Search found 52 matches
- Wed Feb 13, 2019 10:58 am
- Forum: Calculating Work of Expansion
- Topic: Work of the system
- Replies: 3
- Views: 7
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: 10
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: 8
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: 5
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: 4
- Views: 18
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: 15
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: 73
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: 47
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: 3
- Views: 197
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: 35
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: 25
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: 26
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: 16
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: 20
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: 19
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: 16
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: 24
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: 22
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: 23
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: 57
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: 23
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: 9
- Views: 86
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: 36
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: 21
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: 32
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: 10
- Views: 167
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: 36
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: 55
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: 17
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: 29
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: 29
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: 30
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: 56
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: 48
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: 30
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: 62
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 7:01 pm
- Forum: Ionic & Covalent Bonds
- Topic: 2A.19 7th edition
- Replies: 3
- Views: 49
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 8:56 pm
- Forum: Lewis Structures
- Topic: How to determine central atom
- Replies: 8
- Views: 93
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 8:53 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Ag+ Configuration
- Replies: 5
- Views: 218
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 8:48 pm
- Forum: *Black Body Radiation
- Topic: Midterm
- Replies: 4
- Views: 104
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 1:39 pm
- Forum: Properties of Light
- Topic: Power calculations
- Replies: 6
- Views: 137
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 9:34 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Magnetic Quantum Number
- Replies: 3
- Views: 45
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 9:26 pm
- Forum: Einstein Equation
- Topic: De Broglie's
- Replies: 4
- Views: 79
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 2:41 pm
- Forum: Einstein Equation
- Topic: Units of Energy
- Replies: 5
- Views: 90
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 2:34 pm
- Forum: Properties of Light
- Topic: Week 3 HW
- Replies: 5
- Views: 100
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 2:25 pm
- Forum: Properties of Light
- Topic: color of light
- Replies: 11
- Views: 132
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 7:43 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Finding the volume of stock solution to dilute
- Replies: 12
- Views: 166
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 7:31 pm
- Forum: Balancing Chemical Reactions
- Topic: States of Matter
- Replies: 11
- Views: 131
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 7:25 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Homework problem E.21
- Replies: 1
- Views: 36
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 5:36 pm
- Forum: SI Units, Unit Conversions
- Topic: Scientific Notation
- Replies: 11
- Views: 142
Scientific Notation
Does anyone know if we have to put our final answers after solving problems in scientific notation?
- Tue Oct 02, 2018 5:24 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Mass calculation
- Replies: 2
- Views: 48
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 5:02 pm
- Forum: Significant Figures
- Topic: Significant Figures
- Replies: 6
- Views: 80
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!