Search found 50 matches

by Angel Ni 2K
Thu Mar 15, 2018 2:04 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Coefficients when writing cell diagrams
Replies: 3
Views: 154

Re: Coefficients when writing cell diagrams

No. Cell diagrams are simply a summary of the players in the redox reactions.
by Angel Ni 2K
Thu Mar 15, 2018 2:00 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Water in Mechanism
Replies: 5
Views: 223

Re: Water in Mechanism

If it is the solvent, then you can leave it out of the rate law. This is because solvents are present in such high concentrations that their concentrations don't change much during the reaction.
by Angel Ni 2K
Sat Mar 10, 2018 7:46 pm
Forum: Balancing Redox Reactions
Topic: 14.5 Part a
Replies: 4
Views: 202

Re: 14.5 Part a

If there are any H+ ions, you need to convert them to H2O using OH-.
by Angel Ni 2K
Sat Mar 10, 2018 7:38 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.49
Replies: 2
Views: 144

Re: 8.49

Using the 8.314 results in the correct units.
by Angel Ni 2K
Sun Mar 04, 2018 4:27 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: K'
Replies: 7
Views: 291

Re: K'

You can also use the formulas given in the equations sheet. Just make sure you understand the formulas and which order reaction to use them for.
by Angel Ni 2K
Sun Mar 04, 2018 4:26 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Independent of rate
Replies: 3
Views: 138

Re: Independent of rate

The rate is independent of the concentration if the reaction is zero order with respect to that reactant.
by Angel Ni 2K
Sun Mar 04, 2018 4:25 am
Forum: General Rate Laws
Topic: 15.13 part a?
Replies: 3
Views: 148

Re: 15.13 part a?

The rate equals k(concentration of H2)(concentration of I2). It is, in a way, k(concentration)^2.
by Angel Ni 2K
Sun Feb 25, 2018 4:49 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: reducing power?
Replies: 5
Views: 232

Re: reducing power?

Reducing power is the ability of something to give up electrons so that those electrons can go reduce some other molecule.
by Angel Ni 2K
Sun Feb 25, 2018 4:46 pm
Forum: General Rate Laws
Topic: rate of consumption sign
Replies: 2
Views: 135

Re: rate of consumption sign

The terms themselves imply the sign. If you have a negative rate of consumption, you would be forming the molecule; it doesn't make sense to call it the rate of consumption. The same goes for rate of formation.
by Angel Ni 2K
Sun Feb 25, 2018 4:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Strongly Reducing Metals
Replies: 5
Views: 201

Re: Strongly Reducing Metals

The lower the standard reduction potential, the more unlikely the metal will get reduced (since more negative E values result in more positive G values).
by Angel Ni 2K
Sun Feb 18, 2018 11:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.15.c
Replies: 2
Views: 129

14.15.c

For this question, the overall equation is given as Cd(s) + 2 Ni(OH)3(s) --> Cd(OH)2(s) + Ni(OH)2(s). However, in the cell diagram, there was a KOH. Where did the potassium come from?
by Angel Ni 2K
Sun Feb 18, 2018 11:52 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.13 d
Replies: 1
Views: 123

14.13 d

What are the rules for balancing a redox equation with only one reactant/product? For example, the equation given in 14.13.d is Au+(aq) --> Au(s) + Au3+(aq). I thought Au+(aq) would be used in both half reactions but the solutions manual chose to use Au(s) for both reactions instead.
by Angel Ni 2K
Sun Feb 18, 2018 11:42 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: G=-nFE
Replies: 3
Views: 198

G=-nFE

Why is the "n" in this equation always positive even when there is a negative change in moles?
by Angel Ni 2K
Wed Feb 07, 2018 10:54 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.51 [ENDORSED]
Replies: 3
Views: 167

Re: 9.51 [ENDORSED]

deltaG = deltaH - TdeltaS. If deltaG is negative, then the reaction is spontaneous. Since deltaH is negative, the reaction will be spontaneous for all positive values of deltaS and small negative values of deltaS.
by Angel Ni 2K
Wed Feb 07, 2018 10:45 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: 9.25
Replies: 2
Views: 120

Re: 9.25

They are asking for molar entropy, so there are 6.02E23 molecules.
by Angel Ni 2K
Wed Feb 07, 2018 10:37 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: 9.25
Replies: 1
Views: 89

Re: 9.25

The question asks for molar entropy, and there are 6.02E23 molecules. 6 orientations and 6.02E23 molecules results in 6^6.02E23. Plug it into the Boltzmann's equation and you will get the answer.
by Angel Ni 2K
Sun Feb 04, 2018 8:04 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 8.53
Replies: 2
Views: 87

Re: 8.53

The problem gives all reactants and products. As for the phases, everything is in gas form at the given temperatures. Water can be liquid, but the problem specifies that the reaction uses water vapor.
by Angel Ni 2K
Sat Feb 03, 2018 7:22 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Which value of R to use?
Replies: 3
Views: 129

Re: Which value of R to use?

The method you mentioned should work as long as you make sure that you end up with the units that correspond to the variable you are solving for.
by Angel Ni 2K
Fri Jan 26, 2018 4:41 pm
Forum: Phase Changes & Related Calculations
Topic: 8.41
Replies: 6
Views: 260

Re: 8.41

Use the specific heat capacity of ice when you are raising the temperature of ice. Because the ice is already at 0C, you don't need to use the specific heat capacity of ice because the ice doesn't get warmer than 0C. Instead, use the heat of fusion to calculate the energy needed to melt the ice, the...
by Angel Ni 2K
Fri Jan 26, 2018 4:29 pm
Forum: Phase Changes & Related Calculations
Topic: When to use Kelvin or Celsius
Replies: 10
Views: 599

Re: When to use Kelvin or Celsius

If the equation requires deltaT, then it doesn't matter whether you use K or C. If the equation requires T and not deltaT, then usually you will need to use K. Make sure to keep track of your units and that after cancelling, your ending units are actually what you are looking for.
by Angel Ni 2K
Fri Jan 26, 2018 4:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Refresher on sig figs
Replies: 3
Views: 165

Re: Refresher on sig figs

The values given in the appendix are accurate to the hundredths place. When you add them, your answer will still be accurate to the hundredths place. It happens that with the hundredths place, you will have 6 sig figs.
by Angel Ni 2K
Sun Jan 21, 2018 1:56 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: change in internal energy
Replies: 4
Views: 143

Re: change in internal energy

deltaU = q + w. When no work is done, U=q. When no heat is transferred, U=w.
by Angel Ni 2K
Sun Jan 21, 2018 1:48 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible and Irreversible
Replies: 4
Views: 201

Re: Reversible and Irreversible

For irreversible reactions, w=-(Pext)(deltaV). For reversible reactions, w=-nRTln(v2/v1).
by Angel Ni 2K
Sun Jan 21, 2018 1:42 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Difference between Closed and Isolated
Replies: 10
Views: 707

Re: Difference between Closed and Isolated

In an isolated system, neither particles nor heat can be transferred. In a closed system, heat can be transferred but particles cannot.
by Angel Ni 2K
Sun Jan 21, 2018 1:41 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.65
Replies: 2
Views: 103

Re: 8.65

The solution stops at 2NO(g) + 3/2O2(g) --> N2O5(g) because you can use the enthalpy of formation of NO(g) to figure out the enthalpy of formation of N2O5(g). For 2NO(g) + 3/2O2(g) --> N2O5(g), deltaH is -169.2 kJ/mol. Thus, 1(deltaHfN2O5) - 2(deltaHfNO) = -169.2 kJ/mol. Using the appendix, 1(deltaH...
by Angel Ni 2K
Sun Jan 21, 2018 1:30 am
Forum: Calculating Work of Expansion
Topic: Reversible vs Isothermal
Replies: 3
Views: 184

Re: Reversible vs Isothermal

A reversible isothermal reaction is one in which the volume changes slowly at a constant temperature. There is no heat transfer, so q=0, so deltaU=w.
by Angel Ni 2K
Sat Jan 20, 2018 1:04 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.37
Replies: 3
Views: 156

8.37

For homework problem 8.37b, we are asked to calculate the enthalpy of vaporization of ethanol (given that 21.2kJ vaporized 22.45 grams). The answer key gives the answer as 43.5kJ/mol, but would 0.944kJ/g also be correct? In other words, what units are we supposed to use for enthalpy of vaporization ...
by Angel Ni 2K
Mon Dec 04, 2017 10:42 pm
Forum: Bronsted Acids & Bases
Topic: ch 12 #33
Replies: 1
Views: 106

Re: ch 12 #33

We are using the equation M1V1=M2V2 because the number of moles is the same between the two solutions. Thus, (0.18M)(0.5000L)=M2(0.00500L). The solution manual simply rearranges this.
by Angel Ni 2K
Mon Dec 04, 2017 10:25 pm
Forum: Lewis Acids & Bases
Topic: 12.27
Replies: 1
Views: 140

Re: 12.27

From the problem, we know that the concentration of HCl in the intended solution is 0.025M. Therefore, [H3O+] in the intended solution is also 0.025M. The number of moles of HCl remains the same between intended and actual solutions. From earlier in the course, we learned that M1V1=M2V2. Thus, using...
by Angel Ni 2K
Mon Nov 27, 2017 9:14 pm
Forum: Lewis Structures
Topic: N2H6
Replies: 2
Views: 723

Re: N2H6

The nitrogen is already very unhappy having 9 outer shell electrons in the single bond. I imagine that it will become suicidal if you decide to give it 10 outer shell electrons with the double bond. It wasn't even supposed to have an expanded octet in the first place. Don't force the relationship or...
by Angel Ni 2K
Mon Nov 27, 2017 9:03 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.1 Homework
Replies: 2
Views: 143

Re: 11.1 Homework

Simply changing the concentration of the reactants or products will not change the equilibrium constant. If you add more reactant, then the reaction will shift to the right. If you add more product, then the reaction will shift to the left. In the end (after you wait a while for the reaction to reac...
by Angel Ni 2K
Wed Nov 22, 2017 1:28 am
Forum: Hybridization
Topic: 4.95 composition of the pi bond
Replies: 2
Views: 137

Re: 4.95 composition of the pi bond

When carbon forms single bonds, it is usually in either sp, sp2, or sp3 hybridization. The single bond is a sigma bond. If the carbon is either sp or sp2 hybridized, then it will have one (in the case of sp2) or two (in the case of sp) unhybridized p-orbitals. The extra p orbitals will form double b...
by Angel Ni 2K
Wed Nov 22, 2017 1:19 am
Forum: Naming
Topic: Ligand IUPAC naming
Replies: 1
Views: 94

Re: Ligand IUPAC naming

He said that there is a newer method, but we will be using the older one.
by Angel Ni 2K
Mon Nov 13, 2017 7:49 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AXE
Replies: 3
Views: 170

Re: AXE

The notation is AX_E_, with the _ indicating the number of terminal atoms (X) or number of lone pairs (E). If there are no lone pairs, simply omit the E (you will end up with AX_). If there is one lone pair, omit the subscript (you will end up with AX_E). If there is more than one lone pair, you wil...
by Angel Ni 2K
Mon Nov 13, 2017 7:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: CO2 vs. H2O
Replies: 6
Views: 566

Re: CO2 vs. H2O

1. Draw VSEPR structures. 2. Draw dipole moments. 3. CO2 has dipole moments, but they cancel out because they are equal in magnitude and opposite in direction. Therefore, CO2 is a nonpolar molecule despite having polar bonds. H2O has dipole moments, but they do not cancel out because they are equal ...
by Angel Ni 2K
Wed Nov 08, 2017 11:40 pm
Forum: Lewis Structures
Topic: Exceptions
Replies: 4
Views: 236

Re: Exceptions

chromium and copper because they only need one electron to fill half or all of the d orbitals
by Angel Ni 2K
Wed Nov 08, 2017 11:38 pm
Forum: Ionic & Covalent Bonds
Topic: Polar vs. Non-polar
Replies: 7
Views: 360

Re: Polar vs. Non-polar

If the molecule is not symmetric, then it is (generally) polar because the dipole moments (if any) do not cancel out. If the molecule is symmetric but the outside atoms are not the same, then it is polar because the dipole moments do not cancel out. If the molecule is symmetric and the outside atoms...
by Angel Ni 2K
Mon Oct 30, 2017 9:24 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2.63
Replies: 2
Views: 159

Re: 2.63

In general, the elements to top right of the periodic table have higher ionization energies. Conversely, the elements to bottom left have lower ionization energies. The elements given in the problem all follow this trend. Just rank them by which ones are higher or righter on the periodic table.
by Angel Ni 2K
Mon Oct 30, 2017 9:06 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Valence-shell Configuration for Transition Metals
Replies: 1
Views: 144

Valence-shell Configuration for Transition Metals

For HW problem 2.55 c, we are asked to write the valence-shell configuration for the Group 5 transition metals. I got (n-1)d3 ns2, but the answer key says (n-1)d5 ns2. Does the question mean to ask for the fifth group of transition metals or is there some special property of Group 5 metals that make...
by Angel Ni 2K
Mon Oct 23, 2017 10:30 pm
Forum: Quantum Numbers and The H-Atom
Topic: "No two electrons are the same..." [ENDORSED]
Replies: 5
Views: 356

Re: "No two electrons are the same..." [ENDORSED]

No two electrons in a single atom can have the same four quantum numbers.
by Angel Ni 2K
Mon Oct 23, 2017 10:26 pm
Forum: Quantum Numbers and The H-Atom
Topic: Abbreviating e- configurations [ENDORSED]
Replies: 7
Views: 453

Re: Abbreviating e- configurations [ENDORSED]

It depends on what the question is asking for. I would use noble gas configuration when the question asks for it.
by Angel Ni 2K
Fri Oct 20, 2017 3:25 am
Forum: Properties of Light
Topic: Angstrom
Replies: 3
Views: 317

Re: Angstrom

It can refer to either. The Angstrom is a unit of length.
by Angel Ni 2K
Fri Oct 20, 2017 3:20 am
Forum: Properties of Light
Topic: Color of visible light
Replies: 11
Views: 574

Re: Color of visible light

No, it is not necessary.
by Angel Ni 2K
Fri Oct 13, 2017 12:46 am
Forum: Properties of Light
Topic: Prefix Conversion
Replies: 12
Views: 546

Re: Prefix Conversion

I will usually convert the nm into m first because most ratios use m (such as speed of light). After I finish solving the problem, I make sure that the answer is in the units that the question asks for. If the question does not satisfy, I will usually just leave it in meters.
by Angel Ni 2K
Wed Oct 11, 2017 11:05 pm
Forum: Properties of Light
Topic: Relationship between the frequency of electromagnetic radiation and electrical field
Replies: 2
Views: 177

Relationship between the frequency of electromagnetic radiation and electrical field

On number 1.3, the question asks for what happens when the frequency of electromagnetic radiation decreases. The solutions manual says that the correct answer is "The extent of the change in the electrical field at a given point decreases". Why is this the correct answer?
by Angel Ni 2K
Fri Oct 06, 2017 11:34 am
Forum: Limiting Reactant Calculations
Topic: M9
Replies: 3
Views: 213

Re: M9

For net ionic equations, the soluble compounds will dissolve in water. Then, if the separated ions are able to form insoluble compounds, we will have a precipitate. In this problem, the precipitate is Cu(OH)2. The only molecules represented in the net ionic equations are precipitates and the aqueous...
by Angel Ni 2K
Fri Oct 06, 2017 11:22 am
Forum: SI Units, Unit Conversions
Topic: Sig Figs [ENDORSED]
Replies: 16
Views: 1886

Re: Sig Figs [ENDORSED]

There are 3 sig figs. The 0's to the left of nonzero numbers do not count as sig figs. However, if there were 0's to the right of nonzero numbers, those 0's would be significant.

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