Search found 43 matches

by Iona Pay
Sat Mar 16, 2019 9:01 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.3 7th edition
Replies: 1
Views: 157

Re: 6N.3 7th edition

You can tell what half reactions to use by looking at the cell diagram - anode (oxidation) on the left side || cathode (reduction) on the right side. For example, part A: Pt(s)|H2(g)|HCl(aq)||HCL(aq)|H2(g)|Pt. From looking at this cell diagram, we can see that both sides of the cell diagram involve ...
by Iona Pay
Sat Mar 16, 2019 8:52 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation energy vs free energy of activation
Replies: 1
Views: 36

Re: Activation energy vs free energy of activation

Activation energy is the minimum amount of energy required for a reaction to occur. Free energy of activation is the difference in free energy (deltaG) between reactants and products.
by Iona Pay
Sat Mar 16, 2019 8:47 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Homework 6N17
Replies: 1
Views: 210

Re: Homework 6N17

Okay, so the ratio they're referring to is Q. This produces a positive cell potential, E, when plugged into the Nernst equation. If you were to plug this value into deltaG = -nFE, it would produce a negative deltaG value (i.e., spontaneous/favorable, and capable of doing work). First, we find cell p...
by Iona Pay
Sat Mar 16, 2019 8:16 pm
Forum: Balancing Redox Reactions
Topic: 6L 5C (7th Edition)
Replies: 1
Views: 174

6L 5C (7th Edition)

The question reads as follows: Write the half reactions, balanced equation, and cell diagram. D. Au+(s) ----> Au(s) + Au3+(aq) The solution manual writes the cell as follows: Au | Au3+ || Au+| Au+. I'm confused as to why we are allowed to use Au for each electrode, even though only one of the redox ...
by Iona Pay
Sat Mar 16, 2019 8:11 pm
Forum: Balancing Redox Reactions
Topic: 6L 3D (7th Edition)
Replies: 1
Views: 131

6L 3D (7th Edition)

The question reads: Write the half reactions and balanced equation for the following galvanic cell: D. Pt(s) | O2(g) | H+(aq) || OH-(aq) | O2(g) | Pt(s) I don't understand how one is able to tell which is oxidation and which one is reduction here - I understand the concept generally, but not in appl...
by Iona Pay
Sat Mar 16, 2019 10:40 am
Forum: General Rate Laws
Topic: Phase of Reactants in Rate Law
Replies: 3
Views: 72

Re: Phase of Reactants in Rate Law

When writing a rate law, you do not include liquid or solid reactants, or water, if it is a solvent and not a reactant. As for any other molecule that is not the solvent, if it is part of a reaction, it can be in the rate law.
by Iona Pay
Sat Mar 16, 2019 12:52 am
Forum: *Enzyme Kinetics
Topic: what will we be given ?
Replies: 3
Views: 217

Re: what will we be given ?

My TA said today that whatever we need to complete calculations will be given to us on the equations and constant sheet, so no need to stress!
by Iona Pay
Sat Mar 16, 2019 12:48 am
Forum: Second Order Reactions
Topic: does the order determine molecularity?
Replies: 2
Views: 188

Re: does the order determine molecularity?

Molecularity refers to the number of molecules that come together to react in an elementary reaction, and is equal to the sum of the coefficients of this elementary reaction. So, if you're talking about an elementary reaction, yes!
by Iona Pay
Sat Mar 16, 2019 12:45 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Cp vs Cv
Replies: 6
Views: 408

Re: Cp vs Cv

It depends on whether the gas in the equation you're working with is under constant pressure (Cp) or constant volume (Cv).
by Iona Pay
Sun Feb 10, 2019 11:25 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Homework
Replies: 1
Views: 62

Re: Homework 4C

We have to multiply the specific heat by either 5/2 or 3/2 because these values allow us to calculate the heat capacities of different types of gases. The molar heat capacity of a monatomic gas at a constant volume is (3/2)R, whereas the molar heat capacity of a linear molecule of a gas is (5/2)R. P...
by Iona Pay
Sun Feb 10, 2019 8:30 pm
Forum: Phase Changes & Related Calculations
Topic: 4A.7
Replies: 1
Views: 47

Re: 4A.7

Assuming this is for the 7th edition here. For anyone who's also having difficulty with this problem and doesn't have the book around, the problem reads: A. Calculate the heat that must be supplied to a copper kettle of mass 400.00 g containing 300.00 g water to raise its temperature from 20C to 100...
by Iona Pay
Sun Feb 10, 2019 6:01 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of Formation and Reaction
Replies: 1
Views: 61

Re: Enthalpy of Formation and Reaction

Yep, that's the main difference! ∆H°, enthalpy of reaction, is the ∆H of the system when all products and reactants are in their standard states. ∆H°f, enthalpy of formation, is the ∆H of the formation of 1 mole of whatever compound when all products and reactants are in their standard states.
by Iona Pay
Sun Feb 10, 2019 5:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard reaction enthalpy vs standard enthalpy of formation
Replies: 2
Views: 66

Re: Standard reaction enthalpy vs standard enthalpy of formation

Standard reaction enthalpy (∆H°) is the ∆H that accompanies a change in system due to a chemical reaction where all reactants and products are in their standard states. Standard enthalpy of formation (∆H°f) is the ∆H during the formation of 1 mole of the substance, with all substances in the reactio...
by Iona Pay
Sun Feb 10, 2019 5:49 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: q and delta H
Replies: 3
Views: 60

Re: q and delta H

q = ∆H when pressure of a system is constant - this is usually written as qp = ∆H. If pressure is not constant, you could calculate q using q = ∆U - w, presuming you know work or total energy change in the system.
by Iona Pay
Sun Feb 10, 2019 5:47 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy change at temp transitions
Replies: 1
Views: 49

Re: Entropy change at temp transitions

Yes, it is similar to calculating ∆H of phase changes, because like enthalpy, entropy is also a state function (meaning change is determined by initial and final state, not the path taken). In taking each step and adding them to find total ∆S, we are using Hess's Law; which states that changes are a...
by Iona Pay
Sun Feb 10, 2019 5:39 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: degeneracy
Replies: 2
Views: 62

Re: Degeneracy

Simply put, degeneracy is the number of different ways energy can exist, or the different configurations (microstates) a substance can take in a particular state. For example, gases have high degeneracy (the molecules are largely free to bounce around whatever container they're in), whereas solids h...
by Iona Pay
Sun Feb 10, 2019 5:25 pm
Forum: Phase Changes & Related Calculations
Topic: Does reversible also imply constant T?
Replies: 1
Views: 43

Re: Does reversible also imply constant T?

If we're talking about expansion of a gas and want to compare the role of temperature in reversible vs irreversible expansions, as we have been in lecture, we could compare these two equations for calculating work: A. w = -nRTln(V1/V2), for isothermal reversible expansion of a gas. B. w = -P∆V, for ...
by Iona Pay
Sun Feb 10, 2019 5:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Ways to find q
Replies: 1
Views: 50

Re: Ways to find q

Depending on what else is known or unknown in the problem, you could use: A. ∆U = q + w, rearranged as q = ∆U - w, if you know the total change in energy in a system. B. q(p) = ∆H, if you know the total change in enthalpy at a constant pressure. C. ∆S(sys) = -q(rev) / T, if you know the total change...
by Iona Pay
Sun Feb 10, 2019 4:44 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Constant Pressue
Replies: 3
Views: 82

Re: Constant Pressure

Yes, that's usually fine. Another indicator that pressure might be constant is if the problem mentions "standard conditions" - this implies a constant temperature of 273K and a constant pressure of 1 atm.
by Iona Pay
Wed Feb 06, 2019 12:06 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Monday: Derivation of Isothermal, Reversible Expansion
Replies: 2
Views: 78

Re: Monday: Derivation of Isothermal, Reversible Expansion

Isothermal (temperature of system remains constant, so change in temperature is 0), reversible (can be reversed by an infinitesimally small change in the system). In an isothermal expansion of a gas, pressure falls as the gas expands because temperature remains constant (no extra energy is added to ...
by Iona Pay
Tue Feb 05, 2019 11:09 pm
Forum: Calculating Work of Expansion
Topic: Focus 4.B Question 5 - Unit Conversion with Ideal Gas Constants
Replies: 1
Views: 45

Focus 4.B Question 5 - Unit Conversion with Ideal Gas Constants

I don't understand how we know to use "the equivalency of the ideal gas constants" to convert L*atm to joules, or what this really means. Why do we know to use (8.314 K/mol)/(.08206 atm/K*mol) specifically?
by Iona Pay
Wed Jan 23, 2019 12:18 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Knowing When to Approximate
Replies: 4
Views: 110

Knowing When to Approximate

I don't understand when/when not to approximate when doing equilibrium concentration or constant calculations. Is there a way to know before completing all calculations? The textbook says that the value needs to be less than 5%, but I'm not clear as to what needs to be less than 5% or in comparison ...
by Iona Pay
Sun Dec 09, 2018 2:04 am
Forum: Naming
Topic: Oxidation Number
Replies: 2
Views: 187

Oxidation Number

How do you find the oxidation number of a metal?
by Iona Pay
Sun Dec 09, 2018 1:11 am
Forum: Naming
Topic: 7th edition 9C.1 table
Replies: 1
Views: 62

Re: 7th edition 9C.1 table

I don't believe he mentioned in lecture? But I'm sure it would be helpful if naming comes up on the final.
by Iona Pay
Sun Dec 09, 2018 1:10 am
Forum: Air Pollution & Acid Rain
Topic: other biological examples
Replies: 1
Views: 175

Re: other biological examples

You might also want to know about buffering in blood - this Khan Academy article explains it well, if you scroll down to "Buffering System of Blood".

https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/a/chemistry-of-buffers-and-buffers-in-blood
by Iona Pay
Sun Dec 09, 2018 12:56 am
Forum: Polyprotic Acids & Bases
Topic: polyprotic acids and bases in equations
Replies: 3
Views: 262

Re: polyprotic acids and bases in equations

If you're writing the proton transfer equation, you should assume that it refers to removing 1 proton - so your conjugate base would be HSO4-, not just SO4-.
by Iona Pay
Sun Dec 09, 2018 12:54 am
Forum: Biological Examples
Topic: coordination compounds
Replies: 2
Views: 172

Re: coordination compounds

I don't remember Dr. Lavelle mentioning specific coordination compounds we should know, but memorizing some of the common ligands might be helpful for naming coordination compounds. If you have the 7th edition, Table 9C.1 on page 724 has a list.
by Iona Pay
Sun Dec 09, 2018 12:35 am
Forum: Hybridization
Topic: Pi bonds
Replies: 8
Views: 239

Re: Pi bonds

by Iona Pay
Sun Dec 09, 2018 12:19 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Difference between Tetrahedral and Square Planar
Replies: 2
Views: 275

Re: Difference between Tetrahedral and Square Planar

A good rule of thumb is that if the compound's complex metal ion is not in group 8 or doesn't have a d8 configuration, it's likely tetrahedral.
by Iona Pay
Sun Dec 09, 2018 12:05 am
Forum: *Shrodinger Equation
Topic: schrodinger wave equation
Replies: 1
Views: 187

Re: schrodinger wave equation

Generally speaking, the Schrödinger equation describes wave-particle duality of a particle over time, so yes.
by Iona Pay
Sat Dec 08, 2018 11:39 pm
Forum: Conjugate Acids & Bases
Topic: Can someone check if I'm right
Replies: 2
Views: 229

Re: Can someone check if I'm right

Yep! As H2SO4 donates a proton, which water accepts, labeling those as acid and base respectively makes sense. Equally, HSO4, is a conjugate base, and hydronium, with its added proton, is the conjugate acid.
by Iona Pay
Sat Dec 08, 2018 11:36 pm
Forum: Conjugate Acids & Bases
Topic: HCO3- an acid or base
Replies: 2
Views: 257

Re: HCO3- an acid or base

A Bronsted acid is a substance that donates a proton, and a Bronsted base is one that accepts a proton. We can see that HCO3- has a negative charge - it's the conjugate base of carbonic acid, H2CO3.
by Iona Pay
Sat Dec 08, 2018 11:23 pm
Forum: DeBroglie Equation
Topic: Calculating Wavelength of Ejected Electron
Replies: 1
Views: 233

Re: Calculating Wavelength of Ejected Electron

I'm also confused by this - I got the same answer, but my TA corrected it as 1.09x10^-7m. Can anyone else who got it correct explain?
by Iona Pay
Sat Dec 08, 2018 11:02 pm
Forum: Lewis Structures
Topic: Acid Lewis Structures
Replies: 1
Views: 218

Re: Acid Lewis Structures

I think the acid's we've had that don't bond normally are oxyacids and acids with multiple protons - I found this hard to explain, so here are a couple articles that do a better job than I can. https://rafamunoa1.wordpress.com/2015/03/19/lewis-structure-of-oxoacids-and-anions-flowchart/ https://web....
by Iona Pay
Sat Dec 08, 2018 10:44 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: List of Intramolecular Vs. Intermolecular Forces
Replies: 1
Views: 360

Re: List of Intramolecular Vs. Intermolecular Forces

Intramolecular forces are forces that hold atoms together within a molecule - listed strongest to weakest, they include metallic bonds, ionic, and covalent (polar or nonpolar) bonds. Intermolecular forces are forces that exist between molecules - listed strongest to weakest, they include dipole-dipo...
by Iona Pay
Sat Dec 08, 2018 10:39 pm
Forum: Amphoteric Compounds
Topic: water
Replies: 4
Views: 210

Re: water

Double headed arrows usually indicate that a reaction can go either forwards (towards the products) or backwards (towards the reactants).
by Iona Pay
Sat Dec 08, 2018 10:24 pm
Forum: Lewis Acids & Bases
Topic: Lewis acids and pH
Replies: 2
Views: 180

Re: Lewis acids and pH

Lewis acids and bases are generally defined as electron pair acceptors and donators respectively. When a Lewis acid and base are combined, they form a Lewis adduct (for our purposes here, a single product of two distinct molecules). So, to understand how Lewis acid/bases affect pH: Think of a proton...
by Iona Pay
Sat Dec 08, 2018 10:06 pm
Forum: Identifying Acidic & Basic Salts
Topic: What are salts...
Replies: 4
Views: 219

Re: What are salts...

Salts are ionic compounds formed by a neutralization reaction between an acid an a base, such as NaCl, or common table salt. Salts can either raise or lower the pH of a solution - if the salt of a strong base and weak acid is dissolved in water, it will form an alkaline (basic) solution, whereas, th...
by Iona Pay
Sun Nov 04, 2018 11:10 pm
Forum: Electronegativity
Topic: Ionization Energy over Electronegativity?
Replies: 4
Views: 133

Ionization Energy over Electronegativity?

Why do we consider ionization energy over electronegativity when deciding which atom should be the center of a Lewis diagram?
by Iona Pay
Sun Nov 04, 2018 11:03 pm
Forum: Lewis Structures
Topic: Lewis Acids and Bases
Replies: 2
Views: 71

Re: Lewis Acids and Bases

We cover up until the end of 2C (7th edition), or 3.11 (6th edition). Wednesday's lecture (last day of material that will be on tomorrow's midterm) covered expanded valence shells, radicals, Lewis acids and bases, and coordinate covalent bonds. Lewis acids and bases, broadly speaking, are defined in...
by Iona Pay
Sun Nov 04, 2018 10:45 pm
Forum: Octet Exceptions
Topic: Incomplete Octet
Replies: 5
Views: 114

Incomplete Octet

Why is boron able to provide both electrons when bonding with fluorine, and be satisfied with an incomplete octet?
by Iona Pay
Thu Oct 25, 2018 11:44 pm
Forum: *Shrodinger Equation
Topic: Using the Schrodinger Equation
Replies: 3
Views: 319

Re: Using the Schrodinger Equation

You would use the Schrödinger equation to find the allowed energy levels for quantum mechanical systems.

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