Search found 30 matches
- Sat Feb 07, 2015 2:37 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Calculating The Energy Changes When Heating An Ideal Gas
- Replies: 4
- Views: 3494
Re: Calculating The Energy Changes When Heating An Ideal Gas
Hi Jennifer, That was not the question I was asking, but thanks anyway! What I meant was why must the expansion process be broken down into two steps? (ie. heating at constant volume to the final temperature and allowing the gas to expand isothermally?) Why does the isothermal expansion in this ques...
- Wed Feb 04, 2015 12:10 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Calculating The Energy Changes When Heating An Ideal Gas
- Replies: 4
- Views: 3494
Calculating The Energy Changes When Heating An Ideal Gas
I do not really understand the concept in Example 7.6 in the textbook: Calculate the final temperature and the change in internal energy when 500.J of energy is transferred as heat to 0.900 mol O2(g) at 298K and 1.00 atm at (a) constant volume (b) constant pressure. Treat the gas as ideal. Why do th...
- Fri Jan 30, 2015 11:21 am
- Forum: Calculating Work of Expansion
- Topic: Isothermal reversible expansion
- Replies: 3
- Views: 3318
Re: Isothermal reversible expansion
I did use w=-nRT ln (V2/V1).
So now I've got -(2.00mol)(8.314J/Kmol)(300K)ln (18.00L/6.00L)=-5.48kJ
As deltaU=0, q=-w =+5.48kJ
But it says the final pressure is 1.20 at when it's supposed to be 1atm which confuses me!
Is there a typo?
So now I've got -(2.00mol)(8.314J/Kmol)(300K)ln (18.00L/6.00L)=-5.48kJ
As deltaU=0, q=-w =+5.48kJ
But it says the final pressure is 1.20 at when it's supposed to be 1atm which confuses me!
Is there a typo?
- Fri Jan 30, 2015 10:37 am
- Forum: Calculating Work of Expansion
- Topic: Isothermal reversible expansion
- Replies: 3
- Views: 3318
Isothermal reversible expansion
I am confused how to answer this question as it has conflicting information: If 2.00 mol of an ideal gas at 300 K and 3.00 atm expands isothermally and reversibly from 6.00 L to 18.00 L and has a final pressure of 1.20 atm, what is w, q, and delta u? Why are there changes in both the pressure and vo...
- Fri Jan 30, 2015 12:22 am
- Forum: Calculating Work of Expansion
- Topic: isothermal reversible expansion with V and P change
- Replies: 8
- Views: 2442
Re: isothermal reversible expansion with V and P change
When using U=3/2 nRT, how do we exactly find delta T? I'm rather confused about this step.
Aren't the moles and temperature constant in the process? How do we get delta T?
Aren't the moles and temperature constant in the process? How do we get delta T?
- Sun Jan 25, 2015 12:01 pm
- Forum: Calculating Work of Expansion
- Topic: Self Test 7.2A Comparing Reversible and Irreversible Expansi
- Replies: 1
- Views: 427
Self Test 7.2A Comparing Reversible and Irreversible Expansi
For this question I calculated the irreversible work: w=-(5.00atm)×(-1.00L) =(5.00Latm)×(101.325J) =506.625 =0.51kJ and the reversible work: w=-(0.100mol)×(8.314J/Kmol)×(303K)×ln(1.00L/2.00L) =174.61J =0.17kJ which is smaller than the value of the irreversible compression. However, the reversible co...
- Sun Jan 25, 2015 11:48 am
- Forum: Calculating Work of Expansion
- Topic: Sig Figs For Thermodynamic Problems?
- Replies: 2
- Views: 1325
Sig Figs For Thermodynamic Problems?
If the question contains a number with two sig figs like 30C, does this mean that all answers have to be 2 sig figs even though "30C" is not used in the question? For Self Test 7.2B, I got -0.20kJ and -1.7kJ for my answers so they had two sig figs. However, the answers are -202J and and 1....
- Sun Jan 11, 2015 3:33 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Are all combustions endothermic?
- Replies: 2
- Views: 9624
Re: Are all combustions endothermic?
You may be confused between the heat of the system and the heat of the surroundings. "Exothermic" and "endothermic" are used to describe the heat of a system. When combustion occurs, the heat of the surroundings INCREASES. This is due to the heat RELEASED from the system. The sys...
- Sat Dec 13, 2014 5:39 pm
- Forum: Photoelectric Effect
- Topic: Video: 2014 Fall Midterm Q4
- Replies: 1
- Views: 554
Video: 2014 Fall Midterm Q4
A video of me working though Q4 from the 2014 Fall Quarter Midterm.
- Sat Dec 13, 2014 4:26 pm
- Forum: Significant Figures
- Topic: Sig Figs in Titrant Volume
- Replies: 2
- Views: 621
Sig Figs in Titrant Volume
Let's say I've got a titrant volume of 25. To find the halfway volume, it would be 12.5 . If the answers have to have two sig figs, do I need to round it off to 12? (I think this would make the following calculations inaccurate.)
- Mon Dec 08, 2014 11:11 pm
- Forum: *Titrations & Titration Calculations
- Topic: Reason for doing Titrations
- Replies: 1
- Views: 457
Reason for doing Titrations
So this is just to confirm that I'm getting this right or not. We do titrations to figure out the concentration of the sample. 1. We know the moles, volume and concentration of the titrant because we made it. 2. We find the volume of the sample by reading off the graph at the stoichiometric point an...
- Thu Dec 04, 2014 7:25 pm
- Forum: Naming
- Topic: Writing the formula
- Replies: 2
- Views: 676
Writing the formula
I thought that we would need to write the ligands according to alphabetical order when writing the formula. However, I saw someone mention that Dr. Lavelle once said that the anions should be listed first then the neutral ions. So which is it? Can someone clarify this?
- Thu Dec 04, 2014 7:22 pm
- Forum: Naming
- Topic: Naming [Co(en)2(CN)Cl]Cl
- Replies: 5
- Views: 4471
Re: Naming [Co(en)2(CN)Cl]Cl
Both chloro and chlorido can be used. Chloro is the old version of naming and chlorido is the new IUPAC name for it. Dr. Lavelle mentioned that both will be accepted but we would generally use chloro in this class.
- Thu Dec 04, 2014 7:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Quiz 3 Preparation Fall 2013 Quiz: #10
- Replies: 9
- Views: 2115
Re: Quiz 3 Preparation Fall 2013 Quiz: #10
Hey Ellie, did you square the concentration of BrCl in your calculations? Coz if you didn't you would end up with 0.26 for your x value which would result in 0.54 + 2 (0.26) = 1.06 which becomes 1.1 after rounding off. Just a suggestion :)
- Wed Dec 03, 2014 10:25 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Quiz 3 Prep #8
- Replies: 1
- Views: 1784
Quiz 3 Prep #8
Consider the following reaction: NH4HS (s) <->NH3 (g) + H2S (g)
If the value of Kp is 0.11atm^2 at 300K, calculate the equilibrium partial pressure of NH3 (g) starting from pure NH4HS(s).
I'm confused about how to solve this question. Help please?
If the value of Kp is 0.11atm^2 at 300K, calculate the equilibrium partial pressure of NH3 (g) starting from pure NH4HS(s).
I'm confused about how to solve this question. Help please?
- Wed Dec 03, 2014 9:04 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Quiz 3 WB #10
- Replies: 6
- Views: 1466
Re: Quiz 3 WB #10
When writing out the expressions for the new equilibrium concentrations, I was confused at first as it didn't really seem as it was following Le Chatelier's principle. However, I went ahead and used 0.54-2x as it is a reactant. After solving the problem, I saw that Le Chatlier's principle would kick...
- Wed Dec 03, 2014 8:49 am
- Forum: Naming
- Topic: Chemical Formula
- Replies: 4
- Views: 1072
Re: Chemical Formula
According to Toolbox 16.1 of the textbook, it says we have to write the chemical symbols of ligands in alphabetical order. Therefore, it should be Cl first then NH3.
- Mon Nov 17, 2014 6:44 am
- Forum: Naming
- Topic: Ligands with Short Forms
- Replies: 1
- Views: 401
Ligands with Short Forms
When naming a complex with ligands like "en", "dien", "ox" or "edta" in it, Do we sort them based on alphabetical order or do we put them in front due to the number of bonds formed? Also, will we be ever required to write out the long form in the chemical form...
- Mon Nov 17, 2014 6:36 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Chelating complexes (16.33 and 16.34)
- Replies: 1
- Views: 627
Re: Chelating complexes (16.33 and 16.34)
Hi! In class, it was mentioned that two atoms separated by two atoms in the middle (with a shape of \_/) is the most convenient structure for bidentate ligands. According to this, the answer for both 16.33 and 16.34 is (b). There may be other possible structures but I'm not sure about those. Hope th...
- Wed Nov 05, 2014 8:38 am
- Forum: Lewis Structures
- Topic: Calculating Number of Electrons
- Replies: 2
- Views: 543
Calculating Number of Electrons
When drawing lewis structures, we add an electron for a negative charge. So, we should subtract an electron for a positive charge, right?
- Wed Nov 05, 2014 8:17 am
- Forum: Octet Exceptions
- Topic: Q9 Fall 2013 Quiz 2
- Replies: 2
- Views: 1612
Q9 Fall 2013 Quiz 2
This is from Q9 in the Fall 2013 Quiz 2 Prep.
Which of the following species has two unpaired electrons?
A. OF+ B. NO+ C. CO+
I don't really understand this question. Does "two unpaired electrons" mean biradicals? Can someone please explain how to approach this question? Thanks!
Which of the following species has two unpaired electrons?
A. OF+ B. NO+ C. CO+
I don't really understand this question. Does "two unpaired electrons" mean biradicals? Can someone please explain how to approach this question? Thanks!
- Wed Nov 05, 2014 8:09 am
- Forum: Ionic & Covalent Bonds
- Topic: Ionic Character and Covalent Character
- Replies: 4
- Views: 1950
Re: Ionic Character and Covalent Character
Just to add, when covalent character occurs, electrons of the atom with lower electronegativity will be pulled towards the atom with higher electronegativity.
- Mon Nov 03, 2014 6:32 pm
- Forum: Octet Exceptions
- Topic: Location of Unpaired Electron
- Replies: 3
- Views: 1076
Re: Location of Unpaired Electron
Which one gets completed first will be the one with the highest electronegativity (electronaffinity or ionization energy). So if there should be a lone pair, it should go to the one with the least electronegativity (electronaffinity or ionization energy). I was actually asking about free radicals. ...
- Mon Nov 03, 2014 3:59 am
- Forum: Octet Exceptions
- Topic: Location of Unpaired Electron
- Replies: 3
- Views: 1076
Location of Unpaired Electron
When drawing Lewis structures, where should I put the unpaired electron? Is there a rule for this?
- Mon Nov 03, 2014 3:27 am
- Forum: Resonance Structures
- Topic: Number of Resonance Structures
- Replies: 1
- Views: 437
Number of Resonance Structures
How many resonance structures can there be for a particular structure? Should we only consider the variations of structures with the best formal charge or all possible structures that conform to the correct number of electrons and the octet rule?
- Fri Oct 31, 2014 2:40 pm
- Forum: Coordinate Covalent Bonds
- Topic: Lewis Acid or Double Bond?
- Replies: 3
- Views: 1711
Re: Lewis Acid or Double Bond?
Oh I see. I tried using formal charge to see which is the best structure for the nitrate ion NO3 and it shows that for the double bond NO3, the single bond Os have an FC of -1 , the double bond oxygen has an FC of 0 and N has an FC of +1. However if N were to have 6 valence electrons it would result...
- Mon Oct 27, 2014 9:41 pm
- Forum: Coordinate Covalent Bonds
- Topic: Lewis Acid or Double Bond?
- Replies: 3
- Views: 1711
Lewis Acid or Double Bond?
In the course reader, it says boron trifluoride has only 6 valence electrons. It completes its octet if it forms a coordinate covalent bond with another atom. Why can't it complete its octet by having 8 valence electrons then share its electrons to have one double bond? On the other hand, the nitrat...
- Mon Oct 27, 2014 9:38 pm
- Forum: Ionic & Covalent Bonds
- Topic: Resonance Structure
- Replies: 3
- Views: 843
Re: Resonance Structure
Resonance is a blending of the structures that we have drawn. None of the lewis structures that we draw is the real structure. The lewis structures that we draw do not change quickly from one to another either. The actual structure is an average of the resonance structures so that more stable bonds ...
- Sun Oct 12, 2014 6:19 pm
- Forum: Properties of Light
- Topic: Diffraction and Incident Light
- Replies: 6
- Views: 1454
Re: Diffraction and Incident Light
Hi. I'm not really sure if what I say here is correct or not, but it helps me grasp the idea of why the waves are circular. I think that the shape of the waves depends on the size of the slit. Imagine a small slit, the waves would have to 'squeeze' through the slit so they become very circular. On t...
- Sun Oct 12, 2014 5:54 pm
- Forum: Properties of Electrons
- Topic: Atoms/ Molecules
- Replies: 2
- Views: 675
Re: Atoms/ Molecules
Hi there!
Atoms in a molecule are held together by covalent bonds. Covalent bonds occur when atoms share electrons with each other.
Hope this answers your question.
Atoms in a molecule are held together by covalent bonds. Covalent bonds occur when atoms share electrons with each other.
Hope this answers your question.