Search found 55 matches

by Scot Widjaja Dis 1J
Mon Jan 18, 2021 12:02 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Difference between pH and pOH
Replies: 12
Views: 61

Re: Difference between pH and pOH

pH is the negative log of the hydronium ion concentration whereas pOH is the negative log of the hydroxide ion concentration.

Kb is the basicity constant of weak bases and pKb is taking the negative log of the Kb.
by Scot Widjaja Dis 1J
Mon Jan 18, 2021 12:01 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Calculating pH/pOH for Weak Acids/Bases
Replies: 2
Views: 13

Re: Calculating pH/pOH for Weak Acids/Bases

Because in weak acids and bases, not all of it will be completely ionized so we cannot assume that X concentration of a weak acid or base will equal X concentration of H30+ or OH-. Therefore, we have to set up an equilibrium table to determine the concentration of either H3O+ or OH-.
by Scot Widjaja Dis 1J
Sun Jan 17, 2021 11:58 pm
Forum: Calculating the pH of Salt Solutions
Topic: pH 1-14
Replies: 4
Views: 122

Re: pH 1-14

I because the concentration H30+ tends to lie somewhere between 1 to 10^-14 mol L^-1. Taking the negative logs of these values will only give pH ranges from 1-14.
by Scot Widjaja Dis 1J
Sun Jan 17, 2021 11:54 pm
Forum: Calculating the pH of Salt Solutions
Topic: NH4F
Replies: 2
Views: 88

Re: NH4F

It will depend on the relative strengths of each respective acid and base since both of these ions when dissolved in water will induce counteracting affects on the pH. NH4+ when dissolved in water will produce hydronium ions which will cause the pH to decrease. On the other hand, F- will react with ...
by Scot Widjaja Dis 1J
Sun Jan 17, 2021 11:49 pm
Forum: Calculating the pH of Salt Solutions
Topic: Why is Cu(NO3)2 Acidic?
Replies: 2
Views: 33

Re: Why is Cu(NO3)2 Acidic?

The general rule of thumb is that transition metals that are highly positive charged like in the case of Cu2+ above will generally cause the pH to decrease less than 7 when dissolved in an aqueous solutions. The reason why the nitrate ion doesn’t affect pH is because it’s a conjugate base of a stron...
by Scot Widjaja Dis 1J
Sun Jan 10, 2021 2:34 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reactions at Equilibrium
Replies: 6
Views: 23

Re: Reactions at Equilibrium

Correct. While the concentrations of reactants and products are not changing at equilibrium, there is still production of both reactants and products.
by Scot Widjaja Dis 1J
Sun Jan 10, 2021 2:29 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Q10 Part1
Replies: 2
Views: 14

Re: Sapling Q10 Part1

1. Write the equlibriium constant expression, Kc.

Kc = (NO2)^2/(N2O4)

2. Substitue the values of the equilibrium concentrations of the reactants and products into the expression

Kc = (1.93)^2/(0.333)

3. Compute

Kc = (1.93)^2/(0.333) = 3.72/0.333 = 11.2

Hope this helps!
by Scot Widjaja Dis 1J
Sun Jan 10, 2021 2:18 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Q9
Replies: 3
Views: 36

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 express...
by Scot Widjaja Dis 1J
Sun Jan 10, 2021 1:33 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solids and Liquids in K Expression
Replies: 2
Views: 5

Solids and Liquids in K Expression

Why aren't solids and liquids included in the equilibrium constant expression?
by Scot Widjaja Dis 1J
Sun Jan 10, 2021 1:27 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Definition of an Inert Gas
Replies: 6
Views: 23

Definition of an Inert Gas

In Dr. Lavelle's lecture on Le Chatelier's Principle, he talks about how adding an inert gas to a container does not effect the reaction since there is no change in the concentration of reactants, products, and volume. What is the exact definition of an inert gas and why does adding one to a contain...
by Scot Widjaja Dis 1J
Sun Dec 06, 2020 5:10 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Memorizing the name of complex ligands
Replies: 6
Views: 48

Memorizing the name of complex ligands

What would be some of the other complex ligand names that we would have to memorize in addition to ligands such as Ethylenediamine? Would they give us a chart during the final exam about the names and formulas of the ligands that we haven't studied before in the past?
by Scot Widjaja Dis 1J
Sun Dec 06, 2020 5:06 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Sapling Week 9 #4
Replies: 5
Views: 42

Sapling Week 9 #4

What is the exact difference between a lewis base and a ligand because don't both those terms mean the same thing in the sense that they both donate electron pairs to another molecule?
by Scot Widjaja Dis 1J
Sun Dec 06, 2020 4:52 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordinate Covalent Bond
Replies: 6
Views: 59

Re: Coordinate Covalent Bond

Yes, in a coordinate covalent bond, the ligands are the molecules that contribute both electron pairs to the coordination complex.
by Scot Widjaja Dis 1J
Sun Dec 06, 2020 4:50 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Sapling #5 for Week 9
Replies: 4
Views: 59

Re: Sapling #5 for Week 9

en stands for ethlyenediamine and it is a bidentate ligand, meaning it can donate two electron pairs to the central transition metal cation. In other words, it can form two bonds with the metal. Knowing this, and knowing the compound formula is [Cd(en)Br2], we know that the coordination number will ...
by Scot Widjaja Dis 1J
Sun Dec 06, 2020 4:33 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Writing name for coordination compound
Replies: 3
Views: 38

Re: Writing name for coordination compound

Here's a list of rules that my TA gave me regarding naming coordination compounds. Hope this helps!
by Scot Widjaja Dis 1J
Sun Dec 06, 2020 4:29 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: how is CO3(-2) both mono and bi-dente?
Replies: 2
Views: 39

Re: how is CO3(-2) both mono and bi-dente?

From my discussion section on Friday, my TA said that they would give you clues on a question to figure out when it would be mono- or bidentate. For example, they may give you a coordination compound (Coordination number: 6) with 5 ligands and then one CO3(-2). In this case, you can figure out that ...
by Scot Widjaja Dis 1J
Sun Dec 06, 2020 4:17 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number Question
Replies: 12
Views: 112

Re: Coordination Number Question

A simple way to think of the definition of Coordination Numbers is the number of bonds that are attached to the central transition metal cation. In your example, the coordination number is 6 because there are 6 covalent bonds with the central metal cation (4 from NH3 and 2 from Br). In this example,...
by Scot Widjaja Dis 1J
Sun Dec 06, 2020 4:12 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation Number
Replies: 4
Views: 48

Re: Oxidation Number

I'd look at the total charge of all the ligands that are forming the coordination compound and compare that to the overall charge. Then figure out what the charge of the transition metal cation has to be in order for the combined charges to equal the charge of the overall compound. For example, in [...
by Scot Widjaja Dis 1J
Mon Nov 30, 2020 12:02 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling Week 8 #3
Replies: 5
Views: 60

Re: Sapling Week 8 #3

Since the shape is trigonal pyramidal, the lone pair will cause additional electron electron repulsion with the other regions of electron density, causing the bond angle to decrease slightly below 109.5 degrees. I think stating numbers like 107, 108, or 109 degrees would be sufficient.
by Scot Widjaja Dis 1J
Sun Nov 29, 2020 11:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles
Replies: 5
Views: 50

Re: Bond angles

The trigonal bipyramidal shape has 5 atoms bonded to the central atom. The 3 atoms that line on the plane have bond angles of 120 degrees and I believe the 2 atoms on the opposite ends (not on the plane) have bond angles of 90 degrees.
by Scot Widjaja Dis 1J
Sun Nov 29, 2020 11:38 pm
Forum: Ionic & Covalent Bonds
Topic: Polar/ Nonpolar
Replies: 23
Views: 166

Re: Polar/ Nonpolar

Yes they can. If you look at the molecules shape and see that all the bond dipoles get cancelled, then you know the molecule is no polar just by observing the structure.
by Scot Widjaja Dis 1J
Sun Nov 29, 2020 11:34 pm
Forum: Bond Lengths & Energies
Topic: LDF Bond Strength
Replies: 11
Views: 90

Re: LDF Bond Strength

The larger the atom, the more easily the electrons in the cloud can get distorted, and this leads to stronger London dispersion forces between the atoms. Since I2 is bigger than Br2, which is bigger than Cl2, I2 has the ability to form stronger attractive forces with other molecules.
by Scot Widjaja Dis 1J
Sun Nov 29, 2020 8:49 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8503
Views: 1469313

Re: Post All Chemistry Jokes Here

If Avogadro calls tell him to leave his number
by Scot Widjaja Dis 1J
Sun Nov 29, 2020 8:47 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8503
Views: 1469313

Re: Post All Chemistry Jokes Here

I’m out of chemistry jokes, I should Zinc for a new one.
by Scot Widjaja Dis 1J
Sun Nov 29, 2020 8:45 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8503
Views: 1469313

Re: Post All Chemistry Jokes Here

Are you copper tellurium, because you’re CuTe.
by Scot Widjaja Dis 1J
Sun Nov 29, 2020 8:45 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8503
Views: 1469313

Re: Post All Chemistry Jokes Here

I tell bad chemistry jokes because all the good ones Argon.
by Scot Widjaja Dis 1J
Sun Nov 15, 2020 10:27 am
Forum: Administrative Questions and Class Announcements
Topic: #Questions on Midterm 2
Replies: 6
Views: 52

#Questions on Midterm 2

How many multiple choice questions will they ask on Midterm 2?
by Scot Widjaja Dis 1J
Sun Nov 15, 2020 10:25 am
Forum: Ionic & Covalent Bonds
Topic: Hydrogen and Covalent Bonds
Replies: 3
Views: 31

Re: Hydrogen and Covalent Bonds

Covalent Bonds are stronger than hydrogen bonds because a covalent bond is an attraction within molecules whereas hydrogen bonds are attractions between molecules and are therefore generally weaker. Within molecules, the electrons of one atom can be more so tightly held with the slight delta positiv...
by Scot Widjaja Dis 1J
Sun Nov 15, 2020 10:18 am
Forum: Octet Exceptions
Topic: Valence electrons for Beryllium
Replies: 2
Views: 27

Valence electrons for Beryllium

How many electrons does Beryllium want to have if Beryllium wants less than an octet?
by Scot Widjaja Dis 1J
Sun Nov 15, 2020 10:12 am
Forum: Formal Charge and Oxidation Numbers
Topic: Sapling Week 5/6 #9
Replies: 2
Views: 45

Sapling Week 5/6 #9

Hey guys,

In question 9 of week 5/6 Sapling Homework, how do I determine which lewis structure of Perchlorate Ion is the most plausible based on the oxidation number? And how does the oxidation number of a central atom determine which lewis structure is most favorable?
by Scot Widjaja Dis 1J
Sun Nov 15, 2020 10:02 am
Forum: Lewis Structures
Topic: How to utilize formal charge
Replies: 2
Views: 32

Re: How to utilize formal charge

We use formal charge to determine which lewis structure is the most stable and favorable. Typically, the most favorable structure is one in which all the atoms have a formal charge of 0. We can use this idea to determine whether an atom should be single, double, or triple bonded to another atom. For...
by Scot Widjaja Dis 1J
Sun Nov 15, 2020 9:56 am
Forum: Lewis Structures
Topic: Lewis Acid and Base Reactions (Sapling Week 5/6 #6)
Replies: 4
Views: 39

Lewis Acid and Base Reactions (Sapling Week 5/6 #6)

Hey guys, are there any strategies or shortcuts I can try to determine whether a certain molecule or ion is a lewis acid/base? I know that a lewis acid accepts an electron pair while a lewis base donates an electron pair, but after doing question 6 on Sapling on Homework Week 5/6, I struggled to det...
by Scot Widjaja Dis 1J
Sun Nov 01, 2020 11:58 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8503
Views: 1469313

Re: Post All Chemistry Jokes Here

Q: 16 sodiums walk into a room. Who's next?

A: Na-Na-Na-Na-Na-Na-Na-Na-Na-Na-Na-Na-Na-Na-Na-Na-Batmaaan
by Scot Widjaja Dis 1J
Sun Nov 01, 2020 11:53 pm
Forum: Einstein Equation
Topic: E=hv vs E=pc?
Replies: 8
Views: 325

Re: E=hv vs E=pc?

I guess it would depend on what variables you were given in the problem. If a question gave you the photon's frequency or wavelength then you would use E=hv. However, if a question gave you the particles mass and velocity, then you would use E=pc. Hope this helps.
by Scot Widjaja Dis 1J
Sun Nov 01, 2020 11:48 pm
Forum: DeBroglie Equation
Topic: Purpose of DeBroglie Equation
Replies: 11
Views: 111

Re: Purpose of DeBroglie Equation

Ok, great! Thanks guys! I found these really helpful.
by Scot Widjaja Dis 1J
Sun Nov 01, 2020 11:47 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: P-, d-, f- Orbitals
Replies: 5
Views: 45

Re: P-, d-, f- Orbitals

Ok, great! Thanks guys!
by Scot Widjaja Dis 1J
Sun Nov 01, 2020 11:46 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Lyman and Balmer Series
Replies: 5
Views: 49

Re: Lyman and Balmer Series

Ok, great! Thanks for the responses guys. I found them really helpful.
by Scot Widjaja Dis 1J
Sun Oct 25, 2020 11:43 am
Forum: Administrative Questions and Class Announcements
Topic: How many questions on Midterm?
Replies: 6
Views: 72

Re: How many questions on Midterm?

I was told from my TA there would be around 10 multiple choice questions ranging of short, simple questions and longer questions that require the use of calculator and formulas.
by Scot Widjaja Dis 1J
Sun Oct 25, 2020 10:49 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Lyman and Balmer Series
Replies: 5
Views: 49

Lyman and Balmer Series

Would the Lyman (UV) and Balmer (Visible) series be the only 2 series we'd have to know for this course? Do we have to also know the Infrared series which would be electrons going from a high energy level down to the n=3 energy level? If so, is there a particular name for the infrared series?
by Scot Widjaja Dis 1J
Sun Oct 25, 2020 10:44 am
Forum: Photoelectric Effect
Topic: Intensity vs. Frequency
Replies: 22
Views: 140

Re: Intensity vs. Frequency

Frequency is a measure of the number of times a wave goes through its cycle per unit of time (seconds). Intensity is a measure of how large or how high the waves are. In other words, it is the amplitude of the waves and the larger the intensity, the higher the number of photons.
by Scot Widjaja Dis 1J
Sun Oct 25, 2020 10:41 am
Forum: DeBroglie Equation
Topic: Purpose of DeBroglie Equation
Replies: 11
Views: 111

Purpose of DeBroglie Equation

What was the De Broglie equation meant to suggest? Based on my understanding from the lectures, the De Broglie equation showed that electrons and other very small particles exhibited wavelike properties. Would this be a sufficient explanation and if not, how can I improve my explanation about what t...
by Scot Widjaja Dis 1J
Sun Oct 25, 2020 10:32 am
Forum: Properties of Electrons
Topic: Number of Questions of Midterm 1
Replies: 8
Views: 82

Re: Number of Questions of Midterm 1

According to my TA, there will be 10 or so multiple choice questions.
by Scot Widjaja Dis 1J
Sun Oct 25, 2020 10:31 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: P-, d-, f- Orbitals
Replies: 5
Views: 45

P-, d-, f- Orbitals

Hey guys,

I just had a quick question from Lecture 9 regarding p-, d-, and f- orbitals. What does Dr. Lavelle mean when he says that p-, d-, and f- orbitals have a nodal plane? And how does having a nodal plane make it so that there is a 0 probability for an orbital to have an electron density?
by Scot Widjaja Dis 1J
Sun Oct 18, 2020 9:02 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Bohr frequency condition
Replies: 5
Views: 44

Re: Bohr frequency condition

The condition is essentially saying that when there is an incoming light with a frequency that matches the energy difference for an electron to move up an energy level, that electron or those electrons will absorb the photon of light and later on be excited to a higher energy level.
by Scot Widjaja Dis 1J
Sun Oct 18, 2020 11:42 am
Forum: Properties of Light
Topic: Photoelectric effect Problem Audio Visual Topics Q28
Replies: 4
Views: 29

Re: Photoelectric effect Problem Audio Visual Topics Q28

The C in the equation C = Wavelength x Frequency stands for the speed of light, which is approximately 3.00 x 10^8 meters.
by Scot Widjaja Dis 1J
Sun Oct 18, 2020 11:35 am
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Reactions Order
Replies: 31
Views: 237

Re: Balancing Chemical Reactions Order

For a combustion reaction, it's easier to balance the oxygen in the reactant last since it only contains one type of atom, whereas the other molecules have more than one atom. Once I've balanced my C's and H's, it's easier to figure out what the coefficient of O should be.
by Scot Widjaja Dis 1J
Sun Oct 18, 2020 10:52 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Frequencies of Wavelength Absorbed
Replies: 3
Views: 17

Re: Frequencies of Wavelength Absorbed

The photons of light will not be absorbed at all unless its energy matches the specific energy level of the atom. This is the Bohr Frequency Condition, whereby if the incoming light frequency matches the energy difference for the electron to make a transition, there will be an absorption of light.
by Scot Widjaja Dis 1J
Sun Oct 18, 2020 10:29 am
Forum: Properties of Light
Topic: Atomic Spectra Module Question
Replies: 5
Views: 61

Re: Atomic Spectra Module Question

I'm confused because when I was watching the Atomic Spectra Lectures, the professor never talked about this topic. Would this be something required to know for the midterm and final?
by Scot Widjaja Dis 1J
Sun Oct 18, 2020 10:24 am
Forum: Properties of Light
Topic: Work Function Question
Replies: 6
Views: 51

Re: Work Function Question

Yes! Threshold energy, work function, and E(Energy to remove an electron) are all synonymous turns and can replace one another in the equation: E(Photon) - E(Threshold) = E(Excess).
by Scot Widjaja Dis 1J
Sun Oct 11, 2020 9:36 am
Forum: Ionic & Covalent Bonds
Topic: Ionic bonds in solutions
Replies: 9
Views: 189

Re: Ionic bonds in solutions

Yes, the ions Na+ and Cl- in salt dissociate and dissolve when mixed with water because the partial negatively charged oxygen atoms in water attract the positively charged sodium ions and the partial positively charged hydrogen atoms attract the negatively charged chloride ions. However, dissolving ...
by Scot Widjaja Dis 1J
Sun Oct 11, 2020 9:21 am
Forum: Significant Figures
Topic: Scientific Notation
Replies: 4
Views: 39

Re: Scientific Notation

You generally should use scientific notation if the numbers you got for your answer are really big or small. I usually write my answers in scientific notation if the answer is above 10^4 or 10^-4.
by Scot Widjaja Dis 1J
Sun Oct 11, 2020 9:15 am
Forum: Empirical & Molecular Formulas
Topic: difference between empirical and molecular
Replies: 15
Views: 70

Re: difference between empirical and molecular

If the empirical formula mass is equal to the molecular formula mass, then empirical formula equals molecular formula.
by Scot Widjaja Dis 1J
Sun Oct 11, 2020 6:14 am
Forum: Empirical & Molecular Formulas
Topic: Sapling HW#9
Replies: 3
Views: 55

Re: Sapling HW#9

Hi, I think the way you figured out the mass of C is correct. I got pretty much the same value for the mass of C and I used your method too. Just be cautious when you try to figure out the mass of H because for H2O, there are 2 moles of H so you need to multiply the moles of H20 by 2 to get an accur...
by Scot Widjaja Dis 1J
Sun Oct 11, 2020 6:02 am
Forum: Properties of Light
Topic: Photoelectric effect Problem Audio Visual Topics Q28
Replies: 4
Views: 29

Re: Photoelectric effect Problem Audio Visual Topics Q28

Hi, Basically, the work function is the minimum energy/work required to remove an electron from a metal surface. To answer A, the kinetic energy of the ejected electron, you need to use the equation for kinetic energy, which is \frac{1}{2}mv^2 . You'll have to know the mass of an electron from a for...

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