Search found 50 matches
- Fri Mar 13, 2020 10:18 pm
- Forum: First Order Reactions
- Topic: rate constants
- Replies: 30
- Views: 1362
Re: rate constants
Yes, they're always positive!
- Fri Mar 13, 2020 9:54 pm
- Forum: First Order Reactions
- Topic: Units for t
- Replies: 30
- Views: 1164
Re: Units for t
The units of t depend on the problem, but be consistent when doing calculations!
- Fri Mar 13, 2020 8:50 pm
- Forum: Administrative Questions and Class Announcements
- Topic: "Open Book" Final?
- Replies: 30
- Views: 1946
Re: "Open Book" Final?
We will be able to use our notes, textbook, and chemistry community! Exam should be short, but he said he'd give us 3-4 hours to complete it. He will give us more info on Saturday!
- Fri Mar 13, 2020 8:45 pm
- Forum: Student Social/Study Group
- Topic: final?
- Replies: 7
- Views: 633
Re: final?
Lavelle will let us know more on Saturday, look out for his emails!
- Fri Mar 13, 2020 8:43 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final
- Replies: 11
- Views: 701
Re: Final
Final will be up on Sunday, and it is timed (3-4 hours). Lavelle will let us know more info Saturday!
- Fri Mar 06, 2020 11:34 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: change in gibbs free energy
- Replies: 4
- Views: 322
Re: change in gibbs free energy
Photosynthesis is not spontaneous and needs an input of energy in order for it to occur. So that's why the answer is ΔG<0
- Fri Mar 06, 2020 11:31 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation Numbers
- Replies: 7
- Views: 636
Re: Oxidation Numbers
For some elements there will be a trend you should follow (look up a periodic table with these trends on google!), and for the unknown you can solve for. The oxidation numbers should add up to the total charge at the end.
- Fri Mar 06, 2020 8:53 pm
- Forum: General Science Questions
- Topic: Test 2 Grades [ENDORSED]
- Replies: 23
- Views: 1552
Re: Test 2 Grades [ENDORSED]
We will most likely get our test grades during discussion of week 10!
- Fri Mar 06, 2020 1:12 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst
- Replies: 10
- Views: 714
Re: Nernst
You can use whichever you want to use!
- Fri Mar 06, 2020 1:10 am
- Forum: Administrative Questions and Class Announcements
- Topic: Test 2 Grades
- Replies: 22
- Views: 1147
Re: Test 2 Grades
We will most likely get our test grades next week during discussion section
- Fri Feb 28, 2020 8:38 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Porous Disk and Salt Bridge
- Replies: 13
- Views: 1158
Re: Porous Disk and Salt Bridge
Since they ultimately have the same function, I believe that one isn't more efficient than the other
- Fri Feb 28, 2020 8:34 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: When to apply Pt into cell diagrams
- Replies: 9
- Views: 499
Re: When to apply Pt into cell diagrams
use Pt(s) when there's no metal conductor
- Fri Feb 28, 2020 8:21 pm
- Forum: Balancing Redox Reactions
- Topic: Writing half reactions
- Replies: 9
- Views: 627
Re: Writing half reactions
Yes! It's best to keep oxidized molecules to the left and reduced molecules to the right, this is also stated in the textbook.
- Fri Feb 28, 2020 8:17 pm
- Forum: Balancing Redox Reactions
- Topic: Test 2
- Replies: 10
- Views: 676
Re: Test 2
Test 2 will cover the rest of outline 4 (what wasn't on the midterm) and Outline 5 only. No kinetics!
- Fri Feb 28, 2020 8:16 pm
- Forum: Balancing Redox Reactions
- Topic: How to tell if its being reduced or oxidized
- Replies: 15
- Views: 1905
Re: How to tell if its being reduced or oxidized
You have to look at Mn only, and we see that it goes from 7+ to 2+, thus being reduced
- Sat Feb 22, 2020 2:03 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding Inert Gas
- Replies: 20
- Views: 1036
Re: Adding Inert Gas
Adding an inert gas doesn’t affect the equilibrium constant
- Fri Feb 21, 2020 3:40 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Adiabatic systems
- Replies: 14
- Views: 775
Re: Adiabatic systems
Yes, ALWAYS! Thats because there is no heat transfer.
- Fri Feb 21, 2020 3:36 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: E
- Replies: 5
- Views: 322
Re: E
E will be positive if reaction is spontaneous!
- Fri Feb 21, 2020 1:04 am
- Forum: Balancing Redox Reactions
- Topic: Reduction vs. oxidation
- Replies: 29
- Views: 1110
Re: Reduction vs. oxidation
Reduction means gain of electron, it becomes more negative. While oxidation is the loss of electron, becomes more positive.
- Fri Feb 21, 2020 1:02 am
- Forum: Balancing Redox Reactions
- Topic: Test 2 [ENDORSED]
- Replies: 12
- Views: 649
Re: Test 2 [ENDORSED]
Test 2 was moved to week 9 so we could have more time with the material! Also, it will include material after the midterm (outlines 4 and 5). It won't include kinetics.
- Sat Feb 15, 2020 4:54 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: spontaneity
- Replies: 39
- Views: 1822
Re: spontaneity
Definitely Gibbs Free energy (delta G)! If delta G is negative then the reaction is spontaneous, but if it’s positive it is not.
- Sat Feb 15, 2020 4:52 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 W
- Replies: 7
- Views: 534
Re: degeneracy W
To find W, you can use the equation W=(P)^a
Where “P” is the number of possible positions and “a” is the number of atoms
Where “P” is the number of possible positions and “a” is the number of atoms
- Tue Feb 11, 2020 12:19 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Test 1 Problem 6
- Replies: 2
- Views: 203
Re: Test 1 Problem 6
Oh sure thing!
The pH of a 0.010 M solution of hydrofluoric acid is 2.63. What are Ka and percent ionization?
The pH of a 0.010 M solution of hydrofluoric acid is 2.63. What are Ka and percent ionization?
- Mon Feb 10, 2020 10:42 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Test 1 Problem 6
- Replies: 2
- Views: 203
Test 1 Problem 6
Can someone explain to me how to solve problem 6 from test 1? Thank you!
- Mon Feb 10, 2020 10:26 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: pKb to pOH
- Replies: 2
- Views: 55
pKb to pOH
How do you find pOH when only given pKb?
- Fri Feb 07, 2020 9:06 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: state occupation of phases
- Replies: 7
- Views: 265
Re: state occupation of phases
Gasses have higher entropy, while solids and liquids have their molecules tightly packed. Gas molecules can be in any location, since they are not tightly packed, which is why they "occupy more space"
- Fri Feb 07, 2020 8:58 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: closed vs isolated
- Replies: 14
- Views: 424
Re: closed vs isolated
A closed system is when a system can only transfer energy (like heat) with its surroundings, meanwhile an isolated system can't transfer anything with its surroundings.
- Fri Feb 07, 2020 8:54 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: isolated system
- Replies: 8
- Views: 457
Re: isolated system
A reaction in a bomb calorimeter is considered an isolated system because the calorimeter is closed and isolated. This means that no energy and no matter is being transferred.
- Fri Feb 07, 2020 8:46 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated vs Closed [ENDORSED]
- Replies: 34
- Views: 4083
Re: Isolated vs Closed [ENDORSED]
A closed system is when a system can only exchange energy (like heat) with its surroundings. Meanwhile, an isolated system is a system that can't exchange anything with its surroundings.
- Thu Feb 06, 2020 11:47 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Grading
- Replies: 7
- Views: 225
Grading
Can someone explain to me how the grading works for this class, I'm a bit confused. Thanks!
- Thu Jan 30, 2020 8:57 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: adiabatic systems
- Replies: 10
- Views: 935
Re: adiabatic systems
Adiabatic means that there is no heat transfer
- Thu Jan 30, 2020 8:52 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Endothermic vs Exothermic
- Replies: 10
- Views: 509
Re: Endothermic vs Exothermic
Yeah you are right. Positive q means reaction is endothermic since the system gained heat. Negative q means reaction is exothermic since heat is released.
- Thu Jan 30, 2020 8:47 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Units for temperature?
- Replies: 11
- Views: 485
Re: Units for temperature?
You can use either unit, but make sure you use the same units throughout the problem.
- Thu Jan 30, 2020 8:42 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Qv vs Qp
- Replies: 7
- Views: 129
Re: Qv vs Qp
Qv is when there's constant volume while Qp is constant pressure
- Thu Jan 30, 2020 5:39 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: delta V & delta U
- Replies: 1
- Views: 88
delta V & delta U
Why is it that when delta V = 0, delta U = q?
- Thu Jan 23, 2020 5:16 pm
- Forum: Phase Changes & Related Calculations
- Topic: removing heat from system
- Replies: 6
- Views: 679
Re: removing heat from system
Yeah, if a reaction is exothermic then temp will decrease. This is because the reaction is releasing heat (delta H is negative).
- Thu Jan 23, 2020 5:02 pm
- Forum: Student Social/Study Group
- Topic: Midterm and Final Question
- Replies: 18
- Views: 1013
Midterm and Final Question
will there be study guides for the midterm and final?
- Thu Jan 23, 2020 4:34 pm
- Forum: Ideal Gases
- Topic: Kc vs Kp
- Replies: 109
- Views: 4369
Re: Kc vs Kp
You use Kc when you are given a concentration, while Kp is used when given partial pressures. However, you can use Kp to find Kc if needed.
- Thu Jan 23, 2020 4:24 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Exothermic vs. Endothermic reactions
- Replies: 12
- Views: 914
Re: Exothermic vs. Endothermic reactions
Yes, you should be able to determine if the reaction is exothermic or endothermic when given delta H.
- Thu Jan 23, 2020 4:21 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: pKa/pKb and Ka/Kb
- Replies: 5
- Views: 153
pKa/pKb and Ka/Kb
What is the difference between pKa/pKb and Ka/Kb?
- Fri Jan 17, 2020 5:28 pm
- Forum: Ideal Gases
- Topic: Partial Pressure
- Replies: 8
- Views: 261
Re: Partial Pressure
Each gas in a reaction has a partial pressure that all come together to make a whole pressure.
- Thu Jan 16, 2020 10:57 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Heat
- Replies: 3
- Views: 82
Re: Heat
In an endothermic reaction, heat is a reactant. So, if temperature increases, reactants increases so it shifts to the right and favors Products. In an exothermic reaction, heat is a product. If temperature is increased, products increase, so it shifts to the left and Reactants are favored.
- Thu Jan 16, 2020 10:20 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: pH
- Replies: 2
- Views: 182
pH
Why doesn't pH have units?
- Thu Jan 16, 2020 10:18 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc & Kp
- Replies: 12
- Views: 281
Kc & Kp
How do you know when to use Kc or Kp when dealing with gasses? For example, in problem 5I.17 we use Kc instead of Kp, why?
- Thu Jan 16, 2020 10:13 pm
- Forum: Phase Changes & Related Calculations
- Topic: Autoprotolysis
- Replies: 15
- Views: 731
Re: Autoprotolysis
Autoprotolysis is when two identical molecules transfer protons.
- Thu Jan 09, 2020 10:23 pm
- Forum: Ideal Gases
- Topic: K value
- Replies: 14
- Views: 1087
Re: K value
if K < 10^-3, then there are more reactants at equilibrium; this means that the equilibrium sits to the left.
if K > 10^3, then there are products at equilibrium; so equilibrium sits ti the right.
if K=1, the concentration of products and reactants are equal, so they have same stabilities.
if K > 10^3, then there are products at equilibrium; so equilibrium sits ti the right.
if K=1, the concentration of products and reactants are equal, so they have same stabilities.
- Thu Jan 09, 2020 10:08 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q vs K
- Replies: 8
- Views: 191
Re: Q vs K
K is an equilibrium constant, while Q is a reaction quotient. K is found when the reaction is at equilibrium, but Q can be calculated at any time during the reaction. You can compare the reaction quotient, Q, to the equilibrium constant, K, to determine the direction of the reaction.
- Thu Jan 09, 2020 7:53 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Why is K unitless?
- Replies: 10
- Views: 562
Re: Why is K unitless?
K is just a ratio of products/reactants, so there are no units. Also, when calculating K, the units just cancel out.
- Thu Jan 09, 2020 7:51 pm
- Forum: Ideal Gases
- Topic: Understanding Q
- Replies: 13
- Views: 472
Re: Understanding Q
Yes, you don't include solids and liquids, only whatever is in gaseous/aqueous states when calculating Q.
- Thu Jan 09, 2020 4:14 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook 5H.1 Part 1
- Replies: 4
- Views: 124
Textbook 5H.1 Part 1
For this part of the problem, why do we get the square root of 41?