Search found 46 matches

by John Huang 1G
Sat Mar 17, 2018 1:36 pm
Forum: *Amines
Topic: Conditions for being an Amine Group
Replies: 1
Views: 639

Re: Conditions for being an Amine Group

To my understanding, an amine group is a Nitrogen bonded to two Hydrogen atoms and an R group (R represents a hydrocarbon group or hydrogen).
by John Huang 1G
Sat Mar 17, 2018 1:28 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: rate and temp in endothermic reaction
Replies: 1
Views: 84

Re: rate and temp in endothermic reaction

To my understanding, it's because of the forward reaction has a higher activation energy than reverse reaction's activation energy in an endothermic reaction. And because the slope of an Arrhenius plot is proportional to Ea, it follows that the higher the activation energy, the stronger is the tempe...
by John Huang 1G
Sat Mar 17, 2018 1:24 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow Step Determining Overall Rate
Replies: 3
Views: 147

Re: Slow Step Determining Overall Rate

To my understanding, it does not matter whether the slow step is the first step of the mechanism or the second step or the last step. The slow step always determines the rate law of the mechanism regardless of whether it takes place in the beginning of the mechanism or at the end.
by John Huang 1G
Tue Mar 06, 2018 11:44 pm
Forum: Zero Order Reactions
Topic: 15.16
Replies: 1
Views: 246

Re: 15.16

I am not too sure on how to make a table chart in chemistry community, but for this problem, it helps to make a table with hypothetical experiments, initial concentrations and initial rates. This is my best try for a table: experiment # | [Fe2+] | [O2] | [H30+] | Initial Rate | 1 | 1 | 1 | 1 | 1 | 2...
by John Huang 1G
Tue Mar 06, 2018 4:07 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.19c
Replies: 6
Views: 231

Re: 15.19c

Also the answer for 15.19d is also wack as heck too. The answer key says: 1.13x10^(-2) mmol*L^(-1)*s^(-1).
To my understanding, this answer would not make sense when compared to the other values in the table.
by John Huang 1G
Tue Mar 06, 2018 4:01 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.19c
Replies: 6
Views: 231

15.19c

for 15.19c, the question asks us to find the rate constant. The answer key says that the rate constant is 2.851x10^(12). Can someone explain to me where the 10^(12) comes from? The answer I calculated was just 2.851.
by John Huang 1G
Mon Feb 26, 2018 9:49 pm
Forum: Second Order Reactions
Topic: Limiting Step
Replies: 7
Views: 453

Re: Limiting Step

Apparently, the step with the higher activation energy is often times the limiting step as well. High activation energies are associated with slower rates due to the large amount of energy needed for the step to be thermodynamically favorable.
by John Huang 1G
Mon Feb 26, 2018 9:44 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy???
Replies: 7
Views: 279

Re: Activation Energy???

Steps with higher activation energy are often the limiting step because higher activation energies indicate a slower process. The slower steps of a reaction are the limiting ones.
by John Huang 1G
Mon Feb 26, 2018 9:42 pm
Forum: First Order Reactions
Topic: Direct Proportions and First Order
Replies: 5
Views: 183

Re: Direct Proportions and First Order

Then what would it mean for a reaction to have a second order or zero order?
by John Huang 1G
Mon Feb 26, 2018 9:40 pm
Forum: General Rate Laws
Topic: Confusion about the Rate Laws
Replies: 1
Views: 90

Confusion about the Rate Laws

Among all of the different rate laws, can someone distinguish for me what kind of information each rate law indicates (differential rate law, integral rate law, and general rate law)? I am getting very confused as to what each one represents, and what kind of graphs they form.
by John Huang 1G
Mon Feb 26, 2018 9:38 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Rate Limiting Step
Replies: 2
Views: 299

Re: Rate Limiting Step

Why is it that a larger activation energy indicates that it is the rate limiting step?? Is it because the step is slower?
by John Huang 1G
Mon Feb 26, 2018 9:37 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Graphs in Lecture
Replies: 2
Views: 129

Graphs in Lecture

Today, in lecture, Lavelle graphed two graphs. One graph was linear and the other was a curved graph. What is the difference between the two graphs???
by John Huang 1G
Thu Feb 15, 2018 10:23 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation 2.303RT/F = .059V
Replies: 4
Views: 1411

Re: Nernst Equation 2.303RT/F = .059V

Hi! Sorry, but I'm not sure in what context your first question is in, so I'm not sure I follow... But for your second question, they could have used ln as well. The only difference between using log and using ln is the difference in constants. So it does not matter if they used log or ln, they will...
by John Huang 1G
Thu Feb 15, 2018 10:16 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 3
Views: 115

Re: Cell Diagrams

I don't believe it matters, as long as you indicate which way the electrons are moving and what substances are being formed/used. Usually you would put the anode half reaction (oxidation) on the left side and the cathode half reaction (reduction) on the right side.
by John Huang 1G
Thu Feb 15, 2018 10:14 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Delta G=-nFE
Replies: 5
Views: 968

Delta G=-nFE

A lot of the problems do not have moles given, so when we are using DeltaG=-nFE, what value would we use for n?
by John Huang 1G
Fri Feb 09, 2018 1:23 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta G=0
Replies: 6
Views: 242

Re: delta G=0

Delta G=0 Does not necessarily mean delta H and delta S are zero as well. Delta G=0 means that the process is at equilibrium.
by John Huang 1G
Fri Feb 09, 2018 1:12 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Problem 9.81
Replies: 1
Views: 101

Problem 9.81

9.81 Which is the thermodynamically more stable iron oxide in air, Fe3O4(s) or Fe2O3(s)? Justify your selection.

How do you determine delta G for either of them if no equation is given? Would we have to formulate one? And how would you know which iron oxide is the product or reactant?
by John Huang 1G
Fri Feb 09, 2018 1:05 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: Problem 9.77
Replies: 1
Views: 200

Problem 9.77

9.77 Suppose that you create two tiny systems consisting of three atoms each, and each atom can accept energy in quanta of the same magnitude. (a) How many distinguishable arrangements are there of two quanta of energy distributed among the three atoms in one of these systems? (b) You now bring the ...
by John Huang 1G
Sun Feb 04, 2018 5:16 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Question about Change in Gibb's Free Energy
Replies: 4
Views: 123

Question about Change in Gibb's Free Energy

If the change in Gibb's Free Energy (Delta G) for a spontaneous process represents the energy that is free to do useful work, then what does G (Gibb's Free Energy) represent?
by John Huang 1G
Sun Feb 04, 2018 5:12 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: The sign of the change in Gibb's Free Energy
Replies: 6
Views: 200

The sign of the change in Gibb's Free Energy

Why is it that when the change in Gibb's Free Energy is negative, the process is considered thermodynamically favorable?
by John Huang 1G
Sun Feb 04, 2018 5:07 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Van't Hoff's Equation [ENDORSED]
Replies: 3
Views: 168

Re: Van't Hoff's Equation [ENDORSED]

You can use the Van't Hoff Equation to find K at different temperatures if the standard change of enthalpy is known.
by John Huang 1G
Tue Jan 23, 2018 11:30 pm
Forum: Phase Changes & Related Calculations
Topic: Combustion of liquids
Replies: 4
Views: 201

Re: Combustion of liquids

Hi! The book states that "the products of the combustion of an organic compound are carbon dioxide gas and liquid water." (on page 291). Additionally, the example given on page 297 shows that liquid water is produced in result of a combustion reaction. So I think that in general, regardles...
by John Huang 1G
Tue Jan 23, 2018 11:22 pm
Forum: Phase Changes & Related Calculations
Topic: Homework Help on 8.67
Replies: 2
Views: 158

Homework Help on 8.67

8.67) Use the information in Tables 8.3, 8.6, 8.7 to estimate the enthalpy of formation of each of the following compounds in the liquid state. The standard enthalpy of sublimation of carbon is +717 kj/mol. (a)H20 (b) Methanol, CH3OH (c) benzene, C6H6 (without resonance) (d) benzene, C6H6 (with reso...
by John Huang 1G
Tue Jan 23, 2018 10:40 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework Help on 8.24
Replies: 1
Views: 95

Homework Help on 8.24

8.24) The enthalpy of combustion of benzoic acid, C6H5COOH, which is often used to calibrate calorimeters, is -3228 kj/mol. When 1.453g of benzoic acid was burned in a calorimeter, the temperature increased by 2.265 degrees Celsius. What is the heat capacity of the calorimeter? I know this isn't one...
by John Huang 1G
Thu Jan 18, 2018 5:46 pm
Forum: Calculating Work of Expansion
Topic: Work equations
Replies: 3
Views: 172

Re: Work equations

Most of the homework problems will require you to use the work equation for irreversible expansions unless stated otherwise.

If the homework problem asks about reversible, isothermal expansions, then you'll use the reversible equation.
by John Huang 1G
Thu Jan 18, 2018 5:41 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Accounting for Copper in 8.19
Replies: 2
Views: 128

Re: Accounting for Copper in 8.19

To account for the heat absorbed the copper kettle, you'll have to use q=(mass of copper)(specific heat of copper)(change in temperature).

To account for both of the heat transfers, just add q(water) and q(copper kettle).
by John Huang 1G
Sat Jan 13, 2018 8:27 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat and Ethalpy
Replies: 3
Views: 142

Re: Heat and Ethalpy

In thermodynamics, heat is the energy transferred as a result of temperature differences. Enthalpy is the amount of heat released or absorbed at a constant pressure. Enthaply has to be measured at a constant pressure. If heat was being transferred under conditions of varying pressures, then we would...
by John Huang 1G
Sat Jan 13, 2018 8:18 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework help on 8.29
Replies: 4
Views: 177

Re: Homework help on 8.29

Nevermind, I have found a better reason for this phenomenon. It is true that molar heat capacity increases with molecular complexity; but apparently, my initial reasoning was incorrect. Molar heat capacities of gases composed of molecules are higher than those of monatomic gases because the molecule...
by John Huang 1G
Sat Jan 13, 2018 6:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework help on 8.29
Replies: 4
Views: 177

Homework help on 8.29

8.29 Which molecular substance do you expect to have the higher molar heat capacity, NO or NO2? Why? My question is, can we follow the line of reason that because NO2 has more bonds than NO, we can expect NO2 to require more energy to break bonds; thus resulting in a higher molar heat capacity in NO2?
by John Huang 1G
Thu Dec 07, 2017 8:38 pm
Forum: Lewis Acids & Bases
Topic: Arrhenius acids/bases
Replies: 1
Views: 169

Re: Arrhenius acids/bases

I don't think its necessary, but the ones we should all know is Lewis, Bronsted, Conjugate, and Amphoteric. It doesn't hurt to learn it though.
by John Huang 1G
Sun Dec 03, 2017 9:55 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Different chemical equations in J.5
Replies: 1
Views: 126

Re: Different chemical equations in J.5

I don’t recall hearing Lavelle discuss this as well, but I think it’s a good concept to look up on. Net-Ionic equations can tell a lot about the reactions and its components. I would not worry too much on this subject.
by John Huang 1G
Sun Dec 03, 2017 9:48 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Homework Help :12.43 pg 513
Replies: 1
Views: 122

Homework Help :12.43 pg 513

The values of Ka for phenol and 2,4,6-trichlorophenol (see following structures) are 1.3x10^10 and 1.0x10^6, respectively. Which is the stronger acid? Account for the difference in acid strength. By what means are we supposed to determine the strength of the acid? Is it simply a matter of which Ka v...
by John Huang 1G
Wed Nov 29, 2017 4:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Water in Equilibrium Expressions [ENDORSED]
Replies: 1
Views: 120

Water in Equilibrium Expressions [ENDORSED]

I understand that we do not include water into equilibrium expressions when it is in the form of a solid and liquid. But does this principle also exclude water in the form of a gas? Do we generally always leave water out of the equilibrium expression?
by John Huang 1G
Sun Nov 26, 2017 10:20 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solids and Liquids in Equilibrium
Replies: 2
Views: 190

Re: Solids and Liquids in Equilibrium

Adding on to Chem_Mod's explanation, we should remember to include the concentrations of aqueous species. We should not leave out aqueous species just because they are dissociated in a solvent liquid. Generally, remember the difference between liquids and aqueous solutions.
by John Huang 1G
Sun Nov 26, 2017 10:16 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Unequal Reactant
Replies: 3
Views: 183

Re: Unequal Reactant

I believe the equilibria sign would lie to the right actually. When you have more reactants than products, the calculated Reaction Quotient (Q) value will be less than one, not the K value. So because the Q value would be less than the K value, the equilibrium would lie to the right because the forw...
by John Huang 1G
Sun Nov 26, 2017 10:10 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework Help 11.59
Replies: 2
Views: 158

Homework Help 11.59

For problem 11.59, I understand that we would be using an ICE chart. But what steps would I take next to find the equilibrium concentrations of each substance?
by John Huang 1G
Sun Nov 26, 2017 10:07 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework Help 11.43
Replies: 1
Views: 119

Homework Help 11.43

For 11.43, the questions asks for an "equilibrium relation." What is an equilibrium relation and how do we find it? Is it just and equation?
by John Huang 1G
Sun Nov 26, 2017 10:00 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q.11.37
Replies: 1
Views: 160

Re: Q.11.37

I don't think an ICE chart would be necessary for this set of problems; and Table 11.2 will only help you to a certain extent. One helpful table to take a look at wold be Table 11.3. Table 11.3 demonstrates the relationships between the equilibrium constants and the format of the chemical equation.
by John Huang 1G
Sun Nov 26, 2017 9:52 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Finding The Direction of Reaction
Replies: 5
Views: 232

Re: Finding The Direction of Reaction

When it says, "The equilibrium is favored to the right," it means that the rate of the forward reaction will be greater than the rate of the reverse reaction. The vice versa for this scenario applies as well. The phrase is not referring to the concentrations of the reactants or products, b...
by John Huang 1G
Sun Nov 26, 2017 9:45 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Homework Question: 17.35 & 17.36
Replies: 1
Views: 96

Homework Question: 17.35 & 17.36

I understand that for 17.35, (B) is the correct answer because of the close proximity between the two Nitrogen lone pairs.

My question is, following the same logic of 17.35, would we select (B) for 17.36 for the same reason? Or would (C) also be a valid choice?
by John Huang 1G
Sun Nov 19, 2017 5:25 pm
Forum: Hybridization
Topic: Homework Help 4.87
Replies: 1
Views: 183

Homework Help 4.87

In addition to forming sigma and pi types of bonds similar to p-orbitals, d-orbitals may overlap to form delta-bonds. (a) Draw overlap diagrams showing three different ways in which d-orbitals can combine to form bonds. (b) Place the three types of d-d bonds—sigma ,pi , and delta —in order of strong...
by John Huang 1G
Mon Nov 13, 2017 3:29 pm
Forum: Hybridization
Topic: Homework Help: Problem 4.73
Replies: 2
Views: 129

Homework Help: Problem 4.73

4.73 (a) Draw a Lewis structure for each of the following species (b) Identify each as a radical or not. (c) Rank them in order of increasing HCH bond angles. Explain your choices. How do I determine the bond angles of a molecule such as (CH3)-? The molecule results in having a central Carbon atom, ...
by John Huang 1G
Mon Nov 13, 2017 3:23 pm
Forum: Hybridization
Topic: Homework Help on Problem 4.45
Replies: 2
Views: 117

Re: Homework Help on Problem 4.45

Ahh I see. Initially I believed there would be 2 sigma bonds because there are 2 single bonds.
I know see that there are 3 sigma bonds and 1 pi bond. The double bond contains one sigma bond and one pi bond. Muchas Gracias
by John Huang 1G
Mon Nov 13, 2017 2:11 pm
Forum: Hybridization
Topic: Homework Help on Problem 4.45
Replies: 2
Views: 117

Homework Help on Problem 4.45

4.45 Describe the structure of the formaldehyde molecule, CH2O, in terms of hybrid orbitals, bond angles, and sigma and pi bonds. The C atom is the central atom to which the other three atoms are attached. I am confused as to how to determine which are sigma bonds and which are pi bonds. How should ...
by John Huang 1G
Mon Oct 16, 2017 11:00 pm
Forum: Photoelectric Effect
Topic: 1.33 Part A
Replies: 4
Views: 254

Re: 1.33 Part A

I would use the Ek formula to solely determine the kinetic energy of the emitted electron. The de Broglie Equation allows you to determine the wavelength.

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