Search found 36 matches

by Leah farhadi 1F
Sun Jul 28, 2019 9:01 pm
Forum: Conjugate Acids & Bases
Topic: Problem 6.21
Replies: 1
Views: 126

Problem 6.21

12.127 The two strands of the nucleic acid DNA are held together by hydrogen bonding between four organic bases. The structure of one of these bases, thymine, is shown below. (a) How many protons can this base accept? (b) Draw the structure of each conjugate acid that can be formed. (c) Mark with an...
by Leah farhadi 1F
Sun Jul 28, 2019 6:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: question 4.19
Replies: 2
Views: 106

Re: question 4.19

I think it means that it is tetrahedral for the C atom and for the Be atom it is linear.
by Leah farhadi 1F
Thu Jul 25, 2019 10:15 am
Forum: Hybridization
Topic: Electrons
Replies: 3
Views: 181

Re: Electrons

This is where the basis of hybridization comes about, as when you draw the electron configuration for C it has 2 unpairs electrons, but it pairs with 4 electrons, so the electrons in the S shell are promoted to the SP^3 hybridization to get 4 unpaired electrons.
by Leah farhadi 1F
Thu Jul 25, 2019 10:06 am
Forum: *Molecular Orbital Theory Applied To Transition Metals
Topic: naming sequence
Replies: 4
Views: 141

Re: naming sequence

1) If there is a cation (i.e K) write it first as its own word and you don’t need to take into account it’s charge 2) start with the ligands and put them in alphabetical order 3) find the oxidation number of the metal 4) out the whole complex in brackets and then if the complex is an ion write the s...
by Leah farhadi 1F
Thu Jul 25, 2019 9:53 am
Forum: Octet Exceptions
Topic: Lewis Acids and Bases
Replies: 10
Views: 317

Re: Lewis Acids and Bases

A Lewis acid is usually a molecule an unfulfilled valence electron configuration, like BH3, where B can accept another atom to fill its shell, another example would be H+, where it can accept electrons to become neutral. A Lewis base donates electrons, like NH3, where the line pairs on N can allow a...
by Leah farhadi 1F
Tue Jul 23, 2019 10:18 am
Forum: Naming
Topic: 9C.1 part c
Replies: 4
Views: 303

Re: 9C.1 part c

There is also a rule that if iron is the central metal and it’s an anion, then you would use Ferrate.
by Leah farhadi 1F
Tue Jul 23, 2019 10:14 am
Forum: Hybridization
Topic: dsp3 vs. sp3d
Replies: 2
Views: 110

Re: dsp3 vs. sp3d

I think lavelle in class said that either way is okay, because in his lecture notes he writes it as dsp^3, but he said that the textbook writes it as sp^3d and both are correct.
by Leah farhadi 1F
Tue Jul 23, 2019 10:10 am
Forum: Hybridization
Topic: Homework Problem 4.43
Replies: 1
Views: 101

Re: Homework Problem 4.43

The less p-value there is in the hybrid the more s character there is. For example, SP (there is 50% S character and 50% P character) with a bond angle 180, for SP^2 (there is 33% S character and 66% P character) with a bond angle 120, for SP^3 (there is 25% S character and 75% P character) with a b...
by Leah farhadi 1F
Sun Jul 21, 2019 6:49 pm
Forum: Hybridization
Topic: Determining how many electron densities
Replies: 2
Views: 103

Re: Determining how many electron densities

There would be four regions of electron densities. When determine shape we look at electron density and lone pairs count towards creating the overall shape and also have an effect on the bind angles.
by Leah farhadi 1F
Thu Jul 18, 2019 4:04 pm
Forum: Bond Lengths & Energies
Topic: Intermolecular vs. Intramolecular forces
Replies: 5
Views: 197

Re: Intermolecular vs. Intramolecular forces

Usually boiling and melting points have to do with intermolecular forces, where the strongest would be ion-ion interactions, then ion-dipole, then dipole-dipole, then London dispersion. Intramolecular forces are those that hold molecules themselves together, so the strongest would be ionic and the w...
by Leah farhadi 1F
Thu Jul 18, 2019 4:00 pm
Forum: Ionic & Covalent Bonds
Topic: Dipoles
Replies: 7
Views: 274

Re: Dipoles

Dipoles are usually polar, and they become a hydrogen bond any time an FON is attached to an H. However, there could be dipole interactions present like in CO2 or CCl4 however these interactions would cancel and the molecule would be considered nonpolar based on shape.
by Leah farhadi 1F
Thu Jul 18, 2019 3:57 pm
Forum: General Science Questions
Topic: Reasoning for Al amphoteric
Replies: 3
Views: 203

Re: Reasoning for Al amphoteric

Al and B can act as a acid, because they are an electron acceptor, because they can form bonds with only three atoms, because they are able to have 6 electrons. Since they can form 3 bonds, they would accept two lone pairs from another molecule, for example NH3, where the two lone pairs would attach...
by Leah farhadi 1F
Thu Jul 18, 2019 3:53 pm
Forum: Formal Charge and Oxidation Numbers
Topic: charges and roman numerals
Replies: 3
Views: 229

Re: charges and roman numerals

I think the roman numerals help to tell us how many electrons the molecule has lost or gained. Especially since In is in group 13 it is hard to tell if it has lost 3 electrons or gained more to achieve an octet, so the roman numeral (III) tells us that it is In3+. Also, it tells us Bi is 3+, or has ...
by Leah farhadi 1F
Thu Jul 18, 2019 3:47 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: removing electrons
Replies: 1
Views: 123

Re: removing electrons

Usually you should pull from the outer to the inner shell, so from p to s to d. It helps if you write out the electron configuration for the neutral atom and then pull or add electrons from there. For example, Br = [Ar] 3d^10 4s^2 4p^5 Then add or remove electrons: Br- = [Ar] 3d^10 4s^2 4p^6 Br+ = [...
by Leah farhadi 1F
Thu Jul 18, 2019 3:41 pm
Forum: Lewis Structures
Topic: Central Atom
Replies: 3
Views: 136

Re: Central Atom

I think there are examples were chlorine is in the center of the lewis structure, i.e. ClH4 were Cl will be in the middle surrounded by hydrogen. However, in most examples I have seen fluorine has not been the central atom. I think this has to do with reasoning that Cl and F only need one more valen...
by Leah farhadi 1F
Sun Jul 14, 2019 6:17 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Which do you prioritize first
Replies: 10
Views: 278

Re: Which do you prioritize first

I usually start with the valence electrons and single bonds then count the number of electrons and adjust the electrons. After, I take into account formal charge and look for the structure with the lowest energy, taking account expanded octets.
by Leah farhadi 1F
Thu Jul 11, 2019 10:05 pm
Forum: Ionic & Covalent Bonds
Topic: Ground State
Replies: 13
Views: 305

Re: Ground State

Since it has a plus charge you would subtract an electron from your ground state configuration. If it were neutral that is when you would give the ground state configuration without subtracting or adding electrons.
by Leah farhadi 1F
Thu Jul 11, 2019 9:43 am
Forum: Properties of Light
Topic: Pre/Post assessment question. [ENDORSED]
Replies: 2
Views: 221

Re: Pre/Post assessment question. [ENDORSED]

In addition, knowing that waves of matter (i.e electrons) interact with each other, especially through a crystal (causing diffraction) supports de Broglie's hypothesis of the wave-like nature of matter.
by Leah farhadi 1F
Thu Jul 11, 2019 9:38 am
Forum: Properties of Light
Topic: VIdeo Module: Photoelectric effect question
Replies: 2
Views: 184

Re: VIdeo Module: Photoelectric effect question

We are given the velocity, so we can plug it into the equation (1/2)mv^2, plugging in the mass of an electron where m 9.109x10^-31. This would be the answer, however since they gave you the work function, you could find the energy of the photon by adding the kinetic energy you found plus the work fu...
by Leah farhadi 1F
Thu Jul 11, 2019 9:32 am
Forum: Molarity, Solutions, Dilutions
Topic: Test 1 number 7
Replies: 4
Views: 273

Re: Test 1 number 7

Since they gave you mass in mg and they have you and molarity, you know to use the equation M=(moles)/Liters. Usually, you would use M1V1=M2V2 when they give you three values or when the question specifically has the word dilute in it. So, you would take the mg and make it into grams them use the mo...
by Leah farhadi 1F
Thu Jul 11, 2019 9:26 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration for 1st row transition metals
Replies: 6
Views: 196

Re: Electron Configuration for 1st row transition metals

In addition, those metals below Cu and Cr follow the same pattern, where the row beginning with Cu is nd^5ns^1 and the row beginning with Cr is nd^10ns^1.
by Leah farhadi 1F
Thu Jul 11, 2019 9:23 am
Forum: SI Units, Unit Conversions
Topic: Moles mols mol? [ENDORSED]
Replies: 21
Views: 975

Re: Moles mols mol? [ENDORSED]

I think moles, mols, mol are all used interchangeably. In the textbook I have seen them use n, but I don't think we have to know that. However, you should use M or mol.L-1 when using molarity.
by Leah farhadi 1F
Sat Jul 06, 2019 11:06 am
Forum: Photoelectric Effect
Topic: kinetic energy of electron
Replies: 8
Views: 261

Re: kinetic energy of electron

I think kinetic energy is the energy left from the photon left over after taken into account the work function. In class I think he said that electrons can be ejected if the energy of the photon is equal to or greater than the energy needed to remove an electron. However, if it is equal to then the ...
by Leah farhadi 1F
Fri Jul 05, 2019 9:28 am
Forum: Molarity, Solutions, Dilutions
Topic: solution problem
Replies: 1
Views: 159

Re: solution problem

For this question they give you grams of Na2CO3 and moles of solute, knowing this we would use the equation M=n/V. If we were given two molarities and a volume, then we can use M1V1=M2V2 to find the correct volume, but because we only have one molarity and moles we use M=n/V First we take grams of N...
by Leah farhadi 1F
Thu Jul 04, 2019 10:02 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Equations
Replies: 6
Views: 167

Re: Balancing Equations

I start with the element that only shows up once on both sides of the equation. Then, I take into account the elements that appear multiple times. This is usually oxygen, especially in a combustion reaction. I try to make the oxygen have an even number on the left side of the equation, because on th...
by Leah farhadi 1F
Thu Jul 04, 2019 9:50 pm
Forum: Properties of Light
Topic: textbook question
Replies: 2
Views: 117

Re: textbook question

Question 1A.11 asks why spectral lines are classified as being in different series. The lines show the energy difference from on discrete energy level to another, i.e from n=4 to n=2. The way that they are classified is based on the lowest energy level, for example Lyman series the lowest energy lev...
by Leah farhadi 1F
Thu Jul 04, 2019 9:29 pm
Forum: Properties of Light
Topic: Balmer series and Lyman series
Replies: 2
Views: 141

Re: Balmer series and Lyman series

The Balmer and Lyman series show the absorption/emission line from a higher energy level to a lower energy level. However, they are different in that the principal quantum number (n) for the lower energy level is different for each series. For example, the Lyman series the lower energy level is n=1 ...
by Leah farhadi 1F
Thu Jul 04, 2019 6:11 pm
Forum: Properties of Light
Topic: 1A.7 Seventh edition
Replies: 1
Views: 130

Re: 1A.7 Seventh edition

In the question we are given frequency (v) and we need to find wavelength (λ). We know that frequency and wavelength are related:c = λ ν But in this problem we only know frequency (v) and c (the speed of light): We rewrite the equation solving for wavelength: c = λ ν (divide both sides by v): c/ν = ...
by Leah farhadi 1F
Tue Jul 02, 2019 4:20 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: the equation of energy level
Replies: 4
Views: 178

Re: the equation of energy level

There is a negative sign present, because it signifies that there is a loss of energy. Since we are taking 0 as our reference point, when electron is completely removed and not interacting with the nucleus, the negative sign signifies the idea that a bound electron has a lower energy level than a fr...
by Leah farhadi 1F
Thu Jun 27, 2019 10:22 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Stoichiometric reactions
Replies: 3
Views: 287

Re: Stoichiometric reactions

Since this is a balanced chemical equation, N2 +3H2 -> 2NH3, the stoichiometric coefficients summarize the number of moles of reactants and products taking part in the reaction. Since we understand this we can make mole-to-mole predictions using mole ration which allows the compounds in the chemical...
by Leah farhadi 1F
Thu Jun 27, 2019 10:12 am
Forum: Empirical & Molecular Formulas
Topic: Homework E.15 Solutions
Replies: 3
Views: 182

Re: Homework E.15 Solutions

We are given that the molar mass of the Metal(M) = 74.10 g.mol^-1 We know using molecular mass that (OH)2 = 34.02 g.mol^-1 So, then we know that the molar mass of the Metal = 74.10 - 34.02 = 40.08 Looking at the periodic table we see that Calcium has an atomic weight of 40.08 Since the question aske...
by Leah farhadi 1F
Thu Jun 27, 2019 10:04 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Moles and Molarity HW Problem E.29b
Replies: 2
Views: 129

Re: Moles and Molarity HW Problem E.29b

We have to multiply 0.0417 twice to get mol Cl, because there are two mol Cl per mole of the compound (CuCl2(2H2O)):

mol Cl = 0.0417 mol CuCl2(2H2O) x (2 mol Cl)/1 mol CuCl2(H2O)) = 0.0834

Using molar ratio, we see that mole CuCl2(2H2O) cancels and we are left with mole Cl
by Leah farhadi 1F
Thu Jun 27, 2019 9:57 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Fundamental Units?
Replies: 2
Views: 133

Re: Fundamental Units?

I think formula units means the actual number of atoms, ions, or molecules in a sample, it is just formally called formula units for the molar mass (mass per mole of its formula units) of an ionic compound. For example, we use avogadro's constant in order to figure out how many atoms are within some...
by Leah farhadi 1F
Thu Jun 27, 2019 12:33 am
Forum: Student Social/Study Group
Topic: Test Studying Strategies
Replies: 6
Views: 208

Re: Test Studying Strategies

I am going to go over the homework problems, the examples given in the textbook, the problems posted on the modules, and the worksheets posted by the UAs. I am also going to go over what we should know conceptually from outline 1 (i.e use SI units, Convert units, ect.).
by Leah farhadi 1F
Thu Jun 27, 2019 12:28 am
Forum: Empirical & Molecular Formulas
Topic: Molar Mass vs. Atomic Weight
Replies: 7
Views: 314

Re: Molar Mass vs. Atomic Weight

I think they are relatively the same, but atomic mass is related to the element itself (found on the periodic table, i.e carbon, oxygen, hydrogen). But molecular mass takes into account that there are multiple elements (atomic masses) that make up the compound (i.e H2O or CO2).
by Leah farhadi 1F
Wed Jun 26, 2019 12:27 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Dot in chemical formula
Replies: 2
Views: 169

Re: Dot in chemical formula

I think that it means that there is 10 moles of H2O molecules in the compound. I think it is written this way as to not get confused with putting it in front of the chemical equation of the compound, as it makes it seem like there are 10 moles of the compound. Also, it helps to not get it confused w...

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