Search found 106 matches
- Tue Mar 10, 2020 11:25 pm
- Forum: Administrative Questions and Class Announcements
- Topic: What is the plan for the final?
- Replies: 16
- Views: 1001
Re: What is the plan for the final?
Along with the final, there will probably be information too about the review sessions and office hours in an upcoming email.
- Tue Mar 10, 2020 11:24 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 2 Grades
- Replies: 22
- Views: 1152
Re: Test 2 Grades
As a last result: If you can't get your test back try asking some friends who had their discussion on Tuesday and look at the answers?
- Tue Mar 10, 2020 11:21 pm
- Forum: Administrative Questions and Class Announcements
- Topic: ENDGAME Review Session
- Replies: 71
- Views: 5467
Re: ENDGAME Review Session
Thank you Lyndon so much for your kindness and compassion when teaching chem 14A/B to us!! We didn't know it at the time, but we were all looking for someone to relate difficult concepts and share funny jokes during workshops. Keep working hard and we will always support you!
- Tue Mar 10, 2020 11:14 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Homework 10
- Replies: 11
- Views: 646
Re: Homework 10
I would just send pictures of the homework to them just in case.
- Tue Mar 10, 2020 11:12 pm
- Forum: Administrative Questions and Class Announcements
- Topic: review sessions and office hours
- Replies: 6
- Views: 515
Re: review sessions and office hours
I think we'll know by tomorrow with an email announcement.
- Thu Mar 05, 2020 9:36 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: lnQ vs logQ
- Replies: 5
- Views: 359
Re: lnQ vs logQ
For the log equation you use it at standard conditions (25 degrees celsius) and the lnQ equation can be used in any situations. My personal preference is the lnQ equation since you can still get the same answer as the log one and don't have to worry about knowing when to apply it.
- Thu Mar 05, 2020 9:34 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: writing cell diagramsl
- Replies: 4
- Views: 284
Re: writing cell diagramsl
Yes I think H2O is the only one left out.
- Thu Mar 05, 2020 9:32 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Platinum in cell diagrams
- Replies: 5
- Views: 311
Re: Platinum in cell diagrams
Now in cases where you don't need Pt(s) is when you already have a conductive solid metal in the solution.
- Thu Mar 05, 2020 9:31 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: finding n in G=-nFE
- Replies: 15
- Views: 979
Re: finding n in G=-nFE
When you find the half reactions, n is the least common multiple of their shared electrons. So you would have to balance them. (Usually n is either 1 or 2).
- Thu Mar 05, 2020 9:28 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Gibbs free energy and balancing redox reactions
- Replies: 2
- Views: 241
Re: Gibbs free energy and balancing redox reactions
Yes so you would find the half reactions and balance them to find the least common multiple of their transferred electrons in the final equation. (Usually it's 1 or 2 in the electrons transferred.)
- Wed Feb 26, 2020 3:48 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Vant Hoff Equation
- Replies: 9
- Views: 696
Re: Vant Hoff Equation
Van't Hoff's Equation along with the Nernst Equation we should know how to derive and calculate both.
- Wed Feb 26, 2020 3:44 pm
- Forum: Van't Hoff Equation
- Topic: Van’t Hoff Equation
- Replies: 11
- Views: 905
Re: Van’t Hoff Equation
Van't Hoff's equation is:
ln(K2/K1)= (-DeltaH/R)(1/T2 - 1/T1)
So the equation relates enthalpy too but this value should be given in the problem.
ln(K2/K1)= (-DeltaH/R)(1/T2 - 1/T1)
So the equation relates enthalpy too but this value should be given in the problem.
- Wed Feb 26, 2020 3:41 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Deriving the Nernst Equation
- Replies: 1
- Views: 130
Re: Deriving the Nernst Equation
You need 2 formulas:
1. DeltaG=-nFE*
2. DeltaG=DeltaG* + RTlnQ
Combine rections:
-nFE(cell)=-nFE*(cell)+RTlnQ
Therefore,
E(cell)= E*(cell)-(RT/nF)lnQ
It is also important to know that at 25 degrees C (so standard conditions),
E(cell)= E*(cell) - (0.0592V/n)logQ
1. DeltaG=-nFE*
2. DeltaG=DeltaG* + RTlnQ
Combine rections:
-nFE(cell)=-nFE*(cell)+RTlnQ
Therefore,
E(cell)= E*(cell)-(RT/nF)lnQ
It is also important to know that at 25 degrees C (so standard conditions),
E(cell)= E*(cell) - (0.0592V/n)logQ
- Wed Feb 26, 2020 3:36 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L.5
- Replies: 2
- Views: 229
Re: 6L.5
When you write the half reactions, you need to have the solid in the equation because it is in its most stable form (gain of electrons to eliminate the +1 and +3 charge in Au). When we are writing the cell notation, we still need to include the solid since it is in our half reactions with a bar sepa...
- Wed Feb 26, 2020 3:29 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff equation
- Replies: 11
- Views: 1232
Re: Van't Hoff equation
The Van't Hoff equation relates K with temperature. K1 corresponds with T1 and K2 corresponds to T2.
- Sat Feb 22, 2020 3:51 pm
- Forum: Balancing Redox Reactions
- Topic: Calculating the reaction Gibbs free energy
- Replies: 7
- Views: 437
Re: Calculating the reaction Gibbs free energy
Also keep in mind that n is the number of moles of electrons being transferred in a half reaction, not the total amount of the two balanced reactions.
- Sat Feb 22, 2020 3:47 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: E cell
- Replies: 3
- Views: 262
Re: E cell
Ecell= E*cell- (RT/nF)lnQ. When a redox reaction is at equilibrium, DeltaG=0, Q=K, and there is no net transfer of electrons. When there is no net change in the number of electrons, Ecell=0 and then our equation turns into E*cell=(RT/nF)lnQ. So yes, Ecell will decrease to reach 0 but also keep in mi...
- Sat Feb 22, 2020 3:40 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Midterm 6D
- Replies: 5
- Views: 431
Re: Midterm 6D
Gases have the highest entropy possible because they take up a lot of space (volume) and can be arranged in multiple positions because of their high speed and free movement. Therefore, option A only had the option of a gas in the products.
- Sat Feb 22, 2020 3:33 pm
- Forum: Balancing Redox Reactions
- Topic: 6K.1
- Replies: 3
- Views: 220
Re: 6K.1
When determining the number of electrons to place on a side, you have to compare the overall charge on the left and right sides. Generally, let's say for example, there is a higher positive charge on the left side, you would add that number of electrons on the right side to balance the difference in...
- Sat Feb 22, 2020 3:30 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff Equation
- Replies: 3
- Views: 268
Re: Van't Hoff Equation
They also correlate with the fact that Temperature affects K, so each K1 would correspond directly to that T1.
- Sat Feb 15, 2020 12:07 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs free energy
- Replies: 5
- Views: 292
Re: Gibbs free energy
At equilibrium, DeltaG=0 because the forward and backward reaction rates are equal. So the formula for nonstandard conditions (including not at equilibrium) is Delta G= DeltaG* + RT lnQ, where Q is the reaction quotient ([Products]/[Reactants]). At equilibrium, the Q variable would become K.
- Sat Feb 15, 2020 12:02 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta U = 0
- Replies: 8
- Views: 508
Re: Delta U = 0
And when Delta U=0 then q=-w.
- Sat Feb 15, 2020 12:00 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Joules or KJ?
- Replies: 14
- Views: 2559
Re: Joules or KJ?
You should always check the units in the constants you plug into your formulas. So it would depend whether it's joules or kilojoules.
- Sat Feb 15, 2020 11:59 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Rules for constant pressure
- Replies: 4
- Views: 250
Re: Rules for constant pressure
These are just a few but at constant pressure, q=DeltaH and w=-PDeltaV
At constant volume, w=0 and you can evaluate the formulas using this information.
At constant volume, w=0 and you can evaluate the formulas using this information.
- Sat Feb 15, 2020 11:55 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Analysis of Gibbs Free Energy Equation
- Replies: 4
- Views: 309
Re: Analysis of Gibbs Free Energy Equation
Delta s=q/T is used when there is a constant temperature. q=DeltaH is used when there is a constant pressure. Q is heat which is separate from Gibbs free energy.
- Sat Feb 08, 2020 2:51 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy equations
- Replies: 2
- Views: 109
Re: Entropy equations
Under the 14B website, there is a list of constants and equations sheet. I believe that the general ones are on there but you have to memorize/know how to derive the more specific ones with changes in volume/temperature.
- Sat Feb 08, 2020 2:42 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Molecular Complexity
- Replies: 4
- Views: 305
Re: Molecular Complexity
Entropy at the molecular level means having more 'microstates', or different ways of arranging atoms. Complex molecules have more atoms, and therefore, more places you can change its composition.
- Sat Feb 08, 2020 2:37 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Molar Entropy
- Replies: 3
- Views: 116
Re: Molar Entropy
Since molecular weight can be similar between different gases, it would be reasonable to assume that degeneracy can truly distinguish them apart better.
- Sat Feb 08, 2020 2:35 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Microstates
- Replies: 6
- Views: 231
Re: Microstates
I wouldn't say they're dependent on the number of bonds but rather on the different placements of atoms (like how many positions they can take). Octahedrals would definitely have more microstates than a tetrahedral, for example.
- Sat Feb 08, 2020 2:32 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Nonlinear vs linear molecules
- Replies: 4
- Views: 883
Re: Nonlinear vs linear molecules
Usually I think we will be given linear molecules in terms of symmetry since they are common ideal gases such as CO2 and O2.
- Wed Jan 29, 2020 3:20 pm
- Forum: Calculating Work of Expansion
- Topic: Negative sign on work equation
- Replies: 3
- Views: 80
Re: Negative sign on work equation
Yes, in expansion there will be a negative sign because the system is losing energy.
- Wed Jan 29, 2020 3:18 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Endothermic vs Exothermic
- Replies: 10
- Views: 509
Re: Endothermic vs Exothermic
Yes, usually when a system gains heat, q will be a positive value.
- Wed Jan 29, 2020 3:13 pm
- Forum: Calculating Work of Expansion
- Topic: expansion vs nonexpansion
- Replies: 5
- Views: 186
Re: expansion vs nonexpansion
When a system expands, you should get a negative answer for work. When a system is compressed, you will get positive work.
- Wed Jan 29, 2020 3:12 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: What systems go with what equations?
- Replies: 2
- Views: 110
Re: What systems go with what equations?
When the pressure is constant, you can also get DeltaU=DeltaH-P(Delta V) from the general formula DeltaU=q+w.
- Wed Jan 29, 2020 3:10 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: internal energy
- Replies: 4
- Views: 178
Re: internal energy
Also another derivation of the formula we learned in class today was DeltaU=DeltaH-P(DeltaV) if the pressure is constant.
- Tue Jan 21, 2020 10:54 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE table
- Replies: 5
- Views: 202
Re: ICE table
Reactants will have a - sign, products will have a + sign. Look for the coefficients in a reaction and that will determine whether you will have a +-2x if you have a 2 moles of that certain element or just a +-x for 1 mol.
- Tue Jan 21, 2020 10:51 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Week 3 hmwrk problems
- Replies: 2
- Views: 108
Re: Week 3 hmwrk problems
Yes, Dr. Lavelle said you can still turn in HW problems from the second week in discussions.
- Tue Jan 21, 2020 10:50 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: effects on pH
- Replies: 7
- Views: 216
Re: effects on pH
I think you're mentioning solubility rules so you don't include groups 1 and 2 in the reaction because they don't affect pH (totally dissolve in water and are present on both sides of the reaction so you can cancel them out). Example is NaOH and also salts like NaCl don't affect pH. Conjugate bases/...
- Tue Jan 21, 2020 10:46 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Approximation
- Replies: 6
- Views: 220
Re: Approximation
It has to be less than so anything 10^-4 and smaller.
- Tue Jan 21, 2020 10:45 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: expanding the volume
- Replies: 3
- Views: 120
Re: expanding the volume
So the shortcut is that whenever you increase volume (by decreasing pressure), you shift the equilibrium to the side with more moles of gas. The technical version is that you actually change concentrations using the PV=nRT formula and n/V is concentration (Molarity). If volume changes (with the conc...
- Wed Jan 15, 2020 3:44 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 1 Topics
- Replies: 4
- Views: 177
Re: Test 1 Topics
I went to his office hours and he said the first test will cover the first two units. I would definitely do all of the hw and understand the ice tables for weak acids and bases. Also looking over the notes and the examples he used in class.
- Wed Jan 15, 2020 3:33 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Endothermic and Exothermic Reactions Class Example
- Replies: 5
- Views: 164
Re: Endothermic and Exothermic Reactions Class Example
A good mnemonic to remember this is BARF which stands for Breaking-Absorbing; Release- Form. So breaking bonds needs to absorb energy and forming bonds releases energy.
- Wed Jan 15, 2020 3:31 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Textbook question 6B.9
- Replies: 1
- Views: 57
Re: Textbook question 6B.9
I think that for when calculating pH, you can drop the negative in the final answer to get 0.18 pH from 1.5 M H3O+ instead of -0.18 M.
So from that you get pOH by doing 14-0.18=13.824.
And the concentration of OH- is 10^-13.824 which equal 1.5*10^-14.
So from that you get pOH by doing 14-0.18=13.824.
And the concentration of OH- is 10^-13.824 which equal 1.5*10^-14.
- Wed Jan 15, 2020 3:21 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: x is small approximation
- Replies: 6
- Views: 498
Re: x is small approximation
Today in lecture he mentioned that 10^-4 is the boundary, so anything 10^-4 and smaller can be approximated. However, he said that if K does equal 10^-4, you should double check your answer at the end (by plugging it back in) to see if there is a difference between your answer and the given because ...
- Wed Jan 15, 2020 3:13 pm
- Forum: Ideal Gases
- Topic: Ideal Gas Law
- Replies: 5
- Views: 214
Re: Ideal Gas Law
So the equation is PV=nRT. An example of using this problem is when we are given pressures and must find Kc. You would have to use the formula to convert to concentrations (n/V) of each individual molecule, then plug it into the Kc formula.
- Wed Jan 08, 2020 9:58 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Question from Module Assessment Part 1A
- Replies: 3
- Views: 177
Re: Question from Module Assessment Part 1A
Also B is incorrect because the equilibrium constant gives us the RATIO of concentrations of products vs. reactants- we cannot calculate their exact rates. C is incorrect because it's irrelevant at the moment- activation energies relate more to the thermodynamic unit.
- Wed Jan 08, 2020 9:52 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pressure changes to equilibrium equations
- Replies: 5
- Views: 239
Re: Pressure changes to equilibrium equations
When you add an inert gas like Helium, (which is NOT needed for the reaction), there will be no effect on the equilibrium constant because there is no change in concentration.
- Wed Jan 08, 2020 9:47 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: No Solvent Concentration in the Calculating Equilibrium Constant
- Replies: 4
- Views: 274
Re: No Solvent Concentration in the Calculating Equilibrium Constant
The same rule applies of omitting solids in the equilibrium constant.
- Wed Jan 08, 2020 9:46 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Solids and Liquids
- Replies: 3
- Views: 86
Re: Solids and Liquids
I feel as though they would be given in the problem but make sure to check if the reaction is balanced.
- Wed Jan 08, 2020 9:43 am
- Forum: Ideal Gases
- Topic: Equilibrium
- Replies: 7
- Views: 204
Re: Equilibrium
K is when the reaction reaches equilibrium. Q is a specific point in time before reaching equilibrium. We often compare Q to K; for example if Q<K then the reaction will shift to the right.
- Sat Dec 07, 2019 4:14 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Spectator Ions?
- Replies: 2
- Views: 266
Spectator Ions?
How do you identify them?
Re: naming
So when naming in alphabetical order, you look at the element/compound described, not the prefix. So in your example, you would put chloro first.
Re: naming
Some common polydentates to recognize are ethylenediamine and its longer chains such as DIEN and EDTA. Another example is oxalate because they can bind in multiple places.
- Thu Dec 05, 2019 1:04 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Acid/Base Trends
- Replies: 6
- Views: 380
Re: Acid/Base Trends
Strong acids dissociate completely. When going down a group, the atoms are getting larger (making a bond longer), and therefore making the bond weaker. Therefore, the strength will increase because the bond is easier to break.
- Thu Dec 05, 2019 1:00 pm
- Forum: Naming
- Topic: Coordination Compound Charges
- Replies: 3
- Views: 191
Re: Coordination Compound Charges
SO4-2 is sulfate, (so it has a -2 charge).
- Thu Dec 05, 2019 12:53 pm
- Forum: General Science Questions
- Topic: Constants and Equations
- Replies: 2
- Views: 369
Re: Constants and Equations
Yes but it includes some equations we haven't covered yet.
- Wed Nov 27, 2019 9:14 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Carboxyl Acidic Hydrogens?
- Replies: 2
- Views: 205
Re: Carboxyl Acidic Hydrogens?
There are significantly more weak acids than strong acids. Weak acids have lower Ka, so larger pKa, meaning they will dissociate more. In class today, he said HI is a strong acid because I is less electronegative and larger, meaning that the bond is longer (weaker) and it will be easier to break. In...
- Wed Nov 27, 2019 9:06 pm
- Forum: Naming
- Topic: Naming coordination compound
- Replies: 3
- Views: 226
Re: Naming coordination compound
After going through the examples given in the book, I don't think there is a difference when going from the name to writing the compound. One potential pattern that I found was that the more positive charge was placed first, but I don't think this significantly matters. Ask your TA though just in ca...
- Wed Nov 27, 2019 8:56 pm
- Forum: Hybridization
- Topic: Hybridized orbital number
- Replies: 1
- Views: 143
Re: Hybridized orbital number
The coefficient in front of the hybridization is the row number. That is why when C is in the second row, it has a 2 sp2 bond hybridization. An example with sp3 hybridization is H2O: the Oxygen will have 2sp3 hybridization because it is in the second row and has 4 regions of electron density (2 sing...
- Wed Nov 27, 2019 8:42 pm
- Forum: Hybridization
- Topic: single vs double vs triple bonds
- Replies: 4
- Views: 244
Re: single vs double vs triple bonds
Single, double, and triple bonds all represent one region of electron density. Therefore, sp hybridization has 2 regions of electron density, sp2 has 3 regions of electron density, sp3 has 4 regions, sp3d has 5 regions, and so on.
- Wed Nov 27, 2019 12:29 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Acid/base strength?
- Replies: 4
- Views: 400
Re: Acid/base strength?
Strong acids and bases will dissociate completely (acids into H3O+ and based into OH-). There are 7 main strong acids. Strong bases are comprised of Group 1 and 2 oxides/hydroxides (use the periodic table).
- Sat Nov 23, 2019 9:30 pm
- Forum: Naming
- Topic: Toolbox 9C.1
- Replies: 2
- Views: 104
Toolbox 9C.1
Why is [Ni(CN)4)]2- tetracyanidonickelATE? Why does it end in -ate instead of just nickel?
- Thu Nov 21, 2019 9:18 am
- Forum: Sigma & Pi Bonds
- Topic: pi bond locations
- Replies: 3
- Views: 243
Re: pi bond locations
Single bond: 1 sigma bond
Double bond: 1 sigma, 1 pi bond
Triple bond: 1 sigma, 2 pi bonds
Sigma bonds form when orbitals overlap end to end.
Pi bonds form when orbitals overlap side by side.
Double bond: 1 sigma, 1 pi bond
Triple bond: 1 sigma, 2 pi bonds
Sigma bonds form when orbitals overlap end to end.
Pi bonds form when orbitals overlap side by side.
- Thu Nov 21, 2019 9:15 am
- Forum: Dipole Moments
- Topic: Intermolecular Forces
- Replies: 7
- Views: 444
Re: Intermolecular Forces
Also every molecule will have London dispersion (induced dipole-induced dipole) forces present.
- Thu Nov 21, 2019 9:12 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Comparing Strength of Hydrogen Bonds
- Replies: 1
- Views: 87
Re: Comparing Strength of Hydrogen Bonds
The molecule with more hydrogen bonds will be stronger. But you can also argue the molecule with stronger London dispersion (induced-induced dipole) forces will be stronger overall. Strong dispersion forces means that the atom compared is bigger (so more electrons), so larger polarizability, and the...
- Thu Nov 21, 2019 9:08 am
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Potential energy
- Replies: 3
- Views: 252
Re: Potential energy
Alpha stands for polarizability and r stands for distance. So, intermolecular forces depend on the strength of an atom to distort electrons as well as how far the two atoms/molecules are away from each other.
- Thu Nov 21, 2019 9:06 am
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Periodic Trends
- Replies: 8
- Views: 652
Re: Periodic Trends
Cations have polarizing power while anions have polarizability. The definition of polarizability is the ability to distort electron clouds. For cations, those that are smaller and highly charged are the most polarizable. For anions, those that are bigger and less charged are the most polarizable. In...
- Thu Nov 14, 2019 9:23 am
- Forum: Ionic & Covalent Bonds
- Topic: Electronegativity
- Replies: 7
- Views: 432
Re: Electronegativity
Usually anything on the far left compared to the far right (fluorine) of the periodic table will have the highest EN difference.
- Thu Nov 14, 2019 9:21 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Axial vs Equatorial Lone Pairs
- Replies: 2
- Views: 189
Re: Axial vs Equatorial Lone Pairs
Also the best way to think about the shapes is to visualize them. The most stable shapes with have electron densities symmetrically arranged around the central atom that will result in the least amount of repulsion.
- Thu Nov 14, 2019 9:14 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Memorization
- Replies: 15
- Views: 952
Re: Memorization
With the shapes, I think it’s also important to know the bond angles associated with them. (Ex. 109.5 degrees for a Tetrahedral).
- Thu Nov 14, 2019 9:12 am
- Forum: Administrative Questions and Class Announcements
- Topic: 14BL
- Replies: 5
- Views: 253
Re: 14BL
I feel if you truly love chemistry and are willing to put in more effort to understand the concepts thoroughly to succeed in both classes, you can take both at once. Otherwise, if you need more time to process the new material I would hold off until the Spring quarter.
- Thu Nov 14, 2019 9:07 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: 3F.1 Part a
- Replies: 4
- Views: 366
Re: 3F.1 Part a
Yes usually each molecule will have London (dispersion) forces.
- Thu Nov 07, 2019 9:50 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Hw 1.43 (sixth edition)
- Replies: 1
- Views: 146
Re: Hw 1.43 (sixth edition)
Yes, usually Delta X is the diameter of the atom. So this means if they give you radius, you have to multiply by 2 to get the diameter. Also remember units have to be in meters so convert if necessary.
- Thu Nov 07, 2019 9:48 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3007372
Re: Post All Chemistry Jokes Here
What did the chemical agent say?
My name is Bond, Ionic Bond. Taken, not shared.
My name is Bond, Ionic Bond. Taken, not shared.
- Thu Nov 07, 2019 9:42 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Bohr Frequency
- Replies: 6
- Views: 300
Re: Bohr Frequency
When energy is absorbed, Delta E is positive. This means the atom is going from a lower quantum energy state to a higher one. For example, going from n=1 to n=3.
- Thu Nov 07, 2019 9:39 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenberg
- Replies: 3
- Views: 231
Re: Heisenberg
Delta X is uncertainty in position (in meters, usually the diameter value of the atom) and Delta P is uncertainty in momentum. Delta P= m x DeltaV, so you can further solve for the uncertainty in velocity.
- Thu Nov 07, 2019 9:37 am
- Forum: Dipole Moments
- Topic: Ionic bonds
- Replies: 5
- Views: 266
Re: Ionic bonds
Yes, for example in KF. F is extremely electronegative, so it will pull electron's closer making it more negatively charged. Therefore, the K will be more positively charged and a dipole moment will occur.
- Wed Oct 30, 2019 9:33 am
- Forum: Lewis Structures
- Topic: Formal charge
- Replies: 9
- Views: 234
Re: Formal charge
When a question asks for the most stable resonance structure, you have to draw the different lewis dot structures (only switching the placement of bonds) and calculate formal charges. The ones closest or equal to 0 will be the most stable and therefore be the answer.
- Wed Oct 30, 2019 9:30 am
- Forum: Octet Exceptions
- Topic: List of Octet exceptions
- Replies: 6
- Views: 294
Re: List of Octet exceptions
Essentially elements can disobey the octet rule in two ways: 1. They can break it by their massive size and extra space of a d-block. (3 row periodic table and below) 2. They don't reach their 'full potential' of the octet rule because of a high ionization energy. (Ex: BF3; Boron will only have 6 va...
- Wed Oct 30, 2019 9:24 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: d block before s block
- Replies: 3
- Views: 207
Re: d block before s block
What also helps me remember that the d block comes before the s block in the electron configuration is that the leading coefficients of d and the blocks before it are the same. For example, 3s2, 3p6, 3d10 (3 is the same) and afterwards, the 4th shell begins.
- Wed Oct 30, 2019 9:17 am
- Forum: Lewis Structures
- Topic: Formal Charge [ENDORSED]
- Replies: 6
- Views: 150
Re: Formal Charge [ENDORSED]
In the formula, instead of using S/2 I just count the number of bonds with that atom and you get the same answer. I think it's a little bit easier since you don't have to divide by two and can subtract that exact number.
- Wed Oct 30, 2019 9:04 am
- Forum: Resonance Structures
- Topic: Delocalization vs. Resonance
- Replies: 8
- Views: 2917
Delocalization vs. Resonance
What is the difference between delocalization and resonance? Does one lead to the other?
- Thu Oct 24, 2019 10:07 am
- Forum: Ionic & Covalent Bonds
- Topic: Properties of Metals/Nonmetals/Metalloids
- Replies: 3
- Views: 212
Properties of Metals/Nonmetals/Metalloids
What are the properties of metals, nonmetals, and metalloids? Also which one loses electrons more easily?
- Thu Oct 24, 2019 10:03 am
- Forum: Trends in The Periodic Table
- Topic: Location of elements
- Replies: 12
- Views: 692
Re: Location of elements
Yes- it will be helpful when recognizing ionic (metal and nonmetal sharing electrons) or covalent bonds (between two nonmetals). Also it's good to keep in mind their valence electrons for when we will be drawing their Lewis Dot Structures.
- Thu Oct 24, 2019 9:54 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Uncertainty value in equation
- Replies: 9
- Views: 341
Re: Uncertainty value in equation
I also asked my TA and she said it would be 6. There was some confusion because the answer key was wrong for one of the homework questions but it should be double the +- value.
- Thu Oct 24, 2019 9:51 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Valence Shell Configuration
- Replies: 1
- Views: 120
Valence Shell Configuration
For homework question 1E.25, it asks for the valence shell configuration of metals. So for example, the Group 5 transition metals are (n-1)d^3ns^2. Can someone please explain what these numbers/orbitals mean in the context of the problem?
- Thu Oct 24, 2019 9:44 am
- Forum: Trends in The Periodic Table
- Topic: Ionization Energy [ENDORSED]
- Replies: 3
- Views: 160
Re: Ionization Energy [ENDORSED]
One helpful tip that helps me remember Ionization Energy increasing along the period is that F (Fluorine) is considered to be the strongest element its ability to remove electrons. So if you just keep in mind that Fluorine is the best, then you can think of the trends more easily.
- Thu Oct 17, 2019 10:53 am
- Forum: Photoelectric Effect
- Topic: Confusion on equations
- Replies: 9
- Views: 349
Re: Confusion on equations
An equation that you could separate from the rest is DeBroglie's equation, which is only used for particles (electrons/protons/neutrons).
- Thu Oct 17, 2019 10:51 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Momentum
- Replies: 7
- Views: 284
Re: Momentum
Delta V is the uncertainty of its position. So for example, if in the given we have 10 m/s +- 1m/s, the delta V would be 1. It's 1 and not 2 because a particle can't go in two directions at once.
- Thu Oct 17, 2019 10:45 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbital shapes
- Replies: 3
- Views: 116
Re: Orbital shapes
The p, d, and f orbitals also have a nodal plane where there is zero electron density (and therefore zero electron probability.) There is a trend to how many 'petals' you draw on the axes as well: S is just a circle because of its symmetric electron distribution. P has 2 horizontal petals. D has 4 p...
- Thu Oct 17, 2019 10:14 am
- Forum: *Black Body Radiation
- Topic: black body
- Replies: 2
- Views: 300
Re: black body
Also black bodies are mainly found in physics, so there shouldn't be a large emphasis on these.
- Thu Oct 17, 2019 10:12 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Determining Orbitals Based on Periodic Table
- Replies: 2
- Views: 104
Re: Determining Orbitals Based on Periodic Table
Dr. Lavelle said that we should most be familiar with the s,p, and d orbitals since they contain elements in biological systems. (The elements towards the bottom of the periodic table are toxic and the last ones are even radioactive). Locations you have to memorize/relatively know placement of: S or...
- Thu Oct 10, 2019 11:19 am
- Forum: Einstein Equation
- Topic: 1B.9 HW
- Replies: 2
- Views: 285
1B.9 HW
How would you solve this problem?
A lamp rated at 32W (1 W= 1 J/s) emits violet light of wavelength 420nm. How many photons of light can the lamp generate in 2 sec? How many moles of photons are emitted in that time interval?
A lamp rated at 32W (1 W= 1 J/s) emits violet light of wavelength 420nm. How many photons of light can the lamp generate in 2 sec? How many moles of photons are emitted in that time interval?
- Thu Oct 10, 2019 11:12 am
- Forum: Empirical & Molecular Formulas
- Topic: Question E9
- Replies: 4
- Views: 231
Re: Question E9
Also within the next few weeks, we will cover nomenclature in class where we will learn all of the rules.
- Thu Oct 10, 2019 11:09 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Rounding with basic calculator
- Replies: 16
- Views: 871
Re: Rounding with basic calculator
I asked one of the T.A.'s this question and he said that as long as in the steps of your calculation, you use more decimals than the required amount of sig figs, then you should be able to receive the correct answer when rounding at the end.
- Thu Oct 10, 2019 11:01 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Photon Absorption/Emission
- Replies: 8
- Views: 393
Re: Photon Absorption/Emission
Delta E will have a negative value when the electron is emitted (decreased energy) and positive sign when the electron is absorbed (increased energy). Energy in itself is always a positive value.
- Thu Oct 10, 2019 10:32 am
- Forum: Properties of Electrons
- Topic: Rydberg formula clarification
- Replies: 3
- Views: 131
Re: Rydberg formula clarification
In essence, Rydberg formula is best used to find the frequency between energy levels and is derived from the energy formula of En=-hR/n^2. Use the energy formula when you want to find the energy at a specific energy level or the difference of energy levels (where you would use Energy(final)-Energy(i...
- Thu Oct 10, 2019 10:25 am
- Forum: Properties of Light
- Topic: Finding Wavelength and Energy of Photon
- Replies: 1
- Views: 71
Finding Wavelength and Energy of Photon
How would you solve this question? Specifically, the energy per one photon of radiation? The meter was defined in 1963 as 1,650,763.73 wavelengths of radiation emitted by krypton-86 (it has since been redefined). What is the wavelength of this krypton-86 radiation? What energy does one photon of thi...
- Tue Oct 01, 2019 10:27 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Finding KE
- Replies: 1
- Views: 169
Finding KE
Use the uncertainty of velocity (delta v= 3.4E10) to calculate the electron's uncertainty in kinetic energy. Then, calculate the uncertainty in kinetic energy per mole of electrons (that is, per mole of hydrogen atoms).
Mass of electron is 9.1E-31 kg.
Mass of electron is 9.1E-31 kg.
- Tue Oct 01, 2019 10:06 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Uncertainty in Speed [ENDORSED]
- Replies: 31
- Views: 16877
Uncertainty in Speed [ENDORSED]
The hydrogen atom has a radius of approximately 0.05 nm. Assume that we know the position of an electron to an accuracy of 1% of the hydrogen radius, calculate the uncertainty in the speed of the electron using the Heisenberg uncertainty principle. So the correct answer is Delta V >= 10^8 m/s. How w...