## Search found 37 matches

Thu Mar 14, 2019 10:09 am
Forum: General Rate Laws
Topic: Explaining 7B.3 c) in 7th edition
Replies: 2
Views: 113

### Re: Explaining 7B.3 c) in 7th edition

Part c) of the question lists a new staring concentration for [A], 0.157 mol/L. First step is to calculate the [A]t by subtracting the conversion of [B] formed from the initial [A] --> [A]t = (.153 mol A / L) - [(2molA/1molB)*(.034 mol B / L)] = 0.085 mol A / L. Finally, using [A]0 and [A]t, solve f...
Thu Mar 14, 2019 9:59 am
Forum: General Rate Laws
Topic: k1 vs k2?
Replies: 4
Views: 260

### Re: k1 vs k2?

K's differ based on different reactions. The question is only about 1 reaction. Therefore there is only one reaction rate constant, K.
Thu Mar 14, 2019 9:57 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetically v. Thermodynamically Controlled Reaction
Replies: 2
Views: 315

### Re: Kinetically v. Thermodynamically Controlled Reaction

It means that the outcome of the reaction is controlled by two factors: stability of products (Thermo) and rate of product production (Kinetics). Temperature comes into play because at low temperatures a reaction would be favored in the forward and relies on the rates of formation. Higher temperatur...
Thu Mar 07, 2019 5:40 pm
Forum: Second Order Reactions
Topic: 6th Edition 15.15
Replies: 2
Views: 124

### Re: 6th Edition 15.15

The answer is saying that each individual reactant is first order, which is shown through the doubling directly doubling the rate. However when combined they do produce a second order reaction with respect to the product.
Thu Mar 07, 2019 5:37 pm
Forum: First Order Reactions
Topic: Half-Life
Replies: 2
Views: 125

### Re: Half-Life

This can be visually shown on a graph because in first order reaction, the time in-between one half reaction and the next is the exact same, the only thing changing would be the slope, or K.
Thu Mar 07, 2019 12:57 pm
Forum: General Rate Laws
Topic: Rate Laws 0-2
Replies: 2
Views: 98

### Re: Rate Laws 0-2

Relating to the graph, you can find what the rate function is by plotting ln[A], 1/[A] and [A] (1st, 2nd, Oth order) versus time. Whatever one is a straight line is the order for that reaction. Hope this help!
Wed Feb 27, 2019 8:29 pm
Forum: Balancing Redox Reactions
Topic: oxidation numbers (hw 6k.1 7th ed)
Replies: 2
Views: 99

### Re: oxidation numbers (hw 6k.1 7th ed)

These different oxidation forms are rare exceptions that I highly doubt we will need to memorize. Just stick with what you know!
Wed Feb 27, 2019 8:27 pm
Forum: Balancing Redox Reactions
Topic: 6K.3
Replies: 1
Views: 87

### Re: 6K.3

I had a discussion with people about this question. The only logical reason is that the question is written down wrong. The correct answer shows that the reduction reaction for this equation is Cl2 + 2e- --> 2Cl-. If this appears on a test for some reason in any similar form I believe you should sti...
Wed Feb 27, 2019 8:23 pm
Forum: Balancing Redox Reactions
Topic: 6th edition, 14.3b
Replies: 1
Views: 172

### Re: 6th edition, 14.3b

So the reaction of S2O3^2- --> SO4^2- is a oxidation reaction because the Chlorine reaction is reduction. Starting off, the left side of the reaction we calculate 2 Sulfur (S) molecules to have a charge of +4 because x-6=-4 so x=+4. On the right, we add a coefficient of 2 in front to make the sides ...
Wed Feb 20, 2019 4:21 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 3
Views: 123

### Re: Salt Bridge

A salt bridge and the porous disk are essentially the same thing; they allow for the ions to travel into each side of the container, whether it be through two separate containers (this would use a salt bridge) or inside the same container (but separated through a porous disk that only allows the ion...
Wed Feb 20, 2019 4:18 pm
Forum: Balancing Redox Reactions
Topic: how to balance
Replies: 5
Views: 167

### Re: how to balance

You will be combining both, however figuring out oxidation numbers such as the example in class today with Manganese being reduced from +7 to +2 allows us to figure out the stoichiometric number for iron being 5. 5Fe^2+-->5Fe^3+ + 5e-
Wed Feb 20, 2019 4:14 pm
Forum: Balancing Redox Reactions
Topic: Cathode and Anode
Replies: 1
Views: 53

### Re: Cathode and Anode

Cathode by definition is a negatively charged electrode that electrons enter. It is paired with a reduction reaction because the electrons are entering the oxidized element and becoming reduced, and they are deposited onto the cathode metal (the electrons have entered the cathode so to speak). The o...
Tue Feb 12, 2019 5:30 pm
Forum: Calculating Work of Expansion
Topic: Proving the work equation
Replies: 2
Views: 140

### Re: Proving the work equation

If you remember that it is always the integral of V1 to V2, and depending on the question, whatever are constants you move to the outside of the integral sign, then you should be fine.
Tue Feb 12, 2019 5:29 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Calculating change in entropy from 1st and 2nd laws of Thermodynamics
Replies: 1
Views: 113

### Re: Calculating change in entropy from 1st and 2nd laws of Thermodynamics

1st law of Thermodynamics deals solely with energy and isn't related to entropy nor can it be calculated from it.
Tue Feb 12, 2019 5:23 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta H
Replies: 3
Views: 161

### Re: Delta H

This only holds true under constant pressure because if there no other work besides expansion on the system and the pressure throughout remains the same, the the change in enthalpy (delta H) is the same as the heat being consumed or released (q).
Tue Feb 05, 2019 9:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 3
Views: 159

### Re: Bond Enthalpies

No it is not necessary, it is completely personal preference. The questions involving bond enthalpies will most likely not be complicated molecules, so the lewis structures will be relatively easy to get.
Tue Feb 05, 2019 9:12 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Work done by expansion
Replies: 3
Views: 113

### Re: Work done by expansion

Pressure can never be negative, however according to the first law of thermodynamics, the negative sign is in there because the energy lost is gained by the system.
Tue Feb 05, 2019 9:10 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: closed systems
Replies: 6
Views: 228

### Re: closed systems

Closed is able to be influenced by heat, however no outside mass can be added. Additionally, volume and pressure are able to stay constant or change.
Tue Jan 29, 2019 9:43 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cp and Cv
Replies: 3
Views: 127

### Re: Cp and Cv

This R in this equation is in fact the ideal gas constant. Gas thermochemistry and ideal gases are intertwined
Tue Jan 29, 2019 9:37 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Specific heat capacity
Replies: 3
Views: 154

### Re: Specific heat capacity

The specific heat capacity is a constant intensive property for a given material. This is calculated using the formula above from the other answers, but in a experiment they are gathered through the use of a calorimeter.
Tue Jan 29, 2019 9:35 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cv and Cp
Replies: 2
Views: 75

### Re: Cv and Cp

Cp for any given gas performs work due to its expansion. Cv is in a fixed container so it is not allowed to expand / do work. That is why the value of Cp is higher the Cv
Thu Jan 24, 2019 11:14 am
Forum: Ideal Gases
Topic: Outline 1 Bullet
Replies: 2
Views: 107

### Re: Outline 1 Bullet

Ideal gas law states that one mole of an ideal gas occupies 22.4 L at STP (Standard Temp and Pressure). For all reaction purposes in this class, they will be ideal gases.
Thu Jan 24, 2019 11:11 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ignoring x validity
Replies: 6
Views: 459

### Re: ignoring x validity

Yes, because anything over 5% alters the value for x. So your answer would be slightly off.
Thu Jan 24, 2019 11:09 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Direction of a Reaction
Replies: 8
Views: 464

### Re: Direction of a Reaction

The problem will always either give you K or the comments to calculate K. Q is useless without knowing K.
Fri Jan 18, 2019 2:38 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: problem 5I.11
Replies: 3
Views: 123

### Re: problem 5I.11

Part (a) is asking to calculate Q. Convert mmol to mol and divide by volume. These are your concentrations. plug it into the formula [P]/[R] making sure to use correct stoichiometric coefficients. This is Q. Part (b) compare the Q to the given K. if Q<K, reaction shifts right. Q>K, reaction shifts l...
Fri Jan 18, 2019 2:32 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Weak Acids and Bases
Replies: 7
Views: 324

### Re: Weak Acids and Bases

Easiest way Dr. Lavelle explains it is if it has a low Ka/Kb value. Most likely all the questions for the test will involve weak acids because we were already tested on strong ones last quarter.
Fri Jan 18, 2019 2:30 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Equations with Salt
Replies: 2
Views: 103

### Re: Equations with Salt

All Salts are ionic compounds. What this means is that in water they will completely dissociate and bond around water. This is not included in the chemical reaction. You only worry about the ions if one of them is either the conjugate base or acid to an added acid or base.
Wed Jan 09, 2019 4:02 pm
Forum: Ideal Gases
Topic: pressure notation
Replies: 2
Views: 96

### Re: pressure notation

It is considered the standard pressure; 1 bar or 0.987 atm.
Wed Jan 09, 2019 3:59 pm
Forum: Ideal Gases
Topic: Ideal gases
Replies: 3
Views: 285

### Re: Ideal gases

Correct assume it is an ideal gas otherwise the solving process would be too advanced for this current topic
Wed Jan 09, 2019 3:56 pm
Forum: Ideal Gases
Topic: Units
Replies: 5
Views: 148

### Re: Units

Correct, however the most commonly used form of these types of questions deal with those specific units. Just always remember to make sure all units cancel!
Sun Dec 02, 2018 7:14 pm
Forum: Lewis Acids & Bases
Topic: 7th Edition Q6A #1
Replies: 1
Views: 99

### Re: 7th Edition Q6A #1

A general trend is that metal oxides such as CaO are basic where as nonmetal oxides such as NO2 are acidic. Oxides are said to be amphoteric if they are attached to Metalloids such as B, As, Si, etc.
Sun Dec 02, 2018 7:10 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Biological Compounds
Replies: 3
Views: 148

### Re: Biological Compounds

I don't believe so because acids like HNO3 have nitrogen in it but there is no lone pair due to the addition of Hydrogen
Sun Dec 02, 2018 7:06 pm
Forum: Naming
Topic: 17.29 6th edition
Replies: 2
Views: 147

### Re: 17.29 6th edition

The reason for writing OH_2 is when you are drawing a structure and the water molecule is attached to the right side of the drawing. It means the exact same thing but its just to show that the "O" is participating in the bonding, not the H.
Mon Nov 26, 2018 12:00 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Unhybridized P orbital
Replies: 2
Views: 77

### Re: Unhybridized P orbital

P orbital is responsible for double and triple and they do contain electrons
Sun Nov 25, 2018 11:59 pm
Forum: Hybridization
Topic: How to find hybridization orbitals 4.35
Replies: 3
Views: 145

### Re: How to find hybridization orbitals 4.35

You have to calculate lewis structure of the two atoms
Sun Nov 25, 2018 11:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Naming Shapes
Replies: 5
Views: 168

### Re: Naming Shapes

It is best to memorize the basic structure because the higher electron densities are pretty straightforward
Sun Nov 04, 2018 10:18 pm
Forum: Lewis Structures
Topic: Lewis Structure for N2O
Replies: 7
Views: 366

### Re: Lewis Structure for N2O

N goes in the center because you want to have the lowest ionization energy element in the center. The structure has a triple bond to the other N atom, and a single on the O atom.