Search found 64 matches
- Sat Dec 07, 2019 9:26 am
- Forum: Photoelectric Effect
- Topic: Midterm Question 4
- Replies: 1
- Views: 411
Midterm Question 4
Hi, this was one of the questions I messed up on on the midterm. I'm redoing the entire test right now to study for the final and I'd love if someone can check my answer for question 4. Question: Light with wavelength 102.557 nm excites a hydrogen atom gas sample. Is the change in energy of a hydrog...
- Fri Dec 06, 2019 11:15 am
- Forum: Administrative Questions and Class Announcements
- Topic: Curving in Chem 14A
- Replies: 7
- Views: 567
Re: Curving in Chem 14A
I've heard in the past Dr. Lavelle has curved the class so the average is a B-, but it's important to note that the class structure has changed since a few years ago (there used to be two midterms, now there is one, etc.) so this could or could not be a thing. I would say don't rely on a curve, prep...
- Fri Dec 06, 2019 11:13 am
- Forum: Administrative Questions and Class Announcements
- Topic: Studying for the Final [ENDORSED]
- Replies: 11
- Views: 730
Re: Studying for the Final [ENDORSED]
I did the Marshmallow review packet and I'm going to the review session for that tonight. I'm also going to be redoing the homework problems, redoing the two tests and the midterm's problems, and possibly watching some Khan Academy videos to fill in extra knowledge. Memorize relevant formulas (from ...
- Fri Dec 06, 2019 11:11 am
- Forum: Administrative Questions and Class Announcements
- Topic: Chemistry Community Posts
- Replies: 10
- Views: 610
Re: Chemistry Community Posts
I asked my TA, apparently it's calculated online by the Chemistry Community system. It does track how many you did each week, and each week "closes" on Sunday at midnight. So if you forgot to post one week and made up for it the second week with ten posts, it won't count those 5 extra post...
- Fri Dec 06, 2019 11:08 am
- Forum: Administrative Questions and Class Announcements
- Topic: Final exam
- Replies: 17
- Views: 891
Re: Final exam
Just to make sure, the final is going to cover all topics we learned this quarter including high school review? Just a prediction given how our tests have been laid out: The test is likely to be heavy on the acids and bases questions and lewis structures (drawing dot structures and doing VSEPR). If...
- Fri Dec 06, 2019 11:03 am
- Forum: Administrative Questions and Class Announcements
- Topic: Final Review Session
- Replies: 6
- Views: 382
Re: Final Review Session
Will there be another practice packet for the final review session given like the midterm? Does anyone know when the answers for this packet will be given? The review session is tonight in Haines 39 from 7:30-10:30. That's where answers will be given in depth. The pdf of the answers will be posted ...
- Wed Dec 04, 2019 5:31 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Why is formic acid stronger than acetic acid?
- Replies: 1
- Views: 139
Re: Why is formic acid stronger than acetic acid?
PS. this is from 6C.21
- Wed Dec 04, 2019 5:30 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Why is formic acid stronger than acetic acid?
- Replies: 1
- Views: 139
Why is formic acid stronger than acetic acid?
I thought because acetic acid has more electronegative atoms in its compound it was the stronger acid. Why is formic acid stronger?
- Wed Dec 04, 2019 3:54 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
- Replies: 115
- Views: 12370
Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
KBELTRAMI_4I wrote:For number 4 how does the hybridization become sp2 if there are 4 p electrons and 2 s electrons?
Because you need three hybrid orbitals for this compound with three areas of electron density, there are 6 electrons to place in total.
- Wed Dec 04, 2019 12:05 pm
- Forum: Lewis Acids & Bases
- Topic: Lewis Structure of CH3S-
- Replies: 2
- Views: 837
Lewis Structure of CH3S-
Based on the Lewis Structure of CH3S-, is this compound more likely to be a Lewis acid or base? This is from TB question 6A14.
- Sun Dec 01, 2019 5:46 pm
- Forum: Lewis Acids & Bases
- Topic: 6.5 - how to identify which is the lewis acid and base?
- Replies: 2
- Views: 265
Re: 6.5 - how to identify which is the lewis acid and base?
If you draw the Lewis structures, look at which have lone pairs. This will give you an indication of which will donate electrons (lewis base) and which will accept electrons (lewis acid)! For H2O2 and SO3, both have lone pairs on them. Would SO3 be the lewis acid because of its resonance structures?
- Sun Dec 01, 2019 5:41 pm
- Forum: Lewis Acids & Bases
- Topic: 6.5 - how to identify which is the lewis acid and base?
- Replies: 2
- Views: 265
6.5 - how to identify which is the lewis acid and base?
6.5 Hydrogen peroxide, H2O2, reacts with sulfur trioxide to form peroxomonosulfuric acid, H2SO5, in a Lewis acid–base reaction. (a) Write the chemical equation for the reaction. (b) Draw the Lewis structures of the reactants and product (in the product, one OOH group in sulfuric acid is replaced by ...
- Sat Nov 30, 2019 8:53 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentate = more than one lone pair?
- Replies: 4
- Views: 255
Polydentate = more than one lone pair?
I know that polydentate ligands must have more than one bonding site (and thus more than one lone pair), but do all ligands with more than one lone pair qualify as polydentate? How can you tell?
- Sat Nov 30, 2019 8:51 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: coordination number
- Replies: 8
- Views: 416
Re: coordination number
Yes, it's just based off the number of bonds, not lone pairs.
- Sat Nov 30, 2019 8:49 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: What is this?
- Replies: 5
- Views: 346
Re: What is this?
You should memorize a few of the common ligands for naming purposes (my TA recommended that we memorize I-, Cl-, Br-, OH-, CN-, C2O4-, H2O, NH3, CO, en). You should know which coordination compounds/ligands can be polydentate due to structure. For coordination number you just need to know how many b...
- Sat Nov 30, 2019 8:46 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: en and edta
- Replies: 2
- Views: 126
en and edta
Doing practice problems (particularly (9C9 from the TB) and came across the ligands en and edta a few times. What are these, how do we name them, and how would we draw them in a lewis structure?
- Mon Nov 25, 2019 11:12 am
- Forum: Hybridization
- Topic: Question 2F.15
- Replies: 2
- Views: 225
Question 2F.15
2F.15 Noting that the bond angle of an sp3 hybridized atom is 109.58 and that of an sp2 hybridized atom is 1208, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-character of the hybrids is increased? The answer is increases. Does anyone know why/can explain ...
- Sun Nov 24, 2019 9:24 pm
- Forum: Naming
- Topic: Week 9 and Week 10 HW?
- Replies: 21
- Views: 969
Re: Week 9 and Week 10 HW?
jvera4b wrote:Does anyone know if the HW for both weeks is due on week 10 for all discussions or only those after Wednesday?
I believe I was told it's for those after wednesday. I have a wednesday discussion so I'm gonna turn 5 in today and 5 in week ten just to be safe.
- Sun Nov 24, 2019 9:22 pm
- Forum: Naming
- Topic: Week 9 and Week 10 HW?
- Replies: 21
- Views: 969
Re: Week 9 and Week 10 HW?
I emailed my TA and he said that would be fine, just draw a line or label what is for week 9 and what is for week 10.
- Mon Nov 18, 2019 9:20 pm
- Forum: Ionic & Covalent Bonds
- Topic: Is ionic or covalent stronger?
- Replies: 31
- Views: 15754
Is ionic or covalent stronger?
I've found conflicting answers on the internet so I wanted to ask here. I was always taught throughout high school that covalent bonds are stronger than ionic bonds. But I came across a question in the textbook asking which of two substances would have a higher boiling point and I know that it has t...
- Sun Nov 17, 2019 8:25 pm
- Forum: Empirical & Molecular Formulas
- Topic: Can someone check this answer?
- Replies: 2
- Views: 350
Re: Can someone check this answer?
I actually got C4H8O. First, I used the grams of CO2 given to determine the grams of carbon. Next, I used the grams of H2O to determine the grams of hydrogen. Then, add these values together and subtract from 2.00 g of the sample compound to determine how many grams of oxygen there are. Afterwards,...
- Sun Nov 17, 2019 6:05 pm
- Forum: Empirical & Molecular Formulas
- Topic: Can someone check this answer?
- Replies: 2
- Views: 350
Can someone check this answer?
Doing a problem from a Test Bank exam, and I just wanted to check my answer. A 2.00 g sample of a compound containing only C, H, and O undergoes complete combustion and gives off 4.86g CO 2 and 2.03g H 2 O. What is the empirical formula of the substance? My answer was C 2 H 4 O 5 but i just wanted t...
- Fri Nov 15, 2019 3:35 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 2E1 - Molecules with bent geometry
- Replies: 7
- Views: 370
Re: 2E1 - Molecules with bent geometry
Do lone pair electrons have a stronger force of repulsion of atoms compared to the strength of atoms repelling against each other? These are the relative strengths of repulsion: lone-lone pair repulsion > lone-bonding pair repulsion > bonding-bonding pair repulsion I've heard from a past student kn...
- Fri Nov 15, 2019 3:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: bond angles
- Replies: 9
- Views: 577
Re: bond angles
Differences in bond angles are dependent on the type of atoms involved in the molecule and their electronegativity and the lone pairs. For example, NH3 and SO32- are both AX3E molecules, but the NH3 has a 107 degree bond angle and SO32- has 106 degree bond angle.
- Fri Nov 15, 2019 3:31 pm
- Forum: Student Social/Study Group
- Topic: Midterm Average
- Replies: 12
- Views: 802
Re: Midterm Average
Wait so regarding the class curve, will that help or hurt our final grades? Does he have a set amount of A's he gives out?
- Fri Nov 15, 2019 3:30 pm
- Forum: Student Social/Study Group
- Topic: Chemistry Youtube Channels
- Replies: 8
- Views: 444
Re: Chemistry Youtube Channels
Crash Course with Hank Green is helpful for a very broad overview of the concepts (plus they're not boring so may be helpful if you get bored with the longer lecture style videos). But I think the Khan Academy videos in their AP chemistry course are really helpful too. Definitely recommend the ones ...
- Fri Nov 15, 2019 3:28 pm
- Forum: Administrative Questions and Class Announcements
- Topic: TEST 2
- Replies: 8
- Views: 417
Re: TEST 2
He confirmed in lecture (2PM) today that the test will not be cumulative, and will cover everything covered after the midterm as well as Monday's lecture. Intermolecular forces, polarity, more lewis dot structures, VSEPR theory.
- Wed Nov 06, 2019 11:05 am
- Forum: Dipole Moments
- Topic: Interactions between Ions and Molecules
- Replies: 5
- Views: 241
Re: Interactions between Ions and Molecules
For example, a hydrogen bond would have an energy of a greater magnitude (a larger negative number) because they are much stronger and require much more energy to break than a dipole-dipole interaction.
- Wed Nov 06, 2019 11:04 am
- Forum: Dipole Moments
- Topic: How do i know if a molecule has a dipole moment?
- Replies: 7
- Views: 375
How do i know if a molecule has a dipole moment?
Is there a certain threshold of electronegativity difference that two atoms in a molecule must have in order to make it a polar molecule with a dipole moment? Also are we going to be given a table with electronegativities on the midterm, or will that info be provided in the question if asked, or not...
- Wed Nov 06, 2019 11:00 am
- Forum: Trends in The Periodic Table
- Topic: Run Down of Trends
- Replies: 4
- Views: 203
Re: Run Down of Trends
Electronegativity increases as you go right and decreases as you go down. So electronegativity is highest in the upper right hand corner of the PT. Ionization energy increases as you go right and decreases as you go down. So ionization energy is highest in the upper right hand corner of the PT. Atom...
- Wed Nov 06, 2019 10:55 am
- Forum: Quantum Numbers and The H-Atom
- Topic: Equations we need for midterm
- Replies: 7
- Views: 621
Re: Equations we need for midterm
Equations we need for the midterm: Unit 1 (HS Review) Dilutions: (M i )V i ) = (M f V f ) Percent yield: Actual/theoretical X 100 M = moles/liters Unit 2 - Quantum Photoelectric effect: E=hv E photon - work function = KE electron (energy of the photon minus threshold energy = kinetic energy of the e...
- Wed Nov 06, 2019 10:46 am
- Forum: Quantum Numbers and The H-Atom
- Topic: Any good practice problems?
- Replies: 1
- Views: 183
Any good practice problems?
Hey, does anyone have any good practice problems for quantum numbers? I'm studying for the midterm right now and I've done mostly all of the probs in the Textbook so if anyone knows of another good source to practice lmk.
- Fri Nov 01, 2019 5:12 pm
- Forum: Lewis Structures
- Topic: Expanded Valence Shells
- Replies: 4
- Views: 215
Re: Expanded Valence Shells
If I'm correctly remembering this, any element in period 3 and beyond can have an expanded valence shell. I don't think there is a limit to how expanded the valence shell can be, but generally, most compounds don't really go past 12-ish VE in their Lewis Dot Structure.
- Fri Nov 01, 2019 5:11 pm
- Forum: Lewis Structures
- Topic: Best way to go about drawing Lewis structures
- Replies: 7
- Views: 329
Re: Best way to go about drawing Lewis structures
Yes, that process will generally get you the correct result. I think a lot of it is just building an intuition around knowing where to place each atom/bond, which gets easier with practice. It's harder when you're doing Lewis structures for a compound consistent of multiple polyatomic ions like H2CN...
- Fri Nov 01, 2019 5:06 pm
- Forum: Ionic & Covalent Bonds
- Topic: Anions and Cations
- Replies: 9
- Views: 441
Re: Anions and Cations
With cations, the electrons are pulled more closely towards the nucleus because there is less electron shielding occurring. Whereas an anion, because of the additional valence electrons, have a larger outer shell.
- Fri Nov 01, 2019 5:05 pm
- Forum: Ionic & Covalent Bonds
- Topic: How does one find a most likely charge for ions for a given element?
- Replies: 6
- Views: 486
Re: How does one find a most likely charge for ions for a given element?
There are so exceptions with the transition metals (they may have different ionic charges depending on what they react with), but in general the elements in groups 1, 2, and 3 will form cations with charges 1+, 2+, and 3+ respectively, while the elements in groups 4,5,6,7 will form anions with charg...
- Fri Nov 01, 2019 5:03 pm
- Forum: Ionic & Covalent Bonds
- Topic: Midterm
- Replies: 28
- Views: 1238
Re: Midterm
Also, Lavelle mentioned that most of the High School Review unit will not be on the test, since we already learned it. Expect heavy focus on quantum and chemical bonds up to 2D.
- Fri Oct 25, 2019 5:24 pm
- Forum: Ionic & Covalent Bonds
- Topic: Identifying Ionic vs Covalent
- Replies: 7
- Views: 271
Re: Identifying Ionic vs Covalent
We will also be able to look at formal charges within the molecule to determine polarity of a covalent bond.
- Fri Oct 25, 2019 5:22 pm
- Forum: Lewis Structures
- Topic: Finding Valence Electrons
- Replies: 8
- Views: 407
Re: Finding Valence Electrons
If you want to be sure, you can think of the electron configuration for the outermost n level. So for an element where the highest energy level is n=2, you can count the number of electrons in the orbitals starting with 2 (in this case 2s and 2p) to get the VE number.
- Fri Oct 25, 2019 5:21 pm
- Forum: Lewis Structures
- Topic: Transition Elements
- Replies: 2
- Views: 122
Re: Transition Elements
In most problems, we should be given the charge for transition metals. I think the only type of problems in which we would need to figure out the charge of a transition metal would be if we are given a compound with a nonmetal that we already know the charge of (for example, we'd be given Zn2O3 and ...
- Fri Oct 25, 2019 5:18 pm
- Forum: Lewis Structures
- Topic: Video Modules
- Replies: 11
- Views: 427
Re: Video Modules
I remember him saying that he only made video modules for the HS review stuff that we were supposed to complete before week zero and that he also made them for quantum topics because those are harder to understand. So my guess is probably not, unfortunately, but I would love to have more video modul...
- Fri Oct 25, 2019 5:16 pm
- Forum: Lewis Structures
- Topic: Steps to drawing a structure
- Replies: 5
- Views: 213
Re: Steps to drawing a structure
I second the above answer. The exception is hydrogen, of course. You never put hydrogen at the center of the molecule when drawing a dot structure.
- Fri Oct 18, 2019 9:32 pm
- Forum: Trends in The Periodic Table
- Topic: Exceptions in Periodic Trends
- Replies: 2
- Views: 2766
Re: Exceptions in Periodic Trends
Yes, there are a few exceptions to the general trends we see on the periodic table. Electronegativity increases as you move to the right of the PT from the metals up to the halogens, but the noble gases do not have electronegativities (unless forced under very extreme pressure/conditions) because th...
- Fri Oct 18, 2019 9:21 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Hund's Rule
- Replies: 4
- Views: 262
Re: Hund's Rule
I believe Dr. Lavelle also said that the electrons choose to occupy different orbitals before pairing up because they are more stable this way.
- Fri Oct 18, 2019 9:19 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Quantum vs Classical
- Replies: 5
- Views: 176
Re: Quantum vs Classical
To echo some of the above responses, quantum mechanics deals in very extreme values (for example, very large numbers for speed/frequency and very low numbers for mass, momentum, wavelength, energy). In quantum mechanics, because the subjects we are calculating for are so small, there is also a certa...
- Fri Oct 18, 2019 9:16 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbital Order
- Replies: 2
- Views: 122
Re: Orbital Order
Yes, Andrew F is right. Even though the 4s orbital is chronologically before the 3d orbital on the periodic table, an orbital's energy level and thus its order of being filled is determined by its first quantum number n, not its quantum number l (which indicates if the orbital is s,p,d,f). Basically...
- Fri Oct 11, 2019 10:49 am
- Forum: Properties of Electrons
- Topic: Constructive and Destructive Interference
- Replies: 4
- Views: 341
Re: Constructive and Destructive Interference
Yes, you can see the effect of the interference in the diffraction pattern, and depending on how in-phase/out of phase the waves are, you will see different patterns. If you have two waves undergoing constructive interference, the amplitude of the resulting wave gets larger, so the light will be bri...
- Fri Oct 11, 2019 10:46 am
- Forum: Properties of Light
- Topic: Clarification on Frequency
- Replies: 8
- Views: 414
Re: Clarification on Frequency
To answer 905289082: The energy of the light is related to the frequency of it, not the intensity per se. Amplitude is intensity (the brighter the light, the higher the amplitude), but the amplitude of the light has no bearing on the equation of the energy. The wavelength of the light has a direct e...
- Fri Oct 11, 2019 10:35 am
- Forum: Properties of Light
- Topic: Electromagnetic Spectrum
- Replies: 4
- Views: 186
Re: Electromagnetic Spectrum
It'll probably be useful, especially with problems from photoelectric effect/atomic spectra lessons. Here's a breakdown by wavelength from smallest wavelengths (highest frequency) to largest wavelength: Gamma rays, <0.01 nm X-rays, 0.01 nm - 10 nm Ultraviolet, 10 nm - 400 nm Visible Light, 400 nm - ...
- Fri Oct 11, 2019 10:32 am
- Forum: Properties of Light
- Topic: models of light
- Replies: 5
- Views: 323
Re: models of light
In this course, Dr. Lavelle won't expect us to know when to use each model, but we should be able to look at an experiment that was covered in class and know which model is appropriate to describe the behavior of light. So if a basic photoelectric effect experiment setup is described in a problem, w...
- Fri Oct 11, 2019 10:28 am
- Forum: Properties of Light
- Topic: Speed of light
- Replies: 9
- Views: 294
Re: Speed of light
In this course we should always be able to assume that it's under a vaccuum. If there are any problems not under a vaccuum, you should be given the appropriate velocity so you're still able to calculate what you need. The relationship between wavelength and frequency is the same with a non-c velocit...
- Thu Oct 10, 2019 9:03 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Electron energy: is it related to physics concepts?
- Replies: 1
- Views: 97
Electron energy: is it related to physics concepts?
Hi, in lecture yesterday Dr. Lavelle was explaining the equation E=-hr/n^2 and how the further away from the nucleus an electron gets, the lower the absolute value of its energy will get. My mind kind of associated this with Coulomb's law and gravitational force which dictates that the farther away ...
- Sat Oct 05, 2019 11:17 am
- Forum: Molarity, Solutions, Dilutions
- Topic: Some practice probs (not from HW) to study for the test!
- Replies: 1
- Views: 368
Re: Some practice probs (not from HW) to study for the test!
My Answers G.3) a) heterogenous, they will separate on their own and you can take the oil from the top. b) heterogenous, use a sifter to separate larger salt crystals from fine chalk dust. c) homogenous, boil the water to evaporate it from the salt. G.6) a) 0.08161 M, b) 0.04080 M G.12) a) 16.72 mL...
- Sat Oct 05, 2019 11:06 am
- Forum: Molarity, Solutions, Dilutions
- Topic: Some practice probs (not from HW) to study for the test!
- Replies: 1
- Views: 368
Some practice probs (not from HW) to study for the test!
Hi guys, I wanted to create a thread for some good practice problems from the TB (not part of the HW questions) to study for the test in week 2. Feel free to share any good practice probs you find so we can all study together! Molarity/Dilution Practice Problems G.3) Identify the following mixtures ...
- Sat Oct 05, 2019 11:00 am
- Forum: Limiting Reactant Calculations
- Topic: Some practice probs (not from HW) to study for the test!
- Replies: 1
- Views: 284
Re: Some practice probs (not from HW) to study for the test!
My answers
2) 43.67% yield
6) 3 moles of N2H4 will not react, you will get approx 36 moles HF, 9 moles N2, and 6 moles Cl2
8) Al2O3 + 3C + 3Cl2 > 2AlCl3 + 3CO, 125 kg of AlCl3 produced
2) 43.67% yield
6) 3 moles of N2H4 will not react, you will get approx 36 moles HF, 9 moles N2, and 6 moles Cl2
8) Al2O3 + 3C + 3Cl2 > 2AlCl3 + 3CO, 125 kg of AlCl3 produced
- Sat Oct 05, 2019 10:48 am
- Forum: Limiting Reactant Calculations
- Topic: Some practice probs (not from HW) to study for the test!
- Replies: 1
- Views: 284
Some practice probs (not from HW) to study for the test!
Hi guys, I wanted to create a thread for some good practice problems from the TB (not part of the HW questions) to study for the test in week 2. Feel free to share any good practice probs you find so we can all study together! Limiting Reagent Calculation Problems M.2) The metal vanadium can be extr...
- Sat Oct 05, 2019 10:15 am
- Forum: Empirical & Molecular Formulas
- Topic: Some good practice problems (not from HW) to study for the test!
- Replies: 1
- Views: 401
Re: Some good practice problems (not from HW) to study for the test!
Answers
F.6) 79.12% C, 9.786% H, 11.09% O
F.28) 76.09%
F.10) C5H14N2
F.16) C17H18F3NO
F.18) C47H51NO14 molecular formula=empirical formula
F.21) mass comp 62.4% C, 8.31% H, 8.93% N, 20.4% O, EF= C8H13NO2, MF= C48H78N6O12
F.6) 79.12% C, 9.786% H, 11.09% O
F.28) 76.09%
F.10) C5H14N2
F.16) C17H18F3NO
F.18) C47H51NO14 molecular formula=empirical formula
F.21) mass comp 62.4% C, 8.31% H, 8.93% N, 20.4% O, EF= C8H13NO2, MF= C48H78N6O12
- Sat Oct 05, 2019 9:48 am
- Forum: Empirical & Molecular Formulas
- Topic: Some good practice problems (not from HW) to study for the test!
- Replies: 1
- Views: 401
Some good practice problems (not from HW) to study for the test!
Hi guys, I wanted to create a thread for some good practice problems from the TB (not part of the HW questions) to study for the test in week 2. Feel free to share any good practice probs you find so we can all study together! Empirical and Molecular Formula derivation + Mass Composition practice Ma...
- Sun Sep 29, 2019 4:47 pm
- Forum: Empirical & Molecular Formulas
- Topic: HW Question L.39 - What in the world is a crucible you guys?
- Replies: 3
- Views: 296
HW Question L.39 - What in the world is a crucible you guys?
L.39 A 1.50-g sample of metallic tin was placed in a 26.45-g crucible and heated until all the tin had reacted with the oxygen in air to form an oxide. The crucible and product together were found to weigh 28.35 g. (a) What is the empirical formula of the oxide? (b) Write the name of the oxide. This...
- Sun Sep 29, 2019 11:31 am
- Forum: Significant Figures
- Topic: How does Significant Figures work? [ENDORSED]
- Replies: 12
- Views: 596
Re: How does Significant Figures work? [ENDORSED]
Also, calculate significant figures using the values given to you in the problem. Scientific constants would not be used to determine the significant figures of your final answer. So you wouldn't use the SF in Avogadro's number or Planck's constant to calculate the SF in your answer. Always stick to...
- Sun Sep 29, 2019 11:27 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Formula Unit
- Replies: 7
- Views: 1080
Re: Formula Unit
Are formula units used to describe ionic compound because they easily disassociate in water/aqueous solutions?
- Sun Sep 29, 2019 11:26 am
- Forum: Empirical & Molecular Formulas
- Topic: Question E29D.
- Replies: 2
- Views: 170
Re: Question E29D.
I first calculated the total molar mass of the compound CuCL 2 4H 2 O, which came out to be 206.51 grams/mol. Dividing the given mass by this molar mass gave me 0.042 moles of the compound. Since the molar ratio of the compound to the oxygen is 1:4, you know you have 0.167 moles of Oxygen in the com...
- Sat Sep 28, 2019 8:29 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Question E.9 - Writing Molecular Formula + Mole Calculations
- Replies: 6
- Views: 307
Re: Question E.9 - Writing Molecular Formula + Mole Calculations
Thank you! Conversely, if anyone has any refresher tips for deriving the name of the compound from the molecular formula that would be much appreciated. For exmaple, being given NH₄NO₃ and having to figure out the proper suffixes/prefixes.
- Sat Sep 28, 2019 6:09 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Question E.9 - Writing Molecular Formula + Mole Calculations
- Replies: 6
- Views: 307
Question E.9 - Writing Molecular Formula + Mole Calculations
Hi! I'm having trouble with question E.9 part a) from the textbook on page F45: Epsom salts consist of magnesium sulfate heptahydrate. Write its formula. Figuring out the correct molecular formula for a given name of a compound was unfortunately not my strong suit in HS chem as my teacher kind of gl...