Search found 102 matches

by kristi le 2F
Tue Mar 10, 2020 12:56 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation
Replies: 4
Views: 24

Re: Arrhenius Equation

Through graphing the Arrhenius equation, we can see that the slope of the Arrhenius plot is proportional to the activation energy. A higher activation energy indicates a stronger temperature dependence of the rate constant.
by kristi le 2F
Tue Mar 10, 2020 12:53 am
Forum: *Enzyme Kinetics
Topic: How do you tell if something is a catalyst vs an intermediate?
Replies: 16
Views: 698

Re: How do you tell if something is a catalyst vs an intermediate?

A catalyst needs to be there in the beginning of reaction to start reaction off. The intermediate will not appear in the beginning of a reaction because it is not a reactant. It is both formed and consumed so that it does not appear in the overall chemical equation.
by kristi le 2F
Tue Mar 10, 2020 12:51 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics v Therodynamics
Replies: 8
Views: 22

Re: Kinetics v Therodynamics

Thermodynamics explains whether or not a reaction will occur while kinetics explains the speed of a reaction. They are very intertwined and related to each other.
by kristi le 2F
Tue Mar 10, 2020 12:50 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: intermediate
Replies: 22
Views: 393

Re: intermediate

The intermediate is both formed and consumed in the reaction but does not appear in the overall chemical equation.
by kristi le 2F
Tue Mar 10, 2020 12:49 am
Forum: Experimental Details
Topic: Which Experiment to Use
Replies: 3
Views: 205

Re: Which Experiment to Use

If used correctly, the experiments that you choose to use should yield the same result. In other cases, there are only certain experiments that can be used to determine what the question is asking.
by kristi le 2F
Tue Mar 10, 2020 12:48 am
Forum: Experimental Details
Topic: determining order of reaction
Replies: 6
Views: 50

Re: determining order of reaction

Also, if you are given the elementary steps of a reaction, you may be able to determine the order of a reaction.
by kristi le 2F
Tue Mar 10, 2020 12:47 am
Forum: Biological Examples
Topic: Catalysts
Replies: 6
Views: 13

Re: Catalysts

Dr. Lavelle also noted the difference between intermediates and catalysts in which catalysts are initially there and then reformed while intermediates are created and consumed in the reaction.
by kristi le 2F
Sun Mar 08, 2020 11:16 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Bimolecular Molecularity
Replies: 2
Views: 17

Re: Bimolecular Molecularity

A bimolecular can have two different molecules interacting (A and B) or 2 of the same molecule interacting (A). The rate laws would be k[A][B] and k[A]^2 respectively.
by kristi le 2F
Sun Mar 08, 2020 10:29 pm
Forum: Second Order Reactions
Topic: half life
Replies: 6
Views: 20

Re: half life

Half life is the time needed for concentration to fall to half its initial value. Half life is independent of initial concentration but is inversely related to the rate constant.
by kristi le 2F
Sun Mar 08, 2020 10:26 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: A
Replies: 8
Views: 26

Re: A

Also, A varies by reaction but is mostly independent of temperature.
by kristi le 2F
Sun Mar 08, 2020 10:25 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: A in the Arrhenius Equation
Replies: 8
Views: 53

Re: A in the Arrhenius Equation

Since molecules need to collide at the correct orientation in order to react, orientation must be accounted for in the Arrhenius equation. This dependence on orientation leads to less molecules reacting than if we only accounted for collisions based on kinetic energy.
by kristi le 2F
Sun Mar 08, 2020 10:22 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Exothermic vs. Endothermic
Replies: 10
Views: 343

Re: Exothermic vs. Endothermic

Endothermic and exothermic reactions both have an activation energy. But for endothermic reactions, the products have higher energy than the reactants and for exothermic reactions, the products have lower energy than the reactants.
by kristi le 2F
Sun Mar 08, 2020 10:21 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: molecularity
Replies: 5
Views: 15

Re: molecularity

Since termolecular was all that was discussed in class, I think so. Especially since termolecular reactions are already fairly uncommon since it requires 3 molecules to simultaneously collide.
by kristi le 2F
Sun Mar 08, 2020 10:20 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 16
Views: 394

Re: Catalysts

Catalysts lower the activation barrier, so a greater fraction of reactants can cross the new lower barrier and convert into products.
by kristi le 2F
Sun Mar 08, 2020 6:42 pm
Forum: General Rate Laws
Topic: slow step
Replies: 4
Views: 42

Re: slow step

The molecule involved in the slow step is what determines the rate generally.
by kristi le 2F
Sun Mar 08, 2020 6:40 pm
Forum: Second Order Reactions
Topic: units
Replies: 5
Views: 227

Re: units

fYou can always solve the units for k by dividing the units for rate (mol x L^-1 x s^-1) by the units of your concentrations (which depend on the order of the reaction).
by kristi le 2F
Sun Mar 08, 2020 6:38 pm
Forum: Second Order Reactions
Topic: Termolecular
Replies: 15
Views: 267

Re: Termolecular

Also, for termolecular reactions, the 3 molecules must simultaneously collide, so termolecular reactions are less common.
by kristi le 2F
Sun Mar 08, 2020 6:37 pm
Forum: Second Order Reactions
Topic: Half Life
Replies: 7
Views: 558

Re: Half Life

They will likely be on the formula sheet, but if you do need to derive the formula, plug in t=1/2 to get the half life formula.
by kristi le 2F
Sun Mar 08, 2020 6:35 pm
Forum: First Order Reactions
Topic: Time Conversions
Replies: 9
Views: 365

Re: Time Conversions

The units should be the same so that they will cancel out when doing calculations. Also, sometimes, the question will ask for the answer in a particular unit.
by kristi le 2F
Sun Mar 08, 2020 6:35 pm
Forum: First Order Reactions
Topic: Finding Order of Reactions
Replies: 4
Views: 233

Re: Finding Order of Reactions

You should get the same rate constant for different experiments if your rate law is correct. You can also do it for multiple experiments if you want to check your answers.
by kristi le 2F
Sun Mar 08, 2020 6:34 pm
Forum: First Order Reactions
Topic: rate constants
Replies: 19
Views: 103

Re: rate constants

Rate constants will be positive, but you can still get a graph with a negative slope, such as in 1st order reactions where the slope is -k.
by kristi le 2F
Sun Mar 08, 2020 6:32 pm
Forum: First Order Reactions
Topic: 7B.1
Replies: 1
Views: 17

Re: 7B.1

Masses and concentrations are proportional. Through using the equation ln[A]t/[A]0, = -kt, we find that the proportion of [A]t to [A]0 is 1/10. So, 10% of the initial drug concentration remains in the body, which is (0.10)(20 mg) = 2.0 mg.
by kristi le 2F
Mon Mar 02, 2020 12:56 am
Forum: Balancing Redox Reactions
Topic: When to add H+ or H20
Replies: 19
Views: 132

Re: When to add H+ or H20

Also, remember to use H+ and H2O to balance acidic solutions and OH- and H2O to balance basic solutions.
by kristi le 2F
Mon Mar 02, 2020 12:55 am
Forum: Balancing Redox Reactions
Topic: Anode and Cathode
Replies: 9
Views: 66

Re: Anode and Cathode

Also, for cell diagrams, the cathode will be depicted on the right, even if the cell reaction is not spontaneous in that direction.
by kristi le 2F
Mon Mar 02, 2020 12:54 am
Forum: Balancing Redox Reactions
Topic: Oxidizing/reducing agent
Replies: 18
Views: 123

Re: Oxidizing/reducing agent

The oxidizing agent is what is causing something else to be oxidized. So, it itself will be reduced in order for this to happen. The same is true for the reducing agent.
by kristi le 2F
Mon Mar 02, 2020 12:53 am
Forum: Balancing Redox Reactions
Topic: Acidic vs. Basic Solutions
Replies: 8
Views: 63

Re: Acidic vs. Basic Solutions

In acidic solutions, the concentration of hydronium ions that the concentration of hydroxide ions so H+ should be used to properly balance the half-rxns. So, for basic solutions, OH- should be used because this is the ion that is at a higher concentration in the solution.
by kristi le 2F
Mon Mar 02, 2020 12:51 am
Forum: Balancing Redox Reactions
Topic: Left and Right
Replies: 4
Views: 39

Re: Left and Right

This way, we can also more clearly see which atoms are being reduced and oxidized and make sure the movement of electrons is accurate.
by kristi le 2F
Sun Feb 23, 2020 11:44 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Derivations
Replies: 5
Views: 47

Re: Derivations

I think we only need to know how to use them, but the derivations can be helpful in understanding the concepts behind the equations.
by kristi le 2F
Sun Feb 23, 2020 11:43 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sign of delta G
Replies: 9
Views: 69

Re: Sign of delta G

Yes, because one of the equations for delta G depends on Q.
by kristi le 2F
Sun Feb 23, 2020 11:42 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: applying gibbs free energy
Replies: 5
Views: 34

Re: applying gibbs free energy

Which equation you use can tell you different things about Gibbs free energy. Look at the different variables in each equation and use what is applicable based on the question.
by kristi le 2F
Sun Feb 23, 2020 11:41 pm
Forum: Van't Hoff Equation
Topic: Constants in Van’t Hoff Equation [ENDORSED]
Replies: 4
Views: 50

Re: Constants in Van’t Hoff Equation [ENDORSED]

The entropy and enthalpy are different at different temperatures but their delta's are the same.
by kristi le 2F
Sun Feb 23, 2020 11:40 pm
Forum: Van't Hoff Equation
Topic: Van’t Hoff Equation
Replies: 11
Views: 93

Re: Van’t Hoff Equation

The vant hoff equation can be used to calculate K at different temperatures if stand enthalpy of real lion is known.
by kristi le 2F
Sun Feb 09, 2020 10:11 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: work/energy units
Replies: 3
Views: 26

Re: work/energy units

Both are probably acceptable for the final answer but we may have to convert in order to do the calculations because only certain units are compatible with certain constants or values (like heat capacity)
by kristi le 2F
Sun Feb 09, 2020 10:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Units for heat of reaction
Replies: 9
Views: 52

Re: Units for heat of reaction

Also, if you keep track of units, it makes it easier to do any calculations you may need.
by kristi le 2F
Sun Feb 09, 2020 10:01 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Favorability of Endothermic Reactions
Replies: 5
Views: 35

Re: Favorability of Endothermic Reactions

yes, because the reaction would have more heat to absorb from the surroundings. Therefore, you can think of it as heat not being a limiting reactant.
by kristi le 2F
Sun Feb 09, 2020 9:57 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Higher the heat capacity
Replies: 4
Views: 23

Re: Higher the heat capacity

The heat capacity is the constant of proportionality between heat supplied to a system and temperature rise that results.
by kristi le 2F
Thu Feb 06, 2020 1:26 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: delta U
Replies: 9
Views: 41

Re: delta U

The equation delta U = q + w works because both heat and work are equivalent means of energy transfer.
by kristi le 2F
Thu Feb 06, 2020 1:21 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: when is w=0 and when is q=0?
Replies: 6
Views: 271

Re: when is w=0 and when is q=0?

Also, if w = 0, the internal energy of the system is determined only by q. If q = 0, the internal energy of the system is determined only by w.
by kristi le 2F
Thu Feb 06, 2020 1:20 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible Reactions
Replies: 5
Views: 33

Re: Reversible Reactions

Reversible reactions in thermodynamics refer to thermal equilibrium when the temperature of the system and surroundings is the same. Thermal equilibrium is dynamic and responsive to change, even infinitesimal.
by kristi le 2F
Thu Feb 06, 2020 1:14 pm
Forum: Phase Changes & Related Calculations
Topic: -w vs w
Replies: 15
Views: 87

Re: -w vs w

the sign of w indicates whether work is being done on the system or the system is working. Remember that the sign of work is in relation to the system.
by kristi le 2F
Thu Feb 06, 2020 1:12 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Expansion work/ Compression
Replies: 7
Views: 43

Re: Expansion work/ Compression

Remember that the sign for work is always in regard to the system. In expansion, the system is doing the work and is therefore losing energy so work is negative. In compression, work is being done on the system, so work will be a positive value.
by kristi le 2F
Thu Feb 06, 2020 1:10 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cp and Cv
Replies: 10
Views: 55

Re: Cp and Cv

I don't think we have to memorize actual values but we will have to know what they mean.
by kristi le 2F
Sun Feb 02, 2020 10:44 pm
Forum: Phase Changes & Related Calculations
Topic: ∆H
Replies: 17
Views: 88

Re: ∆H

You can also look at the temperature change of the surroundings and use that to conclude whether the reaction is exothermic or endothermic. If a reaction is exothermic, it releases heat into surroundings. If a reaction is endothermic, it absorbs heat from the surroundings.
by kristi le 2F
Sun Feb 02, 2020 10:40 pm
Forum: Phase Changes & Related Calculations
Topic: about system and surroundings
Replies: 8
Views: 51

Re: about system and surroundings

The system is the region of interest and the surroundings is everything else. So, in these cases, the thermometer and the engine would be the systems. Everything else would be the surroundings.
by kristi le 2F
Sun Feb 02, 2020 10:38 pm
Forum: Phase Changes & Related Calculations
Topic: State Functions
Replies: 9
Views: 49

Re: State Functions

A state function is a property that depends only on the current state of a system, independent on how the state was prepared. For example, internal energy, pressure, volume, temp, and density are state functions. Work and heat are not.
by kristi le 2F
Sun Feb 02, 2020 10:36 pm
Forum: Phase Changes & Related Calculations
Topic: internal energy
Replies: 11
Views: 65

Re: internal energy

Also, heat and work are equivalent means of energy transfer and are the only to change the internal energy of a system.
by kristi le 2F
Sun Feb 02, 2020 10:34 pm
Forum: Phase Changes & Related Calculations
Topic: Open vs Isolated System
Replies: 15
Views: 69

Re: Open vs Isolated System

Also, the first law of thermodynamics states that the internal energy of an isolated system is constant. This would not be true for an open system where the system can exchange both matter and energy with the surroundings.
by kristi le 2F
Thu Jan 23, 2020 11:43 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: H20 in the ICE table
Replies: 26
Views: 136

Re: H20 in the ICE table

whether we leave out water in the ICE table is dependent on the question, so make sure to read the chemical equation carefully.
by kristi le 2F
Thu Jan 23, 2020 11:42 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5% rule
Replies: 13
Views: 61

Re: 5% rule

The % ionization is the concentration of the molecule in the ionized state divided by the concentration of the molecule in the unionized state. If this is less than 5%, not a significant amount of the molecule ionized compared to the initial concentration.
by kristi le 2F
Thu Jan 23, 2020 11:40 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Water in K constant
Replies: 6
Views: 35

Re: Water in K constant

water is not included in the K constant when it is a solvent because it is viewed as pure. Liquids and solids are not included in the K constant since their concentrations do not significantly change.
by kristi le 2F
Mon Jan 20, 2020 5:47 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Relationship between pressure and volume
Replies: 10
Views: 37

Re: Relationship between pressure and volume

Pressure and volume are inversely proportional because conceptually, the smaller the volume/space, the less room the gases have and therefore the higher the pressure.
by kristi le 2F
Mon Jan 20, 2020 5:42 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Conjugate Acids and Bases
Replies: 4
Views: 20

Re: Conjugate Acids and Bases

it is also helpful to know that if there is a strong acid, it will have a weak conjugate base and a strong base will have a weak conjugate acid. Therefore, by knowing the strength of the conjugate, we can determine the strength of the acid or base.
by kristi le 2F
Sat Dec 07, 2019 10:26 pm
Forum: Naming
Topic: Ligands
Replies: 4
Views: 40

Re: Ligands

Bidentate is a form of polydentate. Polydentate can also refer to tridentate, tetradentate. Chelating are polydentate, but polydentate is not necessarily chelating.
by kristi le 2F
Sat Dec 07, 2019 10:25 pm
Forum: Naming
Topic: Metals
Replies: 6
Views: 39

Re: Metals

You only use the Latin name + ate when the overall charge of the compound is negative.
by kristi le 2F
Sat Dec 07, 2019 10:22 pm
Forum: Naming
Topic: Explanation of overall charge of ion
Replies: 2
Views: 26

Re: Explanation of overall charge of ion

Each Cl inside the bracket is one negative. But also there are 2 Cl, each one negative, for a combination of -4. So, Pt must have an oxidation number of 4 for the total complex to be neutral.
by kristi le 2F
Sat Dec 07, 2019 10:19 pm
Forum: Naming
Topic: (en), (dien), etc.
Replies: 6
Views: 64

Re: (en), (dien), etc.

Both the abbreviation and the full names are acceptable for naming.
by kristi le 2F
Sat Dec 07, 2019 10:16 pm
Forum: Biological Examples
Topic: Chemotherapy drugs
Replies: 7
Views: 77

Re: Chemotherapy drugs

We should know cisplatin and how its shape affects its function
by kristi le 2F
Mon Nov 25, 2019 10:37 pm
Forum: Naming
Topic: Coordination compounds
Replies: 2
Views: 60

Re: Coordination compounds

A coordination compound is an electrically neutral compound, in which at least 1 of the ions is a complex of a central metal with other molecules attached.
by kristi le 2F
Mon Nov 25, 2019 10:35 pm
Forum: Naming
Topic: Correct naming conventions
Replies: 5
Views: 46

Re: Correct naming conventions

Also, the -ate is added to the stem of the metal's name. For example, iron would be named ferrate.
by kristi le 2F
Mon Nov 25, 2019 10:34 pm
Forum: Naming
Topic: roman numerals
Replies: 7
Views: 55

Re: roman numerals

The roman numerals refer to the oxidation number of the central metal atom or ion. It can be determined by finding the difference between the charges of the ligands and the overall charge of the molecule.
by kristi le 2F
Mon Nov 25, 2019 10:31 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: brackets
Replies: 13
Views: 78

Re: brackets

Anything that is outside the brackets is not bound to the central metal atom or ion.
by kristi le 2F
Mon Nov 25, 2019 10:29 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: coordination number
Replies: 3
Views: 38

Re: coordination number

en is bidentate, meaning it has two binding sites, so each en will contribute a coordination number of 2. edta is hexadentate, so it has 6 binding sites.
by kristi le 2F
Sun Nov 24, 2019 11:13 pm
Forum: Naming
Topic: adding O
Replies: 3
Views: 33

Re: adding O

i think the anionic ligands end in -o. And if the anion ends in -ide, it becomes -ido, -ate becomes -ato, and -ite becomes -ito.
by kristi le 2F
Sun Nov 24, 2019 11:11 pm
Forum: Naming
Topic: Metallocene
Replies: 1
Views: 28

Re: Metallocene

A metallocene is a "sandwich compound" in which the ligands act as the outside pieces or "bread" and the metal atom is the "filling"
by kristi le 2F
Sun Nov 24, 2019 11:08 pm
Forum: Naming
Topic: Cobalt vs. Cobaltate
Replies: 4
Views: 33

Re: Cobalt vs. Cobaltate

Additionally, sometimes the -ate is added to the stem of the metal's name not the metal name as it appears on the periodic table. For example, iron is denoted ferrate.
by kristi le 2F
Sun Nov 24, 2019 11:07 pm
Forum: Naming
Topic: Roman Numerals
Replies: 3
Views: 34

Re: Roman Numerals

If you know the charges of the other ligands or anions, and the overall charge of the molecule, you can figure out the oxidation state of the transition metal because it must add up to the overall charge.
by kristi le 2F
Sun Nov 24, 2019 11:04 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands
Replies: 4
Views: 38

Re: Ligands

A ligand is a a Lewis base attached to the central metal atom/ion. Each ligand typically has at least 1 lone pair, which forms a coordinate covalent bond with the metal.
by kristi le 2F
Sun Nov 17, 2019 8:48 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: Boiling Points
Replies: 7
Views: 54

Re: Boiling Points

Boiling points increase as the strength of the intermolecular forces increases. For example, a molecule with Hydrogen bonds will likely have a higher boiling point than a molecule with only induced dipole forces because the Hydrogen bonds require more energy to break. Higher temperatures have more e...
by kristi le 2F
Sun Nov 17, 2019 8:43 pm
Forum: Bond Lengths & Energies
Topic: Angle for bond
Replies: 3
Views: 39

Re: Angle for bond

The bond angle would be less than 109.5 because the lone pair repulsion is greater than bonding pair repulsion.
by kristi le 2F
Sun Nov 17, 2019 8:41 pm
Forum: Formal Charge and Oxidation Numbers
Topic: formal charge
Replies: 6
Views: 84

Re: formal charge

Also, with enough practice, you can remember how many lone pairs and bonding pairs like to have. For example, Oxygen likes to have 2 lone pairs and 2 bonding pairs because this gives it a formal charge of zero.
by kristi le 2F
Sun Nov 17, 2019 8:40 pm
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 18
Views: 117

Re: Drawing Lewis Structures

The formal charges don't necessarily have to be zero, but you should try to minimize formal charge as much as possible for a more stable molecule.
by kristi le 2F
Sun Nov 17, 2019 8:39 pm
Forum: Dipole Moments
Topic: Cancelling dipole moments
Replies: 9
Views: 109

Re: Cancelling dipole moments

The dipoles will cancel if they are in opposite direction and of same magnitude. They will be same magnitude if they involve the same atoms. If the dipoles cancel, the resulting molecule will be non polar with polar bonds.
by kristi le 2F
Fri Nov 15, 2019 5:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape v Electron Geometry
Replies: 4
Views: 38

Re: Molecular Shape v Electron Geometry

Lone pairs do influence molecule shape but only atom positions are used to name the shape.
by kristi le 2F
Fri Nov 15, 2019 5:36 pm
Forum: Dipole Moments
Topic: Can nonpolar molecules with polar bonds have dipole dipole interactions?
Replies: 4
Views: 45

Re: Can nonpolar molecules with polar bonds have dipole dipole interactions?

Yes, because the molecule still has dipoles. What makes the molecule non polar overall is likely that the dipoles cancel out.
by kristi le 2F
Fri Nov 15, 2019 5:35 pm
Forum: Dipole Moments
Topic: Polarity
Replies: 12
Views: 102

Re: Polarity

A polar molecule must have polar bonds and dimples that do not cancel. A non polar molecule must have zero electric dipole moment.
by kristi le 2F
Fri Nov 15, 2019 5:34 pm
Forum: Bond Lengths & Energies
Topic: Bond lengths
Replies: 8
Views: 56

Re: Bond lengths

It did say in the textbook that a single bond would not be three times longer than a triple bond or a single bond would not be two times longer than a single bond.
by kristi le 2F
Fri Nov 15, 2019 5:32 pm
Forum: Bond Lengths & Energies
Topic: Boiling and Melting points
Replies: 8
Views: 66

Re: Boiling and Melting points

I think we should just know between two molecules with different interactions, we should be able to dictate which molecule will have the higher boiling and melting point. Typically, it will be the molecule with the stronger interactions that will have higher boiling and melting points.
by kristi le 2F
Sun Nov 03, 2019 8:57 pm
Forum: Ionic & Covalent Bonds
Topic: Distortion
Replies: 4
Views: 37

Re: Distortion

When a cation exerts an electrostatic attraction on the electrons surrounding the anion, the anion's electrons are pulled into the Bonding region/internuclear area. When there is electron density in the region between the nuclei, the spherical electron cloud of the anion is no longer spherical due t...
by kristi le 2F
Sun Nov 03, 2019 8:49 pm
Forum: Electronegativity
Topic: Electron affinity vs electronegativity
Replies: 4
Views: 38

Re: Electron affinity vs electronegativity

Electronegativity has the same trend as electron affinity. However, the mathematical definition of electronegativity is Ionization Energy + Electron Affinity divided by two. In other words, electronegativity is the average between ionization energy and electron affinity.
by kristi le 2F
Sun Nov 03, 2019 8:48 pm
Forum: Bond Lengths & Energies
Topic: dissociation energy
Replies: 7
Views: 62

Re: dissociation energy

Breaking a bond requires energy since bound atoms have lower energy than free atoms. Therefore, forming a bond releases energy.
by kristi le 2F
Sun Nov 03, 2019 8:47 pm
Forum: Resonance Structures
Topic: Drawing Resonance Structures
Replies: 4
Views: 42

Re: Drawing Resonance Structures

I went to a review session, and the TA said that you can either draw all the structures and explain that the actual structure is a hybrid or for example, if it is a double bond resonance, you can draw a single line and a dotted line for the second bond to represent the resonance.
by kristi le 2F
Sun Nov 03, 2019 12:17 am
Forum: Lewis Structures
Topic: Lewis Structures
Replies: 9
Views: 70

Re: Lewis Structures

Also, you can check which Lewis structure has the lowest energy by checking the formal charges. You want the most neutral/nonzero charges as possible.
by kristi le 2F
Sat Oct 26, 2019 11:25 pm
Forum: Properties of Light
Topic: Threshold Frequency
Replies: 5
Views: 57

Re: Threshold Frequency

The threshold frequency is synonymous with work function, which is the Energy needed to remove an electron. However, each individual photon must reach this threshold frequency, dependent on wavelength, not intensity. Therefore, light is acting like a particle, not like in the wave model.
by kristi le 2F
Fri Oct 25, 2019 11:53 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Conserved in Chem Rxn
Replies: 5
Views: 127

Re: Conserved in Chem Rxn

Also, while this isn't directly related to what you asked, also remember that energy is conserved in a reaction as well.
by kristi le 2F
Fri Oct 25, 2019 11:52 pm
Forum: SI Units, Unit Conversions
Topic: Percent Yield
Replies: 6
Views: 113

Re: Percent Yield

Normally, the higher the percent yield (the closer to 100%), the better the experiment because that means not much reaction was stuck to the side or involved in side reactions.
by kristi le 2F
Fri Oct 25, 2019 11:50 pm
Forum: Significant Figures
Topic: How many significant figures are in 7.00 x 10^2?
Replies: 12
Views: 188

Re: How many significant figures are in 7.00 x 10^2?

The fact that the decimal is purposefully placed in the number means that you must count the zeroes after the decimal as significant. The power of 10 is not counted when considering significant figures.
by kristi le 2F
Fri Oct 25, 2019 11:48 pm
Forum: Balancing Chemical Reactions
Topic: Importance of the State of Molecules
Replies: 6
Views: 137

Re: Importance of the State of Molecules

Also, clarifying the state of molecules can be important for molecules like water, that can exist in multiple forms.
by kristi le 2F
Fri Oct 25, 2019 11:47 pm
Forum: SI Units, Unit Conversions
Topic: Angstrom
Replies: 16
Views: 249

Re: Angstrom

Dr. Lavelle regularly uses the Angstrom to describe bond length in lecture so I think this is a good indicator that is an important unit to know, even if it is not an SI unit.
by kristi le 2F
Fri Oct 25, 2019 11:45 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: EM radiation
Replies: 3
Views: 88

Re: EM radiation

It may also be good to know the general trends of EM radiation. For example, gamma rays have short wavelength and high frequency while radio waves have long wavelength and low frequency with visible light in the middle.
by kristi le 2F
Fri Oct 25, 2019 11:40 pm
Forum: DeBroglie Equation
Topic: When to combine equations
Replies: 10
Views: 97

Re: When to combine equations

Combining equations will often be necessary as you normally will not have all the requirements for a certain equation given to you easily. Practicing combining equations will help you recognize when to combine.
by kristi le 2F
Fri Oct 25, 2019 11:36 pm
Forum: Einstein Equation
Topic: When do we use the Einstein Equation?
Replies: 14
Views: 184

Re: When do we use the Einstein Equation?

The equation E=hv can also easily be rearranged to be used to solve for v as well if you know Energy. Planck's constant will always be the same.
by kristi le 2F
Fri Oct 25, 2019 11:34 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Energy of Electrons
Replies: 6
Views: 53

Re: Energy of Electrons

Electrons have higher energy when they are at a higher energy level because it requires more energy for them to be farther from the positive pull of the nucleus.
by kristi le 2F
Fri Oct 25, 2019 11:33 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity
Replies: 4
Views: 37

Re: Electron Affinity

Is electron affinity the same as electronegativity?
by kristi le 2F
Fri Oct 25, 2019 11:32 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy
Replies: 7
Views: 118

Re: Ionization Energy

Also, electron repulsion before the first electron was removed helps keep the ionization energy lower. Once the first electron is removed, there will be less electron repulsion, so the electron will be even harder to remove.
by kristi le 2F
Fri Oct 25, 2019 11:27 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum Numbers
Replies: 7
Views: 84

Re: Quantum Numbers

Also, no two electrons can have the same four quantum numbers. If two electrons share the first three quantum numbers (n, l, ml), their spins must be different. One will be +1/2 while the other will be -1/2.
by kristi le 2F
Fri Oct 25, 2019 11:26 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Purpose of the Equation
Replies: 9
Views: 65

Re: Purpose of the Equation

If one property is known, the other cannot be known simultaneously. For example, if one knows the position of an electron, it is impossible to simultaneously know the momentum.
by kristi le 2F
Fri Oct 25, 2019 11:24 pm
Forum: Properties of Electrons
Topic: Mass of an Electron
Replies: 14
Views: 173

Re: Mass of an Electron

Electrons should have the same mass in all the elements. The same goes for protons and neutrons. It is the number of each that affects the overall mass of the atom.
by kristi le 2F
Thu Oct 24, 2019 6:05 pm
Forum: Balancing Chemical Reactions
Topic: Balancing equations.
Replies: 12
Views: 199

Re: Balancing equations.

Also, when balancing equations, you can check your work when you're done to make sure you did it right. This has helped me catch errors multiple times.
by kristi le 2F
Wed Oct 23, 2019 6:14 pm
Forum: Electronegativity
Topic: Electronegativity values
Replies: 3
Views: 36

Re: Electronegativity values

I think we just need to know the general trends of electronegativity across the periodic table. For example, electronegativity increases across a period due to the increased number of protons in nucleus.
by kristi le 2F
Wed Oct 23, 2019 6:12 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration Exceptions:
Replies: 3
Views: 30

Re: Electron Configuration Exceptions:

Half filled subshells and full filled subshells are more stable. For the d subshell, having 5 or 10 electrons in the subshell is favorable because it is a lower energy state.

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