## Search found 64 matches

Wed Mar 13, 2019 10:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.9) 7th edition [ENDORSED]
Replies: 1
Views: 24455

### 4D.9) 7th edition[ENDORSED]

Does anyone know why for problem 4D.9 of the 7th edition of the textbook, the enthalpy density is reported as a positive value, when the standard enthalpy of the reaction that was calculated was a negative value? Thank you!!
Wed Mar 13, 2019 12:48 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Assuming ideal gas
Replies: 3
Views: 352

### Assuming ideal gas

When can we assume that a gas is behaving in an ideal manner? For example, in 4D.7) of the 7th edition of the textbook, the solutions manner uses the ideal gas equation to solve for the work, and eventually the change in internal energy (but the book never says that the gas is ideal). How would I kn...
Mon Mar 11, 2019 2:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Determining stability based on K
Replies: 1
Views: 80

### Determining stability based on K

How can you tell, if given two separate chemical reactions with a different reactant in each, which reactant is more stable based on the equilibrium constant, K?
Thu Mar 07, 2019 9:21 pm
Forum: General Rate Laws
Topic: Units for Rate Constants
Replies: 5
Views: 205

### Units for Rate Constants

Is there an easy way to determine the units for rate constants for zeroth, first, and second-order reactions? Thank you!
Thu Mar 07, 2019 9:19 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert Electrode
Replies: 2
Views: 128

### Inert Electrode

Is there another inert electrode you could use in a galvanic cell diagram other than Pt(s) when there is no solid otherwise present in the reaction?
Thu Mar 07, 2019 9:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7 part a 7th edition
Replies: 1
Views: 131

### 6L.7 part a 7th edition

For problem 6L.7 part (a) in the 7th edition of the textbook, you are asked to devise a galvanic cell for AgBr(s) becoming Ag+(aq) and Br-(aq) using the half-reactions. In the solutions manual, the half reactions that are used for the problem are Ag+(aq) becoming Ag(s) and also AgBr(s) decomposing d...
Wed Feb 27, 2019 2:50 pm
Forum: Balancing Redox Reactions
Topic: 6K.5 7th edition
Replies: 1
Views: 82

### 6K.5 7th edition

For problem 6K.5) of the 7th edition of the textbook, does the O3(aq) and O2(aq) still have a charge even though none was written in the chemical equation? If so, how would we determine their charges?
Wed Feb 27, 2019 1:30 pm
Forum: Balancing Redox Reactions
Topic: Oxidized vs oxidizing agent
Replies: 6
Views: 164

### Oxidized vs oxidizing agent

Is there a difference between being oxidized versus being the oxidizing agent? Thank you!
Tue Feb 26, 2019 10:44 pm
Forum: Balancing Redox Reactions
Topic: 6K.1 7th edition
Replies: 1
Views: 93

### 6K.1 7th edition

Could someone explain why for the balanced redox reaction in problem 6K.1) of the 7th edition of the textbook, there ends up being 3 C2H5OH(aq) and 3 C2H4O(aq) as opposed to just the coefficient of 1 for each of these compounds? Thank you!
Thu Feb 21, 2019 12:39 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 4J.5) 7th edition of the textbook
Replies: 2
Views: 114

### 4J.5) 7th edition of the textbook

For question 4J.5) of the 7th edition of the textbook, after finding the standard enthalpy and standard entropy you can calculate the standard Gibbs free energy. The solutions manual does this by using the temperature of 298K. When can you assume the temperature to be 298K?
Thu Feb 21, 2019 12:34 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 4J.7) 7th edition of the textbook
Replies: 2
Views: 126

### 4J.7) 7th edition of the textbook

In part (b) of problem 4J.7) in the 7th edition of the textbook, you have to calculate the standard reaction enthalpy of the equation 2F2(g) + 2H20(l) produces 4HF(aq) + O2(g). Why does the solutions manual only take into account the enthalpy of formation for HF and H2O when calculating the standard...
Thu Feb 21, 2019 12:29 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Problem 4J.15) 7th edition of the textbook
Replies: 1
Views: 120

### Problem 4J.15) 7th edition of the textbook

In problem 4J.15) of the 7th edition of the textbook, you have to calculate the standard entropy of the compound SO2(g). To do this you set up the chemical equation which is S(s) + O2(g) produces SO2(g). In order to find the standard entropy, I had to look at the value of molar entropy for S(s), whi...
Wed Feb 13, 2019 10:58 am
Forum: Calculating Work of Expansion
Topic: Work of the system
Replies: 3
Views: 157

### Work of the system

When can you assume that the work of the system equals zero, or when no work is done?
Wed Feb 13, 2019 10:57 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Change in Internal Energy
Replies: 3
Views: 170

### Change in Internal Energy

When does the change in internal energy equal zero?
Tue Feb 12, 2019 5:33 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 4F.11) 7th edition
Replies: 1
Views: 89

### 4F.11) 7th edition

In the solutions manual for problem 4F.11) of the 7th edition of the textbook, they use the formula for change of entropy that delta S = nRln(T2/T1). Is this a formula that we can normally use? I thought it only applied to changes in volume.
Sat Feb 09, 2019 3:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.7) 7th edition
Replies: 1
Views: 111

### 4D.7) 7th edition

Why in problem 4D.7 of the 7th edition of the textbook, does the solution manual make the temperature equal to 298K even though it was never stated in the original problem? Is there a rule for this assumption?
Thu Feb 07, 2019 3:08 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of phase change
Replies: 5
Views: 396

### Enthalpy of phase change

In the example given in class, to calculate the net enthalpy change of the reaction of Br2(l) becoming 2Br(g), why is the change of enthalpy of vaporization added to the change of bond enthalpy?
Wed Feb 06, 2019 4:16 pm
Forum: Phase Changes & Related Calculations
Topic: Problem 4B.1) 7th edition
Replies: 2
Views: 125

### Problem 4B.1) 7th edition

In problem 4B.1 of the 7th edition of the textbook, it says that a piston compresses the gas, doing 340 kJ of work. Does this mean that the value of work is positive rather than negative?
Wed Feb 06, 2019 10:36 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Chem 14B Midterm
Replies: 3
Views: 223

### Chem 14B Midterm

In the announcement made about what was going to be covered on the midterm for chem 14B, it said everything we have covered until the end of entropy. Does this mean for thermodynamics (2nd and 3rd laws), sections 4F-4I of the 7th edition of the textbook (Basically, only excluding section 4J in outli...
Wed Jan 30, 2019 2:30 pm
Forum: Phase Changes & Related Calculations
Topic: 4.1 7th edition
Replies: 1
Views: 160

### Re: 4.1 7th edition

Are you sure you input all of your calculations correctly? When i plugged in the equation you provided I got 132 kJ, not 128kJ. Maybe try inputting your values again into your calculator.
Wed Jan 30, 2019 2:23 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Problem 4A.9) 7th edition of the textbook [ENDORSED]
Replies: 7
Views: 36612

### Problem 4A.9) 7th edition of the textbook[ENDORSED]

For problem 4A.9 of the 7th edition of the textbook, I got the correct final temperature to be 25 degrees Celsius. However, when I plugged this value back into the equation in which I solved for final temperature, the value was not checking out. I was wondering, is there a way in which to check in t...
Wed Jan 30, 2019 2:16 pm
Forum: Phase Changes & Related Calculations
Topic: J vs. kJ
Replies: 9
Views: 321

### J vs. kJ

When considering the units for work, are we supposed to give our final answer in J or kJ? Thanks!
Thu Jan 24, 2019 2:35 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6A.19 7th edition of the textbook
Replies: 1
Views: 303

### 6A.19 7th edition of the textbook

For 6A.19 of the 7th edition of the textbook, why does the answer for part c contain 10^-12 for scientific notation instead of 10^-15? The solutions manual converted 3.1 from mmol to mols, but it was already given in mol so I'm confused. Thanks!
Wed Jan 23, 2019 5:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE boxes
Replies: 5
Views: 190

### ICE boxes

Can you use an ICE box in essentially the same way whether you are using partial pressure versus molar concentration? Thanks!
Tue Jan 22, 2019 9:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Using partial pressure versus molar concentration
Replies: 2
Views: 87

### Using partial pressure versus molar concentration

Can I use partial pressure to solve for K if there are only solids, liquids, and gases in the chemical equation since you do not include solids and liquids in the K expression?
Tue Jan 22, 2019 9:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Problem 5G.1) 7th edition of textbook
Replies: 1
Views: 94

### Problem 5G.1) 7th edition of textbook

Hello! I'm confused about the answer to problem 5G.1 of the 7th edition of the textbook. In the solutions manual, the answer for part b states the "equilibrium reactions are affected by the presence of both products and reactants" and then for part c states that "the value of the equi...
Thu Jan 17, 2019 9:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5H.1 7th edition
Replies: 1
Views: 64

### 5H.1 7th edition

Hello! I am slightly confused as to why for part b of problem 5H.1 of the 7th edition of the textbook the K value of 41 from equation 1 is square rooted to find the K value of equation b. If anyone could explain this to me that would be great!
Thu Jan 17, 2019 8:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Problem 5I.11 7th
Replies: 1
Views: 74

### Re: Problem 5I.11 7th

The question says there are 0.50 mmol of O2, so you need to convert this number to moles and then divide by the volume of the vessel in liters to get (5.0 X 10^-4)/0.500 as the concentration of 02.
Tue Jan 15, 2019 11:37 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 5I.35 7th edition
Replies: 1
Views: 62

### 5I.35 7th edition

Does anyone know why for problem 5I.35 in the 7th edition of the textbook the p in the numerator of the correct equilibrium relation is squared? Does it have to do with setting up the ICE box?
Wed Jan 09, 2019 3:12 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: example in class
Replies: 3
Views: 145

### Re: example in class

Using the ICE box he subtracted the initial molarity from the equilibrium molarity to find the change in molarity.
Wed Jan 09, 2019 3:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5H.3 7th edition
Replies: 2
Views: 110

### Re: 5H.3 7th edition

it helps if you write out the K values for all of the equations 2BrCl >>> Br2 + Cl2 H2 +Cl2 >>> 2HCl ----------------------- 2BrCl + H2 >>> Br2 + 2HCl K1 = [Br2][Cl2]/[BrCl]^2 K2 = [HCl]^2/[H2][Cl2] K3 = [Br2][HCl]^2/[H2][BrCl]^2 = K1 x K2 Hope this helps! Thank you so much, your explanation really...
Wed Jan 09, 2019 2:36 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q
Replies: 6
Views: 147

### Re: Q

To find Q, or the reaction quotient, you would need to use the same equation used to find K, or the equilibrium constant. Also only include gases and aqueous phases in your equation to find Q.
Wed Jan 09, 2019 2:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5H.3 7th edition
Replies: 2
Views: 110

### 5H.3 7th edition

Does anyone know why for problem 5H.3 of the 7th edition of the textbook, the answer is the result of multiplying the two equilibrium constants of two chemical equations from the table 5G.2? I am confused why in order to find K of the chemical equation given, I would multiply the K's of the other tw...
Tue Dec 04, 2018 10:39 pm
Forum: Electronegativity
Topic: Trend of Electronegativity
Replies: 18
Views: 2981

### Re: Trend of Electronegativity

Electronegativity increases across a period and up a group, so it is the same trend as ionization energy.
Tue Dec 04, 2018 10:35 pm
Forum: Naming
Topic: 9C.1 7th edition
Replies: 1
Views: 115

### 9C.1 7th edition

For 9c.1 of the 7th edition of the textbook, how do you determine the oxidation number of the metals?
Tue Dec 04, 2018 10:31 pm
Forum: Bronsted Acids & Bases
Topic: Homework Fundamentals J.9
Replies: 1
Views: 144

### Re: Homework Fundamentals J.9

B is the answer because a strong acid is completely deprotonated in solution, meaning that every acid molecule/ion has lost its hydrogen, and in the image b all of the hydrogens have separated from the Cl.
Tue Nov 27, 2018 7:16 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent vs. Ionic
Replies: 2
Views: 160

### Covalent vs. Ionic

Does anyone know if we were asked to determine if a compound was ionic vs covalent, would we be given a chart of electronegativity for test 3?
Tue Nov 27, 2018 6:58 pm
Forum: *Liquid Structure (Viscosity, Surface Tension, Liquid Crystals, Ionic Liquids)
Topic: Shape and Boiling Point
Replies: 12
Views: 1581

### Re: Shape and Boiling Point

Would the presence of a dipole moment contribute to the boiling point being higher?
Tue Nov 27, 2018 5:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipole moment
Replies: 1
Views: 93

### Dipole moment

Why does CN2H2 have a dipole moment? When drawing the Lewis structure, it looks to be symmetrical when the arrows point toward the two nitrogens, so I'm confused why the molecule has a dipole moment. Thanks!
Tue Nov 20, 2018 10:19 pm
Forum: Lewis Structures
Topic: Lewis structure for POCl3
Replies: 7
Views: 491

### Re: Lewis structure for POCl3

P is the central atom because it is the least electronegative in comparison to O and Cl, and it also has the ability to be an expanded octet, which makes the drawing of the lewis structure accurate.
Tue Nov 20, 2018 10:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.1
Replies: 2
Views: 50

### Re: 2E.1

I believe that option b may have lone pairs because if a lone pair was added to each side of the central atom, the overall shape would appear as depicted and not bent like a.
Mon Nov 19, 2018 11:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 7th edition problem 2E.5
Replies: 2
Views: 94

### 7th edition problem 2E.5

For this problem, you have to come up with the shape of a ClO2+ ion. In the solutions manual it says the shape is angular, but that it has an trigonal planar arrangement. Which one of these would be the correct answer/how did the book come up with these answers?
Tue Nov 13, 2018 10:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.1
Replies: 2
Views: 63

### Re: 2E.1

There must be lone pairs because since the shape is bent, and not linear, you can recognize that lone pairs are causing repulsion and with that, the bent shape.
Tue Nov 13, 2018 10:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lowest Energy Lewis Structures
Replies: 3
Views: 171

### Re: Lowest Energy Lewis Structures

Yes, I always use the Lewis structure with the lowest energy by looking at the formal charges because this corresponds to the most likely molecular shape of the compound. And also make sure you satisfy the octet rule and its exceptions!
Tue Nov 13, 2018 10:07 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework Focus 2A
Replies: 3
Views: 213

### Re: Homework Focus 2A

I think that the answer the textbook gave corresponds to Cu+ and not Cu2+.
Tue Nov 06, 2018 9:28 pm
Forum: Ionic & Covalent Bonds
Topic: O vs N [ENDORSED]
Replies: 4
Views: 188

### Re: O vs N[ENDORSED]

Oxygen has a lower ionization energy because, even though it is technically further down the period than Nitrogen, its p orbital is half-filled, making it more stable and so harder to remove an electron.
Tue Nov 06, 2018 9:24 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent bonds
Replies: 3
Views: 165

### Re: Covalent bonds

Yes, two atoms of the same element are bonded as a covalent bond, sharing the electrons equally between the two atoms.
Tue Nov 06, 2018 9:21 pm
Forum: Lewis Structures
Topic: Identifying the element
Replies: 8
Views: 377

### Re: Identifying the element

Yes, I believe that answer would be fine. I also explained in mine how I was able to figure out that the element had 5 valence electrons by totaling the number of electrons in the lewis structure, and then subtracting the valence electrons of the other elements.
Wed Oct 31, 2018 8:01 pm
Forum: Ionic & Covalent Bonds
Topic: 2A.19 7th edition
Replies: 3
Views: 161

### 2A.19 7th edition

Hello! Could someone please explain to me why for part e) of this question the electron configuration of Ni^+2 is [Ar]3d^8 instead of [Ar]3d^6 4s^2. Thank you!
Tue Oct 30, 2018 9:56 pm
Forum: Lewis Structures
Topic: How to determine central atom
Replies: 8
Views: 361

### Re: How to determine central atom

The central atom of the lewis structure is the atom with the lowest ionization energy.
Tue Oct 30, 2018 9:53 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ag+ Configuration
Replies: 5
Views: 1084

### Re: Ag+ Configuration

It's because the electron is taken from the outermost shell, which would be 5s orbital, leaving 4d^10 which since it is a full shell, is stable.
Tue Oct 30, 2018 9:48 pm
Forum: *Black Body Radiation
Topic: Midterm
Replies: 4
Views: 408

### Re: Midterm

I am not going to study black body radiation because we were told not to study it for test 2, so I'm assuming it would not be on the midterm either.
Tue Oct 23, 2018 2:39 pm
Forum: Properties of Light
Topic: Power calculations
Replies: 6
Views: 417

### Re: Power calculations

I have this problem often as well, so I usually just do the calculations without the powers, then figure out the powers separately, and then finally input them in to the final answer. This also helps me check my work and that I have the correct scientific notation.
Mon Oct 22, 2018 10:34 pm
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic Quantum Number
Replies: 3
Views: 191

### Re: Magnetic Quantum Number

Given the magnetic quantum number you can differentiate the specific orbitals within a subshell. The magnetic quantum number also states the orientation of the orbital.
Mon Oct 22, 2018 10:26 pm
Forum: Einstein Equation
Topic: De Broglie's
Replies: 4
Views: 493

### Re: De Broglie's

The problem would give you the information on whether you are entering the mass of a neutron or proton into De Broglie's equation.
Tue Oct 16, 2018 3:41 pm
Forum: Einstein Equation
Topic: Units of Energy
Replies: 5
Views: 261

### Units of Energy

How is 1 Joule expressed in terms of SI base units? When would we convert J into SI base units in order to solve an equation?
Tue Oct 16, 2018 3:34 pm
Forum: Properties of Light
Topic: Week 3 HW
Replies: 5
Views: 272

### Re: Week 3 HW

Yes, you would turn in another seven problems from the quantum world section. For the seventh edition of the textbook, he gave us the following options for homework problems: 1A: 3, 5, 7, 9, 11, 15; 1B: 3, 5, 7, 9, 15, 19, 21, 23, 25, 27; 1D: 1, 9, 11, 13, 15, 17, 19, 21, 23, 25; 1E: 1, 5, 7, 9, 11,...
Tue Oct 16, 2018 3:25 pm
Forum: Properties of Light
Topic: color of light
Replies: 11
Views: 451

### Re: color of light

The wavelength or the frequency can determine the color of light because of the equation c = wavelength x frequency. The color of light is more commonly identified by wavelength however, because this is seen based on the values on the electromagnetic spectrum in nm.
Mon Oct 08, 2018 8:43 pm
Forum: Molarity, Solutions, Dilutions
Topic: Finding the volume of stock solution to dilute
Replies: 13
Views: 751

### Finding the volume of stock solution to dilute

Does anyone know if when solving for an initial volume using the formula M(inital)V(inital) = M(final)V(final), would I have to convert the final volume originally given in mL to liters? In other words, when is it necessary to convert mL to liters? Thanks!
Mon Oct 08, 2018 8:31 pm
Forum: Balancing Chemical Reactions
Topic: States of Matter
Replies: 11
Views: 441

### Re: States of Matter

I do not believe that the states of matter have any effect on balancing chemical equations. However when given the states of matter in a problem, it is best if you include them when writing out the chemical equations for the reactions.
Mon Oct 08, 2018 8:25 pm
Forum: Molarity, Solutions, Dilutions
Topic: Homework problem E.21
Replies: 1
Views: 99

### Homework problem E.21

Hello! For part b) of problem E.21 in the 7th edition of the textbook, both of my answers for the amount of moles and molecules of HF included four significant figures because the problem initially gave the mass of HF to be 25.92 mg. However, in the solutions manual, the final answers for part b) ar...
Tue Oct 02, 2018 6:36 pm
Forum: SI Units, Unit Conversions
Topic: Scientific Notation
Replies: 11
Views: 498

### Scientific Notation

Does anyone know if we have to put our final answers after solving problems in scientific notation?
Tue Oct 02, 2018 6:24 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Mass calculation
Replies: 2
Views: 139

### Re: Mass calculation

I was curious about this too, because when I checked the molar mass I found it to be 176.12 gmol^-1. I believe the empirical formula is accurate even though the molar mass calculated is .02 off of the 176.14gmol^-1 given. I do not think it has to do with significant figures, but I would appreciate h...
Tue Oct 02, 2018 6:02 pm
Forum: Significant Figures
Topic: Significant Figures
Replies: 6
Views: 363

### Re: Significant Figures

Does anyone know why you would round to the nearest even number if the number ends in 5? For example if 2.85 was to have two significant figures, why would I write 2.8 instead of round up to 2.9? Thanks!

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