Search found 114 matches
- Wed Mar 10, 2021 5:15 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
If you are not part of the solution, you are part of the precipitate!
- Wed Mar 10, 2021 5:12 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 490
- Views: 606043
Re: Saying Thank You to Dr. Lavelle
Dr. Lavelle, After 2 quarters of your chemistry classes, I truly want to thank you for teaching me chemistry. I can not believe how much material I have learned in the last 2 quarters and I am very thankful to you for that. You truly do love chemistry and it is always incredible to learn from a prof...
- Wed Mar 10, 2021 5:06 pm
- Forum: Environment, Ozone, CFCs
- Topic: catalysis vs intermediate
- Replies: 25
- Views: 2096
Re: catalysis vs intermediate
An intermediate is a species formed and then later consumed by the reaction. A catalyst is not used by the reaction but is presented first on the reactants, then on the products side. They will both cancel out of the overall equation. The best way to determine is to see which side of the equation th...
- Wed Mar 10, 2021 4:58 pm
- Forum: *Enzyme Kinetics
- Topic: catalyst and A
- Replies: 2
- Views: 328
Re: catalyst and A
I do not think we will have to worry too much about this on the exam, but I do think catalysts increase the value of A (in some cases). A is primarily impacted by molecule orientation, so if 2 molecules have to collide on specific planes for each molecules, the value of A will be fairly small like 0...
- Wed Mar 10, 2021 4:55 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Temperature and Rate Constant
- Replies: 3
- Views: 288
Re: Temperature and Rate Constant
yes! the rate constant always increases even in exothermic reactions. If we think about the collision theory, higher energy molecules have a greater tendency to collide, even in higher energy reactions. Le Chatelier's explains that with an increase in temperature in an exothermic reaction, the react...
- Sat Mar 06, 2021 2:46 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: kinetics vs. thermodynamics
- Replies: 23
- Views: 1322
Re: kinetics vs. thermodynamics
thermodynamics only lets us know if the reaction is spontaneous or not. Not every spontaneous reaction happens readily. If the reaction is spontaneous and not happening, it is said to be kinetically controlled.
- Sat Mar 06, 2021 2:44 pm
- Forum: Zero Order Reactions
- Topic: 0 order
- Replies: 14
- Views: 1564
Re: 0 order
A zero order reaction, while not very common, is independent of the concentration of the reactants. This can happen when the reaction has some type of catalyst in it. hope this helps!
- Sat Mar 06, 2021 2:39 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
what type of dogs do scientists have?
Laboratory retrievers!
Laboratory retrievers!
- Sat Mar 06, 2021 2:37 pm
- Forum: First Order Reactions
- Topic: Graphing
- Replies: 20
- Views: 1026
Re: Graphing
can someone sort of summarize what characteristics of the line give away what order it is? or maybe link a different question thread that answers this please? I think the best way to determine what order the graph is is to look at what the axes labels are and if that graph has a straight line. A fi...
- Sat Mar 06, 2021 2:25 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Explaining Le Chatelier's Principle
- Replies: 14
- Views: 1149
Re: Explaining Le Chatelier's Principle
I like to think of Le Chatelier's as minimizing the effects of a change in the system on the equilibrium. Le Chatelier works to get Q closer to K. If you think about it this way, it helps see which way the reaction goes. More reactants makes Q smaller, so to get back to K, there needs to be more pro...
- Sat Mar 06, 2021 2:16 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5% rule
- Replies: 4
- Views: 319
Re: 5% rule
you can approximate I believe when K is less than 10^-4. With acids always check because in order for this to be accurate the percentage deprotonation needs to be less than 5%.
- Thu Feb 25, 2021 8:07 pm
- Forum: Balancing Redox Reactions
- Topic: E naught
- Replies: 15
- Views: 988
Re: E naught
you are exactly right. It is an intensive property such as density that does not change with the amount of the material present. The only thing that does change based on the reaction is the sign, so be sure to flip the sign if you are flipping the equation!
- Thu Feb 25, 2021 8:05 pm
- Forum: Balancing Redox Reactions
- Topic: sapling q.3
- Replies: 3
- Views: 255
Re: sapling q.3
Basically, atoms in their natural state have a oxidation number of 0. Oxygen pretty much always (there are some small number of exceptions) has an oxidation number of -2. Moreover, in an ion the sum of the oxidation numbers needs to add up to the charge of the ion itself. So we know the oxidation nu...
- Thu Feb 25, 2021 8:01 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cathode vs. Anode
- Replies: 8
- Views: 743
Re: Cathode vs. Anode
Hey! so cathode is always the reduced and anode is always the oxidized species. The current travels from anode to cathode regardless of the positioning of the beaker. You could look at the flow of the current or standard electrode values to determine which is the cathode and which species is the ano...
- Thu Feb 25, 2021 7:59 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 30
- Views: 1467
Re: Salt Bridge
Without the salt bridge, there would be a build up of positive and negative ions on either side. The salt bridge allows the reactions to continue. Without the salt bridge, the reaction will not continue.
- Thu Feb 25, 2021 7:57 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Ranking Species according to standard potentials
- Replies: 2
- Views: 200
Re: Ranking Species according to standard potentials
Hey! So a reducing agent is the species that is being oxidized and most standard E are given in terms of reduction. If a species has a negative reduction potential, it means that species is better oxidized. The more negative a species is the more it is oxidized, therefore the better the reducing age...
- Thu Feb 18, 2021 3:08 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Constant Volume
- Replies: 15
- Views: 929
Re: Constant Volume
Cv refers to the constant when volume is constant, for an ideal gas it is 3/2*8.314. Cp refers to when the pressure is constant and this value is higher at 5/2*8.314. Hope this helps!
- Thu Feb 18, 2021 3:01 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Systems and Examples
- Replies: 2
- Views: 248
Re: Systems and Examples
While I am not entirely sure if we will be tested on these, I definitely think it is a good skill to be able to identify which system is which. The first thing I do is determine if the system can exchange matter with the environment (if stuff can leave). For example, in 4A.1 they gave the example of...
- Thu Feb 18, 2021 2:55 pm
- Forum: Balancing Redox Reactions
- Topic: Redox Mnemonic
- Replies: 11
- Views: 1089
Re: Redox Mnemonic
my chem teacher would always say LEO the lion says GER! It is a great way to remember a basic concept of redox!
- Thu Feb 18, 2021 2:50 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Self Test 4A.3A
- Replies: 4
- Views: 604
Re: Self Test 4A.3A
I believe this is because you are looking at delta T, not T. A change from 25 celsius to 900 celsius is 875 Celsius and a change from 298 Kelvin to 1173 Kelvin is 875 Kelvin. An increase in temp of one degree celsius is equal to an increase in temp of one degree Kelvin. You always can convert to Kel...
- Thu Feb 18, 2021 2:45 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Textbook Question 4A.7
- Replies: 4
- Views: 465
Re: Textbook Question 4A.7
Think about when you put a kettle on the stove, once you let it heat up you need something like an oven mitt to take it off because the kettle itself got heated up as well. In this case, you have a copper kettle weighing 400 grams that will also take in heat to warm it to the same 100 degrees. Becau...
- Mon Feb 15, 2021 10:55 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Section 4C.3 (origin of the heat capacity of gases)
- Replies: 2
- Views: 173
Section 4C.3 (origin of the heat capacity of gases)
Do we need to know the material in this section for the midterm, if so do you guys have any good mnemonics or memory tools for this section? thanks!
- Wed Feb 10, 2021 12:30 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
What did the weak acid say to the strong acid??
you are overreacting!
you are overreacting!
- Wed Feb 10, 2021 12:27 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: q vs deltaH
- Replies: 4
- Views: 246
Re: q vs deltaH
They are not the same thing, but there are subtle differences between the two. delta H is defined as q at constant pressure. q is more generally heat. So when you see a problem with constant pressure, you can sub in the value for delta H.
- Wed Feb 10, 2021 12:25 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: PΔV Question
- Replies: 4
- Views: 354
Re: PΔV Question
As Dr. Lavelle explained, theoretically the molecules in the desk of the lecture hall are expanding or contracting, but it is so so small that it is not necessary to calculate and can be ignored. If you think about the pressure you put on objects like a wooden chair, when you sit on them you can't s...
- Wed Feb 10, 2021 12:20 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: delta q
- Replies: 3
- Views: 269
Re: delta q
by definition, delta h is the value of q at constant pressure. delta u = q +w. we are aware that w is the integral of pressure x change in volume, but if volume is constant, that whole term will just end up being 0, so all thats left is q. If you are still confused about when to use each equation, I...
- Wed Feb 10, 2021 12:13 pm
- Forum: Calculating Work of Expansion
- Topic: 1L=1000cm^3
- Replies: 4
- Views: 332
Re: 1L=1000cm^3
Like everyone else is saying, 1 mL = 1 cm^3 so 1 liter (1000 mL) is 1000 cm^3. While it may be on the conversion sheet, you can use the prefixes learned in chem 14A to determine this. milli is 10^-3 so there would 1000 more milliliters in a liter, so if you have any one conversion from cm^3 to liter...
- Sun Feb 07, 2021 8:41 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
My chemistry experiment exploded...
It's ok oxidants happen!
It's ok oxidants happen!
- Sun Feb 07, 2021 8:36 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Sapling Week 3 and 4, Q5
- Replies: 5
- Views: 988
Re: Sapling Week 3 and 4, Q5
It is very helpful in these situations to write out all the equations (and phases) on paper! I like to put times 1 or -2 depending on if the reaction is flipped or not. Then just go through and cross out what is on both the reactants and products side. You should be left with only what was in the or...
- Sun Feb 07, 2021 8:27 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat of combustion sign
- Replies: 2
- Views: 137
Re: Heat of combustion sign
While I am not entirely sure when to use the absolute value of the heat of combustion value, heroes how I go about solving problems. Combustion is exothermic in nature so it should have a negative q. Look at what your system is, what way the reaction is and what equation you are using to solve. I ju...
- Sun Feb 07, 2021 8:23 am
- Forum: Phase Changes & Related Calculations
- Topic: Boiling water
- Replies: 25
- Views: 3114
Re: Boiling water
When water is boiled, the water molecules need to go from lower energy liquid phase molecules to higher energy gaseous molecules. Water is capable of hydrogen bonding so it has strong intermolecular forces. It takes energy to break these hydrogen bonds as the molecules become more spread out.
- Sun Feb 07, 2021 8:18 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Differences between the two heat (q) equations
- Replies: 11
- Views: 416
Re: Differences between the two heat (q) equations
One helpful tool to determining what equation to use is seeing what is given. If you write out all of your given values, you will be able to determine which equations you can use. You can even convert between the different q values using molar mass.
- Tue Jan 26, 2021 9:40 am
- Forum: Phase Changes & Related Calculations
- Topic: heating curve
- Replies: 8
- Views: 323
Re: heating curve
Basically, when water reaches 100 degrees celsius, its boiling point it still needs energy to become a gas. Once it hits this temperature, we see a horizontal line with energy still entering the system but no increase in temperature. In this case this energy is used to help the phase change, higher ...
- Tue Jan 26, 2021 9:37 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: UA worksheet question
- Replies: 2
- Views: 218
Re: UA worksheet question
One way you can look at this is the energy released from making bonds versus the energy needed for breaking bonds. We see because there is a negative enthalpy value that more energy is released from the formation of CO2 than energy required to break the bonds on the reactant side.
- Tue Jan 26, 2021 9:35 am
- Forum: Phase Changes & Related Calculations
- Topic: Sublimation
- Replies: 13
- Views: 1761
Re: Sublimation
Sublimation is endothermic because you are changing from a solid to a gas. Gaseous molecules are higher energy than solid molecules and therefore energy has to be put into the system for these reactions to occur.
- Tue Jan 26, 2021 9:33 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
What kind of dogs do chemists have? Laboratory retrievers!
- Tue Jan 26, 2021 9:31 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ICE Chart Question
- Replies: 26
- Views: 1645
Re: ICE Chart Question
Lets say your equation is O2 +2H2 -> 2H2O and you start with only 1 mol hydrogen gas and oxygen. For every two water molecule made you will loose 2 hydrogens and 1 oxygen, so your ICE table would have -x for change for oxygen, -2x for hydrogen and +2x for water. In your equilibrium it would be 1-x a...
- Fri Jan 22, 2021 1:00 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: endothermic vs. exothermic
- Replies: 11
- Views: 561
Re: endothermic vs. exothermic
I like thinking about them by their latin roots "exo" means outer and "therm" means heat. Exothermic reaction heat the outside (release heat). "endo" is inside and therefore endothermic reactions heat the inside (absorb heat) and cool the the outside. Hope this helps!
- Fri Jan 22, 2021 12:53 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Studying for Midterm #1
- Replies: 63
- Views: 3042
Re: Studying for Midterm #1
The best thing to do is the textbook problems. I also really like using the audio visual post test as a way to study and see what I got right and wrong as those questions are separated by topic and designed by Lavelle!
- Fri Jan 22, 2021 12:49 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
Oxygen and Magnesium were going out together.
I said "OMg that is a party!"
I said "OMg that is a party!"
- Fri Jan 22, 2021 12:46 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: steam causing burns
- Replies: 40
- Views: 1454
Re: steam causing burns
Hi! I think when you look at the energy released it makes the most sense. So to get to from 100 degree water to 25 degree water that will be the same for both the water and the steam once the steam becomes water. For the phase change to happen, steam absorbs quite a bit of heat and therefore when it...
- Fri Jan 22, 2021 12:41 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: R values
- Replies: 9
- Views: 277
Re: R values
The R values are only different due to the the different units of pressure and their conversions. In order to know which R value to use, just see what units fit correctly! I am pretty sure Lavelle's constant sheet has units and that can be a great way to figure out the right R value, especially on t...
- Wed Jan 13, 2021 12:49 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: q vs k
- Replies: 62
- Views: 2883
Re: q vs k
Q should reach K if the reaction is left alone. Once Q equals K the reaction is at equilibrium and the forward and reverse rates of the reaction are the same. If Q > K more reactants will be formed and if Q<K more products will be formed until these values are the same.
- Wed Jan 13, 2021 12:42 pm
- Forum: General Science Questions
- Topic: Acid & Base Equilibria Lecture Question
- Replies: 7
- Views: 377
Re: Acid & Base Equilibria Lecture Question
H2O is a liquid, therefore it is not included in K. Moreover, there would also be a large amount of H2O in the numerator as solvents tend to be in large excess. Instead of writing water in both the numerator and denominator, we just ignore it all together. I really liked Dr. Lavelle's millionaire an...
- Wed Jan 13, 2021 12:37 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
What do you call a mixture of carbon and aluminum?
The second best public university in the nation!
The second best public university in the nation!
- Wed Jan 13, 2021 12:35 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pressure Rule
- Replies: 29
- Views: 1539
Re: Pressure Rule
We are always trying to see how Q compares to K when trying to see what will happen with non-equilibrium conditions, and solids and liquids are not included in the equation for K, so they should be disregarded. Also, pressure really only relates to gases anyways.
- Wed Jan 13, 2021 12:32 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Change in K (P&T)
- Replies: 9
- Views: 388
Re: Change in K (P&T)
The only change to a system that will change the value of K is temperature. Pressure is really changing the number of mols by changing the volume. Therefore, depending on how the mols change, the equilibrium will shift to get back to that constant K. Temperature does not change the number of mols of...
- Thu Jan 07, 2021 9:26 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Aqueous in Partial Pressure K
- Replies: 2
- Views: 225
Aqueous in Partial Pressure K
I know that with concentrations both aqueous and gaseous substances are included in the equation, but what happens when you are trying to calculate Kp and there are aqueous substances in the equation? Can there be a partial pressure for an aqueous substance? Should you convert the gaseous pressures ...
- Wed Jan 06, 2021 12:20 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
Why do chemists learn about ammonia first?
Because its pretty BASIC stuff
Because its pretty BASIC stuff
- Wed Jan 06, 2021 12:18 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Partial Pressure
- Replies: 4
- Views: 175
Re: Partial Pressure
From my understanding, the partial pressure is the pressure of the specific gas if it occupied the volume by itself. We can find the partial pressure if we have the number of moles, volume, temperature, and R value using PV=nRT. The sum of all of the partial pressure is the pressure. I hope this hel...
- Wed Jan 06, 2021 12:12 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: When There is Too Much Product
- Replies: 2
- Views: 249
Re: When There is Too Much Product
I am not totally sure if this is going to answer what you were asking but I will give it my best shot. Equilibrium reactions generally have both a forward and reverse reaction component to them. If Q>K (too much product), the reverse reaction will take place and the product will react and become rea...
- Wed Jan 06, 2021 12:05 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q and K
- Replies: 17
- Views: 827
Re: Q and K
In cases of adding more reactants or products, K does not change, but Q will change as you are no longer in equilibrium. If you add more products Q will now be greater than K and if you add more reactants Q will now be less than K
- Wed Jan 06, 2021 12:02 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Sapling 10: le chatelier's and reverse reactions
- Replies: 5
- Views: 233
Re: Sapling 10: le chatelier's and reverse reactions
I went to a TA office hour as I had the same issue and we discovered it is in fact a typo. Using the method with the correct initial value, in your case the 0.494 + x, you will get the correct answer. The feedback/hint section is incorrect but the solution guide is correct. Just use the correct numb...
- Wed Jan 06, 2021 11:59 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Quadratic Equations
- Replies: 7
- Views: 375
Re: Quadratic Equations
Hi! I always just look at the values to see which one makes more sense in context. Also, if you already know K and are evaluating using non-equilibrium conditions, you can check your work by plugging in the answer. Generally, the smallest positive answer works, but I would always check to see which ...
- Sun Dec 13, 2020 7:09 am
- Forum: Administrative Questions and Class Announcements
- Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
- Replies: 115
- Views: 13730
Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Does anyone know how to approach 33B and C? Thanks!! Yes! So NaOH is a strong base, which means it dissociates 100%, so the concentration of NaOH is also our OH concentration when dissociated. To calculate the pH, I first got the pOH, by doing -log(0.55) and then to convert to pH, I did 14-pOH. For...
- Sat Dec 12, 2020 8:58 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
- Replies: 115
- Views: 13730
Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Screenshot (23).png For 41D, which 6 atoms can form a hydrogen bond? I thought a hydrogen bond was when H is bonded to two highly electronegative atoms. Therefore, H2O could only form hydrogen bonds with 4 atoms (the two N atoms and the two H atoms bonded to N). Hi! I think there are also lone pair...
- Mon Dec 07, 2020 10:13 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
A photon checks into a hotel. They ask if he needs any help with his luggage. He responds...
No, I am traveling light!
No, I am traveling light!
- Mon Dec 07, 2020 10:10 am
- Forum: Air Pollution & Acid Rain
- Topic: acid rain
- Replies: 13
- Views: 1292
Re: acid rain
With the burning of natural gases and coal, sulfur dioxide is released into the air. The equation he showed demonstrates how sulfur dioxide and water together create acid rain. Acid rain really hurts the environment, especially our oceans. Acid rain continues to be an environmental problem that is v...
- Mon Dec 07, 2020 10:07 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Relative Acidity
- Replies: 3
- Views: 203
Re: Relative Acidity
When the H breaks off from the Cl-O-H structure, the Oxygen is left with a negative charge. Since the bond breaking is the same on all of these structures, we look at the resulting anion. There is not resonance, so we can look at the anion to see what happens. Chlorine being highly electronegative p...
- Mon Dec 07, 2020 10:03 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Final Exam Material [ENDORSED]
- Replies: 7
- Views: 499
Re: Final Exam Material [ENDORSED]
does anyone now the breakdown of the final? Like what portions will be predominately featured etc. Dr. Lavelle said the final will be cumulative and sections will be on there according to the amount of time we spent on them. We spent the most time on quantum, so that will be the most, but topics li...
- Mon Dec 07, 2020 10:00 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Negative pH of acid
- Replies: 16
- Views: 754
Re: Negative pH of acid
Yes. If for example there was a strong acid with a molarity greater than 1M, it would have a pH less than 0. In the same way, if a strong base had a molarity greater than 1M it could have a pH greater than14. For chem 14A, I believe it is not important that we know this.
- Fri Dec 04, 2020 11:11 am
- Forum: Amphoteric Compounds
- Topic: Memorization?
- Replies: 10
- Views: 480
Re: Memorization?
Memorizing a couple examples can be very helpful to understanding the topic! If you know a couple, you can generally apply that knowledge to other parts of the periodic table.
- Fri Dec 04, 2020 11:08 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
why are chemists so great at solving problems?
because they have so many solutions!
because they have so many solutions!
- Fri Dec 04, 2020 11:04 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Sapling Week 9 #5
- Replies: 3
- Views: 244
Re: Sapling Week 9 #5
I first look at the CO. I know this is mono dentate and there are 2 of them. The en is bidentate which means it ends in 2 spots. So we do 2x2+2 to get a final coordination number of 6. The amount of times each ligand is attached is super important to determining the coordination number!
- Fri Dec 04, 2020 10:56 am
- Forum: Biological Examples
- Topic: Enzyme Function
- Replies: 9
- Views: 576
Re: Enzyme Function
Hello! these transitions metals can help in the active site. The active site is essential to the enzyme as this is where the substrate binds.
Re: Naming
You are totally right... ironate does sound weird. These are derived from latin and there are some notable exceptions that you should know. I think these just have to be memorized, something that kind of helps me is that these already tend to have strange abbreviations. Iron is Fe not I or Ir like w...
- Fri Nov 27, 2020 1:10 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
What do you do with a dead chemist...
Barium!
Barium!
- Fri Nov 27, 2020 1:09 pm
- Forum: Hybridization
- Topic: 2sp^2 vs 3sp^2
- Replies: 6
- Views: 490
Re: 2sp^2 vs 3sp^2
Yes, the number before the sp2 refers to the energy level of that. So Silicon would have 3sp3 hybridization if it was bonded to 4 atoms.
- Fri Nov 27, 2020 1:08 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Shape Names
- Replies: 50
- Views: 2649
Re: Shape Names
The shape of the water molecule or any AX2E2 molecule is bent or angular. The electron density distribution is in a tetrahedral shape however.
- Fri Nov 27, 2020 1:06 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 25
- Views: 1048
Re: Bond Angles
Yes. I do believe we will have to know the bond angles for the common geometries and we should be able to know how lone pairs impact these bond angles. We will have to know the general bond angle for that shape, but not the specific, experimentally derived values for each molecule.
- Fri Nov 27, 2020 1:04 pm
- Forum: Hybridization
- Topic: e density
- Replies: 30
- Views: 1148
Re: e density
Regions of electron density are counted by adding the number of lone pairs (not each electron in the lone pair) to the number of bonded atoms. For example, H2O has 4 regions of electron density.
- Sun Nov 22, 2020 8:24 pm
- Forum: Ionic & Covalent Bonds
- Topic: Rules of ionization energy
- Replies: 18
- Views: 1844
Re: Rules of ionization energy
I like to think about periodic trends in the way that makes sense instead of memorizing how they move, there are quite a few trends and it can be easy to get them muddled if you do not think about how it may work. Ionization energy is the amount of energy required to remove an electron from a gaseou...
- Sun Nov 22, 2020 8:09 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 21
- Views: 788
Re: Bond Angles
Bond angles in specific molecules are calculated experimentally. We can tell by the structure what the approximate bond angles may be. We also know that lone pairs cause more repulsion, so bond angles away from the lone pair may be smaller. We can not determine to what extent they will be smaller, h...
- Sun Nov 22, 2020 8:06 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
When do I tell bad chem jokes?
Only periodically
Only periodically
- Sun Nov 22, 2020 8:01 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 14B Enrollment [ENDORSED]
- Replies: 67
- Views: 18225
Re: 14B Enrollment [ENDORSED]
Does anyone know if 14B sessions will be recorded lectures as well? There is a fiat lux I would like to do, but it is at the same time as my chem lecture and I was hoping to just watch the chemistry lecture recording and go to my fiat lux live.
- Thu Nov 19, 2020 9:42 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final [ENDORSED]
- Replies: 5
- Views: 422
Re: Final [ENDORSED]
I do believe the final will be different. It has a longer time segment and should therefore have more questions. If I am not mistaken I believe it is also cumulative. Moreover, as we are all taking it at the same time, the proctoring may be a little different.
- Thu Nov 12, 2020 4:48 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
I tell a lot of chem jokes, but I never get a reaction!
- Thu Nov 12, 2020 4:46 pm
- Forum: Naming
- Topic: Nomenclature
- Replies: 5
- Views: 519
Re: Nomenclature
While I am not exactly sure if naming polyatomic atoms will be on the exam, I expect that we should be able to take an ion name and transform that to a chemical formula. For example if they say Magnesium chloride, you should be able to know that is MgCl2.
- Thu Nov 12, 2020 4:38 pm
- Forum: Lewis Structures
- Topic: Lewis structures with Noble gases
- Replies: 5
- Views: 312
Re: Lewis structures with Noble gases
Expanded octets occur when elements have access to the d-block. So neon for example could not have an expanded octet.
- Thu Nov 12, 2020 4:37 pm
- Forum: Resonance Structures
- Topic: structure of lower energy
- Replies: 5
- Views: 290
Re: structure of lower energy
In this case, you want the configuration that has the lowest formal charge possible. That may mean making double bonds or rearranging electrons so that it is most favorable with the lowest number of atoms with formal charge. You may also have to look at which atoms have a formal charge, fluorine for...
- Thu Nov 12, 2020 4:32 pm
- Forum: Ionic & Covalent Bonds
- Topic: Textbook Problem 2.A.15
- Replies: 2
- Views: 178
Re: Textbook Problem 2.A.15
We can look at trends in the periodic table to determine what charge ion an element is most likely to form. a)Sulfur is group 16, so it is most likely to have a charge of -2 b)Tellurium is also group 16 so it will likely have a charge of -2 c)Rubidium is group 1 so it will most likely have a charge ...
- Wed Nov 04, 2020 10:44 am
- Forum: Ionic & Covalent Bonds
- Topic: NH4+
- Replies: 5
- Views: 360
Re: NH4+
This relates I believe to the ion in NH4+. If you look at NH3 is does follow the principle that you were stating before. The cation means that an electron needs to be subtracted from the total number of electrons. I hope this helps a little bit. Many times the rules we learn can be broken in specifi...
- Wed Nov 04, 2020 10:39 am
- Forum: Student Social/Study Group
- Topic: Midterm Partial Credit
- Replies: 19
- Views: 1154
Re: Midterm Partial Credit
There are many steps in some of the mathematical problems we are doing. There is an answer that may be one of the steps, but is not fully there. For example, a problem could ask for the number of kJ/mol released, and you likely calculated the number of J per atom first. That could be an answer choic...
- Wed Nov 04, 2020 10:35 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge Equation
- Replies: 16
- Views: 656
Re: Formal Charge Equation
L represents lone pairs. It is the number of dots surrounding an atom. Count each dot around the atom as 1 for L.
- Wed Nov 04, 2020 10:29 am
- Forum: Resonance Structures
- Topic: Limitations of Lewis Structures
- Replies: 6
- Views: 942
Re: Limitations of Lewis Structures
Lewis structures are a great way to visually represent a molecule, but do have many limitations. Resonance is not in itself a limitation but a factor to be considered. Resonance is the idea that multiple bonds can be shared in multiple locations. For example, through bond lengths we see in the nitra...
- Wed Nov 04, 2020 10:24 am
- Forum: Lewis Structures
- Topic: Electrons in Lewis Structures
- Replies: 8
- Views: 415
Re: Electrons in Lewis Structures
It helps to look at the groups! For groups 1 and 2 it is pretty simple, but for groups 13 through 18, 10 needs to be subtracted to determine the number of valence electrons. Remember that the periodic table is grouped by quantum numbers and is why 10 needs to be subtracted from the group.
- Wed Nov 04, 2020 10:17 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
I post pretty corny chemistry jokes because all of the good ones Argon!
- Sun Nov 01, 2020 9:18 am
- Forum: Quantum Numbers and The H-Atom
- Topic: Nodal Planes
- Replies: 10
- Views: 603
Re: Nodal Planes
A nodal plane is a region where the probability of finding an electron is 0. This has more to do with how bonding and atomic structure relate than just quantum numbers.
- Sun Nov 01, 2020 9:17 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: d orbitals
- Replies: 17
- Views: 780
Re: d orbitals
If you remember Dr. Lavelle's drawings it can help you see how the d orbitals work. There is only one orbital s can be (a sphere), p has 3 different orbitals and d has 5 orbitals.
- Thu Oct 29, 2020 7:45 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
What is the 2nd best public university's favorite element?
Berkelium!
Berkelium!
- Mon Oct 26, 2020 12:15 pm
- Forum: DeBroglie Equation
- Topic: Sapling Hw #23
- Replies: 4
- Views: 267
Re: Sapling Hw #23
To convert eV/atom to kJ/mole you need to use the conversion from eV to J. From there multiple by 10^-3 to convert from J to kJ. Lastly multiply by Avogadro's number to get from kJ/atom to kJ/mole. Hope this helps!
- Mon Oct 26, 2020 11:53 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Change in Velocity
- Replies: 5
- Views: 235
Re: Change in Velocity
Yes! Delta v is uncertainty in velocity. If your velocity is 10+/- 2 you could have a velocity of either 8 or 12, so there is a difference of 4. This is the value you will plug into the equation.
- Mon Oct 26, 2020 11:48 am
- Forum: Properties of Light
- Topic: Midterm
- Replies: 42
- Views: 1716
Re: Midterm
Has anyone found a good way to prop your phone up to let it see your workspace. I am using my phone, but struggling to find a clear way to have it point at my workspace.
- Mon Oct 26, 2020 11:47 am
- Forum: Properties of Light
- Topic: Midterm
- Replies: 42
- Views: 1716
Re: Midterm
Has anyone found a good way to prop your phone up to let it see your workspace. I am using my phone, but struggling to find a clear way to have it point at my workspace.
- Thu Oct 22, 2020 6:38 pm
- Forum: Einstein Equation
- Topic: Rydberg's Equation
- Replies: 9
- Views: 320
Re: Rydberg's Equation
It is final - initial. In the case of energy being emitted it will be positive and absorbed will be negative. While your equation is correct, I find it easier to use v=R(n1^-2 - n2^-2). Hope this helps!
- Thu Oct 22, 2020 6:30 pm
- Forum: Photoelectric Effect
- Topic: Do we need to know about the Paschen or Brackett series for midterm 1?
- Replies: 7
- Views: 318
Re: Do we need to know about the Paschen or Brackett series for midterm 1?
I think it would be good to know about Paschen (n=3), but I do not think it is necessary to know Brackett. I think you should be able to explain that as energy levels get higher they get closer together and patterns like this but not necessarily the name.
- Thu Oct 22, 2020 6:27 pm
- Forum: Properties of Electrons
- Topic: intensity vs energy
- Replies: 29
- Views: 3428
Re: intensity vs energy
This statement is False. The way I determined this is through the E=hv equation. An increase in intensity does not increase the energy of the photon as it does not change the constant h or increase the the value of v.
- Thu Oct 22, 2020 6:19 pm
- Forum: Properties of Light
- Topic: Units for wavelength/frequency
- Replies: 18
- Views: 1413
Re: Units for wavelength/frequency
Wavelength can be measured in many different quantities, but in formulas you should use meters. Through the sapling hw, I have seen nm, m and angstrom. When you see these different notations, just adjust the scientific notation accordingly.
- Thu Oct 22, 2020 6:17 pm
- Forum: DeBroglie Equation
- Topic: DeBroglie Importance
- Replies: 8
- Views: 234
Re: DeBroglie Importance
I found the greatest importance in DeBroglie in that all matter in motion displays wavelength, but things with lots of mass (like things we see in everyday life) have such small wavelength that we can not see it. I think the baseball in motion example gave me much greater understanding. In this situ...
- Thu Oct 22, 2020 6:12 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3851675
Re: Post All Chemistry Jokes Here
why did the white bear dissolve in water?
because he was POLAR!
because he was POLAR!