## Search found 52 matches

Wed Mar 14, 2018 12:12 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Replies: 5
Views: 469

Because t cannot equal 0, but Q=0 is an adiabatic process always occurring in a closed system?
Wed Mar 14, 2018 12:06 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Isothermal Changes
Replies: 2
Views: 207

### Isothermal Changes

An isothermal change is when the temperature remains constant... but how is it able to exchange heat with its surroundings without the temperature rising or lowering? Would isothermal changes always be apart of an isolated system then?
Tue Mar 13, 2018 11:57 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Cell Concentration
Replies: 3
Views: 337

### Cell Concentration

On one of the bullet points on the electrochemistry outline says "understand how a concentration cell works and give an example." What is an example of cell concentration, or what is Lavelle looking for when answering this?
Mon Mar 12, 2018 11:34 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Profiles
Replies: 2
Views: 195

### Reaction Profiles

Just to be clear, is the reaction profile is just a diagram that shows and x axis (potential energy) and y axis (progress of a reaction) with reactants, products, and activation energy? Is there anything else that needs to be know specifically for the reaction profile besides that they can be endoth...
Wed Mar 07, 2018 8:45 am
Forum: Second Order Reactions
Topic: 15.35
Replies: 1
Views: 349

### 15.35

In part a) you plug in 1/ .84/16 for [A] which flips and is basically 16/.84 but in part b) you get 1/ .84/4 for [A] and you don’t flip this one and get 1/.21. Why do you flip part a but not part b fraction wise?
Tue Mar 06, 2018 10:22 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 5
Views: 411

### Catalysts

Can someone explain how a catalyst can lower activation energy but increase the rate of a reaction? I need help with the conceptual understanding of this
Tue Mar 06, 2018 10:09 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Unstable Compounds
Replies: 1
Views: 165

### Unstable Compounds

The three different classifications of thermodynamically unstable compounds include labile, non labile, and inert.
Will we need to be able to identify the different types within an equation or would it be given in a question? And if we have to identify it how would we be able to?
Tue Mar 06, 2018 10:04 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Four Cases
Replies: 2
Views: 187

### Four Cases

What are the four cases of spontaneity on ΔS and ΔH for a system at constant T and P? Whats an easy way to memorize these?
Tue Mar 06, 2018 10:01 am
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: Thermodynamic vs Molecular Approach [ENDORSED]
Replies: 1
Views: 225

### Thermodynamic vs Molecular Approach[ENDORSED]

When using the Boltzmann's equation, there is a thermodynamic approach and a molecular approach, whats the difference between the two? When would you know to use which one?
Tue Mar 06, 2018 9:56 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isobaric vs. Isochoric [ENDORSED]
Replies: 2
Views: 711

### Isobaric vs. Isochoric[ENDORSED]

What is the difference between Isobaric (P) and Isochoric (V) and how do you identify it in an equation?
Tue Mar 06, 2018 9:47 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: infinitesimal change
Replies: 3
Views: 673

### infinitesimal change

What is an infinitesimal change and how do you identify it?
Tue Mar 06, 2018 3:46 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cell Potential
Replies: 1
Views: 122

### Galvanic Cell Potential

Why cant a single standard galvanic cell have a potential larger than about 6 V?
Tue Mar 06, 2018 3:42 am
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Primary vs. Secondary Cells
Replies: 1
Views: 237

### Primary vs. Secondary Cells

Whats the difference between primary and secondary cells and how would you be able to spot which is which in a problem?
Tue Mar 06, 2018 3:38 am
Forum: General Rate Laws
Topic: Average vs. Unique Average Reaction Rate
Replies: 1
Views: 127

### Average vs. Unique Average Reaction Rate

What's the difference between an average reaction rate and an unique average reaction rate? And how would you be able to distinguish it in a problem?
Tue Mar 06, 2018 3:31 am
Forum: General Rate Laws
Topic: Isolation Method
Replies: 2
Views: 147

### Isolation Method

Can someone explain the isolation Method and in what circumstance you would use it?
Thu Feb 22, 2018 10:21 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Spontaneous Directions [ENDORSED]
Replies: 7
Views: 522

### Spontaneous Directions[ENDORSED]

How do you predict the spontaneous direction of a redox reaction using standard reduction potentials.
Thu Feb 22, 2018 9:49 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electromotive Force
Replies: 3
Views: 253

### Electromotive Force

What's the definition of the electromotive force (emf, ℰ)? and why does it represent the maximum potential difference?
Thu Feb 22, 2018 12:03 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electrolytic Cells
Replies: 1
Views: 175

### Electrolytic Cells

For an electrolytic cell, is it possible to produce a gas for an aqueous solution? Why? and if so is it at the cathode or anode?
Thu Feb 22, 2018 12:00 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Difference between galvanic and electrolytic cells
Replies: 1
Views: 154

### Difference between galvanic and electrolytic cells

Is the anode a negative terminal for a Galvanic cell because the anode is the source of the electrons where oxidation occurs?
I need help with clarification
Wed Feb 21, 2018 11:52 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Conceptual of Nernst Equation [ENDORSED]
Replies: 1
Views: 188

### Conceptual of Nernst Equation[ENDORSED]

To understand the Nernst equation correctly is it that...
Increasing the concentration of the reactants will increase the value of Ecell?
Is this all that needs to be known for this equation?
Tue Feb 13, 2018 8:34 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: Microstates
Replies: 2
Views: 325

### Microstates

I'm still very confused on how to calculate the number of microstates in a particle. Can some one simplify it in a way thats easier it understand??
Mon Feb 12, 2018 10:57 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Laws of Thermodynamics
Replies: 2
Views: 252

### Laws of Thermodynamics

First law of thermodynamics - enthalpy (heat)
second law of thermodynamics - entropy (disorder)
third law of thermodynamics - entropy of a perfect crystal is equal to zero
Is this the general basis of the laws of thermodynamics and/or is this an ok way of thinking of it?
Tue Feb 06, 2018 10:29 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 4 cases for change in entropy
Replies: 1
Views: 105

### 4 cases for change in entropy

I know that ΔS and ΔSsurr can each be either positive (+) or negative (–) but im still confused on how to figure out the spontaneity of these. can someone explain the four cases?
Tue Feb 06, 2018 10:20 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: production vs consumption
Replies: 1
Views: 165

### production vs consumption

if the is a net production of gas in a reaction then ΔS° is positive and if there is a net consumption of gas in a reaction then ΔS° is negative? is this right?
Wed Jan 17, 2018 1:08 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat output of a reaction
Replies: 1
Views: 134

### Heat output of a reaction

Given the temperature change of a calorimeter, how do you determine the heat output of a reaction?
Wed Jan 17, 2018 1:05 am
Forum: Phase Changes & Related Calculations
Topic: standard state [ENDORSED]
Replies: 1
Views: 105

### standard state[ENDORSED]

how do you recognize when a substance is in its standard state?
Wed Jan 17, 2018 1:03 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: standard enthalpies of formation v standard enthalpy of a reaction [ENDORSED]
Replies: 1
Views: 108

### standard enthalpies of formation v standard enthalpy of a reaction[ENDORSED]

Can someone better explain/distinguish the difference between these two or are they the same thing?
Standard enthalpies of formation vs standard enthalpies of reaction
Wed Jan 17, 2018 12:56 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.41
Replies: 1
Views: 85

### 8.41

The question asks, "A 50.0-g ice cube at 0.0 'C is added to a glass containing 400.0 g of water at 45.0 'C. What is the fi nal temperature of the system (see Tables 8.2 and 8.3)? Assume that no heat is lost to the surroundings." how do you find the heat that is absorbed vs the heat that is...
Wed Jan 17, 2018 12:51 am
Forum: Phase Changes & Related Calculations
Topic: 8.5
Replies: 5
Views: 242

### 8.5

the homework question is "A gas sample in a cylinder is supplied with 524 kJ of energy as heat. At the same time, a piston compresses the gas, doing 340 kJ of work. What is the change in internal energy of the gas during this process?" To answer this question would it just be 524+340 to eq...
Wed Jan 17, 2018 12:43 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.49
Replies: 1
Views: 101

### 8.49

The question states "Oxygen difluoride is a colorless, very poisonous gas that reacts rapidly with water vapor to produce O2, HF, and heat: OF2(g) + H2O(g) ---> O2(g) + 2 HF(g) Delta H = -318 kJ What is the change in internal energy for the reaction of 1.00 mol OF2?" Are we supposed to use...
Wed Dec 06, 2017 12:24 am
Forum: Naming
Topic: 17.40 [ENDORSED]
Replies: 1
Views: 152

### 17.40[ENDORSED]

what is a structural isomerism? and how do you find it in this compound - [Cr(en)3][Co(ox)3]
Tue Dec 05, 2017 11:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.5
Replies: 4
Views: 389

### 4.5

The questions says, "what is the shape of the ClO2+ ion? what is the expected OClO bond angle?" I'm still slightly confused on how to determine bond angles. Can you use the example in the question to explain how to determine the bond angle? thanks
Tue Dec 05, 2017 11:42 pm
Forum: Ionic & Covalent Bonds
Topic: 3.29
Replies: 2
Views: 447

### 3.29

In this homework problem it asks us to predict which of the following pairs of ions would have the greatest coulombic attraction in a solid compound: a) K+,O-
b) Ga3+, O2- c) Ca2+, O2-
what is a coulombic attraction, and how do you find it in this question?
Tue Dec 05, 2017 11:35 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 12.23 [ENDORSED]
Replies: 7
Views: 646

### 12.23[ENDORSED]

The question asks, " The value of Kw for water at body temperature (37 degrees Celcius) is 2.1x10^-14. what is the molarity of H3O+ ions and the pH of neutral water at 37 degrees Celcius? what is the molarity of OH- in neutral water at 37 degrees Celcius? I'm having a hard time understanding th...
Tue Dec 05, 2017 11:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.9
Replies: 2
Views: 258

### 11.9

The question states, "balance the following equations using the smallest whole number coefficients, then write the equilibrium expression Kc for each reaction:". what is it asking for when it asks to use the smallest whole number? And an example given was a) CH4(g) + Cl2(g) <=> CHCl3(g) + ...
Sat Dec 02, 2017 1:38 pm
Forum: Administrative Questions and Class Announcements
Topic: chemistry community posts [ENDORSED]
Replies: 1
Views: 180

### chemistry community posts[ENDORSED]

how can I check how many times I've posted? I want to make sure I can get all my points for posting but I'm not sure where to go to find it. Thanks!
Sat Dec 02, 2017 1:32 pm
Forum: Naming
Topic: Naming with prefixes [ENDORSED]
Replies: 1
Views: 156

### Naming with prefixes[ENDORSED]

how do you know which prefix to use? For example, di or bis, tri or tris, tetra or tetrakis.
Sat Dec 02, 2017 1:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Gases [ENDORSED]
Replies: 3
Views: 258

### Gases[ENDORSED]

How do you know when a gas is ideal?
Sun Nov 26, 2017 10:58 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chemical Equilibrium
Replies: 3
Views: 237

### Chemical Equilibrium

By watching the modules posted by Dr. Lavelle, will we be able to get all the information needed for chapter 11 in preparation for test #4?
Sun Nov 26, 2017 10:56 am
Forum: Student Social/Study Group
Topic: Chapter 17
Replies: 1
Views: 266

### Chapter 17

What do we specifically need to know from chapter 17 for the test? I wasn't in class on Wednesday so maybe I missed some of that information. Thank you!
Fri Nov 10, 2017 4:26 pm
Forum: Lewis Structures
Topic: Lewis acids and bases [ENDORSED]
Replies: 3
Views: 327

### Lewis acids and bases[ENDORSED]

whats the definition of a lewis acid and lewis base? Doesn't one of them give up an electron and the other absorb one?
Fri Nov 10, 2017 4:22 pm
Forum: Dipole Moments
Topic: Midterm [ENDORSED]
Replies: 5
Views: 493

### Re: Midterm[ENDORSED]

Does anyone know when we will be getting our scores back from the midterm?
Thu Nov 02, 2017 10:52 pm
Forum: Bond Lengths & Energies
Topic: Bond Order
Replies: 6
Views: 608

### Bond Order

how do you find the bond order? why is the bond order in H2 equal to 1?
Thu Nov 02, 2017 10:49 pm
Forum: Ionic & Covalent Bonds
Topic: Metallic Bond
Replies: 4
Views: 315

### Metallic Bond

Do we need to know this and if so what is a metallic bond or what does it do?
Wed Oct 25, 2017 5:30 pm
Forum: Lewis Structures
Topic: Coulomb Potential Energy
Replies: 2
Views: 172

### Coulomb Potential Energy

Can someone explain the Coulomb potential energy formula?
Wed Oct 25, 2017 4:48 pm
Forum: Lewis Structures
Topic: Double or single bonds
Replies: 4
Views: 265

### Double or single bonds

How do you determine whether a Lewis structure has a single or double bond?
Wed Oct 18, 2017 3:45 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8042
Views: 1412375

### Re: Post All Chemistry Jokes Here

I am out of chemistry jokes, I should zinc of a new one.
Wed Oct 18, 2017 3:42 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8042
Views: 1412375

### Re: Post All Chemistry Jokes Here

Do you have 11 protons?
Because you are sodium fine ;)
Wed Oct 18, 2017 3:39 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8042
Views: 1412375

### Re: Post All Chemistry Jokes Here

"oh my gosh, I've lost a neutron"
"Don't worry; you can get a new one "free of charge."
Mon Oct 09, 2017 11:46 pm
Forum: Properties of Light
Topic: Chapter 1 Question 9
Replies: 4
Views: 360

### Chapter 1 Question 9

In the table, what conversion formula would we use to find wave length and energy of photon from the frequency 8.7x10^14 Hz?
Sat Oct 07, 2017 11:45 am
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Equations
Replies: 5
Views: 468

### Balancing Chemical Equations

When trying to balance a chemical equation and it includes a triangle (delta) symbol, does that affect how I balance the equation?
Sat Oct 07, 2017 11:37 am
Forum: Limiting Reactant Calculations
Topic: Finding Excess Reactant [ENDORSED]
Replies: 2
Views: 238

### Finding Excess Reactant[ENDORSED]

How do you find the excess reactant in an equation? How do you find a limiting reactant? Are both required in an equation?