Search found 60 matches

by Jessica Helfond 2F
Tue Mar 12, 2019 9:25 pm
Forum: First Order Reactions
Topic: Graphs
Replies: 2
Views: 35

Graphs

Why does the graph of time versus concentration need to be linear?
by Jessica Helfond 2F
Tue Mar 12, 2019 9:22 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics and Thermodynamics
Replies: 1
Views: 114

Kinetics and Thermodynamics

How do kinetics and thermodynamics interact to control reactions? How do they each impact a reaction differently?
by Jessica Helfond 2F
Tue Mar 12, 2019 9:19 pm
Forum: First Order Reactions
Topic: Order of a Reaction
Replies: 2
Views: 42

Order of a Reaction

How can you tell what the order of a reaction is?
by Jessica Helfond 2F
Tue Mar 05, 2019 7:51 pm
Forum: First Order Reactions
Topic: First Order Reaction
Replies: 3
Views: 41

First Order Reaction

If [A]₀ is the initial concentration of A, then what does [A] represent?
by Jessica Helfond 2F
Tue Mar 05, 2019 7:48 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Rate Constant
Replies: 3
Views: 44

Rate Constant

Could someone explain what the rate constant (k) actually represents within a reaction?
by Jessica Helfond 2F
Tue Mar 05, 2019 7:46 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Activation Energy
Replies: 2
Views: 52

Activation Energy

How do temperature and activation energy impact the rate constant?
by Jessica Helfond 2F
Mon Feb 25, 2019 6:35 pm
Forum: Van't Hoff Equation
Topic: Equilibrium
Replies: 3
Views: 127

Equilibrium

How does the Van't Hoff equation relate to equilibrium?
by Jessica Helfond 2F
Mon Feb 25, 2019 6:28 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 2
Views: 42

Cell Diagrams

How do you know what order to put the reactants and products in when constructing a cell diagram?
by Jessica Helfond 2F
Mon Feb 25, 2019 6:27 pm
Forum: Balancing Redox Reactions
Topic: Balancing Electrons
Replies: 3
Views: 38

Balancing Electrons

How do you find the number of electrons to balance a redox reaction?
by Jessica Helfond 2F
Fri Feb 22, 2019 2:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridges
Replies: 3
Views: 57

Salt Bridges

Do salt bridges and porous disks both allow ion transfer in the same way? Or would we use one instead of the other in certain situations?
by Jessica Helfond 2F
Fri Feb 22, 2019 2:24 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneity
Replies: 8
Views: 137

Spontaneity

How does Gibbs free energy relate to the spontaneity of a reaction?
by Jessica Helfond 2F
Fri Feb 22, 2019 2:22 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy
Replies: 2
Views: 56

Gibbs Free Energy

Could someone explain what Gibbs free energy actually is? And how does that relate to entropy and enthalpy?
by Jessica Helfond 2F
Mon Feb 11, 2019 8:08 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Deriving Formulas
Replies: 2
Views: 53

Deriving Formulas

Will we need to know how to derive formulas for the midterm? Or is it just something he showed us in class in order to provide background for the concept?
by Jessica Helfond 2F
Mon Feb 11, 2019 8:04 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Determining of there is Change
Replies: 2
Views: 54

Determining of there is Change

Will we be told is there is changed/constant volume or temperature? Or is it something we will have to figure out using PV=nRT?
by Jessica Helfond 2F
Mon Feb 11, 2019 8:03 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy Equations
Replies: 2
Views: 54

Entropy Equations

In what circumstances will we use equations with the Boltzmann equation versus nrtln(v2/v1) or nrtln(t2/t1)?
by Jessica Helfond 2F
Mon Feb 04, 2019 10:35 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ΔU=q+w
Replies: 1
Views: 53

ΔU=q+w

Could someone explain conceptually why this equation works? I know what each of them means but I'm not sure why the internal energy is equal to the heat plus work.
by Jessica Helfond 2F
Mon Feb 04, 2019 10:33 pm
Forum: Calculating Work of Expansion
Topic: Converting between units?
Replies: 2
Views: 37

Re: Converting between units?

I'm pretty sure we would be given any constant we need to convert between units of pressure and volume. That being said, I think 1L*atm=101.325J is just like any other constant on the constant sheet we're given, we don't need to know where it comes from.
by Jessica Helfond 2F
Mon Feb 04, 2019 10:31 pm
Forum: Calculating Work of Expansion
Topic: Difference between reversible and irreversible expansion?
Replies: 2
Views: 72

Re: Difference between reversible and irreversible expansion?

A reversible reaction does more work than an irreversible reaction. This is because we change the volume infinitesimally, so we push against the force little by little to change the volume. This means a reversible reaction is slower, but more efficient. On the other hand, irreversible is fast but in...
by Jessica Helfond 2F
Wed Jan 30, 2019 8:29 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Thermodynamics vs Enthalpy
Replies: 2
Views: 56

Thermodynamics vs Enthalpy

How is thermodynamics different from enthalpy? I get that thermodynamics is heat transfer, but how does that differ from enthalpy, which is the heat absorbed or released?
by Jessica Helfond 2F
Wed Jan 30, 2019 8:27 pm
Forum: Calculating Work of Expansion
Topic: Reversible Process
Replies: 1
Views: 38

Reversible Process

What does calculating the infinitesimal change in volume mean? I get that it's when the volume is changing in very small steps, but what does that mean for the system in the big picture?
by Jessica Helfond 2F
Wed Jan 30, 2019 8:21 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Specific Heat Capacity
Replies: 2
Views: 48

Specific Heat Capacity

What is the difference between heat capacity and specific heat capacity? Why is one extensive and the other intensive?
by Jessica Helfond 2F
Tue Jan 22, 2019 10:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: acids and base
Replies: 1
Views: 45

Re: acids and base

To go from pH to concentration, you can do 10^-pH. You then use this concentration in the ICE box and solve for x to find Ka.
by Jessica Helfond 2F
Tue Jan 22, 2019 10:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Protonation
Replies: 2
Views: 39

Re: Protonation

Protonation is the addition of a proton (H+). Conversely, deprotonation is the removal of a proton (H+). Protonation occurs for bases, while deprotonation occurs for acids. The percent protonated is the amount of base that gets a H+ in the process of the reaction. If it's strong, the percent will be...
by Jessica Helfond 2F
Tue Jan 22, 2019 10:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Strong acids and bases
Replies: 6
Views: 103

Re: Strong acids and bases

I think we should be familiar with what strong acids/bases are going to be (for example, HCl/NaOH) so we can recognize them. Additionally, Lavelle said if the Ka is smaller than 10^-3, it means it's a weak acid. The same goes for bases I'm pretty sure.
by Jessica Helfond 2F
Sat Jan 19, 2019 11:48 am
Forum: Identifying Acidic & Basic Salts
Topic: Salts
Replies: 1
Views: 103

Salts

How do you know if something is a salt? How do you know if it will create an acidic or basic solution?
by Jessica Helfond 2F
Sat Jan 19, 2019 11:45 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6D.15
Replies: 1
Views: 45

Re: 6D.15

I'm pretty sure Ka values will be given to us either in the problem or in a table with other Ka values. For this specific problem, it's probably given in a table somewhere in the textbook. Hope this helps!
by Jessica Helfond 2F
Sat Jan 19, 2019 11:42 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strong vs Weak Acids
Replies: 2
Views: 52

Strong vs Weak Acids

How do we know if an acid is strong or weak? Similarly, how do we know if a base is strong or weak?
by Jessica Helfond 2F
Fri Jan 11, 2019 7:33 pm
Forum: Ideal Gases
Topic: Ideal Gases
Replies: 3
Views: 65

Ideal Gases

How do we know if a gas is ideal? Do we just assume it is in most scenarios?
by Jessica Helfond 2F
Fri Jan 11, 2019 7:31 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changes in Systems
Replies: 3
Views: 59

Changes in Systems

In lecture, Lavelle's slides said for changes in pressure, K does not change, whereas for changes in temperature, K does change. Was this just an example or is this always the case? If it's always the case, why does K change for temperature and not pressure?
by Jessica Helfond 2F
Fri Jan 11, 2019 7:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constant Values
Replies: 3
Views: 74

Equilibrium Constant Values

Will we always be given the numbers for the equilibrium constants of the products or reactants? Or will we have to find them ourselves?
by Jessica Helfond 2F
Sun Dec 02, 2018 1:56 pm
Forum: Naming
Topic: re: Bond Length and Resonance
Replies: 2
Views: 50

Re: re: Bond Length and Resonance

I don't think we'll be given a chart. I think we're just supposed to generally know how to name ligands and coordination compounds.
by Jessica Helfond 2F
Sun Dec 02, 2018 1:51 pm
Forum: Lewis Acids & Bases
Topic: Strong/Weak Acids & Bases
Replies: 2
Views: 57

Strong/Weak Acids & Bases

How can you tell if an acid/base is strong or weak?
by Jessica Helfond 2F
Sun Dec 02, 2018 1:46 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Sphere
Replies: 4
Views: 78

Coordination Sphere

What does it mean if something is outside of the coordination sphere? How does that work structurally?
by Jessica Helfond 2F
Mon Nov 26, 2018 11:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone PR and Bonding PR
Replies: 2
Views: 45

Re: Lone PR and Bonding PR

There are quite a few molecular shapes we need to know for the test. I think it makes the most sense to look at them in terms of how many regions of electron density there are within the molecule. For molecules that have two regions of electron density, the molecule is linear. If there are three reg...
by Jessica Helfond 2F
Mon Nov 26, 2018 11:25 pm
Forum: Dipole Moments
Topic: Dipole Moment Calculation
Replies: 3
Views: 72

Dipole Moment Calculation

Do we need to be able to use the equation m=q x d to calculate the dipole moment? We took notes on this in class but never did any calculations with it. Is it just a concept we need to be familiar with or will we have to calculate the dipole moment within molecules?
by Jessica Helfond 2F
Sat Nov 24, 2018 8:11 pm
Forum: Hybridization
Topic: Sigma/Pi Bonds
Replies: 5
Views: 67

Sigma/Pi Bonds

Could someone explain how we know how many sigma/pi bonds there are within a molecule?
by Jessica Helfond 2F
Sun Nov 18, 2018 6:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 7th edition 2E. 21
Replies: 4
Views: 52

Re: 7th edition 2E. 21

It's not necessary for us to know the exact angle, I think it was just a specific example to show us the proof that the bond length was less. As long as you know it's less than 109.5, you should be good.
by Jessica Helfond 2F
Sun Nov 18, 2018 6:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.1 7th Edition
Replies: 2
Views: 56

2E.1 7th Edition

Could someone explain why in part b the solution says it's possible to have lone pairs? If the two atoms have a bond length of 180 degrees, wouldn't the lone pair push them closer together and then the bond length would be less than 180 degrees?
by Jessica Helfond 2F
Sun Nov 18, 2018 6:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 7th edition 2E.13
Replies: 3
Views: 65

Re: 7th edition 2E.13

From what I understand, it shouldn't matter whether you draw it vertically or horizontally. The electron and bond positions would be the same, which is what is most important.
by Jessica Helfond 2F
Tue Nov 13, 2018 2:42 pm
Forum: Bond Lengths & Energies
Topic: Bond Lengths
Replies: 4
Views: 123

Re: Bond Lengths

Additionally, as a general rule, triple bonds are going to be the shortest because they are the strongest. Double bonds are the next shortest and strongest, and single bonds are going to be the longest and therefore the weakest.
by Jessica Helfond 2F
Tue Nov 13, 2018 2:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electron Density
Replies: 2
Views: 40

Electron Density

Are single/double/triple bonds the only scenario in which there is high electron density that we need to know in terms of VSEPR model?
by Jessica Helfond 2F
Tue Nov 13, 2018 2:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Trigonal Bypyramidal
Replies: 1
Views: 52

Trigonal Bypyramidal

Could someone explain the bond angles in the trigonal bypyramidal shape? Specifically, how/where there are 120 degree angles?
by Jessica Helfond 2F
Sat Nov 03, 2018 10:22 pm
Forum: Electronegativity
Topic: Electronegativity Calculation
Replies: 5
Views: 107

Re: Electronegativity Calculation

There's also a periodic table with the elements and their electronegativity numbers, but I'm pretty sure Lavelle said we don't have to memorize the exact values. If we needed to know the precise numbers, it would be given to us.
by Jessica Helfond 2F
Sat Nov 03, 2018 10:14 pm
Forum: Octet Exceptions
Topic: Lewis acids and bases
Replies: 4
Views: 79

Lewis acids and bases

Could someone explain Lewis acids and bases? And how does it relate to coordinate covalent bonds?
by Jessica Helfond 2F
Sat Nov 03, 2018 10:11 pm
Forum: Octet Exceptions
Topic: Radicals
Replies: 3
Views: 51

Radicals

In what context would there be a radical? If they're so unstable, how do they exist?
by Jessica Helfond 2F
Sat Oct 27, 2018 1:15 pm
Forum: Ionic & Covalent Bonds
Topic: Lowest Energy
Replies: 4
Views: 54

Lowest Energy

What does it mean by achieving "lowest energy" when bonding?
by Jessica Helfond 2F
Sat Oct 27, 2018 1:10 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: D-block Question
Replies: 2
Views: 53

D-block Question

Could someone explain why we write the 3d block before the 4s block when 4s occurs first on the periodic table? Which would get removed first when bonding?
by Jessica Helfond 2F
Sat Oct 27, 2018 1:07 pm
Forum: Trends in The Periodic Table
Topic: Atomic Radius
Replies: 7
Views: 138

Atomic Radius

Could someone explain why removing the second ionization energy of an element is always higher than the first?
by Jessica Helfond 2F
Sun Oct 21, 2018 9:39 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: S,P,D,F
Replies: 6
Views: 138

Re: S,P,D,F

From what I understand, these are the five different ml numbers for a d orbital. Three of the ml numbers are similar to the way we've been writing them: d(xy), d(yz), and d(zx). Another is written as dx^2-dy^2. The final way is dz^2. I think the variances have to do with the different e- densities o...
by Jessica Helfond 2F
Sun Oct 21, 2018 9:32 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Wave Functions
Replies: 4
Views: 74

Re: Wave Functions

From what I understand, in the magnetic quantum number (ml), for l=1, ml= -1,0,+1. Because the subscript goes px, py, pz, py is the middle term, just as 0 is the middle term. Thus, py=0. I believe px and pz would be interchangeable for -1 and +1. Hope this helped!
by Jessica Helfond 2F
Sun Oct 21, 2018 9:25 pm
Forum: *Shrodinger Equation
Topic: Equation Question
Replies: 2
Views: 137

Equation Question

Could someone explain what the H in the Schrodinger equation represents? I can't seem to find it in my notes or the textbook.
by Jessica Helfond 2F
Mon Oct 15, 2018 1:14 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Indeterminacy Equation
Replies: 4
Views: 107

Heisenberg Indeterminacy Equation

Could someone explain why we have to account for the difference in position and momentum (why it's Δp and Δx instead of just p and x)? Why aren't we able to determine the precise value of the two?
by Jessica Helfond 2F
Mon Oct 15, 2018 1:02 pm
Forum: DeBroglie Equation
Topic: 1B.9
Replies: 3
Views: 84

Re: 1B.9

Watts is equivalent to Joules per second. So in this problem, 32 W=32J/s. Then you can find the amount of photons the lamp generates, and then convert the photons to moles by using Avogadro's constant. Hope this helped!
by Jessica Helfond 2F
Mon Oct 15, 2018 12:58 pm
Forum: DeBroglie Equation
Topic: Rest Mass?
Replies: 4
Views: 113

Re: Rest Mass?

In simple terms, resting mass is just when an object has mass when it's stationary. Hope this helped!
by Jessica Helfond 2F
Mon Oct 08, 2018 7:33 pm
Forum: Properties of Light
Topic: Wavelength vs Frequency
Replies: 7
Views: 93

Wavelength vs Frequency

Could someone explain how wavelength and frequency are different? Or are they related?
by Jessica Helfond 2F
Mon Oct 08, 2018 7:30 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect
Replies: 4
Views: 58

Photoelectric Effect

Why was the photoelectric effect unexpected? What did they think would happen instead?
by Jessica Helfond 2F
Mon Oct 08, 2018 7:26 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect
Replies: 6
Views: 71

Photoelectric Effect

Could someone explain what the formula Ek=1/2 Me- * Ve-^2 represents?
by Jessica Helfond 2F
Mon Oct 01, 2018 12:54 pm
Forum: Limiting Reactant Calculations
Topic: Limiting reagents
Replies: 12
Views: 181

Re: Limiting reagents

A one step chemical reaction can only have one limiting reagent because (as long as the 2 reactants are present in different amounts and/or you need different amounts for the reaction) you will run out of one first. Therefore, the reaction will not be able to continue because you will be out of one ...
by Jessica Helfond 2F
Mon Oct 01, 2018 12:47 pm
Forum: Significant Figures
Topic: Significant Figures [ENDORSED]
Replies: 6
Views: 137

Significant Figures [ENDORSED]

Could someone explain why we use significant figures? Wouldn't keeping more decimals be more precise in the answer, or should we just always go by how many sig figs are given in the question?
by Jessica Helfond 2F
Mon Oct 01, 2018 12:40 pm
Forum: Balancing Chemical Reactions
Topic: States of Matter
Replies: 11
Views: 329

States of Matter

Can someone explain to me what an aqueous solution is? And why do we need to include the state of matter when we write and balance chemical reactions?

Go to advanced search