Search found 67 matches

by austin-3b
Fri Mar 05, 2021 9:52 pm
Forum: Second Order Reactions
Topic: half life for second-order reactions
Replies: 9
Views: 38

Re: half life for second-order reactions

I think it's because second order depends on the concentration. The half life is different for each concentration, you can't just do that to find 1/2, 1/4, 1/8, and so on.
by austin-3b
Fri Mar 05, 2021 9:49 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6N.17 Textbook Question
Replies: 3
Views: 10

Re: 6N.17 Textbook Question

I believe you find the delta E (it's a concentration cell) and know that the amount of electrons transferred is 1. Then, use -nFE.
by austin-3b
Fri Mar 05, 2021 9:44 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 6L.1
Replies: 3
Views: 9

Re: 6L.1

I believe n is the amount of moles of electrons transferred.
by austin-3b
Fri Mar 05, 2021 9:42 pm
Forum: Calculating Work of Expansion
Topic: Work sign
Replies: 46
Views: 95

Re: Work sign

When system does work, it's negative. When work is done on the system, it's positive.
by austin-3b
Fri Mar 05, 2021 9:40 pm
Forum: First Order Reactions
Topic: Graphing
Replies: 8
Views: 31

Re: Graphing

Not sure if we need to plot but it's important to recognize what order it is if given on a graph.
by austin-3b
Sat Feb 27, 2021 10:36 pm
Forum: Balancing Redox Reactions
Topic: 6L.7
Replies: 1
Views: 12

6L.7

I am confused on how to start these 6L.7 Write the half-reactions and devise a galvanic cell (write a cell diagram) to study each of the following reactions (a) AgBr(s)⇌Ag+(aq)+Br−(aq),a solubility equilibrium (b) H+(aq)+OH−(aq)→H2O(l),the Brønsted neutralizationreaction (c) Cd(s)+2Ni(OH)3(s)→Cd(OH)...
by austin-3b
Sat Feb 27, 2021 10:31 pm
Forum: Balancing Redox Reactions
Topic: 6L.5 [ENDORSED]
Replies: 1
Views: 42

6L.5 [ENDORSED]

I am confused for part C. For the half-cell diagram, do we include HCl? The solutions manual does not.
by austin-3b
Sat Feb 27, 2021 10:29 pm
Forum: Balancing Redox Reactions
Topic: 6L.3
Replies: 1
Views: 5

6L.3

How do you balance 6L.3 part d? It seems a little confusing to me.
by austin-3b
Sat Feb 27, 2021 12:13 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Gibbs Free Energy Equation and n
Replies: 13
Views: 26

Re: Gibbs Free Energy Equation and n

N is the amount of moles of electrons. If one electron is transferred, n is one and if two are transferred, n is two and so on.
by austin-3b
Sat Feb 27, 2021 12:12 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode/Cathode
Replies: 45
Views: 81

Re: Anode/Cathode

Anode is usually on the left and cathode is usually on the right.
by austin-3b
Sat Feb 27, 2021 12:11 am
Forum: Balancing Redox Reactions
Topic: Acidic vs. Basic
Replies: 20
Views: 34

Re: Acidic vs. Basic

You can use H+ or H2O for acidic solutions but for basic solutions, you use OH- and H2O
by austin-3b
Sat Feb 27, 2021 12:11 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Spontaneity and Galvanic Cells
Replies: 5
Views: 14

Re: Spontaneity and Galvanic Cells

Positive E indicates that it is spontaneous and negative E indicates that it is not.
by austin-3b
Sat Feb 27, 2021 12:10 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridges
Replies: 37
Views: 70

Re: Salt Bridges

It helps maintain neutrality I believe.
by austin-3b
Sat Feb 20, 2021 12:12 am
Forum: Van't Hoff Equation
Topic: Delta H naught VS delta H
Replies: 14
Views: 56

Re: Delta H naught VS delta H

Delta H naught is just the specific standard conditions.
by austin-3b
Sat Feb 20, 2021 12:11 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: When does delta H = q?
Replies: 15
Views: 49

Re: When does delta H = q?

It is usually the case with constant pressure.
by austin-3b
Sat Feb 20, 2021 12:10 am
Forum: Calculating Work of Expansion
Topic: unit of w
Replies: 17
Views: 53

Re: unit of w

It's in joules. P is in atm, volume is in liters. You have L*atms and when you multiply by 101.325 (J/L*atm) correct me if I'm wrong, then you get joules.
by austin-3b
Sat Feb 20, 2021 12:08 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Thermodynamically Favorable
Replies: 27
Views: 65

Re: Thermodynamically Favorable

When delta G is negative, it's favorable because of spontaneity.
by austin-3b
Sat Feb 20, 2021 12:07 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gas Constant R
Replies: 42
Views: 69

Re: Gas Constant R

Depends on what you are trying to find. If joules, use 8.314, if not then you use 0.0821.
by austin-3b
Sat Feb 20, 2021 12:06 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm 2 and Final
Replies: 25
Views: 139

Re: Midterm 2 and Final

I believe so.
by austin-3b
Mon Feb 15, 2021 5:22 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff [ENDORSED]
Replies: 6
Views: 75

Van't Hoff [ENDORSED]

What type of problems do we need to use Van't Hoff equations for?
by austin-3b
Sun Feb 14, 2021 2:54 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 4J.13 Question
Replies: 3
Views: 11

Re: 4J.13 Question

At a more negative delta G, it tends to form the substance spontaneously because it's more stable, more favorable. So choose those with a negative delta g, those will be the most stable.
by austin-3b
Sun Feb 14, 2021 2:48 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm 2 Content
Replies: 18
Views: 104

Re: Midterm 2 Content

It covers everything up until Friday's lecture I think.
by austin-3b
Fri Feb 12, 2021 1:04 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs and Equilbrium constant
Replies: 3
Views: 20

Gibbs and Equilbrium constant

How do you relate the two? On Sapling, the last couple problems deal with this.
by austin-3b
Fri Feb 12, 2021 1:02 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 4F.9
Replies: 3
Views: 17

Re: 4F.9

You use P1/P2 instead because when you do the proportions with P and V, you get

P1V1=P2V2

V2/V1 = P1/P2
by austin-3b
Fri Feb 12, 2021 1:01 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Sapling #14B W3/4
Replies: 4
Views: 35

Re: Sapling #14B W3/4

Since you are dealing with an irreversible problem, you use the external pressure (1.43). Then, you multiply that by the delta V (VF-VI). Finally, you multiply that by 101.325 to go from L*atm to joules.

-p(deltaV) * 101.325
by austin-3b
Fri Feb 12, 2021 12:58 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: textbook 4.15
Replies: 2
Views: 18

Re: textbook 4.15

This is because when setting q (system) equal to q(surroundings), in this case, the reaction and water, the other side has to be negative.
by austin-3b
Fri Feb 12, 2021 12:55 am
Forum: Calculating Work of Expansion
Topic: Textbook problem 4B.13
Replies: 6
Views: 17

Re: Textbook problem 4B.13

For irreversible, you always use the external pressure because that is what the system is pushing against.
by austin-3b
Fri Feb 05, 2021 12:48 pm
Forum: Calculating Work of Expansion
Topic: Spontaneous
Replies: 25
Views: 93

Re: Spontaneous

Spontaneous means a reaction can operate on its own without any extra input. To determine spontaneity, delta H would help, but it doesn't tell the full story. You would have to find delta G. In order to do that you would need to have the delta H (enthalpy) minus delta S (entropy) times T(temp).
by austin-3b
Fri Feb 05, 2021 12:46 pm
Forum: Calculating Work of Expansion
Topic: Work notation
Replies: 10
Views: 47

Re: Work notation

It is written as a lowercase w. Uppercase is for degeneracy.
by austin-3b
Fri Feb 05, 2021 12:44 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Adiabatic systems
Replies: 14
Views: 302

Re: Adiabatic systems

q will always be zero since there's no heat coming in or out.
by austin-3b
Fri Feb 05, 2021 12:42 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: R Constant
Replies: 89
Views: 249

Re: R Constant

That is correct. However, when you use the constant to find work (joules), then you use 8.314.
by austin-3b
Fri Feb 05, 2021 12:41 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Examples for types of systems
Replies: 8
Views: 43

Re: Examples for types of systems

An example of an open system is a glass of water. An example of a closed system is an ice pack. An example of an isolated system is a substance in an insulator.
by austin-3b
Thu Feb 04, 2021 6:54 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Textbook Problem 4.5
Replies: 1
Views: 12

Textbook Problem 4.5

I'm not really sure how to approach this problem 4.5 In 1750, Joseph Black performed an experiment that eventually led to the discovery of enthalpies of fusion. He placed two samples of water, each of mass 150 g, at 0.00 °C (one ice and one liquid) in a room kept at a constant temperature of 5.00°C....
by austin-3b
Sun Jan 31, 2021 11:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: is HClO3 weak or strong? [ENDORSED]
Replies: 49
Views: 259

Re: is HClO3 weak or strong? [ENDORSED]

I believe it's one of the strong acids.
by austin-3b
Sun Jan 31, 2021 11:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Taking the Anti-Log
Replies: 37
Views: 124

Re: Taking the Anti-Log

You would do 10 to the negative pka (that dictates the exponent)

10^(-pka)
by austin-3b
Sun Jan 31, 2021 10:52 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: isolated system
Replies: 9
Views: 49

Re: isolated system

I would assume no energy change is occurring because nothing can go in or out of the system.
by austin-3b
Thu Jan 28, 2021 11:24 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Value for energy released
Replies: 1
Views: 32

Value for energy released

UA Worksheet: The value of ΔH for this reaction is -1107 kJ: 2Ba(s) + O​ (g) → 2BaO(s) How many kJ of heat are released when 5.75 g of BaO (s) is produced? When asking how many kJ of heat released, do you put the answer as a negative sign or positive sign? I know if it asks for the change in enthalp...
by austin-3b
Wed Jan 27, 2021 12:27 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K for stability [ENDORSED]
Replies: 1
Views: 28

K for stability [ENDORSED]

I know if 10^-3 < K < 10^3, you can't determine if reactant or product is favored. Is that case for stability for products vs. reactants? Like if k falls between these numbers, are you unable to determine if the products or reactants are more stable?
by austin-3b
Wed Jan 27, 2021 12:22 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Effect of Pressure (contraction) in reaction
Replies: 8
Views: 36

Effect of Pressure (contraction) in reaction

If there are zero moles on one side of the reaction (solid only) and you compress the system, does the reaction shift to that side or does it not (because the solid does not contribute to equilibrium)?

Example
A(s) --> B (aq) + C (g)
by austin-3b
Mon Jan 25, 2021 5:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Favorability/Stability of Products or Reactants at K
Replies: 2
Views: 16

Favorability/Stability of Products or Reactants at K

Is there a 10^-3 -10^3 cutoff for favorability/stability of products or reactants in a reaction? Like if the k falls in between those values, are neither products nor reactants favored?
by austin-3b
Sun Jan 24, 2021 8:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6.19
Replies: 1
Views: 15

6.19

How are we supposed to approach this? Hemoglobin (Hb) molecules in blood carry O2 molecules from the lungs, where the concentration of oxygen is high, to the tissues where it is low (see the Interlude following Focus 5). In the tissues the equilibrium H3O+(aq) + HbO2−(aq) ⇌ HHb(aq) + H2O(l) + O2(aq)...
by austin-3b
Sat Jan 23, 2021 6:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Le Chatlier (solids)
Replies: 2
Views: 19

Le Chatlier (solids)

Would the reaction not shift to the left (more A made) if you add the amount of substance B because solids aren't part of equilibrium constant?

A(s) --> B (g) + C(aq)
by austin-3b
Sat Jan 23, 2021 5:47 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard State Elements
Replies: 5
Views: 23

Standard State Elements

Beside diatomic molecules and graphite carbon, how do we know if an element is in its standard state?
by austin-3b
Sat Jan 23, 2021 12:04 am
Forum: Phase Changes & Related Calculations
Topic: Elements Not in standard state
Replies: 5
Views: 46

Elements Not in standard state

When given a reaction, how do we deal with an element not in its standard state?
by austin-3b
Fri Jan 22, 2021 10:23 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Change
Replies: 2
Views: 54

Phase Change

For the calculating the enthalpy of formations, how do we account for phase changes? Are there times where we look at the table of enthalpies of an element and have to account for phase changes (add or subtract)? Or do we just look at the molecule and the phase it is and use it straight up?
by austin-3b
Fri Jan 22, 2021 1:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.23
Replies: 2
Views: 40

4D.23

We are given two equations to find the enthalpy of formation for dinitrogen pentoxide. How come we multiply the bottom equation (with N2O5 as a product) by half and not the top by 2 order to cancel out the intermediate NO2s? Also, how do we do the second part (and from the standard enthalpy of forma...
by austin-3b
Fri Jan 22, 2021 12:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.15
Replies: 1
Views: 26

4D.15

How come we don't multiple the last combustion equation by 2 based on the coefficients? Is it because you can use half coefficients for Hess's Law?

H2 + O2--> H2O
by austin-3b
Fri Jan 22, 2021 12:56 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Textbook 4D.11 Part B
Replies: 2
Views: 24

Re: Textbook 4D.11 Part B

The gas constant you use depends on the units given. In this case, you use 0.0821.
by austin-3b
Fri Jan 22, 2021 12:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: steam causing burns
Replies: 40
Views: 157

Re: steam causing burns

Even though steam may have the same temperature as liquid, there is more heat in the system because bonds are being broken. According to the graph, when heat is being transferred to the skin, steam has more energy to release than liquid. This is why it hurts more when you have hot steam.
by austin-3b
Fri Jan 22, 2021 12:53 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Endothermic vs Exothermic Stabilities
Replies: 8
Views: 112

Re: Endothermic vs Exothermic Stabilities

You are correct. Exothermic reactions where things that go to a lower energy state are generally more stable. Endothermic is vice versa. If elements go to a higher energy state, they are generally less stable.
by austin-3b
Fri Jan 15, 2021 10:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When x is negligible in Equilibrium constant
Replies: 34
Views: 160

Re: When x is negligible in Equilibrium constant

It has to be 10^-4 or smaller, but you can always check using the 5% rule. If x is less than 5% of initial, the approximation is valid.
by austin-3b
Fri Jan 15, 2021 10:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pH of conjugate acid/base
Replies: 3
Views: 47

pH of conjugate acid/base

Once we calculate the pH of a certain substance, do we need to know how to calculate the pH of its conjugate. Is it like pka and kb where subtracting 14 from the ph gives you the ph of its conjugate?
by austin-3b
Fri Jan 15, 2021 6:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6D1 - tables?
Replies: 2
Views: 20

Re: 6D1 - tables?

I think it tells you to refer to them.
by austin-3b
Thu Jan 14, 2021 2:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6D.15
Replies: 1
Views: 16

6D.15

6D.15
Calculate the pH of
(a) 0.19 M NH4Cl(aq) (b) 0.055 M AlCl3 (aq).

How are we supposed to know if AlCl3 is an acid or a base?
by austin-3b
Wed Jan 13, 2021 7:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Increase in Pressure
Replies: 31
Views: 89

Increase in Pressure

For increases in pressure (decreases in volume), the reaction goes toward the side with less moles. When finding out which side has the least amount of moles, do you also include aqueous solutions or only gases?
by austin-3b
Wed Jan 13, 2021 7:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: [H30+]=[OH-] ???
Replies: 8
Views: 66

Re: [H30+]=[OH-] ???

Since it's neutral, you can assume these concentrations are equal. Therefore, you can assign the same variable (x). You do that, square root every side and you get 1 * 10^-7.
by austin-3b
Tue Jan 12, 2021 12:06 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: H2O as a Gas
Replies: 69
Views: 459

Re: H2O as a Gas

Normally, you would exclude it. But if it's a gas, you put it in the ICE Table. Anything that isn't a solid or liquid is included.
by austin-3b
Tue Jan 12, 2021 12:05 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q and K
Replies: 46
Views: 206

Re: Q and K

Yes, Q is any time. You would measure Q at that moment to determine the direction of the reaction.

If Q<K, the reaction is going right; more products are made
If Q>K, the reaction is going left; more reactants are made
by austin-3b
Sun Jan 10, 2021 8:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Removing product
Replies: 5
Views: 22

Re: Removing product

If you remove the product then you lower the Q at that moment. Since Q (the reaction quotient) is lower, it will make more product to get back to the level desired.
by austin-3b
Thu Jan 07, 2021 5:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: concentration or partial pressure
Replies: 7
Views: 39

Re: concentration or partial pressure

I don't think you have to convert unless it asked for Kp. You can use the concentrations for this case.
by austin-3b
Tue Jan 05, 2021 12:01 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 1A module #18
Replies: 5
Views: 60

Re: 1A module #18

Since it's k, it's the equilibrium concentration. If it was asking for q, then it would be for the initial concentrations.
by austin-3b
Mon Jan 04, 2021 11:56 pm
Forum: Ideal Gases
Topic: Converting to Concentration and Pressure Values
Replies: 7
Views: 69

Re: Converting to Concentration and Pressure Values

P= pressure of the gas (atm)
V= volume of gas (L)
n= number of moles
r= gas constant
T= Temp (Kelvin)
by austin-3b
Mon Jan 04, 2021 11:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc favoring products
Replies: 10
Views: 101

Re: Kc favoring products

You are correct; even though 61 seems like a big number, you can only conclude that it favors products when it's 10^3 and above and reactants when it's 10^-3 and below.
by austin-3b
Mon Jan 04, 2021 11:50 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Qc vs Kc
Replies: 15
Views: 633

Re: Qc vs Kc

When Qc is more than Kc, reactants would be formed to get that ratio back to equilibrium.
When Qc is less than Kc, products would be formed to get the ratio up to equilbrium.
When they are equal, it's at equilibrium.
by austin-3b
Mon Jan 04, 2021 11:48 pm
Forum: Ideal Gases
Topic: Kc vs Kp
Replies: 109
Views: 1004

Re: Kc vs Kp

You use Kc when having the molar concentrations of the particles and Kp for when given the pressures (I think only gases have kp values).
by austin-3b
Mon Jan 04, 2021 11:46 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Temperature/Pressure Effect on Equilibirum (Le Chatlier)
Replies: 4
Views: 39

Temperature/Pressure Effect on Equilibirum (Le Chatlier)

Why does the increasing/decreasing of temperature affect the Keq value. Also, why does changing the pressure make the reaction favor the side with more or less moles, depending on how you change it?

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