation
- Topic: 7th Edition Book, Section 1.A #9
- Replies: 2
- Views: 572
Re: 7th Edition Book, Section 1.A #9
As stated above, there were four different events listed: reading, getting a dental x-ray, making popcorn in a microwave oven, and acquiring a suntan. Keep in mind that these all have different wavelengths.
- Fri Nov 02, 2018 9:44 am
- Forum: DeBroglie Equation
- Topic: Momentum
- Replies: 10
- Views: 1467
Re: Momentum
If the momentum is not provided, you can calculate it with p = mv, where m is mass and v is velocity. Since h is in terms of J, don't forget to convert mass to kg and velocity to m/s!
- Fri Nov 02, 2018 9:41 am
- Forum: DeBroglie Equation
- Topic: De Broglie vs. speed of light/Einstein equation
- Replies: 3
- Views: 554
Re: De Broglie vs. speed of light/Einstein equation
The Einstein equation can only be used for photons, while the De Broglie equation can be used for anything.
- Fri Oct 26, 2018 7:12 am
- Forum: Trends in The Periodic Table
- Topic: Transition metal question
- Replies: 3
- Views: 330
Re: Transition metal question
Often times, the amount can vary depending on the transition metal. Usually, it's just a matter of memorizing which ones tend to lose how many electrons.
- Fri Oct 26, 2018 7:08 am
- Forum: Trends in The Periodic Table
- Topic: Isoelectronic Atoms
- Replies: 4
- Views: 380
Re: Isoelectronic Atoms
Atoms of different elements still have their respective number of protons in the nucleus. Properties of elements depend on their nucleus. Electrons mainly affect bonding.
- Fri Oct 26, 2018 7:05 am
- Forum: Quantum Numbers and The H-Atom
- Topic: Quantum numbers
- Replies: 3
- Views: 477
Re: Quantum numbers
In addition to the previous response, the principle quantum number is usually determined by the period the atom is in in the periodic table. For example, an atom ending in 3p will have the principle quantum number 3.
- Thu Oct 18, 2018 4:07 pm
- Forum: *Black Body Radiation
- Topic: What is a black body? [ENDORSED]
- Replies: 7
- Views: 1500
Re: What is a black body? [ENDORSED]
A black body is a material that can hypothetically absorb all light frequencies.
- Thu Oct 18, 2018 3:58 pm
- Forum: Properties of Light
- Topic: Intensity vs. Amplitude
- Replies: 5
- Views: 375
Re: Intensity vs. Amplitude
Light intensity is proportional to the number of protons. The more intense a light is, the more photons it has.
- Thu Oct 18, 2018 3:55 pm
- Forum: Properties of Light
- Topic: Wave/particles
- Replies: 5
- Views: 492
Re: Wave/particles
Light acts as a particle because it releases in streams of photons, and it acts as a wave because it can be intensified.
- Thu Oct 11, 2018 3:35 pm
- Forum: Properties of Electrons
- Topic: Atomic Spectrum
- Replies: 2
- Views: 276
Atomic Spectrum
Can someone explain the importance of the atomic spectrum and what we use it for?
- Thu Oct 11, 2018 3:29 pm
- Forum: Properties of Light
- Topic: Threshold Energy
- Replies: 11
- Views: 830
Threshold Energy
Can someone explain what the threshold energy in the photoelectric experiment is?
- Thu Oct 11, 2018 12:26 pm
- Forum: Properties of Light
- Topic: Wavelength
- Replies: 10
- Views: 508
Wavelength
When calculating wavelength, does it matter what the unit is? For example, the speed of light is measured in meters per second, but some wavelengths are given in terms of nanometers. Should I convert it to meters first, plug it into an equation, then re-convert it back afterwards, or does it not mat...
- Thu Oct 04, 2018 5:12 pm
- Forum: Empirical & Molecular Formulas
- Topic: Question F9
- Replies: 5
- Views: 500
Question F9
For question F9 (7th edition), the question asks for the ratio of C:H:O, given certain mass percentages. Should we answer in the form of an empirical formula, or in the form of an actual ratio (#:#:#)?
- Thu Oct 04, 2018 5:08 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Avogadro's Number
- Replies: 9
- Views: 1073
Re: Avogadro's Number
Avogadro's number isn't just limited to just atoms or molecules, but you can even describe 6.0221 x 10^23 cups as a mole of cups. Avogadro's number can be used for anything!
- Thu Oct 04, 2018 5:05 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: diatomic molecules
- Replies: 5
- Views: 396
Re: diatomic molecules
The diatomic molecules are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine. Most of these are located in the upper right corner of the periodic table. You can also think of it as the halogens + HNO!