## Search found 53 matches

Sat Mar 17, 2018 5:56 pm
Forum: General Rate Laws
Topic: Rate Law where a concentration is to a negative power
Replies: 2
Views: 328

### Rate Law where a concentration is to a negative power

When a rate law = k*([A]^3/[B]^-1), what does the negative power mean? I was thinking it was an inhibitor of some kind since it reduces the order of the reaction?
Sat Mar 17, 2018 5:52 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Pressure and Volume in a Bomb Calorimeter
Replies: 1
Views: 240

### Pressure and Volume in a Bomb Calorimeter

In a calorimeter, since w = -PdeltaV and deltaV=0 and w=0 does that mean that P=0. Or does that imply that the change in P would be 0?
Sat Mar 17, 2018 5:45 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Q5 on the midterm
Replies: 1
Views: 252

### Q5 on the midterm

In step 1 we find that the work done by the system is -158J. How can we make the conclusion that in step 2, our U = +158J? I thought that since there is no heat exchange, w=U.
Fri Mar 09, 2018 10:44 pm
Forum: *Nucleophiles
Topic: What is a nucleophile? [ENDORSED]
Replies: 6
Views: 719

### What is a nucleophile?[ENDORSED]

What exactly is a nucleophile? Also, can there be more than one nucleophile with molecule interactions?
Fri Mar 09, 2018 11:14 am
Forum: Second Order Reactions
Topic: Units of k for orders above 2nd
Replies: 6
Views: 511

### Units of k for orders above 2nd

So I noticed a trend with the units of k, we keep dividing each one by M (molarity) i.e. zero order is k M/s, first order is k 1/s, second order is k 1/M.s. Does this trend continue for 3rd, 4th, and 5th orders?
Fri Mar 09, 2018 11:08 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 5
Views: 443

### Re: Catalysts

The concept part of it would be that there is an inverse relationship between the activation energy and the rate of a reaction: the lower the activation energy, the higher the rate of the reaction. A catalyst offers an alternative pathway with a lower activation energy, therefore, the reaction goes ...
Fri Mar 02, 2018 9:56 pm
Forum: Zero Order Reactions
Topic: Relation between rate law and zero order [ENDORSED]
Replies: 3
Views: 247

### Relation between rate law and zero order[ENDORSED]

I noticed that in lecture we were given an experimentally determined rate law equal to k[NO2]^2 and made the connection that since the other reactant, CO, when not present in this given rate law it was of zero order. Can we always make this connection? Also, how would this look in a reaction with mo...
Fri Mar 02, 2018 9:52 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Number of steps to reach the overall reaction
Replies: 3
Views: 275

### Number of steps to reach the overall reaction

Will the number of steps used in order to find the overall reaction equal the number of reactants? Are there any exceptions?
Fri Mar 02, 2018 9:46 pm
Forum: First Order Reactions
Topic: Psuedo 1st order rate law [ENDORSED]
Replies: 2
Views: 214

### Psuedo 1st order rate law[ENDORSED]

What exactly is a pseudo 1st order rate law and how is it different from a normal 1st order rate law? It was mentioned in lecture on Friday and I don't fully understand the concept.
Thu Feb 22, 2018 2:46 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Diamond and graphite
Replies: 8
Views: 1972

### Re: Diamond and graphite

With that example he gave in lecture, he drew a diagram showing that while graphite is at lower and a more stable energy, the activation energy required to turn diamond into graphite is too large for it to spontaneously happen (at least at standard conditions).
Thu Feb 22, 2018 2:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Standard E values and inverse values
Replies: 2
Views: 213

### Standard E values and inverse values

If we have a hypothetical A ---> B E= 123, does that mean that B ---> A E= -123?
Thu Feb 22, 2018 2:14 pm
Forum: General Rate Laws
Topic: Rate Law
Replies: 2
Views: 207

### Rate Law

I understand that aA's rate would be (-1/a)*(dA/dt). Does this mean 1/a*A's rate is (-a)*(dA/dt)? Thank you!
Sat Feb 17, 2018 10:50 pm
Forum: Balancing Redox Reactions
Topic: Significance of electrons transferred in half reactions
Replies: 2
Views: 146

### Significance of electrons transferred in half reactions

Will "n" value in the Nernst Equation always just be the number of electrons used to balance the half reactions?
Sat Feb 17, 2018 10:47 pm
Forum: Balancing Redox Reactions
Topic: Basic v Acidic
Replies: 2
Views: 228

### Basic v Acidic

How do we know when to balance the equation using basic or acidic methods? Is it possible to use both when balancing the same equation?
Thu Feb 15, 2018 7:55 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework #8.55 Hess's Law
Replies: 2
Views: 190

### Homework #8.55 Hess's Law

I think there is a typo/error in #8.55. The solutions manual says to that the second reaction given (2Al + O2 ----> Al2O3) doesn't change its enthalpy value even though the book differs from the manual. Basically, the book says the second reaction is 2Al + O2 ----> Al2O3 while the solutions manual s...
Fri Feb 09, 2018 11:57 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Change in Entropy in Surroundings [ENDORSED]
Replies: 2
Views: 230

### Change in Entropy in Surroundings[ENDORSED]

Why is it that when involved in an isothermal reversible expansion, the change in S of surroundings is equal to the opposite sign of the change in S of the system but when involved in an isothermal nonreversible free expansion, the change in S of surroundings is equal to zero?
Fri Feb 09, 2018 11:20 pm
Forum: Balancing Redox Reactions
Topic: Anode vs cathode
Replies: 6
Views: 294

### Re: Anode vs cathode

Side note: an easy way to remember that oxidation is the loss of e- and reduction is gain of e-, use OIL RIG. OIL = Oxidation Is Loss, RIG = Reduction Is Gain
Tue Feb 06, 2018 8:34 pm
Forum: Balancing Redox Reactions
Topic: Solutions in beakers
Replies: 2
Views: 193

### Solutions in beakers

During the lecture on Monday, there was a graphic of two beakers with an electron flow filled with similar solution. What is this solution? I was assuming it is water but can it be any liquid?
Sun Feb 04, 2018 4:04 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: Perfect Crystal
Replies: 9
Views: 606

### Re: Perfect Crystal

The perfect crystal is related to the third law of thermodynamics which is about systems in equilibrium at absolute zero (0 Kelvin). It states that the entropy of a perfect crystal at absolute zero is exactly equal to zero.
Sun Feb 04, 2018 3:52 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Periodic Trends
Replies: 4
Views: 336

### Periodic Trends

Is there a periodic trend when it comes to heat capacities? If so, what is it and is this useful in making calculations?
Sun Feb 04, 2018 3:51 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacities of Dense Elements
Replies: 2
Views: 196

### Heat Capacities of Dense Elements

Do dense elements have a higher heat capacity than less dense elements? Also, does the heat capacity have more to do with density, atom structure, or bond energies?
Sat Jan 27, 2018 10:35 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Relationship between entropy and volume in liquids
Replies: 5
Views: 277

### Relationship between entropy and volume in liquids

I know that when you increase the volume of a gas, you increase the entropy since the gas now has more positions available to it, however, is this the same with liquid? Or do you have to take gravity into account since that would limit its positions? For example, would entropy increase for a liquid ...
Sat Jan 27, 2018 10:28 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Increasing temperature to make G negative
Replies: 3
Views: 297

### Increasing temperature to make G negative

The textbook (example 9.16) presents an example of an endothermic reaction becoming exothermic due to an increase in temperature. Is this the case for all endothermic processes? Or are there some cases where an increase in temperature will never make an endothermic process exothermic?
Sat Jan 27, 2018 9:20 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Relationship between entropy and spontaneity
Replies: 3
Views: 810

### Relationship between entropy and spontaneity

In Friday's lecture, Lavelle had on is powerpoint, "In any spontaneous process there is an increase in entropy." Does this mean that in any non-spontaneous process there is a decrease in entropy?
Sat Jan 20, 2018 11:18 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible and Irreversible
Replies: 4
Views: 302

### Reversible and Irreversible

What makes a reaction reversible versus irreversible? Also, what relevance would this have when considering how to solve a problem with the condition of reversible/irreversible?
Sat Jan 20, 2018 11:09 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Heat v Thermal Energy
Replies: 3
Views: 169

### Heat v Thermal Energy

Is there a difference between heat and thermal energy or can they be used interchangeably?
Sat Jan 20, 2018 9:56 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Perfect Isolated System
Replies: 3
Views: 213

### Perfect Isolated System

Is there such a thing as a "perfect" isolated system? What I mean by that is a system where over an infinite amount of time, there is no exchange of heat or matter?
Sat Jan 13, 2018 8:23 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Infinite Forms of Hess's Law
Replies: 5
Views: 181

### Infinite Forms of Hess's Law

Are there infinite forms of Hess's Law? All the problems I have encountered usually have between 2-4 chemical reactions to use, but is it possible to have more than that in one problem? Or are we limited to the number of reactions?
Sat Jan 13, 2018 8:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Delta H and Delta U
Replies: 3
Views: 134

### Delta H and Delta U

Why can we equate delta H (heat transfer at constant pressure) and delta U (heat transfer at constant volume)?
Sat Jan 13, 2018 8:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat and Ethalpy
Replies: 3
Views: 185

### Heat and Ethalpy

What is the difference between heat and enthalpy? From my understanding, enthalpy is the measurement of the change of heat after a reaction. Is this correct, wrong, or correct but too simplistic?
Sat Dec 09, 2017 9:08 pm
Forum: Naming
Topic: Memorizing all the names???
Replies: 4
Views: 529

### Memorizing all the names???

Do we need to know the full name of en (ethylenediamine) or can we just put "en" when naming a compound? I've been told that we do but some people and we don't by others so I'm confused.
Sat Dec 09, 2017 8:46 pm
Forum: Naming
Topic: Polydentates
Replies: 4
Views: 448

### Re: Polydentates

One pattern I noticed was that the number of Nitrogens in a compound gave away whether it was mono, bi, etc. So 1 Nitrogen is mono, 2 Nitrogens is bi, etc. There may be acceptions but this is what I have noticed.
Sat Dec 09, 2017 8:43 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Finding pH when given pOH
Replies: 1
Views: 185

### Finding pH when given pOH

How do you find pH when you are given/find a value of pOH? Is this when you use the formula pH = 14 - pOH?
Sat Dec 09, 2017 8:30 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Isoelectronic
Replies: 14
Views: 957

### Isoelectronic

What does isoelectronic mean? It was #5D on the midterm. The question asked to choose the two ions that were not isoelectronic with fluoride ion (F-). I answered correctly with the ions O- and N2- but I do not fully understand the concept.
Sat Dec 09, 2017 8:25 pm
Forum: Lewis Acids & Bases
Topic: 4C
Replies: 2
Views: 251

### Re: 4C

Ni3+ is the Lewis Acid because it is the metal in this compound and metals are always the electron acceptors when they have ligands surrounding them.
Sun Dec 03, 2017 10:23 pm
Forum: Lewis Acids & Bases
Topic: Donating electrons versus protons [ENDORSED]
Replies: 4
Views: 405

### Donating electrons versus protons[ENDORSED]

How can you tell when an atom is donating a proton versus an electron? Does it work as in when a proton is donating electrons it is always donating protons? Therefore a Lewis base is always a Bronsted acid?
Sun Dec 03, 2017 10:22 pm
Forum: Bronsted Acids & Bases
Topic: Donating protons versus electrons [ENDORSED]
Replies: 1
Views: 416

### Donating protons versus electrons[ENDORSED]

How can you tell when an atom is donating a proton versus an electron? Does it work as in when a proton is donating electrons it is always donating protons? Therefore a Lewis base is always a Bronsted acid?
Sat Nov 25, 2017 11:40 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Temperature and K [ENDORSED]
Replies: 3
Views: 271

### Re: Temperature and K[ENDORSED]

According to Le Chatelier's principle, the effect of temperature on equilibria involves a change in the equilibrium constant as well.
Sat Nov 25, 2017 11:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electronegativity
Replies: 3
Views: 307

### Re: Electronegativity

The general rule is that the farther away the elements are, the more polar, and the closer they are, the more nonpolar.
Sat Nov 18, 2017 10:21 pm
Forum: Naming
Topic: Roman Numerals
Replies: 3
Views: 921

### Roman Numerals

I understand that if the oxidation number of a compound is 2+ (for example) we will use the Roman Numerals (II) when we write out the name. If the oxidation number was negative, is there a way to indicate that when naming a compound? Would there be negative Roman numerals?
Sat Nov 18, 2017 10:14 pm
Forum: Determining Molecular Shape (VSEPR)
Replies: 4
Views: 358

Can there be two or more radicals in the same molecule? All previous examples we have used in class or discussion have only described one.
Sun Nov 12, 2017 12:00 am
Forum: DeBroglie Equation
Topic: When to use DeBroglie Equation
Replies: 4
Views: 322

### When to use DeBroglie Equation

Do you only use this equation when finding wavelengths of objects with mass? Also, is it still valid when the said object is not in motion?
Sat Nov 11, 2017 11:57 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Book Exercises
Replies: 3
Views: 114

### Re: Book Exercises

In a molecule, nonpolar atoms tend to have a low difference in electronegativity while polar atoms tend to have a high difference in electronegativity. Also, electrons in a nonpolar molecule are shared equally while electrons in a polar molecule are shared unequally, creating a dipolar moment.
Sun Nov 05, 2017 12:01 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Shapes
Replies: 2
Views: 225

### Shapes

How do you know when the shape is bent when writing out a formation?
Sun Nov 05, 2017 12:00 am
Forum: Lewis Structures
Topic: Bonds
Replies: 1
Views: 141

### Bonds

How can many bonds at once be formed? does it only go up to triple bond?
Sat Oct 28, 2017 11:21 pm
Forum: Lewis Structures
Topic: Placement [ENDORSED]
Replies: 6
Views: 419

### Placement[ENDORSED]

When constructing Lewis structures, how do you know which element to put in the middle?
Sat Oct 28, 2017 8:11 pm
Forum: Ionic & Covalent Bonds
Topic: Lewis Structure [ENDORSED]
Replies: 3
Views: 206

### Re: Lewis Structure[ENDORSED]

Also I just realized that I may have posted this in the wrong section, but I would still appreciate an answer. Thank you!
Sat Oct 28, 2017 8:06 pm
Forum: Ionic & Covalent Bonds
Topic: Lewis Structure [ENDORSED]
Replies: 3
Views: 206

### Lewis Structure[ENDORSED]

During lecture, Lavelle mentioned that a double bond is shorter than a single bond. Can someone explain why this is?
Sat Oct 21, 2017 10:27 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Module #23?
Replies: 4
Views: 440

### Re: Heisenberg Module #23?

In order to find the speed, you must use the values given to you and plug it into the Heisenberg equation. The only value you should be missing is speed since for the momentum part of the equation is equal to (mass)(velocity). The rest of the equation is either constants or given to you in the equat...
Sat Oct 21, 2017 10:19 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Periodic Table
Replies: 2
Views: 171

### Re: Periodic Table

Oh, ok. That makes sense, thank you!
Sat Oct 21, 2017 9:14 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Periodic Table
Replies: 2
Views: 171

### Periodic Table

In the periodic table, why doesn't the d block align its numbers with the s and p blocks? For example, the "4s" row directly leads into the "3d" row.
Thu Oct 05, 2017 2:06 pm
Forum: Empirical & Molecular Formulas
Topic: Mass Percent Composition
Replies: 4
Views: 373

### Re: Mass Percent Composition

But wouldn't you have to find the mass percentage composition in order to go through the next steps of dividing what you find by the smallest number and then finding out whether it is the empirical or molecular function?
Thu Oct 05, 2017 1:14 pm
Forum: General Science Questions
Topic: Sig Figs
Replies: 9
Views: 1171

### Re: Sig Figs

Personally, I would try to let the calculator do all the work and then round at the very end, so you get the most accurate answer possible.