Search found 40 matches
- Sat Mar 17, 2018 7:53 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Practice Midterm W18 #3A
- Replies: 3
- Views: 539
Practice Midterm W18 #3A
Can someone please explain how I would go about solving this problem? It reads: Lex Luthor finds a sealed box that has two compartments. He puts 9.00g of Helium gas in the first compartment, and 125g of Krypton gas in the second. The compartment with Krypton is 3 times the size of the compartment wi...
- Thu Mar 15, 2018 9:27 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity of Water
- Replies: 4
- Views: 744
Re: Heat Capacity of Water
You are correct. It takes a lot of energy to break the hydrogen bonds in water. Also water is slightly polar so energy is also needed to break the bonds between H2O molecules.
- Wed Mar 14, 2018 10:07 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: I'm confused on the formula for calculating cell potential?
- Replies: 1
- Views: 377
Re: I'm confused on the formula for calculating cell potential?
When you use the equation given on the equations sheet for tests, you always subtract E°cathode-E°anode leaving the numbers as they are given to you. Another way to solve for E°cell is to determine which is the cathode and which is the anode. Once you have determined which is the anode you change th...
- Wed Mar 14, 2018 10:02 pm
- Forum: General Rate Laws
- Topic: Powers of Concentrations in Rate Law`
- Replies: 2
- Views: 413
Re: Powers of Concentrations in Rate Law`
The order of a rate law is determined experimentally using the method of initial rates or by looking at the graphs. When the observed rate law is given along with the elementary steps of a reaction, you can use the pre-equilibrium approach to determine the slow step that determines the rate of the o...
- Wed Mar 14, 2018 9:58 pm
- Forum: Phase Changes & Related Calculations
- Topic: Test 1 Question 7
- Replies: 1
- Views: 300
Re: Test 1 Question 7
The equation to use here is q=mCΔT. The heat lost by the tea will be transferred to the ice , therefore q(ice)= -q(tea). However, the ice will melt as it heats up so the ΔH(fusion) of water must be added to the side with the q(ice). Plug in the values and leaving T(final) as x for both sides. Solve ...
- Wed Mar 14, 2018 9:50 pm
- Forum: Balancing Redox Reactions
- Topic: Lecture 3/14
- Replies: 3
- Views: 483
Re: Lecture 3/14
For a galvanic cell the over charge of the cell must be positive, so you determine which one to switch based on which one will make the charge positive.
- Wed Mar 14, 2018 9:49 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Pre-Equilibrium Approach
- Replies: 1
- Views: 294
Re: Pre-Equilibrium Approach
The problem will likely not tell you. You determine the slow step by finding the rates of every step starting in step 1. If the rate for step 1 does not match the overall rate law then it is not the slow step and you will have to check step 2. You go in order finding the rate laws of each elementary...
- Wed Mar 14, 2018 9:47 pm
- Forum: General Rate Laws
- Topic: Rate Law
- Replies: 6
- Views: 1139
Re: Rate Law
The order of a rate law is determined experimentally and cannot be determined using the coefficients in the reaction. However, when using the pre-equilibrium approach you use the coefficient as the exponent, but this can only be done when the observed rate law is given and you are trying to determin...
- Wed Mar 14, 2018 9:42 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: delta s surrounding and system
- Replies: 3
- Views: 4808
Re: delta s surrounding and system
The equation for entropy is q rev/ T. The heat lost by the system will be gained by the surroundings and vice versa. So on the equations for entropy will have -q. Furthermore, when the system loses entropy, the surroundings gain it. Hope this helps!
- Wed Mar 14, 2018 7:26 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: delta s surroundings
- Replies: 3
- Views: 601
Re: delta s surroundings
This is because any heat lost by the system is gained by the surroundings and vise versa; therefore, q has opposite signs.
- Tue Mar 13, 2018 9:09 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: catalysts and intermediates
- Replies: 2
- Views: 430
Re: catalysts and intermediates
I believe catalysts are in the first step as a reactants and get cancelled out later in the mechanism. An intermediate is produced within the mechanism and then cancelled out. Both are cancelled, but a catalyst is a reactant in the beginning of the whole mechanism while an intermediate is made withi...
- Tue Mar 13, 2018 9:08 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Question 15.47
- Replies: 4
- Views: 511
Re: Question 15.47
Chlorine is an intermediate because it is produced in step 1, but it is used as a reactant in step 2; therefore, they cancel out, and the overall reaction does not include it.
- Tue Mar 13, 2018 9:01 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Coefficients in oxidation
- Replies: 2
- Views: 463
Re: Coefficients in oxidation
Coefficients do not matter when determining oxidation states. They only matter when determining how many electrons were transferred.
- Tue Mar 13, 2018 8:57 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Oxidizing and reducing agents
- Replies: 2
- Views: 419
Re: Oxidizing and reducing agents
I do not fully understand your question, but the reducing agent gives electrons while the oxidizing agent receives electrons. Sometimes an element or compound can act as both.
- Sun Mar 04, 2018 9:26 pm
- Forum: Zero Order Reactions
- Topic: Determining Reactions
- Replies: 2
- Views: 387
Re: Determining Reactions
One way we have learned to determine the order of each reactant in a reaction is the method of initial rates. Using this method we run many experiments and determine the order of each reactant by seeing how a change in initial concentration of a reactant changes the initial rate of the reaction. Add...
- Sun Mar 04, 2018 9:23 pm
- Forum: General Rate Laws
- Topic: Stoichiometry coefficients
- Replies: 3
- Views: 567
Re: Stoichiometry coefficients
The rate law is determined experimentally; the stoichiometric coefficients are not enough to write a rate law and determine the order.
- Sun Mar 04, 2018 8:03 pm
- Forum: General Rate Laws
- Topic: Half Life
- Replies: 6
- Views: 751
Half Life
Can someone explain what the half life of a reaction is? And why would we be interested in a half life of a reaction?
- Sun Mar 04, 2018 7:57 pm
- Forum: Balancing Redox Reactions
- Topic: Test 2, Q5
- Replies: 4
- Views: 555
Re: Test 2, Q5
I believe their order is determined based on their standard reduction potentials. The ones with the smallest reduction potentials are the ones with the most reducing power.
- Thu Mar 01, 2018 10:55 pm
- Forum: General Rate Laws
- Topic: Determining Order [ENDORSED]
- Replies: 8
- Views: 994
Re: Determining Order [ENDORSED]
To determine the order of the overall reaction you add the orders of the reactants.
- Mon Feb 26, 2018 1:04 am
- Forum: Balancing Redox Reactions
- Topic: Water in balancing reactions
- Replies: 4
- Views: 519
Re: Water in balancing reactions
Yes, water is always necessary to balane the oxygen in both basic and acidic solutions. In basic solutions, water is also needed to balance out the hydrogen.
- Sun Feb 25, 2018 10:46 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Midterm Q3A
- Replies: 2
- Views: 561
Re: Midterm Q3A
To solve this problem you find the heat needed to raise the temperature of the pot to 100 degrees C and the heat required to raise the temperature of the water to 100 degrees C. You add the heat values to answer the first question. To find the percentage of heat used on the water, you divide the hea...
- Sun Feb 25, 2018 10:43 pm
- Forum: General Rate Laws
- Topic: rate constants
- Replies: 7
- Views: 859
Re: rate constants
A rate constant represents how fast a chemical reaction will take place based on the concentrations of the reactants and products. You find it by plugging in the molar concentrations into your rate equation with their respective order and equaling it to the rate of the reaction.
- Sun Feb 18, 2018 6:30 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Notation
- Replies: 1
- Views: 274
Re: Cell Notation
Pt(s) is included in the outer portion of cell notation when it is being used as an electrode. Pt(s) is used as an electrode when there is no solid in the half reaction. It is needed to transport or receive electrons, but it does not react.
- Sun Feb 18, 2018 6:19 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell diagrams
- Replies: 1
- Views: 220
Re: Cell diagrams
It does not necessarily have to be like that, but people and textbooks usually put the anode on the left. However, on an exam it could be the other way around. Essentially it does not matter. You just have to make sure which is which by checking the half reactions.
- Sun Feb 18, 2018 6:10 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.11
- Replies: 2
- Views: 400
Re: 14.11
The anode half cell is where oxidation happens. The cathode part is where reduction happens. During oxidation there is a loss of electrins. Dheing reduction there is a gain of electrons.
- Tue Feb 13, 2018 3:58 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: delta U [ENDORSED]
- Replies: 10
- Views: 2940
Re: delta U [ENDORSED]
Can someone explain why delta U is 0 in the isothermal expansion of an ideal gas?
- Sun Feb 11, 2018 11:09 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Midterm 2018W [ENDORSED]
- Replies: 4
- Views: 520
Re: Midterm 2018W [ENDORSED]
Hello Diego!
Yes there will be lecture that day.
Yes there will be lecture that day.
- Sun Feb 11, 2018 9:25 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Different ways to calculate deltaG
- Replies: 2
- Views: 386
Re: Different ways to calculate deltaG
We use an equation to calculate delta G based on the information we are given in the problem.
- Sun Feb 11, 2018 9:20 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Maximum Potential
- Replies: 2
- Views: 756
Maximum Potential
Can someone elaborate on what the max potential of a cell means?
- Wed Feb 07, 2018 12:16 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta G
- Replies: 3
- Views: 436
Delta G
What is the difference between ∆G and ∆G°?
- Mon Jan 22, 2018 4:47 pm
- Forum: Calculating Work of Expansion
- Topic: expansion work
- Replies: 2
- Views: 325
Re: expansion work
In expansion work the pressure is usually constant and given in the problem; therefore the equation is work=−PΔV.
- Mon Jan 22, 2018 1:12 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Internal Energy and Enthalpy [ENDORSED]
- Replies: 2
- Views: 463
Internal Energy and Enthalpy [ENDORSED]
Under what conditions if any is the change in internal energy and the change in enthalpy the same?
- Sun Jan 21, 2018 11:33 pm
- Forum: Phase Changes & Related Calculations
- Topic: enthalpy vs. heat
- Replies: 2
- Views: 326
Re: enthalpy vs. heat
Heat is a path function because the amount of heat a system has is based on how it went from one state to another; however, enthalpy only depedns on the final and initial states.
- Sun Jan 21, 2018 11:23 pm
- Forum: Student Social/Study Group
- Topic: First Test Topics
- Replies: 2
- Views: 641
Re: First Test Topics
Test 1 will not have calculations on work and internal energy. Only conceptual questions will appear on these topics. We do not have to read 8.18 and 8.20.
- Sun Jan 21, 2018 11:14 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: the sign of q
- Replies: 5
- Views: 435
Re: the sign of q
If it is said that system requires heat then the sign of q will be positive because the system is absorbing heat. You can tell the sign of q based on the wording. If a system cools down or gives off heat then the sign of q will be negative.
- Fri Dec 08, 2017 12:21 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Equilibrium Shift
- Replies: 2
- Views: 207
Re: Equilibrium Shift
Will there be any approximation chemical equilibrium problems on the final?
- Sun Dec 03, 2017 8:57 pm
- Forum: Sigma & Pi Bonds
- Topic: What is a localized and delocalized Bond?
- Replies: 5
- Views: 32451
Re: What is a localized and delocalized Bond?
Localized electrons stay in between two atoms. Delocalized electrons are not confined to any space and go outside their boundaries.
- Wed Nov 29, 2017 9:06 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: 17.35 Chelating Complexes
- Replies: 4
- Views: 632
17.35 Chelating Complexes
Can someone explain chelating complexes to me, and why is 17.35 have B as the one to form a chelating complex?
- Thu Nov 16, 2017 11:08 pm
- Forum: Hybridization
- Topic: Hybridization in Carbon
- Replies: 3
- Views: 348
Re: Hybridization in Carbon
The double bond counts as one domain of electron density and when determining hybridization the type of bond does not matter. Only the number of electon domains, so it would be sp^2.
- Thu Nov 16, 2017 4:31 pm
- Forum: Hybridization
- Topic: Hybridization and lone pairs
- Replies: 2
- Views: 387
Re: Hybridization and lone pairs
Each pair of electrons occupies one sp^3 orbital. There is no different rule for hybridization of central atoms with lone pairs; therefore, the oxygen in water has 4 sp^3 orbitals.