## Search found 127 matches

Mon Mar 16, 2020 12:51 pm
Forum: *Enzyme Kinetics
Topic: Catalysts and enthalpy
Replies: 4
Views: 100

### Re: Catalysts and enthalpy

If you consider the graphs we often use to represent these processes, a catalyst lowers the peak of the activation energy (Ea). However, the initial and final energy values of the curve remain unchanged.
Mon Mar 16, 2020 12:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pH as Kw
Replies: 2
Views: 93

### Re: pH as Kw

K = [products]/[reactants]. Therefore, given H2O(l) --> H3O+(aq) + OH-(aq), Kw = [H3O+][OH-]. Because H3O+ and OH- are in a 1:1 molar ratio, their concentrations will be equivalent. Thus, Kw = x•x = x^2. As explained by Michelle, take the square roof Kw to solve for x. This is the concentration of [...
Mon Mar 16, 2020 12:34 pm
Forum: Ideal Gases
Topic: Equation
Replies: 4
Views: 121

### Re: Equation

When using the Ideal Gas Law typically, following units are used. However, they may be converted appropriately.
P = atm
V = L
n = moles
R = 0.08206 (Latm)/(molK)
T = K

PV=nRT is also often manipulated to become P=(n/V)RT = CRT, where C = concentration (M=mol/L)
Fri Mar 13, 2020 6:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Review Question #2
Replies: 2
Views: 83

### Re: Review Question #2

For gases, an increase in volume without an increase in moles would result in a decrease in concentration. Thus, increasing volume by an amount would be a similar type of problem to decreasing moles by a ratio. I believe there was one like this on Pizza Rolls. You would have to know the molar ratios...
Fri Mar 13, 2020 6:31 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Week 10 Review Problems (pg.7)
Replies: 2
Views: 89

### Re: Week 10 Review Problems (pg.7)

You could possibly argue that two solids would not be a homogeneous mixture as two aqueous solutions would be. However, I would take Charlyn's advice and use a comma if it comes up.
Fri Mar 13, 2020 6:27 pm
Forum: Balancing Redox Reactions
Topic: intensive and extensive
Replies: 3
Views: 28

### Re: intensive and extensive

Intensive properties do not change with changes to amount. For example, the density of water is always 1g/mL regardless of how much water you have.

Extensive properties do depend on amount. For example, mass and volume
Fri Mar 13, 2020 3:53 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7D.1 Formula
Replies: 1
Views: 37

### 7D.1 Formula

7D.1 The rate constant of the first-order reaction 2 N2O(g) + 2 N2(g) --> O2(g) is 0.76 s^-1 at 1000. K and 0.87 s^-1 at 1030. K. Calculate the activation energy of the reaction. The solutions manual seems to have manipulated the Arrhenius equation to ln\frac{k_{1}}{k_{2}} = \frac{E_{a}}{R}\cdot \f...
Fri Mar 13, 2020 12:10 pm
Forum: General Rate Laws
Topic: 7A.15a
Replies: 4
Views: 85

### 7A.15a

For homework problem 7A.15, how do you know which experiments to use to calculate the order? For example for A, if you used experiments 1 and 3 instead of experiments 2 and 4, you would get a=3 instead of a=1.
Fri Mar 13, 2020 12:06 pm
Forum: First Order Reactions
Topic: 7A.7bc
Replies: 1
Views: 25

### 7A.7bc

7A.7 Express the units for rate constants when the concentrations are in moles per liter and time is in seconds for (a) zeroth-order reactions; (b) first-order reactions; (c) second-order reactions.

Why do you divide by mol/L for first and second order reactions?
Sat Mar 07, 2020 11:45 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: Predicting Standard Potential
Replies: 2
Views: 101

### Re: Predicting Standard Potential

Do you have an example of a problem? I don't believe you'll never have to come up with the Eº values on your own since they are experimentally derived values. The only one might be a hydrogen electrode, which is 0V since it's the baseline.
Tue Mar 03, 2020 11:11 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Equilibrium Constant K (Q) Units
Replies: 3
Views: 50

### Equilibrium Constant K (Q) Units

Why can you use partial pressure and concentration together when calculating K or Q in the Nernst equation. Also, why can you use different units. 6N.3 combines atm and [ ], and 6N.5 combines bars and [ ]
Tue Mar 03, 2020 10:49 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7b
Replies: 3
Views: 141

### Re: 6L.7b

How do we know that there is elemental oxygen present? Usually we can only balance redox reactions with H2O, OH-, and H+
Tue Mar 03, 2020 8:38 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.5
Replies: 1
Views: 50

### 6M.5

6M.5 For each reaction that is spontaneous under standard con- ditions (that is, K . 1), write a cell diagram, determine the stan- dard cell potential, and calculate DG8 for the reaction: (a) 2NO3-(aq) + 8H1(aq) + 6Hg(l) --> 3 Hg2^2+(aq) + 2 NO(g) + 4 H2O(l) (c) Cr2O7^+2(aq) + 14 H+(aq) + 6 Pu3+(aq...
Mon Mar 02, 2020 11:01 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 5J.15
Replies: 1
Views: 29

### 5J.15

5J.15 Calculate the equilibrium constant at 25 8C and at 150 8C for each of the following reactions, using data available in Appendix 2A. (a) NH4Cl(s) <--> NH3(g) + HCl(g) (b) H2(g) + D2O(l) <--> D2(g) + H2O(l) For these problems, why do you have to use ∆Hº and ∆Sº instead of directly using ∆G?
Sat Feb 29, 2020 7:43 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.5b
Replies: 2
Views: 39

### 6L.5b

(b) Ce4+(aq) + I-(aq) --> I2(s) + Ce3+(aq) The solution says, "An inert electrode such as Pt is necessary when both oxidized and reduced species are in the same solution." What does this mean? The iodine and the cerium are in separate electrodes of the cell. I understand that the two aque...
Sat Feb 29, 2020 7:19 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.3d
Replies: 1
Views: 31

### 6L.3d

Pt(s)|O2(g)|H+(aq)||OH-(aq)|O2(g)|Pt(s)

How would you reason through separating this cell into its half-reactions? How do you know where to include H2O?
Sat Feb 29, 2020 6:39 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 6L.1b Ecellº
Replies: 1
Views: 34

### 6L.1b Ecellº

6Fe^3+(aq) + 2Cr^3+(aq) + 7H2O(l) --> 6Fe^2+(aq) + Cr2O7^2-(aq) + 14H+(aq), Ecellº=-1.29V I tried calculating the Ecellº on my own for practice and didn't get -1.29V. From the Appendix: Fe^3+(aq) --> 6Fe^2+(aq), Eº=+0.77V Cr2O7^2-(aq) + 14H+(aq) --> 2Cr^3+(aq) + 7H2O(l), Eº=+1.33 V Wouldn't Eºcell ...
Sat Feb 29, 2020 3:40 pm
Forum: Balancing Redox Reactions
Topic: 6K5a Oxygen Oxidation Numbers
Replies: 1
Views: 52

### 6K5a Oxygen Oxidation Numbers

O3(aq) + Br-(aq) --> O2(g) + BrO3-(aq) in basic solution

Why isn't O3 reduced to BrO3- if the oxidation number is changing from 0 to 2-? O3 to O2 is still 0 to 0.
Sat Feb 29, 2020 3:33 pm
Forum: Balancing Redox Reactions
Topic: 6K3d Reduction Reaction
Replies: 2
Views: 45

### 6K3d Reduction Reaction

Cl2(g) --> HClO(aq) + Cl2(g)

The oxidation half-reaction is the easiest to see: Cl2 has an oxidation number of 0. The Cl in HClO has an oxidation number of +1.

What is the reduction half of the reaction?
Sun Feb 23, 2020 1:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagrams
Replies: 2
Views: 43

### Re: Cell diagrams

Hopefully these diagrams will show with an arrow the direction of the flow of electrons. The side that the electrons are moving towards are gaining electrons. Thus this side would be the anode/reduction.
Sun Feb 23, 2020 1:03 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Potential Difference Compared to Hydrogen [ENDORSED]
Replies: 2
Views: 42

### Potential Difference Compared to Hydrogen[ENDORSED]

Why do we need to measure potential difference with reference to hydrogen? Why can't we measure the flow of electrons from the anode to the cathode as a value on its own?
Sun Feb 23, 2020 12:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: determining if a metal will dissolve in a solution
Replies: 2
Views: 18

### Re: determining if a metal will dissolve in a solution

In galvanic cells, the metal that is being oxidized will start to dissolve. As the element's oxidation number increases from 0 to a +#, the atom becomes an ion. These ions then enter the solution rather than being solid metal on the probe. In contrast, the metal that is being reduced will experience...
Sun Feb 23, 2020 12:55 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Conductors vs. Nonconductors
Replies: 3
Views: 21

### Re: Conductors vs. Nonconductors

He hasn't explained how to do this, so unless you find something in the textbook, I don't think so! Just for sure know that platinum is the most common.
Sun Feb 23, 2020 12:52 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Textbook Example 6L.2
Replies: 1
Views: 19

### Re: Textbook Example 6L.2

I believe it is in included in the Hg2Cl2 half-reaction since it's part of the solid and relevant to Hg's chemical change. For the H half-reaction, the Cl- is completely dissociated from HCl and therefore is not affecting the H reaction.
Sun Feb 23, 2020 12:46 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode and Cathode
Replies: 4
Views: 34

### Re: Anode and Cathode

Since Dr. Lavelle has been emphasizing left/right so much, yes I believe we can safely assume that. However, I would recommend checking if you can. A quick way to do this is to see which direction the electrons are flowing as it is often included in the diagram. The side that is G aining electrons w...
Thu Feb 20, 2020 12:24 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Charge Buildup
Replies: 3
Views: 38

### Charge Buildup

What is meant by "a charge buildup" regarding the salt bridge? Why does this prevent electron transfer?
Tue Feb 11, 2020 9:29 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Pizza Rolls 6 (pt.1)
Replies: 10
Views: 227

### Pizza Rolls 6 (pt.1)

"... First you perform an isobaric compression of the container to 10.0L...."

Why is ∆U=0 for the first part of the problem if the process is isobaric, not isothermic?

Also, why is ∆S=0? Wouldn't a decrease in volume cause a decrease in number of possible positions?
Tue Feb 11, 2020 9:14 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Pizza Rolls 5A Substituting q and w
Replies: 1
Views: 50

### Pizza Rolls 5A Substituting q and w

As used in Pizza Rolls 5, how do you know when you can substitute w=-nRTln(T2/T1) into ∆S=qrev/T? Why is this process considered reversible for you to do this?
Tue Feb 11, 2020 6:50 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 4I.9 Irreversible Expansion
Replies: 2
Views: 32

### 4I.9 Irreversible Expansion

4I.9 Initiallyanidealgasat323Koccupies1.67Lat4.95atm.The gas is allowed to expand to 7.33 L by two pathways: (a) isothermal, reversible expansion; (b) isothermal, irreversible free expansion. Calculate DStot, DS, and DSsurr for each pathway. How do these two processes differ? Why is no work done by...
Tue Feb 11, 2020 12:57 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: 4G.5 Trans Isomer
Replies: 1
Views: 19

### 4G.5 Trans Isomer

Why does the trans isomer of a MX2Y4 molecule have 3 different orientations? If the radial atoms are all identical, wouldn't this be the only possible configuration?
Tue Feb 11, 2020 12:08 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 4F.3 Reversible Process
Replies: 2
Views: 24

### 4F.3 Reversible Process

Calculate the change in entropy of a block of copper at 25ºC that absorbs 65J of energy from a heater.

Why can we assume that this is a reversible process?
Sun Feb 09, 2020 8:46 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Enthalpy and Temperature
Replies: 1
Views: 43

### Enthalpy and Temperature

As applied to ∆S=∆H/T, for example, what does it mean that temperature remains constant as enthalpy changes? Wouldn't an increase/decrease in energy cause the temperature to go up/down?
Wed Feb 05, 2020 1:39 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard State of Compounds
Replies: 2
Views: 37

### Standard State of Compounds

Our TA explained that substances in their standard state have a standard enthalpy of formation of 0. In lecture, Dr. Lavelle did an example in which we calculated the standard enthalpy of the combustion of methane. He stated that gases are in their standard state at 1atm and pure liquids are always ...
Mon Feb 03, 2020 8:56 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4B.9e
Replies: 1
Views: 19

### 4B.9e

4B.9 In an adiabatic process, no energy is transferred as heat. Indicate whether each of the following statements about an adia- batic process in a closed system is always true, always false, or true in certain conditions (specify the conditions): (a) ∆U=0; (b) q=0; (c) q<0; (d) ∆U=q; (e) ∆U=w. Why...
Mon Feb 03, 2020 8:41 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4B.5 Conversion
Replies: 4
Views: 48

### 4B.5 Conversion

As used in 4B.5, how do you convert Torr(mL) to J?
Mon Feb 03, 2020 3:35 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isobaric Reversible Expansion
Replies: 4
Views: 52

### Re: Isobaric Reversible Expansion

I guess I'm asking, how would this piston function in practice/how could you model this experimentally?
Mon Feb 03, 2020 1:06 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isobaric Reversible Expansion
Replies: 4
Views: 52

### Isobaric Reversible Expansion

Today (Monday Week 5), Dr. Lavelle talked about isothermic reversible reactions. The external pressure decreases gradually, allowing heat to instantaneously enter the system as it does work. What would this process look like for reversible expansions for which we use the formula -\int_{V_{1}}^{V_{2}...
Mon Jan 27, 2020 4:16 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimetry and Mass
Replies: 2
Views: 29

### Calorimetry and Mass

Why doesn't the calorimetry formula q=-C∆T include mass like q=mC∆T. And why is the q value negative if the calorimeter is gaining the energy lost by the reaction?
Mon Jan 27, 2020 3:38 pm
Forum: Phase Changes & Related Calculations
Topic: Reversible Expansion
Replies: 1
Views: 42

### Reversible Expansion

4A.5 A piston confines 0.200 mol Ne(g) in 1.20 L at 25 8C. Two experiments are performed. (a) The gas is allowed to expand through an additional 1.20 L against a constant pressure of 1.00 atm. (b) The gas is allowed to expand reversibly and isothermally to the same final volume. Which process does ...
Sun Jan 26, 2020 10:06 pm
Forum: Phase Changes & Related Calculations
Topic: Heat capacities
Replies: 6
Views: 71

### Re: Heat capacities

What is heat capacity?
Sat Jan 25, 2020 1:41 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Change
Replies: 4
Views: 41

### Re: Phase Change

The information should be given, possibly in a phase change graph. I believe it would be the difference in y-value between two of the horizontal lines (the height of the diagonal) as this would be the energy into the system to bring the substance from one state up to the next.
Sat Jan 25, 2020 1:28 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy
Replies: 2
Views: 25

### Re: Enthalpy

You can think of enthalpy as the energy stored in the bonds (technically there's heat but don't get it mixed up with the T, temperature). So a certain amount of energy is needed to break the energy of bonds (+∆H), and energy is released when energetically favorable bonds are formed (–∆H).
Sat Jan 25, 2020 1:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Internal Energy of Systems
Replies: 2
Views: 31

### Re: Internal Energy of Systems

What do the variables w and U stand for?
Tue Jan 21, 2020 9:06 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 6A.19c
Replies: 1
Views: 32

### 6A.19c

6A.19 Calculate the molar concentration of OH2 in solutions with the following molar concentrations of H3O1: (a) 0.020 mol/L-1; (b) 1.0x10^-5 mol/L-1; (c) 3.1 mol/L-1. c. Why do you divide \frac{1.0\times 10^{-14}}{3.1\times 10^{-3}} , not \frac{1.0\times 10^{-14}}{3.1} , since [H3O+] = 3.1 M (like...
Tue Jan 21, 2020 7:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When to Use Q
Replies: 3
Views: 43

### When to Use Q

5I.25.) A reaction mixture is prepared by mixing 0.100 mol SO2, 0.200 mol NO2, 0.100 mol NO, and 0.150 mol SO3 in a reaction vessel of volume 5.00 L. The reaction SO2(g) 1 NO2(g) ∆ NO(g) 1 SO3(g) is allowed to reach equilibrium at 460 8C, when Kc 5 85.0. What is the equilibrium concentration of each...
Sun Jan 19, 2020 11:30 pm
Forum: Ideal Gases
Topic: Partial Pressure
Replies: 4
Views: 62

### Re: Partial Pressure

Dr. Lavelle went over it in lecture, so I believe it would be a fair question.

You would need to apply the ideal gas equation: PV=nRT. Divide V over to get P = (n/V)RT. (n/V) is concentration, which should be given, and RT are constant so just solve for P, your partial pressure
Sun Jan 19, 2020 11:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Different ways to write K
Replies: 3
Views: 36

### Re: Different ways to write K

I think we should include the subscript just to be safe! Especially for reactions involving gases. If given a unitless value for K, the reader would need to know if it's for pressure or concentration and they need to convert
Sun Jan 19, 2020 11:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reaction mixture at equilibrium
Replies: 2
Views: 15

### Re: Reaction mixture at equilibrium

This state is called a dynamic equilibrium. Even though it seems like the reaction has stopped, the forward and reverse reactions continue to proceed, just at equivalent rates so it is unnoticeable. But why certain reactions favor specific ratios, however, is beyond what we know in 14B
Sun Jan 19, 2020 11:19 pm
Forum: Ideal Gases
Topic: Partial Pressures
Replies: 4
Views: 60

### Re: Partial Pressures

I'm not sure how it would be possible to increase the pressure of one type of gas in the same reaction vessel as the other. However, assuming that this change in pressure essentially causes a change in concentration, the other reactant would only be affected as a result of LeChatellier's principle. ...
Sun Jan 19, 2020 11:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5% rule
Replies: 8
Views: 70

### Re: 5% rule

Yes, that expression refers to "percent protonation." Take note that these are the concentrations of the "primary" compounds involved in the reaction. For example, regarding NH3 + H2O --> NH4+ + OH-, you would only use [NH4+] formed /[NH3] initial, not including [H2O] and [OH-] A...
Sun Jan 19, 2020 11:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE tables for reverse rxns
Replies: 4
Views: 43

### Re: ICE tables for reverse rxns

For some problems (i.e. 5I.25), you have to calculate the Q value first and then compare it with K. If Q<K, the reaction will move forward, and if the Q>K, the reactions will move in reverse. This is all relative to how the chemical reaction is written. Then, set up your Ka expression and ICE table ...
Sun Jan 19, 2020 10:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Applying Kw
Replies: 2
Views: 30

### Applying Kw

In lecture, Dr. Lavelle did an example using Ba(OH)2 to show that Kw, a special value of Ka, can be used to determine [H3O+]. Why is this possible? Don't all aqueous reactions have different Ka values, so shouldn't Ba2+ affect the value of Ka/Kw?
Sun Jan 12, 2020 1:18 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: changing conditions
Replies: 6
Views: 59

### Re: changing conditions

Removing some of the product would decrease its concentration/partial pressure value. Mathematically the ratio [P]/[R] would be smaller. Since Q<K, the forward reaction will be favored until Q=K again
Sun Jan 12, 2020 1:14 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Significance of principle
Replies: 6
Views: 51

### Re: Significance of principle

One of the most well-known applications of Le Chatelier's Principle is the production of NH3 for fertilizer. Dr. Lavelle mentioned it in lecture and one of the TA's talked about it in discussion N2(g) + 3H2(g) --> 2NH3(g) Chemist Fritz Haber highly pressurized the NH3 gas (with a catalyst) so that i...
Sun Jan 12, 2020 1:03 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium and Limiting Reagent
Replies: 2
Views: 23

### Equilibrium and Limiting Reagent

How does what we're learning about equilibrium relate to what we learned in 14A about limiting reagents? Wouldn't those calculations be invalid since we were assuming that the reactions ran to completion?
Sun Jan 12, 2020 12:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Write reaction quotient Q
Replies: 2
Views: 21

### Re: Write reaction quotient Q

I believe both are correct if not specified. As long as you remember that partial pressure only applies to gases and not aqueous solutions
Sun Jan 12, 2020 12:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentration and partial pressure
Replies: 2
Views: 19

### Re: Concentration and partial pressure

Concentration and partial pressure can be converted using a form of the ideal gas equation: PV = nRT --> P = (n/V)R, where n/V is concentration. Equilibrium expressions using concentration (Kc) will contain brackets ("[X]") and expressions using partial pressures (Kp) will contain the vari...
Mon Jan 06, 2020 3:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: H3O and OH
Replies: 5
Views: 64

### H3O and OH

Regarding the Chemical Equilibrium Pt 1B Pre-Assessment, for reactions that involve liquid water as a product and H3O+(aq) or OH-(aq) as a product, are the H3O/OH included in the K calculation?
Sat Dec 07, 2019 1:47 pm
Forum: Identifying Acidic & Basic Salts
Topic: HW 6D11
Replies: 7
Views: 128

### Re: HW 6D11

How would you know that the coordinator for hydrated Al is 6?
Fri Dec 06, 2019 1:07 am
Forum: Biological Examples
Topic: Cisplatin H2O
Replies: 2
Views: 50

### Cisplatin H2O

I was wondering how cisplatin binds to DNA since Cl doesn't typically form coordinating covalent bonds. Google says that the Cl is replaced with H2O. What drives this process?
Fri Dec 06, 2019 12:20 am
Forum: Naming
Topic: Isocyanido
Replies: 2
Views: 48

### Isocyanido

Is it correct to call CN "cyanido" or does it have to be "isocyanido"? (in reference to Table 9C.1)
Thu Dec 05, 2019 10:51 pm
Forum: Naming
Topic: (diqaua)
Replies: 1
Views: 37

### (diqaua)

For 9C.3d "sodiumbisoxalato(diaqua)ferrate(III)", why is diaqua written in parentheses? Also, why does it come after the bisoxalato?
Wed Dec 04, 2019 12:18 am
Forum: Lewis Structures
Topic: 6.5b
Replies: 2
Views: 126

### 6.5b

Why doesn't H2SO5 have cis/trans isomers?
Mon Dec 02, 2019 5:19 pm
Forum: Lewis Structures
Topic: 2.61
Replies: 2
Views: 140

### 2.61

In the radical HOCO, how do you know that the carbon would have the unpaired electron? Isn't oxygen more electronegative?
Mon Dec 02, 2019 5:09 pm
Forum: Hybridization
Topic: Energy Level
Replies: 2
Views: 31

### Energy Level

Are all sp(1,2,3) hybridized orbitals in the 2nd energy level?
Mon Dec 02, 2019 4:17 pm
Forum: Hybridization
Topic: 2F.3b
Replies: 1
Views: 39

### 2F.3b

Why does SO2 have two resonance structures? Doesn't the one with two double bonds have formal charges of 0, and the one with only one double bond have formal charges of +/-1?
Mon Dec 02, 2019 4:01 pm
Forum: Hybridization
Topic: Lone Pairs
Replies: 2
Views: 47

### Lone Pairs

How does hybridization work for atoms with lone pair electrons? For example, HS2
Sun Dec 01, 2019 8:44 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pKa
Replies: 3
Views: 38

### Re: pKa

"p" means to take the -log of a value. Just as pH is the -log[H+], pKa is the -log(Ka).

For example, NH4+ has a Ka = 5.6x10^-10
pKa = -log(5.6x10^-10) = 9.25
Sun Dec 01, 2019 8:35 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Concentration
Replies: 2
Views: 38

### Re: Concentration

I'm sure it would have to be given in the problem. But if, for example, you were given an OH- concentration of 1x10^-8 M, you could calculate that the H3O+ concentration is 1x10^-6 M, since [H3O+] x [OH-] = 1x10^-14. You can also do this using pH values. The pOH for this solution would be 8. pH + pO...
Sun Dec 01, 2019 8:29 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH scale
Replies: 12
Views: 111

### Re: pH scale

Solutions can fall outside the 0-14 range. Dr. Lavelle mentioned "superacids" which have a H3O+ concentration > 1x10^0 M and thus would have a negative pH. However, these are uncommon, especially in biological systems. I'm sure the same is true for bases.
Sun Dec 01, 2019 8:25 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH Calculation explanation
Replies: 1
Views: 26

### Re: pH Calculation explanation

Concentrations for H3O+ (and OH-) are very small, so they will have a negative exponent in their molarity value. For example: [H3O+] = 1x10^-7 M. Since logarithms calculate the value of the exponent, log[H3O+] = -7. Negative numbers aren't as nice to work with as positives, so we just add the negati...
Sun Dec 01, 2019 8:22 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strong Acids
Replies: 3
Views: 37

### Re: Strong Acids

Why do the halogens form the strong acids? Why would they have the weakest bonds if they have the smallest atomic radius in each period?
Sat Nov 23, 2019 9:05 am
Forum: Naming
Topic: Diethylenetriamine
Replies: 2
Views: 36

### Diethylenetriamine

In "diethylenetriamine," why does ethylene come before amine? Not A before E as would be for alphabetical order? In the other example "pentaamminechlorocobalt(II) chloride hydriate," "ammine" comes before "chloro" regardless of the prefix. *Also is NH3 spelled...
Sat Nov 23, 2019 8:58 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: [Fe(CN)6]4-
Replies: 5
Views: 66

### [Fe(CN)6]4-

In lecture, Dr. Lavelle used the example [Fe(CN)6]4-:

a. How is CN a ligand? Unless it's CN-, it would have an unpaired electron and wouldn't be able to form a coordinate covalent bond?
b. Why is the charge 4-?
Tue Nov 19, 2019 10:11 pm
Forum: Bond Lengths & Energies
Topic: Interaction Potential Energy and Radius
Replies: 2
Views: 106

### Interaction Potential Energy and Radius

If interaction potential energy is given by the formula: Ep (is proportional to) $\frac{\alpha_{1} \alpha_{2} }{r^{6}}$, then why does attractive force increase as atomic size increases?
Tue Nov 19, 2019 12:20 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Pentagonal Bipyramidal
Replies: 8
Views: 98

### Re: Pentagonal Bipyramidal

What other VSEPR structures do we need to know that Dr. Lavelle didn't go over in lecture?
Tue Nov 19, 2019 12:17 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Pi Bond Rotation
Replies: 2
Views: 45

### Pi Bond Rotation

What does the pi bond's inability to rotate mean when determining VSEPR structure? How is this concept applied?
Mon Nov 18, 2019 3:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Component Orbitals of pi Bonds
Replies: 3
Views: 29

### Component Orbitals of pi Bonds

The course outline says we need to be able to "distinguish pi bonds by their component orbitals." What are the component orbitals of pi bonds? Doesn't it depend on each individual molecule's central atom configuration?
Mon Nov 18, 2019 3:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.25a
Replies: 1
Views: 23

### 2E.25a

Why is CH2Cl2 a polar molecule? If drawn with the Cl's opposite of each other, wouldn't the dipoles cancel out?
Sat Nov 16, 2019 11:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Pentagonal Bipyramidal
Replies: 8
Views: 98

### Re: Pentagonal Bipyramidal

What is the VSEPR formula (AXE) for this?
Fri Nov 15, 2019 3:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 6
Views: 77

### Re: Bond Angles

109.5 you'll just to memorize, but the others you can tell from their shape. Trigonal planar has three atoms spread out evenly on a single plane. 360/3 = 120 degrees Trigonal bipyramidal has 2 axial elements coming out from both sides of the trigonal planar shape, so you should be able to visualize ...
Fri Nov 15, 2019 3:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: varying VSEPRs
Replies: 7
Views: 107

### Re: varying VSEPRs

No, and even better, the shape of an AXE molecule will always be the same, regardless of the atoms
Fri Nov 15, 2019 3:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Prefixes
Replies: 2
Views: 62

### Re: Prefixes

In today's Friday lecture, we also learned the organic chemistry prefixes cis- and trans-. I don't think we should need to know how to draw organic molecules, but I think we should be familiar with general polarity. "Cis-" means same and "trans-" means opposite, so in general, wh...
Fri Nov 15, 2019 3:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: T shape
Replies: 7
Views: 79

### Re: T shape

Why wouldn't this be a trigonal planar shape with the electron clouds in the axial positions? Didn't we talk about the electron clouds wanting to be as far apart as possible to minimize repulsion and make the molecule more stable?
Fri Nov 15, 2019 3:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent shape and angles
Replies: 6
Views: 68

### Re: Bent shape and angles

The VSPER theory only gives qualitative, not quantitative descriptions of the shape of molecules, so although we know how the atoms are arranged, we cannot predict exactly what their angles will be. AX2E will be less than 120 degrees, and AX2E2 will be less than 109.5 degrees. Those are the expected...
Wed Nov 06, 2019 4:02 pm
Forum: Trends in The Periodic Table
Topic: Electrostatic Forces vs Effective Nuclear Charge
Replies: 1
Views: 66

### Electrostatic Forces vs Effective Nuclear Charge

What’s the difference between “electrostatic force/potential energy” and “effective nuclear charge?
Tue Nov 05, 2019 11:25 pm
Forum: Lewis Structures
Topic: 2B.11c
Replies: 1
Views: 49

### 2B.11c

"Draw the complete Lewis structure for glycine, H2C(NH2)COOH." The molecule is drawn H2–N-CH2-CO-OH (if that makes sense). How would you know that the nitrogen is on the end and not in between the two carbons? It's written in the middle of the given formula and usually they give structural...
Tue Nov 05, 2019 3:48 pm
Forum: Properties of Electrons
Topic: Schrodinger Equation
Replies: 2
Views: 163

### Re: Schrodinger Equation

I think we only need to know the basics that we put the wave function ($\psi$) into the "Hamiltonian operator" and get out energy (E) values that are interpreted to give the shapes of the s, p, d, etc. orbitals that we are familiar with.

$H\psi =E\psi$
Tue Nov 05, 2019 3:42 pm
Forum: Properties of Electrons
Topic: Multi-electron atom
Replies: 2
Views: 126

### Re: Multi-electron atom

Multi-electron atoms must follow the Aufbau principle, which states that electrons fill the lowest-energy orbitals before the largest. So s<p<d<f within the same energy level. For us, be able to write and interpret quantum numbers (n, l, ml, ms) and electron configurations.
Tue Nov 05, 2019 3:23 pm
Forum: Ionic & Covalent Bonds
Topic: 2D.3
Replies: 3
Views: 72

### Re: 2D.3

How would we know this without a table with values? I'm pretty sure they've said we shouldn't have to remember specific values.
Tue Nov 05, 2019 3:18 pm
Forum: Ionic & Covalent Bonds
Topic: Mini Dino Nuggets 2b
Replies: 6
Views: 101

### Mini Dino Nuggets 2b

Which bond has more ionic character, C–F or C–Br? Why?

C-F (look at electronegativity difference)

Why isn't the electronegativity difference greater between C and Br since Br is farther away on the periodic table?
Mon Nov 04, 2019 3:39 pm
Forum: Lewis Structures
Topic: 2B.1b
Replies: 3
Views: 53

### 2B.1b

Why can't the molecule be drawn Cl-C-O-Cl rather than centered around C? The formal charges would all be 0 instead of +1/-1.
Sat Nov 02, 2019 4:41 pm
Forum: Ionic & Covalent Bonds
Topic: Homework 2D #15
Replies: 5
Views: 84

### Re: Homework 2D #15

This is referencing the concept of bond length that Dr. Lavelle explained during Friday's lecture using the example of the strong acids: HF > HCl > HB > HI. Bond strength decreases as atomic radius of increases because the atoms are farther apart and easier to pull apart. Thus, among CF4, CCl4, CBr4...
Sat Nov 02, 2019 4:35 pm
Forum: Ionic & Covalent Bonds
Topic: The net energy decrease when Na and Cl form NaCl
Replies: 2
Views: 40

### Re: The net energy decrease when Na and Cl form NaCl

Hmm, I think this is a little more detailed than necessary. I believe it's explaining that all processes require energy, and the formation of ionic bonds is driven by the cation in the compound. More than the electron affinity of the anion, the ionization energy of the cation wanting to lose its ext...
Sat Nov 02, 2019 4:25 pm
Forum: DeBroglie Equation
Topic: Dino Nuggets 13a
Replies: 1
Views: 87

### Dino Nuggets 13a

Essentially, the question is "what is the kinetic energy of one potassium ion with a wavelength of 11.23 nm?" We used the mass 39.1 g/mol for the potassium ion. Does that mean that the mass of ions and neutral elements are the same? Why wouldn't we have to subtract 9.11x10-31kg from the ma...
Wed Oct 30, 2019 7:35 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration of Tungsten
Replies: 1
Views: 66

### Electron Configuration of Tungsten

Why does tungsten have 4 electrons in the d-orbital? If element #57 is a lanthanide and the additional electron would go into the f-orbital, wouldn't tungsten have 3 electrons in the d-orbital?
Wed Oct 30, 2019 7:27 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Valence-Shell Configuration
Replies: 1
Views: 51

### Valence-Shell Configuration

1E.25 Give the notation for the valence-shell configuration (including the outermost d-electrons) of (a) the alkali metals; (b) Group 15 elements; (c) Group 5 transition metals; (d) the "coinage" metals (Cu, Ag, Au). What is the "valence-shell configuration"? What does n and (n-...
Wed Oct 30, 2019 7:24 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Expanded Octet
Replies: 2
Views: 38

### Re: Expanded Octet

P, S, and Cl are the only elements that we need to know since we will only be covering elements from the first 3 energy levels, I believe.
Thu Oct 24, 2019 4:01 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Inverse Relation
Replies: 3
Views: 88

### Re: Inverse Relation

It has to do with the impact of detection on the position of the object being detected. When the photons from the measuring device reaches the electron, the electron is pushed off course, altering it's velocity and thus also momentum. Therefore, the more certain we are about the electron's position,...
Thu Oct 24, 2019 3:57 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Minimum Uncertainty
Replies: 2
Views: 54

### Re: Minimum Uncertainty

The Heisenberg equation is expressed as $\Delta p\Delta x\geq \frac{h}{4\pi}$, meaning that the uncertainty is greater than or equal to that value. Thus, the "minimum uncertainty" would be when the uncertainty is equal to h/(4$\pi$). So just change >/= to =.