## 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: 358

### 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: 314

### 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: 382

### 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: 191

### 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: 85

### 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: 135

### 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: 139

### 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: 179

### 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
Replies: 13
Views: 566

### 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: 121

### 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: 108

### 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: 108

### 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: 175

### 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: 76

### 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: 375

### 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: 228

### 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: 138

### 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: 89

### 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: 98

### 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: 311

### 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: 122

### 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: 293

### 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: 99

### 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: 118

### 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: 175

### 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: 112

### 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: 407

### 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: 46

### 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: 287

### 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: 184

### 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: 151

### 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: 797

### 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: 614

### 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: 205

### 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: 286

### 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: 407

### 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: 474

### 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: 109

### 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: 273

### 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: 96

### 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: 177

### 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: 803

### 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: 179

### 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: 206

### 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: 290

### 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: 393

### 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: 817

### 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: 357

### 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: 145

### 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: 160

### 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: 246

### 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
Topic: What is a black body? [ENDORSED]
Replies: 7
Views: 1011

### 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: 119

### 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: 214

### 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: 112

### 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: 325

### 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: 149

### 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: 250

### 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
Replies: 9
Views: 602