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by kausalya_1k
Sat Mar 14, 2020 5:58 pm
Forum: Balancing Redox Reactions
Topic: Oxidation/Reduction
Replies: 17
Views: 159

Re: Oxidation/Reduction

I believe we look at the ion itself (Within the molecule) to calculate the oxidation number and then determine which species gained an electron and which one lost an electron
by kausalya_1k
Sat Mar 14, 2020 5:57 pm
Forum: General Rate Laws
Topic: half life
Replies: 5
Views: 37

Re: half life

you would use the integrated rate law in order to find it for values after 1/2 (such as 1/4 and 1/16)
by kausalya_1k
Sat Mar 14, 2020 5:56 pm
Forum: General Rate Laws
Topic: Stoichiometric Coefficients
Replies: 3
Views: 26

Re: Stoichiometric Coefficients

I also thought molecularity describes rate law. Could you explain why you think it's the other way around?
by kausalya_1k
Sun Mar 08, 2020 6:34 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Using partial pressure in Q
Replies: 6
Views: 53

Re: Using partial pressure in Q

Just like K, Q can be calculated in terms of partial pressures or concentrations. Therefore there is no need to convert pressure to concentration (also because as someone pointed out earlier, using the PV=nRT will just cancel out the units anyways).
by kausalya_1k
Sun Mar 08, 2020 6:32 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Determining the cathode/anode
Replies: 9
Views: 94

Re: Determining the cathode/anode

the anode is the more negative cell potential and the cathode is the more positive one
by kausalya_1k
Sun Mar 08, 2020 6:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram Order
Replies: 8
Views: 83

Re: Cell Diagram Order

the order doesn't matter just remember that the anode is on the left and the cathode is on the right
by kausalya_1k
Thu Mar 05, 2020 8:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Question 6M.11
Replies: 2
Views: 20

Question 6M.11

Suppose that each of the following pairs of redox couples is combined to form a galvanic cell that generates a current under standard conditions. Identify the oxidizing agent and the reducing agent, write a cell diagram, and calculate the standard cell potential from the standard potentials of the e...
by kausalya_1k
Thu Mar 05, 2020 12:56 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Do you make the Standard Cell Potential negative when you reverse a reaction?
Replies: 1
Views: 20

Do you make the Standard Cell Potential negative when you reverse a reaction?

I know the standard cell potential (E o) isn't affected by balancing the equation, but what about when you reverse one of the half reactions?
by kausalya_1k
Sun Mar 01, 2020 11:55 pm
Forum: Balancing Redox Reactions
Topic: Acidic vs. Basic Solutions
Replies: 8
Views: 79

Re: Acidic vs. Basic Solutions

The main difference is that in acidic redox solutions you balance the H with H+. However, with basic solutions, you would balance the hydrogens using OH-.
by kausalya_1k
Sun Mar 01, 2020 11:54 pm
Forum: Balancing Redox Reactions
Topic: Determining direction of flow
Replies: 15
Views: 121

Re: Determining direction of flow

ursulavictorino1K wrote:Why does the reaction always go from the anode to the cathode?


Electrons always flow from loss of electrons (oxidation, occurs at the anode) to the side where electrons are gained (reduction, occurs at the cathode).
by kausalya_1k
Sun Mar 01, 2020 11:53 pm
Forum: Balancing Redox Reactions
Topic: balancing redox reactions
Replies: 3
Views: 49

Re: balancing redox reactions

If it's in an acidic solution, you would first balance everything except H and O. Then, balance O using H2O. Then, balance H with H+ If it's in a basic solution, you would first balance everything except H and O. Then, balance O using H2O. Then, balance H with OH- and add anymore H2O's that need to ...
by kausalya_1k
Sun Mar 01, 2020 11:51 pm
Forum: Balancing Redox Reactions
Topic: oxidation numbers
Replies: 3
Views: 56

Re: oxidation numbers

We already know that O has an oxidation number of -2
so,
2Cr +7(-2)=-2
Cr=+6
We also already know that H has an oxidation number of +1
so,
2C+6(+1)+1(-2)=0
C=-2
by kausalya_1k
Fri Feb 28, 2020 10:26 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.1
Replies: 4
Views: 53

Re: 6M.1

Make sure to start with the equation of E cell = E cathode - E anode. Once you put it in the equation, you can solve for the remaining or missing variable. -0.689 V = -1.038 V - E anode E anode = -0.349 V. The negative signs can be confusing, but as long as you plug it in for specific variables and...
by kausalya_1k
Fri Feb 21, 2020 1:07 am
Forum: Balancing Redox Reactions
Topic: Homework problem 6K.1
Replies: 5
Views: 53

Re: Homework problem 6K.1

Start by identifying the oxidized and reduced species. The oxidation number for Cr changes from +6 to +3, indicating reduction (gain of 3 electrons). The oxidation number for C changes from -2 to -1, indicating oxidation (loss of 1 electron). You now have the skeleton for your half-reactions: (Cr2O...
by kausalya_1k
Tue Feb 18, 2020 12:04 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Boltzmann Formula
Replies: 11
Views: 158

Re: Boltzmann Formula

W here represents the degeneracy
it can be calculated by (# of states possible)^(# of particles involved)
by kausalya_1k
Tue Feb 18, 2020 12:02 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cv vs Cp
Replies: 17
Views: 225

Re: Cv vs Cp

we use Cv for when volume is constant (isochoric) and Cp when pressure is constant (isobaric)
by kausalya_1k
Mon Feb 17, 2020 11:57 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: standard entropies vs. entropies
Replies: 5
Views: 103

Re: standard entropies vs. entropies

standard entropy is calculated when the system is at standard/lab conditions
by kausalya_1k
Mon Feb 17, 2020 11:55 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: R constants
Replies: 21
Views: 599

Re: R constants

You would use the constant that has all the units that you need to cancel out
so if you are given a volume in L, a pressure in atm, and a temperature given in K, you would use R=.0206 L*atm/(K*mol)
by kausalya_1k
Mon Feb 17, 2020 11:17 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Van't Hoff
Replies: 6
Views: 48

Re: Van't Hoff

since van't hoff is derived from gibbs free energy which assumes constant pressure, we can again assume constant pressure for van't hoff
by kausalya_1k
Mon Feb 17, 2020 11:11 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: ∆G = ∆Gº + RT lnQ
Replies: 12
Views: 110

Re: ∆G = ∆Gº + RT lnQ

deltaG knot is for when the system is at its standard state
by kausalya_1k
Mon Feb 17, 2020 9:55 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: thermodynamically stable
Replies: 6
Views: 51

Re: thermodynamically stable

A reaction is thermodynamically stable if it's spontaneous (aka when deltaG<0)
by kausalya_1k
Mon Feb 17, 2020 6:49 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: sign of delta G
Replies: 9
Views: 98

Re: sign of delta G

When deltaG=0, the system is at equilibrium (the forward and reverse reactions occur at the same rate)
When deltaG is negative, the forward reaction is spontaneous
When deltaG is positive, the reverse reaction is spontaneous
by kausalya_1k
Mon Feb 17, 2020 6:47 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Signs for Gibbs Free Energy
Replies: 11
Views: 90

Re: Signs for Gibbs Free Energy

When deltaG is less than 0 (negative) the forward reaction is spontaneous. When deltaG is positive, the reverse reaction is spontaneous. When deltaG=0, the system is at equilibrium.
by kausalya_1k
Mon Feb 17, 2020 6:43 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: G vs G knot
Replies: 15
Views: 100

Re: G vs G knot

G knot is for when everything is in its standard state.
An equation that relates the two terms is deltaG=deltaGknot + RTlnQ
by kausalya_1k
Tue Feb 11, 2020 11:58 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4C.3
Replies: 2
Views: 96

4C.3

Hi, I'm confused on question 4C.3: Calculate the final temperature and the change in enthalpy when 765 J of energy is transferred as heat to 0.820 mol Kr(g) at 298 K and 1.00 atm (a) at constant pressure; (b) at constant vol- ume. Treat the gas as ideal. More specifically, I was wondering, how would...
by kausalya_1k
Sun Feb 09, 2020 11:33 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: constant p
Replies: 4
Views: 40

Re: constant p

the definition of enthalpy is heat at constant pressure, so enthalpy (delta H) is the same as heat (q), which is why in an isobaric problem you can use q=deltaH
by kausalya_1k
Sun Feb 09, 2020 11:31 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: mCdeltaT
Replies: 3
Views: 32

Re: mCdeltaT

you would use q=mcdeltaT when the temperature is changing, usually during a time when the phase is changing (so on a graph this area would be slanted)
if the temperature is not changing (isothermal), and the phase isn't changing (so in the plateau of a graph), you would use q=mdeltaH
by kausalya_1k
Sun Feb 09, 2020 11:29 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Enthalpy versus heat
Replies: 11
Views: 85

Re: Enthalpy versus heat

so enthalpy is basically like heat but only during isobaric (deltaP=0) situations
basically, enthalpy is always heat, but heat is not always enthalpy.
by kausalya_1k
Sun Feb 09, 2020 11:28 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat is enthalpy or Q?
Replies: 2
Views: 26

Re: Heat is enthalpy or Q?

in isobaric reactions (deltaP=0), enthalpy (deltaH)=heat (q)
by kausalya_1k
Sun Feb 09, 2020 11:22 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Useful Summary of Thermodynamic Definitions
Replies: 34
Views: 14512

Re: Useful Summary of Thermodynamic Definitions

Would someone be able to briefly explain the difference between isobaric, isochoric, and isothermal? I have these definitions written down and I've read through the textbook, but I feel as though I've memorized the differences and don't fully grasp the concept. Thanks! The way I personally remember...
by kausalya_1k
Sun Feb 02, 2020 4:16 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 4A.1
Replies: 12
Views: 60

Re: 4A.1

In a closed system, only energy (but not matter) can be exchanged. In an isolated system, neither energy nor matter can be exchanged.
by kausalya_1k
Sun Feb 02, 2020 4:13 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated System
Replies: 4
Views: 30

Re: Isolated System

in an isolated system, energy and matter cannot be exchanged. So, q=0 and w=0, which means that delta q=0.
by kausalya_1k
Sun Feb 02, 2020 4:10 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated vs Closed [ENDORSED]
Replies: 34
Views: 417

Re: Isolated vs Closed [ENDORSED]

An open system is where energy and matter can be exchanged. A closed system is where energy can be exchanged, and an isolated system is where nothing can be exchanged between the system and surroundings.
by kausalya_1k
Sat Feb 01, 2020 9:46 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test 1 # 4
Replies: 10
Views: 94

Re: Test 1 # 4

You use PV=nRT to solve for n. Then use molar mass of Xe to convert n from moles to grams using stoichiometry.
by kausalya_1k
Wed Jan 29, 2020 11:54 pm
Forum: Calculating Work of Expansion
Topic: 4A.3
Replies: 8
Views: 85

Re: 4A.3

Should we always convert to J (using the 101325 Pa value) on exams? Correct me if I'm wrong, but I don't recall hearing that in lecture?
by kausalya_1k
Sun Jan 26, 2020 11:43 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Reaction Shifts Left or Right
Replies: 15
Views: 113

Re: Reaction Shifts Left or Right

Since heat is on the right side of the equation, adding heat to the system will promote the reverse reaction (produce more reactants).
by kausalya_1k
Sun Jan 26, 2020 11:41 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Gas Constant
Replies: 13
Views: 71

Re: Gas Constant

It honestly depends what units P, V, and T are given. Typically we use .08206 L atm/mol K, but it really depends on units for the given values.
by kausalya_1k
Sun Jan 26, 2020 10:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Percent Ionization
Replies: 12
Views: 70

Re: Percent Ionization

% ionization=[h3o]/[acid]
by kausalya_1k
Sun Jan 26, 2020 10:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp to Kc
Replies: 11
Views: 55

Re: Kp to Kc

Yeah
The only time you’d exclude h2o is if it were in liquid or solid form
by kausalya_1k
Sun Jan 26, 2020 10:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE
Replies: 20
Views: 132

Re: ICE

You would use an ICE table when you are trying to find one of the concentrations that is unknown. You will usually be given a K value.
by kausalya_1k
Sun Jan 19, 2020 6:44 pm
Forum: Ideal Gases
Topic: ph
Replies: 10
Views: 100

Re: ph

i believe that it's possible, but for the scope of this class i don't think we don't need to worry about that
by kausalya_1k
Sun Jan 19, 2020 6:42 pm
Forum: Ideal Gases
Topic: concentration
Replies: 5
Views: 32

Re: concentration

Using the ideal gas law,
PV=nRT
we can derive it to calculate concentration:
n/v=P/(RT) since n/V=concentration
then just plug in the partial pressure and temperature (which are given) and the r constant
by kausalya_1k
Sun Jan 19, 2020 6:40 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE Tables
Replies: 13
Views: 75

Re: ICE Tables

It's because H2O is usually provided in excess during experimental conditions. Also, since it's a liquid, it will have a concentration of 1 always.
by kausalya_1k
Sun Jan 19, 2020 6:38 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pH vs. pOH
Replies: 13
Views: 97

Re: pH vs. pOH

pOH=-log[OH-] and you would use that for bases
pH=-log[H3O+] and you would use this for acids
pH+pOH=14
by kausalya_1k
Sun Jan 19, 2020 6:37 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: X was ignored
Replies: 27
Views: 167

Re: X was ignored

x was ignored in this case because K is less than 10^-3 so you know that x is going to be too small for it to make a difference in that case. You can test to see if this approximation is accurate as long as your final answer is less than 5% of the initial
by kausalya_1k
Sat Jan 11, 2020 11:55 am
Forum: Ideal Gases
Topic: Solids and liquids [ENDORSED]
Replies: 6
Views: 57

Re: Solids and liquids [ENDORSED]

Liquids are considered pure substances, so their concentration wouldn't change in a reaction. Therefore, their activity is equal to 1 (just like solids) which is why we don't include it in the K calculation.
by kausalya_1k
Sat Jan 11, 2020 10:35 am
Forum: Ideal Gases
Topic: Solving for K when only given balanced equation [ENDORSED]
Replies: 6
Views: 67

Re: Solving for K when only given balanced equation [ENDORSED]

The P is used to denote partial pressures. To solve for K for gases, you would use P to denote partial pressure. However, if you are asked to solve for Kc, you use the [] concentrations (as the c in Kc stands for concentration).
by kausalya_1k
Sat Jan 11, 2020 9:56 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatlier Principle
Replies: 10
Views: 1105

Re: Le Chatlier Principle

Adding a catalyst will speed up both the forward and reverse reaction rates. However, as long as both the forward and reverse reaction rates are still equal to each other, then the reaction is still at equilibrium.
by kausalya_1k
Sat Jan 11, 2020 9:51 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Knowing it's an Equilibrium Reaction
Replies: 4
Views: 41

Re: Knowing it's an Equilibrium Reaction

I also agree that there needs to be a double arrow in the equation for us to know that it is able to reach equilibrium. The definition of chemical equilibrium is the point at which the forward reaction and the reverse reaction are occurring at the same rate. Therefore, the equation must be able to h...
by kausalya_1k
Fri Jan 10, 2020 10:51 pm
Forum: Ideal Gases
Topic: R in PV=nRT
Replies: 34
Views: 553

Re: R in PV=nRT

The R represents the ideal gas constant.
Depending on units, it is equal to R=8.314 J·K-1·mol-1= = 8.206 x 10-2 L·atm·K-1·mol-1 = 8.314 x 10-2 L·bar·K-1·mol-1.

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