Search found 99 matches

by Robert Tran 1B
Sun Feb 23, 2020 5:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating Cell Potentials
Replies: 2
Views: 7

Calculating Cell Potentials

When we calculate cell potential, do we always subtract the potential of the right cell by that of the left cell?
by Robert Tran 1B
Sun Feb 23, 2020 5:38 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: how to get n in equation
Replies: 8
Views: 22

Re: how to get n in equation

Look at the balanced half reactions and determine how many electrons are being transferred in the redox reaction.
by Robert Tran 1B
Sun Feb 23, 2020 5:37 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Concentration and cell potential
Replies: 6
Views: 15

Re: Concentration and cell potential

Another way to see cell potential is the potential of the cell to do work. If there is a greater difference between the concentrations of the reactants in a spontaneous reaction, it will be able to do more work.
by Robert Tran 1B
Sun Feb 23, 2020 5:32 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum Cell Diagram
Replies: 2
Views: 15

Re: Platinum Cell Diagram

Although iodine is a solid, it is not a conductor. Thus, we need to put a conducting metal (platinum) in order for the reaction to occur.
by Robert Tran 1B
Sun Feb 23, 2020 5:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: neg vs pos
Replies: 9
Views: 22

Re: neg vs pos

If the voltage of the cell is negative, then the cell does not have a spontaneous reaction in the specified direction.
by Robert Tran 1B
Sun Feb 23, 2020 5:27 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: chemistry community posts
Replies: 12
Views: 32

Re: chemistry community posts

The posts are usually counted at the end of the quarter. You should do 5/week to stay on track, but as long as you have 50 by the end of the quarter and you didn't do a bunch of them at the same time, you'll be good.
by Robert Tran 1B
Sun Feb 23, 2020 5:25 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 9
Views: 15

Re: Salt Bridge

The salt bridge ensures that the solution in the anode and the cathode stays neutral. Since electrons are being transferred as the redox reaction occurs, the charges of the anode and the cathode are changing. The salt bridge dispenses ions as they change to ensure that there is no polarization that ...
by Robert Tran 1B
Wed Feb 12, 2020 1:45 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy Change over the Course of Thermodynamic Processes
Replies: 3
Views: 18

Re: Entropy Change over the Course of Thermodynamic Processes

The change in entropy is zero because the final state of the system is the same as the initial state. Since entropy is a state function and there is no overall change in the conditions, the entropy does not change.
by Robert Tran 1B
Wed Feb 12, 2020 1:41 pm
Forum: Calculating Work of Expansion
Topic: A system doing no work
Replies: 4
Views: 25

Re: A system doing no work

So far in the course, the only form of work we have learned is the system expanding and pushing against the surroundings.
by Robert Tran 1B
Wed Feb 12, 2020 1:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Buffer Solution
Replies: 4
Views: 24

Re: Buffer Solution

I also got pH = 4.545!
by Robert Tran 1B
Wed Feb 12, 2020 1:14 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Difference between equations
Replies: 2
Views: 13

Re: Difference between equations

nRln(V2/V1) only works when the temperature is constant because it is derived from the equation (delta)S = q/T, which assumes that temperature is constant.
by Robert Tran 1B
Wed Feb 12, 2020 1:03 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Temperature Changes Along Irreversible Pathway
Replies: 3
Views: 22

Re: Temperature Changes Along Irreversible Pathway

During a reversible expansion, the change in volume is slow enough that the temperature can stay constant. However, in an irreversible change, the process occurs too quickly to keep the temperature constant.
by Robert Tran 1B
Wed Feb 12, 2020 12:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acid and [H3O] Midterm Q
Replies: 3
Views: 31

Re: Acid and [H3O] Midterm Q

Since HA is a weak acid, it will not completely dissociate into H3O+ ions. This means that the initial concentration of HA will not be the same as the final concentration of H3O+ ions.
by Robert Tran 1B
Mon Feb 10, 2020 9:13 pm
Forum: Calculating Work of Expansion
Topic: calculating work of a reversible reaction
Replies: 5
Views: 24

Re: calculating work of a reversible reaction

Work will be negative if the volume is increasing. You should always keep the negative if you are calculating the work being done on the system.
by Robert Tran 1B
Mon Feb 10, 2020 8:47 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Delta S sub m
Replies: 2
Views: 10

Delta S sub m

I noticed one of the practice problems wrote entropy as ΔSm. Does anyone know what the "m" stands for in this term?
by Robert Tran 1B
Wed Feb 05, 2020 9:50 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Microstates
Replies: 7
Views: 34

Re: Microstates

A microstate is a possible arrangement of molecules in a given space. If there are more degenerate microstates, meaning that they all have the same energy, then the entropy is higher.
by Robert Tran 1B
Wed Feb 05, 2020 9:47 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Heat capacity
Replies: 4
Views: 20

Re: Heat capacity

If C is not given in the problem, you can use the equation Cv = (delta)U/(delta)t or Cp = (delta)H/(delta)T.
by Robert Tran 1B
Tue Feb 04, 2020 1:39 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Relation between Entropy and Enthalpy
Replies: 1
Views: 15

Relation between Entropy and Enthalpy

I understand how the equation (delta)S = (delta)H/T is mathematically derived, but I don't understand conceptually why it makes sense that change in enthalpy, temperature, and change in entropy can be related to each other. Does anyone have an explanation?
by Robert Tran 1B
Thu Jan 30, 2020 10:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law vs. Standard Enthalpies of Formation
Replies: 5
Views: 31

Re: Hess's Law vs. Standard Enthalpies of Formation

If multiple reactions are given, the Hess's Law should be applied. If one reaction and the standard enthalpies of formation are given, then you should subtract the standard enthalpies of formation of the products by that of the reactants.
by Robert Tran 1B
Thu Jan 30, 2020 9:54 pm
Forum: Phase Changes & Related Calculations
Topic: Units
Replies: 16
Views: 52

Re: Units

Since this chapter mostly deals with changes in temperatures, it does not matter whether Kelvins or Celsius are used because they are scaled the same.
by Robert Tran 1B
Thu Jan 30, 2020 9:51 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed vs isolated systems
Replies: 24
Views: 65

Re: Closed vs isolated systems

Closed systems can exchange energy with their surroundings. On the other hand, isolated systems cannot exchange energy with its surroundings. This means that closed systems can transfer heat, but isolated systems cannot.
by Robert Tran 1B
Thu Jan 30, 2020 9:49 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible Process
Replies: 1
Views: 21

Reversible Process

What is the meaning of a reversible process and what are the implications of it having an infinitesimal changes?
by Robert Tran 1B
Thu Jan 30, 2020 9:38 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity
Replies: 2
Views: 15

Re: Heat Capacity

The standard enthalpy of formation should be multiplied by the amount of moles reacted.
by Robert Tran 1B
Sat Jan 25, 2020 6:39 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Water Properties
Replies: 3
Views: 27

Re: Water Properties

In addition to what was already said, an amphiprotic substance is always amphoteric. However, an amphoteric compound is not always amphiprotic.
by Robert Tran 1B
Sat Jan 25, 2020 6:33 pm
Forum: Phase Changes & Related Calculations
Topic: Steam v. liquid
Replies: 7
Views: 47

Re: Steam v. liquid

Yes, because steam must lose energy to convert into a liquid when it condenses on your skin. This is in addition to the heat released by the temperature change in the water when it touches your skin, which would be the only source of heat for a liquid burn.
by Robert Tran 1B
Sat Jan 25, 2020 6:31 pm
Forum: Ideal Gases
Topic: final exam pickup
Replies: 10
Views: 88

Re: final exam pickup

Pickup is at the mailing center in Young Hall. Be sure to bring your BruinCard or some form of ID when you pick it up.
by Robert Tran 1B
Sat Jan 25, 2020 6:28 pm
Forum: Phase Changes & Related Calculations
Topic: Endothermic and Exothermic
Replies: 13
Views: 33

Re: Endothermic and Exothermic

In an endothermic reaction, the reaction removes heat from the surroundings. In an exothermic reaction, the reaction adds heat to the surroundings. However, all reactions take some heat to begin (activation energy), so the previous statements are based on net changes.
by Robert Tran 1B
Mon Jan 20, 2020 4:48 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 6D 15
Replies: 1
Views: 14

Re: 6D 15

Since Al(3+) is a small, highly charged cation, it can act as an acid when it is a hydrate in the form Al(H2O)63+. The Ka value for this can be found in the text.
by Robert Tran 1B
Mon Jan 20, 2020 4:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Buffer Practice Problems
Replies: 1
Views: 37

Buffer Practice Problems

Has anyone seen homework problems that have to do with buffers? Also, will it be on the test this week?
by Robert Tran 1B
Sun Jan 19, 2020 1:00 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Quick way
Replies: 7
Views: 34

Re: Quick way

When the pressure increases, the reaction will shift to the side that produces less moles of gas. Conversely, when the pressure decreases, the reaction will shift to the side that produces more moles of gas.
by Robert Tran 1B
Sun Jan 19, 2020 12:55 pm
Forum: Ideal Gases
Topic: R Constant
Replies: 7
Views: 20

Re: R Constant

You should use the R constant that has units that cancel out with the other units in the equation. For example, in PV=nRT, we use 0.08206 (L*atm)/(mol*K) because it cancels with the pressure, volume, moles, and temperature.
by Robert Tran 1B
Sun Jan 19, 2020 12:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endothermic vs. exothermic
Replies: 5
Views: 15

Re: Endothermic vs. exothermic

The equilibrium will shift towards the right. This is because endothermic reactions take up heat, so forming more products would lessen the effect of the increase in temperature.
by Robert Tran 1B
Sun Jan 19, 2020 12:50 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5% rule
Replies: 10
Views: 41

Re: 5% rule

If the percent deprotonation is less that 5%, then when we calculate equilibrium concentrations, we can ignore the x values relative to the initial concentration because it is not significant.
by Robert Tran 1B
Sun Jan 19, 2020 12:48 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q < K
Replies: 16
Views: 43

Re: Q < K

Yes, because in a chemical equation, the products are on the right side. Thus, a shift to the right means more products will form.
by Robert Tran 1B
Sat Jan 11, 2020 1:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Significant Figures
Replies: 8
Views: 39

Re: Significant Figures

Both the K constant and the initial concentrations should be used when calculating sig figs because they are both used in the overall calculation.
by Robert Tran 1B
Sat Jan 11, 2020 1:05 pm
Forum: Ideal Gases
Topic: The Difference between Q and Kc [ENDORSED]
Replies: 18
Views: 1011

Re: The Difference between Q and Kc [ENDORSED]

Kc is calculated when the reaction is at equilibrium. On the other hand, Q is calculated when the reaction is at any other state.
by Robert Tran 1B
Fri Jan 10, 2020 9:36 pm
Forum: Ideal Gases
Topic: K value
Replies: 14
Views: 60

Re: K value

If the K value is large, the reaction favors the products. On the other hand, if the K value is small, the reaction favors the reactants.
by Robert Tran 1B
Fri Jan 10, 2020 9:34 pm
Forum: Ideal Gases
Topic: Ideal Gas Law
Replies: 6
Views: 32

Re: Ideal Gas Law

The ideal gas law can be used to solve for pressure, volume, temperature, and amount of moles. In class, we also used it to convert from partial pressure to concentration and vice versa.
by Robert Tran 1B
Fri Jan 10, 2020 9:31 pm
Forum: Ideal Gases
Topic: ICE table
Replies: 7
Views: 298

Re: ICE table

Maggie Eberhardt - 2H wrote:Sorry if this is a stupid question, but when/why do we use ICE table?


We use an ICE table when we are given the initial concentration and want to determine the final concentration values after equilibrium is reached.
by Robert Tran 1B
Thu Dec 05, 2019 10:22 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6B1
Replies: 2
Views: 33

Re: 6B1

Since pH uses a log scale, the initial molar concentration does not matter. To answer this problem, you can use any arbitrary value for the initial molarity and get the same answer.
by Robert Tran 1B
Mon Dec 02, 2019 8:59 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Carbonate Ion
Replies: 2
Views: 25

Carbonate Ion

Question 9C.5 part b asks how many places (CO3)2- can bind to a single metal center. The answer says that it can be mono or bidentate. Why can it be both?
by Robert Tran 1B
Sun Dec 01, 2019 12:42 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH Scale is broken?
Replies: 6
Views: 48

Re: pH Scale is broken?

pH values are not solely confined to the values 0-14. However, most solutions fall within this range.
by Robert Tran 1B
Fri Nov 29, 2019 6:43 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: triple equal sign
Replies: 2
Views: 28

Re: triple equal sign

This is likely not a typo, because the triple equal sign means "is equivalent to," which is more specific than "is equal to."
by Robert Tran 1B
Fri Nov 29, 2019 6:41 pm
Forum: General Science Questions
Topic: hydrogen vs hydronium
Replies: 5
Views: 37

Re: hydrogen vs hydronium

The hydrogen ion is often used in place of hydronium to simplify things. However, you should know that the hydronium ion better represents what is actually seen.
by Robert Tran 1B
Sun Nov 24, 2019 11:24 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Cisplatin and Transplatin
Replies: 2
Views: 24

Re: Cisplatin and Transplatin

Cisplatin stops DNA replication by bonding to two exposed guanines. This prevents the enzymes from replicating the DNA. Transplatin does not stop DNA replication because its shape only allows it to bind to one guanine. This bond is not strong enough to prevent replication.
by Robert Tran 1B
Sun Nov 24, 2019 11:18 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted vs Lewis acids
Replies: 5
Views: 26

Re: Bronsted vs Lewis acids

There isn't a clear definition for acids, just different theories. Thus, we have different classifications such as Bronsted and Lewis.
by Robert Tran 1B
Sun Nov 24, 2019 11:08 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: EDTA
Replies: 1
Views: 15

Re: EDTA

EDTA can remove harmful metals such as lead from the body because it is able to bind to the metals.
by Robert Tran 1B
Tue Nov 19, 2019 2:53 pm
Forum: Dipole Moments
Topic: Polar or nonpolar
Replies: 8
Views: 68

Re: Polar or nonpolar

O2 is nonpolar because there is no difference in electronegativity, and therefore, no dipole moment between the atoms.
by Robert Tran 1B
Tue Nov 19, 2019 2:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bent v. angular
Replies: 20
Views: 109

Re: bent v. angular

Bent and angular mean the same thing. There are also several names for other structures, such as seesaw (disphenoidal).
by Robert Tran 1B
Tue Nov 19, 2019 2:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 4
Views: 32

Re: Bond Angles

The bond angle will be less than expected if there is a lone pair present, because the electron-electron repulsions will push the bonds closer together.
by Robert Tran 1B
Tue Nov 19, 2019 2:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear Shape
Replies: 6
Views: 33

Re: Linear Shape

A linear bond can be polar if the dipole moments are unequal, and therefore, do not cancel out.
by Robert Tran 1B
Tue Nov 19, 2019 2:41 pm
Forum: Hybridization
Topic: test 2
Replies: 6
Views: 51

Re: test 2

Hybridization will not be tested on Test 2. Only content from after the midterm to sigma and pi bonds will be tested.
by Robert Tran 1B
Mon Nov 18, 2019 1:12 pm
Forum: Lewis Structures
Topic: Oxygen
Replies: 9
Views: 71

Re: Oxygen

Oxygen can have all types of bonds, but it usually does not have triple bonds because the formal charge of oxygen would be more likely to have a nonzero value. This is because oxygen has 6 valence electrons and a triple bond would cause the formal charge to usually be 1.
by Robert Tran 1B
Mon Nov 18, 2019 1:07 pm
Forum: Octet Exceptions
Topic: Antioxidants
Replies: 9
Views: 86

Re: Antioxidants

Radicals are highly reactive because they have one unpaired electron. Antioxidants prevent them from reacting by donating an electron to make an electron pair.
by Robert Tran 1B
Mon Nov 18, 2019 1:03 pm
Forum: Student Social/Study Group
Topic: Test 2
Replies: 5
Views: 38

Re: Test 2

Only sigma and pi bonds from today's lecture will be covered on Test 2.
by Robert Tran 1B
Mon Nov 18, 2019 1:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AXE notation
Replies: 10
Views: 47

Re: AXE notation

A is the central atom, X is the amount of bonded atoms, and E is the amount of lone pair electrons.
by Robert Tran 1B
Mon Nov 18, 2019 1:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Why is SF4 Polar?
Replies: 6
Views: 25

Re: Why is SF4 Polar?

Since the S--F bond has a dipole moment and the seesaw shape does not allow the dipole moments to cancel out, the molecule is polar. If all the bonds were arranged symmetrically, in a tetrahedral shape, for example, the molecule would not be polar.
by Robert Tran 1B
Mon Nov 18, 2019 12:57 pm
Forum: Bond Lengths & Energies
Topic: Curve
Replies: 4
Views: 64

Re: Curve

There's no curve for the midterm, but if the average grade is low enough, there will be a curve applied to the final grade.
by Robert Tran 1B
Sat Nov 16, 2019 2:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Acids and Bases
Replies: 4
Views: 26

Re: Acids and Bases

I think since that was covered before the midterm, we will not need to know how to identify acids and bases for test #2.
by Robert Tran 1B
Sat Nov 16, 2019 2:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sulfite Ion example in class
Replies: 6
Views: 27

Re: Sulfite Ion example in class

The lone pairs in the sulfite ion cause the bond angles to be slightly smaller because the electron-electron repulsion pushes the bonds closer together.
by Robert Tran 1B
Sat Nov 16, 2019 2:32 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Dipole-Dipole vs. Dipole-Induced Dipole
Replies: 4
Views: 21

Re: Dipole-Dipole vs. Dipole-Induced Dipole

A permanent dipole is caused by a difference in electronegativity. An induced dipole is caused by a charged atom or dipole that pulls electrons in one side, which causes a temporary dipole.
by Robert Tran 1B
Sat Nov 16, 2019 2:29 pm
Forum: Dipole Moments
Topic: Hydrogen bonds
Replies: 17
Views: 88

Re: Hydrogen bonds

Hydrogen bonds can only form with N, O, and F because they are the only elements that have a high enough electronegativity to create a strong dipole moment.
by Robert Tran 1B
Sat Nov 16, 2019 2:28 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Strength of bonds
Replies: 3
Views: 13

Re: Strength of bonds

No, we do not need to calculate the strength of bonds. However, we should be able to recognize trends in bond lengths.
by Robert Tran 1B
Sat Nov 16, 2019 2:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: All VSEPR structures or just ones from class?
Replies: 11
Views: 66

Re: All VSEPR structures or just ones from class?

I think all of them have to be memorized. He just demonstrated how to determine the shapes of a couple molecules in class just as an example.
by Robert Tran 1B
Sat Nov 16, 2019 2:25 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSPER Formula for Compounds with No Lone Pairs
Replies: 4
Views: 27

Re: VSPER Formula for Compounds with No Lone Pairs

The VSPER formula would be AX4, since there is one central atom and four bonded atoms. The E will not be included since there are no lone pair electrons.
by Robert Tran 1B
Wed Nov 06, 2019 1:07 pm
Forum: Administrative Questions and Class Announcements
Topic: Equation Sheet
Replies: 2
Views: 30

Re: Equation Sheet

Yes, on previous midterms there was an equation/constant sheet and periodic table attached to the back.
by Robert Tran 1B
Wed Nov 06, 2019 1:01 pm
Forum: Lewis Structures
Topic: Expanded Octets
Replies: 6
Views: 36

Re: Expanded Octets

Expanded octets would be used if it's clear that there is more than 4 atoms bonded to the central atom (ex: XeF5). Also, the octet can be expanded if the formal charge favors it in the lewis structure.
by Robert Tran 1B
Wed Nov 06, 2019 12:51 pm
Forum: Ionic & Covalent Bonds
Topic: C, N, O, and F
Replies: 13
Views: 104

Re: C, N, O, and F

There are some exceptions to the octet rule for these atoms. For example, CH3 is a radical, so it only has seven electrons around it, which breaks the octet rule.
by Robert Tran 1B
Wed Nov 06, 2019 12:48 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: smaller cations
Replies: 3
Views: 27

Re: smaller cations

I'm assuming if you're asked to find the smallest cation, it is given that all the cations have the same amount of valence electrons. In this case, the smallest cation would have the highest amount of protons because this would mean the nucleus has a stronger pull on the electrons.
by Robert Tran 1B
Wed Nov 06, 2019 12:44 pm
Forum: Lewis Structures
Topic: Odd Number of V e-
Replies: 3
Views: 27

Re: Odd Number of V e-

You would need to calculate the formal charges of the atoms and add the single electron to the atom that would make all of the formal charges closest to zero.
by Robert Tran 1B
Sat Nov 02, 2019 1:54 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic/Covalent
Replies: 6
Views: 41

Re: Ionic/Covalent

An ionic compound has at least two atoms. Even in the atom that donated an electron, the nucleus still exerts a small attractive force on the electrons of the other atom(s). This causes them to be pulled slightly in one direction, which means they are slightly covalent.
by Robert Tran 1B
Sat Nov 02, 2019 1:50 pm
Forum: Resonance Structures
Topic: Delocalization
Replies: 4
Views: 34

Re: Delocalization

Delocalization also occurs in other molecules, such as metals. However, as far as what we have learned in class, delocalization only applies to resonance structures.
by Robert Tran 1B
Wed Oct 30, 2019 6:13 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic Bonds
Replies: 6
Views: 37

Re: Ionic Bonds

Yes, because if there is a substantial difference in electronegativity, one element is more likely to give up electrons, while the other element is likely to take electrons.
by Robert Tran 1B
Wed Oct 30, 2019 6:07 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity
Replies: 8
Views: 29

Re: Electron Affinity

Electron affinity is not as periodic as ionization energy. Thus, although electron affinity tends to increase going right and up, there are many exceptions to this.
by Robert Tran 1B
Wed Oct 30, 2019 6:05 pm
Forum: Octet Exceptions
Topic: Radicals
Replies: 9
Views: 79

Re: Radicals

To identify a radical, you usually have to look at the molecule's lewis structure and determine if there is an unpaired electron. If so, the molecule would be a radical.
by Robert Tran 1B
Thu Oct 24, 2019 2:46 pm
Forum: Properties of Electrons
Topic: Anions and Cations
Replies: 4
Views: 33

Re: Anions and Cations

If we are considering the anions and cations of one element, then the anion should be larger than the cation. This is because the anion will have more electrons, which creates more electron repulsion within the atom and increases the size of the electron cloud.
by Robert Tran 1B
Thu Oct 24, 2019 2:43 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Energy of spdf orbitals
Replies: 11
Views: 87

Re: Energy of spdf orbitals

As "l" (the number corresponding to the orbital) increases, the orbitals become increasingly less likely to penetrate the nucleus. Since the electrons spend more time further from the nucleus as l increases, they also experience more repulsion from other electrons. This means that the ener...
by Robert Tran 1B
Tue Oct 22, 2019 1:48 pm
Forum: Quantum Numbers and The H-Atom
Topic: Frequency
Replies: 15
Views: 145

Re: Frequency

ATingin_3I wrote:Also speaking of frequency, is frequency always measured in terms of Hz?


The SI unit for frequency is Hz (s^-1). However, 1 divided by any unit of time can be used to measure frequency (ex: 1/hr). These are often not seen though because it is impractical for chemistry.
by Robert Tran 1B
Tue Oct 22, 2019 1:32 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Spin Magnetic Quantum #
Replies: 6
Views: 87

Re: Spin Magnetic Quantum #

There are only two possibilities for the spin direction of an atom: upwards and downwards. Because of this, there are also only two possible spin magnetic quantum numbers. I believe the numbers +1/2 and -1/2 were chosen somewhat arbitrarily.
by Robert Tran 1B
Tue Oct 22, 2019 1:30 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Atomic Radius
Replies: 18
Views: 117

Re: Atomic Radius

The atomic radius is usually determined experimentally by halving the distance between the nuclei of two atoms. There isn't a formula that I know of that can allow us to solve for the atomic radius of a given element/ion.
by Robert Tran 1B
Tue Oct 22, 2019 1:28 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals / Quantum Numbers
Replies: 3
Views: 23

Re: Orbitals / Quantum Numbers

Each subshell has its own unique label, so you basically just have to memorize these. The common ones include s - l=0, p - l=1, d - l=2, f - l=3.
by Robert Tran 1B
Sat Oct 19, 2019 2:11 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals vs. Shells
Replies: 5
Views: 43

Re: Orbitals vs. Shells

Shells describe a general energy level, while the orbital shows where the electron is likely to be. Although orbitals can also differ slightly in energy levels, orbitals within the same shell are clumped around the same energy level.
by Robert Tran 1B
Sat Oct 19, 2019 2:01 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: electron spin arrows
Replies: 6
Views: 27

Re: electron spin arrows

When you are drawing the spin diagrams, the electrons are paired if there are two arrows in the same orbital. Electrons are parallel if the spin arrows face the same direction but are in different orbitals in the same subshell.
by Robert Tran 1B
Sat Oct 19, 2019 1:55 pm
Forum: DeBroglie Equation
Topic: SI Units
Replies: 4
Views: 43

Re: SI Units

Since 1 J = 1 kg*m^2/s^2, this will allow the kg and m to cancel out. Thus, you should convert the pm to m, but you can leave the kg alone so that it cancels out. Just make sure that your units always cancel out to determine whether you need to convert them or not.
by Robert Tran 1B
Sat Oct 19, 2019 1:54 pm
Forum: DeBroglie Equation
Topic: SI Units
Replies: 4
Views: 43

Re: SI Units

Since 1 J = 1 kg*m^2/s^2, this will allow the kg and m to cancel out. Thus, you should convert the pm to m, but you can leave the kg alone so that it cancels out. Just make sure that your units always cancel out to determine whether you need to convert them or not.
by Robert Tran 1B
Tue Oct 15, 2019 8:45 pm
Forum: Properties of Light
Topic: Electromagnetic Radiation
Replies: 3
Views: 28

Re: Electromagnetic Radiation

From lowest to highest energy, it goes: microwaves, visible light, UV rays, x-rays, gamma rays
by Robert Tran 1B
Tue Oct 15, 2019 8:41 pm
Forum: Photoelectric Effect
Topic: Speed of Light
Replies: 29
Views: 158

Re: Speed of Light

The speed of light will always be 3.0 * 10^8 m/s in a vacuum. This value is a constant; however, the speed of light can vary depending on the medium it is passing through.
by Robert Tran 1B
Wed Oct 09, 2019 11:58 pm
Forum: Photoelectric Effect
Topic: Kinetic Energy from the Photoelectric Effect
Replies: 5
Views: 54

Re: Kinetic Energy from the Photoelectric Effect

The excess energy is represented in the velocity of the electron after it is ejected. Any object that is moving has kinetic energy, so a stable object needs to have energy added to it in order for it to move.
by Robert Tran 1B
Wed Oct 09, 2019 11:56 pm
Forum: Quantum Numbers and The H-Atom
Topic: Frequency
Replies: 15
Views: 145

Re: Frequency

When the energy difference is higher, more energy is emitted from the electron. This also means the frequency is higher, because it takes more energy to create a wave of higher frequency. Think of it like trying to make waves by shaking a rope. If you move your hands faster and increase the frequenc...
by Robert Tran 1B
Tue Oct 08, 2019 5:40 pm
Forum: Balancing Chemical Reactions
Topic: Combustion
Replies: 17
Views: 220

Re: Combustion

Combustion is when a compound reacts with oxygen to create water and carbon dioxide. In a chemical equation, the oxygen should be on the reactants side and the water and carbon dioxide should be on the products side.
by Robert Tran 1B
Tue Oct 08, 2019 5:35 pm
Forum: Significant Figures
Topic: Answer being a tad bit off
Replies: 8
Views: 160

Re: Answer being a tad bit off

I'm not sure if points will be deducted for this, but the way you can avoid this error is by storing all calculated values in your calculator until the final value is reached. If you round the values before the final step, you may obtain an error in your final calculation.
by Robert Tran 1B
Tue Oct 08, 2019 5:30 pm
Forum: Balancing Chemical Reactions
Topic: Question about hydroxide
Replies: 5
Views: 82

Re: Question about hydroxide

The calcium ion has a 2+ charge, while the hydroxide ion has a 1- charge. Since calcium hydroxide does not have a charge, we need one calcium ion and two hydroxide ions to make the molecule neutral. Thus, the formula is Ca(OH)2.
by Robert Tran 1B
Mon Sep 30, 2019 10:04 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Formula Units
Replies: 4
Views: 57

Formula Units

Is there a difference between atoms/molecules and formula units? Do formula units change when an ionic compound is dissolved?
by Robert Tran 1B
Mon Sep 30, 2019 9:48 pm
Forum: Limiting Reactant Calculations
Topic: 2 Limiting Reactants
Replies: 9
Views: 66

Re: 2 Limiting Reactants

In theory, there can be two limiting reactants if two reactants are present in the exact amounts necessary to use up both reactants. However, in practice, it's extremely unlikely that two reactants are present in the exact same amounts, so there is only one limiting reactant. For example, if two rea...
by Robert Tran 1B
Sun Sep 29, 2019 10:13 pm
Forum: Significant Figures
Topic: Sig Figs in Scientific Notation
Replies: 5
Views: 93

Re: Sig Figs in Scientific Notation

The amount of sig figs that are used in the answer are determined by the lowest amount of sig figs in the raw data used in the calculations. Because of this, the amount of sig figs we use in scientific notation is determined by the accuracy of the raw data. When we use scientific notation the amount...
by Robert Tran 1B
Sun Sep 29, 2019 10:00 pm
Forum: Balancing Chemical Reactions
Topic: Balancing equations
Replies: 7
Views: 82

Re: Balancing equations

Although other people would be able to understand the equation if there is a decimal or fraction in a balanced equation, it is not good scientific style. It is much easier to understand a ratio if all the numbers are written in whole numbers, so it is best to multiply the decimals and fractions by a...
by Robert Tran 1B
Sun Sep 29, 2019 9:48 pm
Forum: Significant Figures
Topic: Calculations With Significant Figures
Replies: 3
Views: 81

Re: Calculations With Significant Figures

You should always store exact values in intermediate calculations, or else there will oftentimes be significant error in the final resulting calculation. The amount of error increases for every calculation if the values are rounded. Because of this, you should only apply significant figures once all...

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