## Search found 58 matches

Sat Jan 16, 2021 6:17 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Determining Percent Protonation
Replies: 3
Views: 10

### Determining Percent Protonation

Hello,
I am stuck on the Sapling HW problems regarding protonation (ex. HW2 #5). I understand how to calculate ionization, but what's the difference between protonation and ionization? Also, how do I calculate protonation?
Sat Jan 16, 2021 6:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE table and Molarity units
Replies: 12
Views: 22

### Re: ICE table and Molarity units

Hi!
When putting in the concentrations into the ICE table, I prefer to make everything into mol/L so that I know I don't need to worry about units later on. I think it is easier if you use mol/L and keep in mind that 1mmol=10^-3 mol.
I hope this helped!
Sat Jan 16, 2021 6:10 pm
Forum: Ideal Gases
Topic: Kc vs. Kp
Replies: 7
Views: 21

### Re: Kc vs. Kp

Hi! To solve for Kc and Kp, it is the same set up of having products/reactants. The only difference is Kc uses the concentrations of the products over the concentrations of the reactants; while Kp uses the Pressure of the products over the pressure of the reactants. The same rules also follow with t...
Mon Jan 11, 2021 2:00 pm
Forum: Ideal Gases
Topic: PV=nRT
Replies: 63
Views: 404

### Re: PV=nRT

P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is temperature. You can manipulate this equation in several ways, one of which being P= (n/V)*RT which can also be rewritten as P=concentration*RT because (n/V) is how concentration is calculated.
Mon Jan 11, 2021 1:58 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: ICE Table
Replies: 9
Views: 34

### ICE Table

Hi! I don't know if this is the correct place to put this question, but when making an ICE table and solving for the equilibrium concentrations, how do we know in the C row which side has the positive and negative values for x. I understand that the coefficients to x are the stoichiometric coefficie...
Sun Jan 10, 2021 12:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Q9
Replies: 3
Views: 34

### Re: Sapling Q9

The first step to solving this is to figure out the value of the Kc expression, which we can do since we our given the equilibrium concentrations of all the species. Since our reaction is N2 + O2 --> 2NO, our Kc expression is (NO)^2/(N2)(O2). Then, plugging the concentration values into this expres...
Sun Jan 10, 2021 11:42 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #5
Replies: 11
Views: 83

### Re: Sapling #5

Hey Dana, So what I did was use the first and third equations given. You want to manipulate the equations so that, when they are added together, they make the equation that is originally given. I multiplied by three to make H2+I2=2HI into 3H2+3I2=6HI (sorry the equal sign should actually be the equ...
Thu Jan 07, 2021 6:02 pm
Forum: Ideal Gases
Topic: Partial Pressure Gas Question
Replies: 4
Views: 23

### Partial Pressure Gas Question

Hi, on the chem equilibrium pt 2 module post assessment I am stuck on a question asking to calculate the partial pressure of each product and reactant. The reaction 2 SO2 (g) + O2 (g) ⇌ 2 SO3 (g) occurs in a 1.00 L flask at 312 K and at equilibrium the concentrations are 0.075 mol.L-1 SO2 (g), 0.537...
Tue Dec 15, 2020 9:23 am
Forum: Conjugate Acids & Bases
Topic: What is the difference between a lewis acid and bases and Bronsted acids and bases?
Replies: 7
Views: 49

### Re: What is the difference between a lewis acid and bases and Bronsted acids and bases?

Lewis acids/bases pertain to the accepting (lewis acid) or donating (lewis base) of electrons. While Bronsted acids/bases have to do with donating H+ protons (Bronsted acid) and accepting H+ protons (bronsted base).
Sun Dec 13, 2020 9:02 am
Forum: Student Social/Study Group
Topic: Final Jitters
Replies: 226
Views: 35927

### Re: Final Jitters

To who ever is reading this, you made it through the whole quarter! You have worked so hard and all the practice problems and hours of work that you've put into this class will pay off. Stay positive, and trust yourself that you know what you are doing!! Best of luck y'all.
Sun Dec 13, 2020 9:00 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Textbook problem 6C.17
Replies: 4
Views: 53

### Re: Textbook problem 6C.17

Just by going off of the previous posts I understand why BrO- is the stronger base, but would we be expected to know how to calculate the pKb for this problem?
Thu Dec 10, 2020 4:12 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Early Quantum Question (from Wilberth's Q&A)
Replies: 4
Views: 74

### Re: Early Quantum Question (from Wilberth's Q&A)

I was confused on a different question in this review. The Uncertainty Problem #1 asks, Take the avg diameter of an alveoli, tiny sacs of air in the lungs, to be 0.23mm. If an oxygen molecule is trapped within the sac, the uncertainty in the position will be 0.12mm. What is the minimum uncertainty i...
Mon Dec 07, 2020 4:37 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelating Complexes
Replies: 2
Views: 34

### Chelating Complexes

What are chelating complexes?
Textbook question 9C.7 asks about them, but I do not even know where to begin..
Mon Dec 07, 2020 4:20 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Homework Problem 9C.5
Replies: 3
Views: 43

### Re: Homework Problem 9C.5

I was also stuck on this question. Is the best way to determine the denticity of a molecule to draw it out and count the number of lone pairs?
Mon Dec 07, 2020 3:51 pm
Forum: Biological Examples
Topic: Difference between Myoglobin and heme complex
Replies: 8
Views: 89

### Re: Difference between Myoglobin and heme complex

In a setup session my UA explained to us that the Heme Complex is one Iron, Fe, surrounded by & bonded to 4 Nitrogens, N. All of the Nitrogens are also connected. The Heme complex is therefore flat (like a pancake) and myoglobin is made up of these Heme Complexes. In myoglobin, O2 molecules wil...
Mon Dec 07, 2020 3:49 pm
Forum: Biological Examples
Topic: Difference between Myoglobin and heme complex
Replies: 8
Views: 89

### Re: Difference between Myoglobin and heme complex

In a setup session my UA explained to us that the Heme Complex is one Iron, Fe, surrounded by & bonded to 4 Nitrogens, N. All of the Nitrogens are also connected. The Heme complex is therefore flat (like a pancake) and myoglobin is made up of these Heme Complexes. In myoglobin, O2 molecules will...
Mon Dec 07, 2020 3:43 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Numbers
Replies: 11
Views: 81

### Re: Coordination Numbers

The central atom is the transition metal, which is typically the first element listed in the coordination sphere brackets.
Mon Nov 30, 2020 7:56 pm
Forum: Administrative Questions and Class Announcements
Topic: PeppermintMocha
Replies: 11
Views: 263

### Re: PeppermintMocha

Thank you so much! Are there answers available to check our work?
Sun Nov 29, 2020 11:39 am
Forum: Dipole Moments
Topic: H-Bonds
Replies: 14
Views: 107

### Re: H-Bonds

Maddie Turk Disc 2C wrote:Is it any time that H is bonded to N, O, or F or does there have to be another requirement met for their to be hydrogen bonding dispersion?

From my understanding, an H has to already be covalently bonded to a N, O, or F for it for form a Hydrogen bond with a different N, O, or F. I hope that helps!
Sun Nov 29, 2020 11:34 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw and T-shapes
Replies: 4
Views: 41

### Seesaw and T-shapes

Hi,
I am having a lot of trouble identifying the seesaw shape and t-shape. What are the lone pairs and number of electron densities for each? What are the bond angles?
Thanks.
Sun Nov 29, 2020 11:32 am
Forum: Hybridization
Topic: Hybridization visually
Replies: 2
Views: 28

### Re: Hybridization visually

Also, in his notes he denoted that the hybridizations correspond to shapes (sp^2 is trigonal planar and sp^3 is tetrahedral). Will this always be true, or does it vary depending on the connectivities and lone pair electrons?
Sun Nov 29, 2020 11:31 am
Forum: Hybridization
Topic: Hybridization visually
Replies: 2
Views: 28

### Hybridization visually

I am confused about the images that Dr. Lavelle drew during lecture depicting the hybridization. He was trying to explain which atom was the s and how it made a p orbital by drawing the shapes, but I was not following. Do we have to recognize which atoms have s and p character in a molecule? Or do w...
Sun Nov 29, 2020 11:27 am
Forum: Determining Molecular Shape (VSEPR)
Topic: What is coplanar?
Replies: 8
Views: 65

### Re: What is coplanar?

When things are coplanar it means it lies in the same plane. There is an x, y, and z plan. So, if something were coplanar all the molecules would be in the same plane. If you picture something that is trigonal planar, it is 'flat' and all the atoms are in the same plane or as explained above all par...
Mon Nov 23, 2020 7:24 pm
Forum: Hybridization
Topic: hybridization of phosphorus (Sapling Q.11)
Replies: 21
Views: 96

### Re: hybridization of phosphorus (Sapling Q.11)

It asks for the hybridization of P, but each structure has 4 regions of electron density so they would all have the same answer. So, is it just a trend that if P has 4 regions of electron density it will always be sp^3
Mon Nov 23, 2020 7:21 pm
Forum: Resonance Structures
Topic: sapling #18 wk 7/8
Replies: 5
Views: 58

### sapling #18 wk 7/8

Hello, In this sapling question, the three resonance structures looked nothing alike(a question asked if any of the resonance structures resembled another). I'm confused because I thought resonance structures meant that the Lewis Structures were similar and the difference would be moving around doub...
Mon Nov 23, 2020 7:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling #18, Week 7/8
Replies: 4
Views: 58

### Re: Sapling #18, Week 7/8

For this question it also tells us that one of the resonance structures is cyclic, what exactly does that mean?
Fri Nov 20, 2020 8:57 am
Forum: Electronegativity
Topic: General Explanation
Replies: 9
Views: 91

### Re: General Explanation

Also, how do we calculate the electronegativity differences when we do not know the values of the atom's electronegativity? Is it just a general estimation?
Fri Nov 20, 2020 8:57 am
Forum: Electronegativity
Topic: General Explanation
Replies: 9
Views: 91

### General Explanation

What is the significance of an atom having high electronegativity? Does it mean it is more reactive? How does it act in reactions?
Sun Nov 15, 2020 9:27 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E.21 (omit c)
Replies: 3
Views: 34

### Re: 1E.21 (omit c)

It helps to draw this out visually for me. So, for the Bi it is in the p block and has 5 valence electrons. You know that the p block has 3 subshells, so draw out the subshells and begin to evenly distribute the electrons to each subshell (Hund's Rule). After doing that you will be able to see that ...
Sun Nov 15, 2020 10:44 am
Forum: Formal Charge and Oxidation Numbers
Topic: Number of Resonance Structures
Replies: 7
Views: 80

### Re: Number of Resonance Structures

Hi! From my understanding, there's no easy way to know or calculate how many resonance structures there are for a molecule, you just have to practice knowing how to identify them when drawing the Lewis structure. Hopefully, we will be given relatively simple ones if asked on the midterm, like C4H4,...
Sat Nov 14, 2020 11:26 am
Forum: Dipole Moments
Topic: H-Bonds
Replies: 14
Views: 107

### Re: H-Bonds

In a H-bond, I think of it like the Hydrogen needs to be sandwiched between two NOF. So this means that one one end, the H need to have a covalent bond to a H,O, or F, and can only then form a H-bond to a different N,O,F if there's a lone pair electron. So in a structure where O has two lone pairs a...
Sat Nov 14, 2020 11:22 am
Forum: Formal Charge and Oxidation Numbers
Topic: Number of Resonance Structures
Replies: 7
Views: 80

### Number of Resonance Structures

How do we know how many resonance structures there are for one molecule? My TA said we need to draw all the Lewis Structures to determine which structure is the most stable (which would be the best answer), but how do we know how many structures we need to draw?
Sat Nov 14, 2020 11:20 am
Forum: Sigma & Pi Bonds
Topic: Triple bond?
Replies: 21
Views: 165

### Re: Triple bond?

For triple bonds, the first bond is a Sigma bond after that the other two bonds are Pi bonds. So, there would be one Sigma and two Pi bonds in a triple bond
Mon Nov 09, 2020 9:10 am
Forum: Lewis Acids & Bases
Topic: Lewis Acids & Bases
Replies: 12
Views: 88

### Re: Lewis Acids & Bases

The way I remember this is Lewis Acids Accept electron pairs (think Acid = Accepts), and Lewis Bases Donate electron pairs. Lewis Acids include cations, electron-deficient central atoms, and polar double bonds. (ex: BF3, H+) Lewis Bases include anions, molecules w lone pairs, atoms w excess electron...
Mon Nov 09, 2020 9:01 am
Forum: Quantum Numbers and The H-Atom
Topic: order of electron cnfiguration
Replies: 13
Views: 114

### Re: order of electron cnfiguration

Adding onto this question, why does the d block start with 3 in front of it when it starts in the 4th period? This is because when n=3, p can be equal to 2 (p = 0 to n-1). So, because the period n=3 can accommodate the d-orbital, d can be labeled 3d. Also, if you look at the energies, 3d becomes lo...
Wed Nov 04, 2020 3:37 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Shortcut for Formal Charge
Replies: 19
Views: 583

### Re: Shortcut for Formal Charge

A trick I learned in a step up session was to look at the element, (for ex. N) and see how many valence electrons it has (look at the group for this). Then subtract that number (in this case 5) by the number of "things" (the bond lines and electron dots). So if this N had a single bond and...
Wed Nov 04, 2020 3:34 pm
Forum: Quantum Numbers and The H-Atom
Topic: order of electron cnfiguration
Replies: 13
Views: 114

### Re: order of electron cnfiguration

Adding onto this question, why does the d block start with 3 in front of it when it starts in the 4th period?
Wed Nov 04, 2020 3:31 pm
Forum: Lewis Structures
Topic: Lone Pair Electrons
Replies: 3
Views: 30

### Lone Pair Electrons

Hi, today in my discussion I was told that lone pair electrons did not need to be represented in a Lewis Structure, however during lecture and on sapling this week the answers only work if they are indicated. I was curious about whether or not the "value" of a Lewis Structure would change ...
Fri Oct 30, 2020 12:00 pm
Forum: Quantum Numbers and The H-Atom
Topic: Number of Electrons per Shell
Replies: 5
Views: 38

### Number of Electrons per Shell

During today's lecture (10/30) Dr. Lavelle mentioned that there is a mathematical way to determine the number of electrons per shell. Would someone mind explaining this to me? I don't know how to determine the number of electrons in a shell when it only gives the quantum number n.
Thu Oct 29, 2020 3:53 pm
Forum: Properties of Electrons
Topic: Sapling Week 4 #25
Replies: 4
Views: 51

### Re: Sapling Week 4 #25

In these types of problems when talking about electrons being emitted or absorbed you know that you need to use the mass of an electron. I didn't realize this, but normally the question will specify what particle you are looking for. In this case, you would use the mass of an electron, 9.109 x 10^-3...
Thu Oct 29, 2020 3:48 pm
Forum: Quantum Numbers and The H-Atom
Topic: Number of electrons
Replies: 4
Views: 63

### Number of electrons

How do we determine how many electrons are in certain quantum numbers?
For example how do you know how many electrons there are when n=3?
I understand that the l value tells the shape, but what does the the n and ml value represent and how do you know how to get those corresponding numbers?
Thu Oct 29, 2020 3:45 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Determining Element with e- Configuration
Replies: 2
Views: 20

### Determining Element with e- Configuration

A question on Sapling asked to identify which element was represented in its excited state and to also write what its ground state would be. The electron configuration is 1s^{2}2s^{2}2p^{3}3s^{1} I do not understand which element this would be because I thought that the 2p had to be ^6 in order for ...
Mon Oct 26, 2020 4:44 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Problem 1B.25
Replies: 6
Views: 85

### Re: Problem 1B.25

Since we cannot ask the same question twice I was also having difficulty with this one. On the solutions manual, the solution is using a different equation than the one listed on our formula sheet. However, even if I use a different formula I should be getting the same answer, however, that is not t...
Sun Oct 25, 2020 9:54 pm
Forum: Einstein Equation
Topic: Rydberg's Equation
Replies: 9
Views: 84

### Re: Rydberg's Equation

Hey again! So when you solve using the equation (solving for the energy of the initial and the energy of the final state and subtracting it) that usually gives you a negative energy, which represent the CHANGE in energy of the ELECTRON after going from the initial state to the final state. Because ...
Sun Oct 25, 2020 3:58 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Specta Post-Module Assessment #41
Replies: 3
Views: 33

### Re: Atomic Specta Post-Module Assessment #41

What's the difference between the equation that was listed above and using the E=hv=(-hR/n^2)-(-hR/n^2) and solving for the other n value. I keep getting the wrong answer when I use that.
Thu Oct 22, 2020 9:00 pm
Forum: Einstein Equation
Topic: Rydberg's Equation
Replies: 9
Views: 84

### Re: Rydberg's Equation

Hello! For the most part, it's Final - Initial. I can't think of a situation where we would use Initial - Final. As for the equation, I've heard that you switch N1 and N2, dependent upon whether you're going to get a negative or positive. So, if the problem mentions absorption you would want a posi...
Thu Oct 22, 2020 5:56 pm
Forum: Einstein Equation
Topic: Rydberg's Equation
Replies: 9
Views: 84

### Rydberg's Equation

Hi! Sorry this might be in the wrong category, but I couldn't find one regarding Rydberg's Equation. Anyways I have some confusion after a UA step up session that I hope can be clarified! In Rydberg's equation, \frac{c}{\lambda R }= ((\frac{1}{n_{1}^{2}})-(\frac{1}{n_{2}^{2}})...
Sun Oct 18, 2020 2:11 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equations vs Dr Lavelle's Empirical Equation
Replies: 2
Views: 29

### Re: Rydberg Equations vs Dr Lavelle's Empirical Equation

I was wondering the same thing, and since we can't have duplicate questions, I was wondering which one is the initial and which is the final in Rydberg's equation. Is n(subscript 1) the initial or final?
Sun Oct 18, 2020 12:21 pm
Forum: Photoelectric Effect
Topic: Kinetic Energy of Electron
Replies: 3
Views: 32

### Re: Kinetic Energy of Electron

Hi Raashi, you don't actually need to factor in the threshold energy in order to calculate the kinetic energy of the outcoming electron. The energy of that electron will just be E=.5mv^2, and since you know the velocity of the electron you just need to use the mass of an electron (9.11x10^-31) to c...
Sun Oct 18, 2020 10:36 am
Forum: Photoelectric Effect
Topic: Kinetic Energy of Electron
Replies: 3
Views: 32

### Kinetic Energy of Electron

Question 28 in Photoelectric Module: Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. Answer the following three questions. A. What is the kinetic energy of the ejected electron? So, if I am given the velo...
Thu Oct 15, 2020 1:35 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Question during Lecture on 10/14
Replies: 4
Views: 40

### Question during Lecture on 10/14

While Dr. Lavelle was going through and explaining Bohr's frequency condition I got a little confused with the model he was drawing. He had a line at the bottom which was n=1 and a line above that was n=2. Between the two lines was an arrow going down from n=2 to n=1 and next to it he had 'e-' or el...
Thu Oct 15, 2020 1:30 pm
Forum: Properties of Light
Topic: Light Intensity
Replies: 8
Views: 66

### Re: Light Intensity

On another note for this, to eject electrons you must have a high enough frequency of light hitting the metal surface to do so, but is that high frequency caused by a short wavelength? Are UV rays the only type of ray with the correct wavelength and frequency to get electrons emitted from a metal su...
Thu Oct 15, 2020 1:27 pm
Forum: Properties of Light
Topic: Light Intensity
Replies: 8
Views: 66

### Light Intensity

I am not totally clear on what light intensity is. I understand that increasing the intensity of light doesn't produce more electrons to be ejected, the ejection of electrons is depended on having a high enough frequency. What is light intensity? What are its units? Is it just the 'amount' of light ...
Thu Oct 08, 2020 5:23 pm
Forum: Limiting Reactant Calculations
Topic: M.9 Clarification
Replies: 8
Views: 68

### Re: M.9 Clarification

I am also confused about this question because I also found online that sodium hydroxide is OH, but I thought it was NaOH (that was already stated in previous replies, but my confusion is I do not see any sodium in the products side of the equation.
Thu Oct 08, 2020 9:15 am
Forum: Limiting Reactant Calculations
Topic: Stoichiometric Coefficients
Replies: 3
Views: 31

### Stoichiometric Coefficients

While ding limiting reactants problems I know that we need to take the stoichiometric coefficients of the balanced equation into account; however, I get confused when trying to figure out which one of the reactants is limited. For example, M5 in the textbook: 6ClO2(g)+2BrF3(l)→6ClO2F(s)+Br2(l) is ca...
Thu Oct 08, 2020 9:05 am
Forum: SI Units, Unit Conversions
Topic: Dimensional Analysis
Replies: 4
Views: 64

### Dimensional Analysis

I'm a little rusty on my chemisty and my stoichiometry in general. I just needed some clarification about the units that are used when doing dimensional analysis... Can you switch around the units so that they work to cancel out? For example the molar mass' units is g/mol, so if I needed to get the ...
Mon Oct 05, 2020 1:00 pm
Forum: Empirical & Molecular Formulas
Topic: Week 1 Sapling HW Chem 14A Problem 9
Replies: 8
Views: 178

### Re: Week 1 Sapling HW Chem 14A Problem 9

I had a lot of difficulty with this question as well and kept on messing up while calculating the mass of Hydrogen. I was making the mistake of not taking into consideration that there are 2 Hydrogens to account for; so, I would have to multiply the value I was getting for 1 Hydrogen (0.0516g) by 2 ...
Mon Oct 05, 2020 12:53 pm
Forum: Empirical & Molecular Formulas
Topic: Sapling Hw Week 1 #10
Replies: 20
Views: 281

### Sapling Hw Week 1 #10

A reaction was performed in which 0.20 mL of 2‑butanone was reacted with an excess of propyl magnesiumbromide to make 0.23 g of 3‑methyl‑3‑hexanol. Calculate the theoretical yield and percent yield for this reaction. I don't know where to start with this problem. Am I supposed to find the empirical ...