Search found 105 matches
- Fri Mar 13, 2020 8:44 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Concentration Cells
- Replies: 8
- Views: 740
Re: Concentration Cells
The standard E cell potential will be 0. However, current is driven by the difference in concentration of the ions, which move from a higher concentration to a lower concentration.
- Fri Mar 13, 2020 8:41 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: electrochemical series
- Replies: 4
- Views: 407
Re: electrochemical series
The more positive the electrode, the more oxidizing the reactant. By looking at the electrochemical series, you can determine which reactants would be better oxidizing or reducing agents.
- Fri Mar 13, 2020 8:33 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Different electrodes
- Replies: 2
- Views: 248
Re: Different electrodes
An inert electrode (Pt) should be used if the reactants cannot act as an electrode. For example, if you have ions or gases then Pt is needed. However, if you have a solid metal, then it can be used as the electrode.
- Fri Mar 13, 2020 8:18 pm
- Forum: Balancing Redox Reactions
- Topic: intensive and extensive
- Replies: 3
- Views: 229
Re: intensive and extensive
Cell potentials are intensive properties. This means that they are independent of the quantity of material present. Thus, multiplying half-reactions when balancing a redox equation does not affect the value of the potential for the reaction.
- Fri Mar 13, 2020 8:11 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Outline 6 Learning Objective
- Replies: 3
- Views: 398
Re: Outline 6 Learning Objective
This learning objective relates to the homework questions 7A.1 and 7A.3. You need to look at the overall stoichiometric coefficients of the equation.
- Sat Mar 07, 2020 10:20 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: 6L.1
- Replies: 2
- Views: 277
Re: 6L.1
In order to find the number of electrons transferred you need to find the two half reactions. Then you need to multiply the half reactions in order to have the same number of electrons transferred in each reaction, which allow the electrons to cancel in the overall reaction. This would give the over...
- Sat Mar 07, 2020 10:13 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6.73
- Replies: 2
- Views: 295
Re: 6.73
The half reaction with the highest standard potential is the cathode. E cell needs to be positive in order for the reaction to be spontaneous.
- Sat Mar 07, 2020 10:08 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6M.11
- Replies: 4
- Views: 438
Re: 6M.11
If the reactant or product is an ion, it is usually aqueous, but if it has no charge then it is in its standard state (solid or gas).
- Sat Mar 07, 2020 10:06 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Question 6.65
- Replies: 2
- Views: 266
Re: Question 6.65
There is also a typo in this question and in the solutions manual. You should find the range in pH from 0 to 14.
- Sat Mar 07, 2020 10:02 pm
- Forum: Balancing Redox Reactions
- Topic: Cathode and Anode
- Replies: 24
- Views: 1632
Re: Cathode and Anode
The work done by the cell is is equal to the change in gibbs free energy. Based on the equation deltaG=-nFE, E needs to be positive so that energy is released (deltaG is negative) and thus the cell does work.
- Sat Feb 29, 2020 10:49 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Gibbs free energy and 6L.1
- Replies: 3
- Views: 283
Re: Gibbs free energy and 6L.1
For the oxidation, 3I- ->I3- +2e-. Since the charges need to balanced on both sides, 2e- need to be added (the charge of the left side is -3 and the charge of the right side is -1). Since there are 2 moles of e- transferred, n=2
- Sat Feb 29, 2020 10:42 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: 6L. 1
- Replies: 2
- Views: 275
Re: 6L. 1
To find n (which are the moles of electrons in a balanced redox reaction) just look at the redox reaction and determine how many electrons are involved. It might be easier to see how many e- are involved by finding the half redox reactions.
- Sat Feb 29, 2020 10:34 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6N.5 a
- Replies: 2
- Views: 251
Re: 6N.5 a
Based on the rule of logs:
0.06V=-0.0129V*In[H+]^2
0.06V=-0.0129V*2*In[H+] since log(x^2)=2log(x)
0.06V=-0.0258V*In[H+]
0.06V=-0.0258V*2.303log[H+]
pH=0.06V/(2.303)*(0.025693V)=1
0.06V=-0.0129V*In[H+]^2
0.06V=-0.0129V*2*In[H+] since log(x^2)=2log(x)
0.06V=-0.0258V*In[H+]
0.06V=-0.0258V*2.303log[H+]
pH=0.06V/(2.303)*(0.025693V)=1
- Sat Feb 29, 2020 10:28 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6N.15
- Replies: 1
- Views: 202
Re: 6N.15
This is a concentration cell so Enot=0V. The Nernst equation can be used to find the cell potential.
- Sat Feb 29, 2020 10:23 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6.57
- Replies: 3
- Views: 352
Re: 6.57
Using the appendix you find that F2+ 2e- -> 2F- gives a value of Enot of +2.87V. Then by using the equation Enot (cathode)- Enot (anode), you can find Enot cell. Then using the equation InK=nFEnot/RT you can find K. To find Ka, just find the square root of K.
- Sat Feb 22, 2020 9:54 pm
- Forum: Balancing Redox Reactions
- Topic: Reducing agent/oxidizing agent
- Replies: 5
- Views: 406
Re: Reducing agent/oxidizing agent
The reducing agent is the reactant being oxidized and the oxidizing agent is the reactant being reduced. For most of these reactions, you need to look at the change in oxidation state of the element.
- Sat Feb 22, 2020 9:42 pm
- Forum: Balancing Redox Reactions
- Topic: Basic conditions
- Replies: 6
- Views: 429
Re: Basic conditions
In a basic solution you add OH- to balance H and in an acidic solution you add H+
- Sat Feb 22, 2020 9:41 pm
- Forum: Balancing Redox Reactions
- Topic: Hw problem 6k.5 b)
- Replies: 2
- Views: 240
Re: Hw problem 6k.5 b)
Br2 is both the oxidizing and reducing agent since it is the only reactant. You have the balance the reduction half reaction and the oxidation half reaction and then combine both reactions.
- Sat Feb 22, 2020 9:33 pm
- Forum: Balancing Redox Reactions
- Topic: 6K. 5a)
- Replies: 5
- Views: 406
Re: 6K. 5a)
You have to first balance the Os and then balance the Hs giving 6OH- + 3H2O +Br- ---> BrO3- + 6H2O. Then you need to balance the charge by adding electrons in order to ensure the charge is equal on both sides of the equations. This gives the half equation 6OH- + 3H2O +Br- ---> BrO3- + 6H2O +6e-
- Sat Feb 22, 2020 9:27 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidizing Agents (6K.5)
- Replies: 2
- Views: 228
Re: Oxidizing Agents (6K.5)
All free uncombined elements have an oxidation number of zero. The oxidation numbers of O2 and O3 are both 0.
- Sat Feb 15, 2020 8:56 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isothermal irreversible reactions
- Replies: 3
- Views: 330
Re: Isothermal irreversible reactions
The internal energy is dependent on temperature and an isothermal reaction takes place at constant temperature. Thus, in any isothermal process involving only ideal gases, delta U=0. This is because the energy gained as heat (q) is equal to the amount of work done by the system (q = -w).
- Sat Feb 15, 2020 8:48 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isothermal Reactions
- Replies: 4
- Views: 346
Re: Isothermal Reactions
In an isothermal process, the temperature is constant. The energy lost in the expansion of the gas is gained by incoming heat so the internal energy change is zero, since internal energy is dependent on temperature.
- Sat Feb 15, 2020 8:37 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Comparing standard molar entropies
- Replies: 6
- Views: 490
Re: Comparing standard molar entropies
There are more possible arrangements of atoms for larger, more complex molecules, increasing the number of possible microstates. So the value of W will be larger, thus causing a larger value of S.
- Sat Feb 15, 2020 8:34 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Different Types of Entropies
- Replies: 6
- Views: 550
Re: Different Types of Entropies
Also when the reaction is reversible delta S total=0 so delta S system= - delta S surroundings
- Fri Feb 14, 2020 2:54 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Midterm Curve
- Replies: 45
- Views: 2275
Re: Midterm Curve
My TA said he will most likely curve the midterm because most people did very bad.
- Fri Feb 07, 2020 10:50 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Molar Entropy
- Replies: 4
- Views: 281
Re: Molar Entropy
Molar entropy is the entropy content of one mole of substance (under a standard state if it is standard molar entropy). The entropy of a substance depends on the amount of substance (extensive property) so it can be described in terms of moles.
- Fri Feb 07, 2020 10:44 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Energy Change
- Replies: 4
- Views: 218
Re: Energy Change
A spontaneous reaction releases energy (it is favorable), and so the sign of ΔG (which is the energy available to do work) must be negative.
- Fri Feb 07, 2020 10:39 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff
- Replies: 6
- Views: 373
Re: Van't Hoff
He hasn't taught this yet. We will learn it after the midterm.
- Fri Feb 07, 2020 10:38 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: open system
- Replies: 5
- Views: 447
Re: open system
An open system allows matter and energy to be exchanged with surroundings. In this case, moles of gas (being matter) and heat (energy) can be transferred to the environment.
- Fri Feb 07, 2020 10:34 pm
- Forum: Phase Changes & Related Calculations
- Topic: Homework 4C 13
- Replies: 7
- Views: 380
Re: Homework 4C 13
For this question, why do we use the specific heat capacity of liquid water instead of ice?
- Fri Jan 31, 2020 3:02 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Types of Systems
- Replies: 4
- Views: 301
Re: Types of Systems
Another example of a closed system would be a pot with a lid because energy can be exchanged with the surroundings.
- Fri Jan 31, 2020 2:58 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Open vs. Closed Internal Energies
- Replies: 3
- Views: 165
Re: Open vs. Closed Internal Energies
The energy of a closed system can be changed by heating/cooling or compression/expansion. So Change in U=q + w. But if the change in volume is 0 (constant volume) then there is no expansion work.
- Fri Jan 31, 2020 2:46 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Test 1 #5
- Replies: 7
- Views: 328
Re: Test 1 #5
I found that the pOH was 12.4
- Fri Jan 31, 2020 2:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Test 1 # 4
- Replies: 10
- Views: 386
Re: Test 1 # 4
You use PV=nRT and then find the number of moles (n). They forgot to give us the molar mass of Xenon on the test but you have to multiply moles by molar mass and it will give you the mass.
- Fri Jan 31, 2020 2:42 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Volume and Pressure
- Replies: 8
- Views: 280
Re: Volume and Pressure
Based on Boyle's law Boyle's volume of a gas have an inverse relationship as long as temperature is held constant. As seen from PV=nRT, if volume increases, then pressure decreases and vice versa.
- Fri Jan 24, 2020 2:21 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Polyprotic Acids
- Replies: 6
- Views: 450
Re: Polyprotic Acids
Polyprotic acids can donate more than one proton. Protons are donated with the acidity constant (K) decreasing significantly with each proton lost Ka1>>ka2>>ka3. However, for most polyprotic acids (except Sulfuric acid), only the first deprotonation (Ka1) should be taken into account since all subse...
- Fri Jan 24, 2020 2:15 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: polyprotic acids
- Replies: 2
- Views: 158
Re: polyprotic acids
H2SO4 is the only strong polyprotic acid and it is the most common for which deprotonation can be complete. The second deprotonation adds to H3O+ concentration so the overall pH of the solution is slightly lower due to first deprotonation alone. All the other polyprotic acids should be treated as we...
- Fri Jan 24, 2020 2:09 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6D.3
- Replies: 3
- Views: 295
Re: 6D.3
It is a base so you need to find the pOH from the pH. Using the pOH, you can then find the concentration of OH- and from that calculate Kb.
- Fri Jan 24, 2020 2:06 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook Problem 5.35
- Replies: 2
- Views: 128
Re: Textbook Problem 5.35
You have to look at the ratio of change for each reactant/product. Since the change is double for C (10) and A (-10) compared to B (5), that means that the reaction is 2A -> B + 2C.
- Fri Jan 24, 2020 2:02 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Test 1 Practice Worksheet #5
- Replies: 6
- Views: 273
Re: Test 1 Practice Worksheet #5
I also got 8.62. You have to convert pKa to pKb
- Fri Jan 17, 2020 12:19 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: pressure change
- Replies: 4
- Views: 154
Re: pressure change
If the volume decreases and more moles of gas are on the left, the reaction shifts to the right. If the volume decreases and there are more moles of gas on the right, then the reaction shifts to the left. The reaction responds to minimize the effect of increasing pressure (by decreasing volume).
- Fri Jan 17, 2020 12:16 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 5
- Views: 448
Re: Le Chatelier's Principle
Le Chatelier's principle states that chemical reactions adjust so as to minimize the effect of changes, which applies to temperature, pressure and concentration.
- Fri Jan 17, 2020 12:11 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Endo/Exothermic Reactions
- Replies: 6
- Views: 388
Re: Endo/Exothermic Reactions
The bond of X2 is broken which requires energy so it is endothermic.
- Fri Jan 17, 2020 12:07 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: inert gas added
- Replies: 4
- Views: 157
Re: inert gas added
Adding an inert gas at constant volume will change the total pressure but not the partial pressures of the other gases in the container. The number of moles per unit volume remains the same so the equilibrium does not change
- Fri Jan 17, 2020 12:04 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert Gas does not change pressure?
- Replies: 7
- Views: 290
Re: Inert Gas does not change pressure?
Increasing the pressure by adding an inert gas at constant volume has no effect because only the partial pressures of the reactants and products are important. Adding an inert gas at constant volume will change the total pressure but not the partial pressures of the other gases in the container. The...
- Wed Jan 08, 2020 3:11 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Reverse reaction
- Replies: 6
- Views: 272
Re: Reverse reaction
Based on le Châtelier’s Principle, when we make changes to a reaction at equilibrium, the equilibrium will respond by trying to undo the change. For example, if the concentration of products increases, then the reaction forming reactants is favored (reverse reaction). Additionally, if the forward re...
- Wed Jan 08, 2020 2:58 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Solvents
- Replies: 5
- Views: 163
Re: Solvents
The change in solvent concentration is insignificant because it is in excess.
- Wed Jan 08, 2020 2:56 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: solids and liquids
- Replies: 2
- Views: 99
Re: solids and liquids
The molar concentration of a pure substance does not change in a reaction so solids and liquids are not included in K expression.
- Wed Jan 08, 2020 2:54 pm
- Forum: Ideal Gases
- Topic: Q and K
- Replies: 7
- Views: 293
Re: Q and K
Q is the reaction quotient while K is the equilibrium constant. Q is used to determine which direction a reaction will shift to reach equilibrium. If K > Q, the reaction will proceed forward but if K < Q, the reaction will proceed in the reverse direction.
- Wed Jan 08, 2020 2:47 pm
- Forum: Ideal Gases
- Topic: K and Q
- Replies: 13
- Views: 376
Re: K and Q
Q is the reaction quotient. It can be used to determine which direction a reaction will shift to reach equilibrium based on the value of K, the equilibrium constant. If Q = K then the system is already at equilibrium.
- Sun Dec 08, 2019 10:52 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 14A FInal
- Replies: 6
- Views: 520
Re: 14A FInal
We will get it back the second week of winter quarter
- Sun Dec 08, 2019 10:50 pm
- Forum: Bond Lengths & Energies
- Topic: Dissociation Bond Length
- Replies: 3
- Views: 497
Re: Dissociation Bond Length
I don't think so. However, we should know how to compare which molecule would have a higher dissociation energy.
- Sun Dec 08, 2019 10:47 pm
- Forum: Air Pollution & Acid Rain
- Topic: Final Exam
- Replies: 5
- Views: 809
Re: Final Exam
He also said we should do acid rain problems from the textbook
- Fri Dec 06, 2019 3:17 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: Question 6D.11
- Replies: 2
- Views: 296
Re: Question 6D.11
I was also really confused by this problem. However, this link helped: https://chemed.chem.purdue.edu/genchem/ ... metals.php
- Fri Dec 06, 2019 3:13 pm
- Forum: Air Pollution & Acid Rain
- Topic: Acid Rain textbook
- Replies: 1
- Views: 325
Acid Rain textbook
Dr. Lavelle said in lecture that we should work on acid rain problems from the textbook. However, none of the homework problems refer to acid rain. I was wondering what pages in the textbook refer to acid rain and what problems is he referring to?
- Fri Nov 29, 2019 9:44 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Inorganic vs Organic Acids
- Replies: 3
- Views: 261
Re: Inorganic vs Organic Acids
What pages can I find information about organic vs. inorganic acids in the textbook?
- Fri Nov 29, 2019 9:37 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: identifying acids and bases
- Replies: 4
- Views: 358
Re: identifying acids and bases
By drawing out the lewis structures, you can see the electron arrangement around the atom. If the atom can donate an electron pair (for example has lone pairs) then it is a lewis base. If the atom is likely to gain electrons, then it is a lewis acid.
- Fri Nov 29, 2019 9:30 pm
- Forum: Conjugate Acids & Bases
- Topic: Delocalization of charge and stability
- Replies: 4
- Views: 1040
Re: Delocalization of charge and stability
Does it say this in the textbook or did Dr. Lavelle mention it in lecture? If it is in the textbook, what page?
- Fri Nov 29, 2019 9:26 pm
- Forum: Conjugate Acids & Bases
- Topic: NH3, acid or base?
- Replies: 12
- Views: 8246
Re: NH3, acid or base?
Ammonia is a weak base. It reacts with water to produce ammonium ions and hydroxide ions.
- Fri Nov 29, 2019 9:20 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: pH vs. pOH
- Replies: 17
- Views: 2502
Re: pH vs. pOH
If you have the pH of a solution, you can calculate its pOH or vice versa. For example, if the pH is 2 then the pOH will be 14-2=12
- Fri Nov 22, 2019 8:13 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Ionic
- Replies: 6
- Views: 460
Re: Ionic
Intramolecular forces are the forces that hold atoms together within a molecule (covalent, ionic bonds). Intermolecular forces are forces that exist between molecules (dipole-dipole, hydrogen bonding, London dispersion interactions).
- Fri Nov 22, 2019 8:05 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: london forces
- Replies: 9
- Views: 500
Re: london forces
The molecule with the highest molar mass (and so size and number of electrons) has the highest polarisability so the electrons in the electron cloud can easily be distorted so it has the strongest london dispersion interactions.
- Fri Nov 22, 2019 8:01 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polar vs. Nonpolar
- Replies: 6
- Views: 319
Re: Polar vs. Nonpolar
I understand that CH2Cl2 is polar because a tetrahedral shape isn't completely symmetrical. However if a shape is symmetrical like a square planar would it be considered nonpolar? For example if it was a square planar with two Cl and two H atoms around a central atom, would it be considered non pol...
- Fri Nov 22, 2019 7:59 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polarity
- Replies: 7
- Views: 319
Re: Polarity
A non polar molecule can have polar bonds. If the VSEPR shape is symmetrical, the dipoles can cancel out making the molecule non-polar.
- Fri Nov 22, 2019 7:56 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: polar vs non polar
- Replies: 6
- Views: 417
Re: polar vs non polar
Victoria Otuya 4F wrote:Does a non-polar molecule mean it has a Dipole-Dipole intermolecular force?
A polar molecule has dipole-dipole interactions. A non-polar molecule has London dispersion interactions (induced-dipole induced-dipole)
- Sat Nov 16, 2019 5:57 pm
- Forum: Bond Lengths & Energies
- Topic: bond lengths
- Replies: 3
- Views: 212
Re: bond lengths
Bond length is determined by the strength of the bond so the stronger the bond, the shorter the length. Single bond is the longest, then double bond and triple bond is the shortest. However, the size of the atom can determine the length of the single bond.
- Sat Nov 16, 2019 5:50 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Melting Points
- Replies: 7
- Views: 484
Re: Melting Points
You should be able to assume the which molecule would have a higher or lower melting point based on their shape and strength of interactions/bonds.
- Sat Nov 16, 2019 5:45 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR and Polarity
- Replies: 4
- Views: 143
Re: VSEPR and Polarity
If one atom is more electronegative than the other, there will be a dipole moment. Although the bonds are polar, the molecule will not if the shape is symmetrical causing the dipoles to cancel out.
- Sat Nov 16, 2019 5:40 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Repulsion
- Replies: 3
- Views: 228
Re: Repulsion
I think we just need to know the number of regions of electrons dedicates the shape and Lone pair>triple>double>single bonds in terms of repulsion.
- Sat Nov 16, 2019 5:36 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Hydrogen Bonding
- Replies: 6
- Views: 416
Re: Hydrogen Bonding
Hydrogen bonding is a special type of Dipole-Dipole as it is considered stronger than a regular dipole-dipole force.
- Fri Nov 08, 2019 7:12 pm
- Forum: Electronegativity
- Topic: memorizing tables
- Replies: 9
- Views: 344
Re: memorizing tables
You do not need need to memorise any values for electronegativity. The only thing you need to know is the trend across a period and down the group in order to be able to assume which element is more/less electronegative than another.
- Fri Nov 08, 2019 7:04 pm
- Forum: Lewis Structures
- Topic: Formal Charges
- Replies: 15
- Views: 981
Re: Formal Charges
505106414 wrote:Is it okay to break the octet rule in order to minimize formal charge?
You can break the octet rule only if the element can hold more than 8 electrons (starting 3p)
- Fri Nov 08, 2019 6:59 pm
- Forum: Dipole Moments
- Topic: Dipole Moments
- Replies: 5
- Views: 462
Re: Dipole Moments
Dipole moments occur because of a separation of charge (caused by a difference in electronegativity). The more electronegative element has the greater share of the electrons than less electronegative element causing it to have a net negative charge. The larger the difference in electronegativity, th...
- Fri Nov 08, 2019 6:54 pm
- Forum: Dipole Moments
- Topic: Relationship with Boiling Point and Shape
- Replies: 2
- Views: 243
Re: Relationship with Boiling Point and Shape
Branched molecules will have a lower boiling point than straight chain molecules because the intermolecular forces are reduced.
- Fri Nov 08, 2019 6:48 pm
- Forum: Bond Lengths & Energies
- Topic: dissociation energy
- Replies: 5
- Views: 372
Re: dissociation energy
Dissociation energy is based on bond strength. The shorter the bond, the stronger it is resulting in a higher dissociation energy. For example, triple bonds have the highest dissociating energy and single bonds have the lowest.
- Fri Nov 08, 2019 6:45 pm
- Forum: Bond Lengths & Energies
- Topic: bond length rules
- Replies: 2
- Views: 286
Re: bond length rules
There are no exceptions: single bond (longest) > double bond > triple bond (shortest) except for resonance structures in which the electrons are delocalised across all bonds.
- Fri Nov 08, 2019 6:41 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Showing Work
- Replies: 6
- Views: 304
Re: Showing Work
You don't need to show the calculation for formal charge as most people directly use the shortcut, but showing work can give you some marks incase you make a calculation error.
- Fri Nov 01, 2019 10:52 pm
- Forum: *Particle in a Box
- Topic: Topic 1C
- Replies: 3
- Views: 503
Re: Topic 1C
I don't think we need to know the material from Topic 1C. He did not talk about most of the information from that section.
- Fri Nov 01, 2019 10:50 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: 1 B27
- Replies: 5
- Views: 531
Re: 1 B27
I am confused as to why we use 5 as the uncertainty in velocity. Aren't we suppose to use 10 as it is +-5m/s?
- Fri Nov 01, 2019 10:46 pm
- Forum: *Shrodinger Equation
- Topic: Schrodinger's equation
- Replies: 2
- Views: 298
Re: Schrodinger's equation
A wavefunction is a mathematical function with values that vary with position. It can give the probability of finding the particle in a region proporitional to the value of the wavefunction squared in that region. Schrodinger's equation is used to calculate the wavefunction for any particle.
- Fri Nov 01, 2019 10:42 pm
- Forum: *Shrodinger Equation
- Topic: wave function
- Replies: 3
- Views: 375
Re: wave function
No, Dr. Lavelle said to omit Topic 1C from the textbook.
- Fri Nov 01, 2019 10:40 pm
- Forum: *Shrodinger Equation
- Topic: shrodinger equation
- Replies: 4
- Views: 288
Re: shrodinger equation
The Schrodinger equation is used to calculate both the wavefunction and the corresponding energy. There is a lot of information about it in Topic 1C in the textbook but we do not need to read that section.
- Fri Nov 01, 2019 10:33 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Work function units
- Replies: 5
- Views: 327
Re: Work function units
Yes, the work function should always be in Joules so the units can later cancel out
- Wed Oct 23, 2019 11:34 am
- Forum: Trends in The Periodic Table
- Topic: Electron Affinity Trends
- Replies: 5
- Views: 656
Re: Electron Affinity Trends
As you go down a group, electron affinity decreases as there is more shielding which decreases the electrostatic attraction between the nucleus and electrons, resulting in less energy released when e- is added to a gas phase atom. However, as you move across the period, electron affinity increases a...
- Wed Oct 23, 2019 11:28 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Writing Electron Configurations Help
- Replies: 3
- Views: 174
Re: Writing Electron Configurations Help
This confused me as well and I am not sure about the textbook. However, in a test the electron configuration should definitely be written from lowest to highest energy level.
- Wed Oct 23, 2019 11:22 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: 4s and 3d
- Replies: 5
- Views: 193
Re: 4s and 3d
The 4s is filled first because it is at a lower energy than 3d. However, Dr. Lavelle wants us to put them from lowest to highest energy level (3d and then 4s) because 4s is ionized first.
- Wed Oct 23, 2019 11:17 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron Configurations
- Replies: 4
- Views: 204
- Wed Oct 23, 2019 11:13 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Exceptions to Electron Configurations
- Replies: 3
- Views: 117
Re: Exceptions to Electron Configurations
Cu and Cr are only one electron away from being in a more stable state. A completely full or half full d sub-level is more stable than a partially filled d sub-level.
- Thu Oct 17, 2019 1:12 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Atomic Radius
- Replies: 18
- Views: 664
Re: Atomic Radius
We won't need to calculate the value of atomic radius. If needed, the values should be given to us.
- Thu Oct 17, 2019 1:04 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Electron configurations
- Replies: 2
- Views: 144
Re: Electron configurations
3d has lower energy when 4s is filled. You should list them in order of energy level
- Thu Oct 17, 2019 12:53 am
- Forum: Properties of Light
- Topic: How does light have momentum but we assume it has no mass?
- Replies: 4
- Views: 202
Re: How does light have momentum but we assume it has no mass?
Light does have momentum however the equation m*v cannot be used in this case to calculate momentum
- Thu Oct 17, 2019 12:41 am
- Forum: Significant Figures
- Topic: Tests and Significant Figures
- Replies: 6
- Views: 363
Re: Tests and Significant Figures
They remove points on tests if the answer does not include the correct number of significant figures (more or less).
- Thu Oct 17, 2019 12:36 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Test 1 [ENDORSED]
- Replies: 107
- Views: 22283
Re: Test 1 [ENDORSED]
DesireBrown3K wrote:Would we be able to go to office hours and review our test with a TA for any problems we got incorrect?
Yes, our TA said to come to office hours if we have questions about the test
- Wed Oct 09, 2019 11:17 am
- Forum: Limiting Reactant Calculations
- Topic: M.9 hw prob
- Replies: 4
- Views: 221
Re: M.9 hw prob
The net ionic equation only lists the species participating in the reaction. We should learn it later in the course so don't worry too much about it for now.
- Wed Oct 09, 2019 11:12 am
- Forum: Molarity, Solutions, Dilutions
- Topic: Polyatomic ions on Test 1
- Replies: 4
- Views: 266
Re: Polyatomic ions on Test 1
The test will provide the chemical formula or equation so we don't need to know polyatomic ions for this test
- Wed Oct 09, 2019 11:09 am
- Forum: Molarity, Solutions, Dilutions
- Topic: E.9
- Replies: 3
- Views: 366
Re: E.9
My TA said we will go over writing formulas later in the course and for now they will provide the formulas on the test.
- Wed Oct 09, 2019 11:06 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Test Equation Sheet
- Replies: 8
- Views: 456
Re: Test Equation Sheet
They include basic equations and unit conversions
- Wed Oct 09, 2019 11:02 am
- Forum: Significant Figures
- Topic: Significant Figures for Test 1
- Replies: 3
- Views: 268
Re: Significant Figures for Test 1
My TA said that they are not very strict regarding significant figures on tests
- Wed Oct 09, 2019 10:59 am
- Forum: Administrative Questions and Class Announcements
- Topic: Week 2 Homework Problems [ENDORSED]
- Replies: 67
- Views: 7833
Re: Week 2 Homework Problems [ENDORSED]
Maya Pakulski 3D wrote:Jaklin Astvatsatryan 3G wrote:Lauren Sanchez 3D wrote:Just to make sure, the homework problems are now due during our actual discussions right?
Yes. Our TA's will be collecting them the day of your discussion.
Our answers on chemistry community will always be due Sunday night though right?
yes, the 5 posts on chemistry community are due Sunday
- Wed Oct 02, 2019 11:12 am
- Forum: Limiting Reactant Calculations
- Topic: Question about E9 [ENDORSED]
- Replies: 3
- Views: 225
Re: Question about E9 [ENDORSED]
Our TA said we shouldn't worry about that until chemistry 14B as they will usually give as the formula