Search found 47 matches

by Elizabeth Kim 4E
Mon Feb 11, 2019 12:10 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard reaction enthalpy vs standard enthalpy of formation
Replies: 2
Views: 15

Re: Standard reaction enthalpy vs standard enthalpy of formation

Standard reaction enthalpy is the enthalpy that occurs in a reaction and the SE of formation is during the formation of 1 mole of something
by Elizabeth Kim 4E
Mon Feb 11, 2019 12:08 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Open vs Closed System
Replies: 13
Views: 61

Re: Open vs Closed System

In a closed system, matter must stay fixed, but an open system is more flexible
by Elizabeth Kim 4E
Mon Feb 11, 2019 12:07 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Units for enthalpy
Replies: 6
Views: 27

Re: Units for enthalpy

I think the SI unit is kJ and is used as the final answer on most of the answer keys, so it would be safer to put the final answer in kJ
by Elizabeth Kim 4E
Mon Feb 11, 2019 12:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of Phase Changes
Replies: 4
Views: 17

Re: Enthalpy of Phase Changes

The enthalpy from liquid to gas is higher because in addition to raising the temperature, more heat is required to separate the molecules to a gas
by Elizabeth Kim 4E
Mon Feb 11, 2019 12:05 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpies of Formation
Replies: 3
Views: 14

Re: Standard Enthalpies of Formation

He will most likely put the specific standard enthalpy we need in the question
by Elizabeth Kim 4E
Mon Feb 11, 2019 12:04 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 5
Views: 23

Re: Hess's Law

I think the test will provide them for us, according to my TA
by Elizabeth Kim 4E
Mon Feb 11, 2019 12:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Conversions
Replies: 4
Views: 15

Re: Conversions

The L*atm to Joules will probably be needed since we use it most in problems but everything else is on the equation sheet
by Elizabeth Kim 4E
Mon Feb 11, 2019 12:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond enthalpies
Replies: 10
Views: 27

Re: Bond enthalpies

You don't need to know the lewis structures for the midterm, but my TA said it was easier to visualize if you drew out the Lewis structure
by Elizabeth Kim 4E
Mon Feb 11, 2019 12:01 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Explaining Hess's Law with enthalpy = a state function?
Replies: 3
Views: 19

Re: Explaining Hess's Law with enthalpy = a state function?

Enthalpy is a state function, so it doesn't matter what path it takes, as long as it reaches enthalpy
by Elizabeth Kim 4E
Mon Feb 11, 2019 12:01 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework during midterm week [ENDORSED]
Replies: 5
Views: 38

Re: Homework during midterm week [ENDORSED]

Any first law or second and third law of thermodynamics problems I'm pretty sure
by Elizabeth Kim 4E
Mon Feb 11, 2019 11:59 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: cooling a system
Replies: 3
Views: 12

Re: cooling a system

Endothermic: reaction will lean towards reactant
Exothermic: reaction will lean towards products
by Elizabeth Kim 4E
Mon Feb 04, 2019 11:30 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: PV=nRT
Replies: 5
Views: 43

Re: PV=nRT

It can only be used on idea gases
by Elizabeth Kim 4E
Mon Feb 04, 2019 11:28 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Material on Midterm?
Replies: 9
Views: 67

Re: Material on Midterm?

Yeah it goes until the end of enthropy
by Elizabeth Kim 4E
Mon Feb 04, 2019 11:27 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: reaction constant P
Replies: 3
Views: 15

Re: reaction constant P

It only works for gases because pressures only affect gases and not solids or liquids
by Elizabeth Kim 4E
Mon Feb 04, 2019 11:19 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 2nd law of thermodynamics
Replies: 5
Views: 24

Re: 2nd law of thermodynamics

Entropy increases, and as the amount of energy used decreases, the amount of energy not used increases
by Elizabeth Kim 4E
Mon Feb 04, 2019 11:17 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: enthalpy of combustion vs formation
Replies: 3
Views: 16

Re: enthalpy of combustion vs formation

The enthalpy of combustion is the energy released as heat when the reaction undergoes combustion. Standard enthalpy of formation is the change of enthalpy when exactly 1 mole of compound is formed.
by Elizabeth Kim 4E
Mon Feb 04, 2019 11:14 pm
Forum: Calculating Work of Expansion
Topic: Difference between reversible and irreversible expansion?
Replies: 2
Views: 14

Re: Difference between reversible and irreversible expansion?

A reversible reaction is more efficient because the volume changes very slowly and can easily be manipulated to reach equilibrium. However, an irreversible reaction moves very fast and uses large amounts, so it is harder to reach equilibrium easily, so therefore it is irreversible.
by Elizabeth Kim 4E
Mon Feb 04, 2019 11:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Midterm
Replies: 12
Views: 76

Re: Midterm

I think there's one next Monday
by Elizabeth Kim 4E
Fri Nov 30, 2018 12:57 am
Forum: Hybridization
Topic: Lone Pairs in hybridization
Replies: 3
Views: 24

Re: Lone Pairs in hybridization

Lone pairs needed to be accounted for in hybridization
by Elizabeth Kim 4E
Fri Nov 30, 2018 12:56 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: test #3
Replies: 14
Views: 165

Re: test #3

Paramagnetic means that there is one electron in the subshell, and diamagnetic means that there are two paired electrons with opposite spin in the same subshell.
by Elizabeth Kim 4E
Thu Nov 29, 2018 2:05 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Ionic Character
Replies: 3
Views: 31

Re: Ionic Character

Knowing how electronegative an element is helps with determining whether there are ionic or covalent bonds, and if covalent, whether they are polar or non-polar.
by Elizabeth Kim 4E
Thu Nov 29, 2018 2:03 am
Forum: Resonance Structures
Topic: Hybrid Resonance
Replies: 4
Views: 74

Re: Hybrid Resonance

It's the average of all of the possible resonance structures which determines the structure
by Elizabeth Kim 4E
Thu Nov 29, 2018 2:00 am
Forum: Resonance Structures
Topic: Labelling Resonance Structures
Replies: 3
Views: 39

Re: Labelling Resonance Structures

I don't think it's necessary either
by Elizabeth Kim 4E
Thu Nov 29, 2018 2:00 am
Forum: Resonance Structures
Topic: Drawing resonance
Replies: 17
Views: 169

Re: Drawing resonance

Even if it isn't required to draw all of the resonance structures, it's probably helpful in the long run to just draw them all out on tests and homework.
by Elizabeth Kim 4E
Thu Nov 29, 2018 1:58 am
Forum: Resonance Structures
Topic: Bond lengths & number of resonance structures
Replies: 3
Views: 44

Re: Bond lengths & number of resonance structures

The average number of resonance structures determine the shape, therefore it is an average number of bond lengths.
by Elizabeth Kim 4E
Thu Nov 29, 2018 1:56 am
Forum: Coordinate Covalent Bonds
Topic: bound atoms vs separate atoms
Replies: 5
Views: 96

Re: bound atoms vs separate atoms

Free moving atoms have more potential energy therefore are more unstable. Bound atoms have less potential energy because they are bound, so they are more stable than the free moving atoms.
by Elizabeth Kim 4E
Thu Nov 29, 2018 1:48 am
Forum: Lewis Structures
Topic: Lewis structure for POCl3
Replies: 7
Views: 53

Re: Lewis structure for POCl3

Phosphorus is unique in that it has an expanded octet and is also the least electronegative which is why it is the central atom.
by Elizabeth Kim 4E
Thu Nov 29, 2018 1:37 am
Forum: Sigma & Pi Bonds
Topic: Why are sigma bonds stronger than pi bonds?
Replies: 10
Views: 79

Re: Why are sigma bonds stronger than pi bonds?

The greater overlap in the sigma bonds makes it stronger than the pi bonds.
by Elizabeth Kim 4E
Thu Nov 29, 2018 1:34 am
Forum: Ionic & Covalent Bonds
Topic: Strength of Bonds?
Replies: 5
Views: 67

Re: Strength of Bonds?

Ionic bonds are stronger due to their particular ionic character. And polarization power depends in covalent bonds.
by Elizabeth Kim 4E
Sun Nov 11, 2018 4:58 pm
Forum: Lewis Structures
Topic: Molecule Shape
Replies: 8
Views: 98

Re: Molecule Shape

VSPER allows you to tell the shape of the structure
by Elizabeth Kim 4E
Sun Nov 11, 2018 4:55 pm
Forum: Lewis Structures
Topic: Atoms with 8+ valence e-
Replies: 6
Views: 146

Re: Atoms with 8+ valence e-

D and f subshells can account for more than 8 electrons, therefore the expanded octet.
by Elizabeth Kim 4E
Sun Nov 11, 2018 4:53 pm
Forum: Lewis Structures
Topic: Lewis Structure
Replies: 10
Views: 101

Re: Lewis Structure

Make sure that the Lewis structure adds up to the amount of valence electrons and there are all complete octets and the formal charges all around are zero.
by Elizabeth Kim 4E
Sun Nov 11, 2018 4:51 pm
Forum: Ionic & Covalent Bonds
Topic: delta positive delta negative
Replies: 15
Views: 201

Re: delta positive delta negative

Delta negative: accepts electrons
Delta positive: donates electrons
by Elizabeth Kim 4E
Sun Nov 11, 2018 4:17 pm
Forum: Ionic & Covalent Bonds
Topic: Chemical Bonds
Replies: 5
Views: 56

Re: Chemical Bonds

Ionic bonds are shorter because they are stronger bonds
by Elizabeth Kim 4E
Sun Nov 11, 2018 4:11 pm
Forum: Ionic & Covalent Bonds
Topic: Strength of Bonds?
Replies: 5
Views: 67

Re: Strength of Bonds?

Covalent bonds share electrons
by Elizabeth Kim 4E
Sun Nov 11, 2018 4:09 pm
Forum: Ionic & Covalent Bonds
Topic: Proportionality of bond strength
Replies: 3
Views: 130

Re: Proportionality of bond strength

Although the number of bonds increase bond strength, you also have to consider the bond lengths, therefore, it isn't just completely linear from a single to double bond
by Elizabeth Kim 4E
Sun Nov 11, 2018 4:08 pm
Forum: Ionic & Covalent Bonds
Topic: Metallic Bond
Replies: 7
Views: 52

Re: Metallic Bond

Bonding between two metal ions
by Elizabeth Kim 4E
Sun Nov 11, 2018 4:07 pm
Forum: Ionic & Covalent Bonds
Topic: Van der Waals vs Dispersion Forces
Replies: 8
Views: 60

Re: Van der Waals vs Dispersion Forces

They are both intermolecular forces that are relatively weak
by Elizabeth Kim 4E
Sun Nov 11, 2018 2:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Geometric Shape and Bond Angle
Replies: 3
Views: 149

Re: Geometric Shape and Bond Angle

The shape is determined by how the atoms are arranged
by Elizabeth Kim 4E
Sun Nov 11, 2018 2:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSPER and bond strength
Replies: 2
Views: 30

Re: VSPER and bond strength

Yes, stronger bonds have greater repulsion
by Elizabeth Kim 4E
Sun Nov 11, 2018 2:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: molecular shapes
Replies: 13
Views: 107

Re: molecular shapes

I don't think we have to
by Elizabeth Kim 4E
Sat Nov 10, 2018 7:10 pm
Forum: Ionic & Covalent Bonds
Topic: Hydrogen bonding
Replies: 7
Views: 112

Re: Hydrogen bonding

H20's bond length is shorter than H2S which means its harder for electrons to break apart, therefore it has a higher boiling point than H2S.
by Elizabeth Kim 4E
Sat Nov 10, 2018 7:08 pm
Forum: Ionic & Covalent Bonds
Topic: Ionization Energies
Replies: 13
Views: 106

Re: Ionization Energies

Yes and it is very hard to release an electron because the electrons are so tightly packed to each other
by Elizabeth Kim 4E
Sat Nov 10, 2018 7:00 pm
Forum: Ionic & Covalent Bonds
Topic: Dissociation Energy
Replies: 3
Views: 43

Re: Dissociation Energy

Dissociation energy is negative when the bond is releasing energy, and it is positive when it is absorbing energy
by Elizabeth Kim 4E
Fri Oct 05, 2018 4:25 pm
Forum: Limiting Reactant Calculations
Topic: Limiting reagents
Replies: 12
Views: 120

Re: Limiting reagents

There cannot be two limiting reactants, because only one can do the limiting to the other. However, there can be no limiting reactants in which the mole ratio for the reactants are equal.
by Elizabeth Kim 4E
Fri Oct 05, 2018 4:23 pm
Forum: SI Units, Unit Conversions
Topic: formula units [ENDORSED]
Replies: 68
Views: 20043

Re: formula units [ENDORSED]

Any ionic or covalent solid compound not just salts
by Elizabeth Kim 4E
Fri Oct 05, 2018 4:19 pm
Forum: Molarity, Solutions, Dilutions
Topic: Rounding molar mass
Replies: 4
Views: 59

Re: Rounding molar mass

I would use the molar mass from the periodic table for a more accurate answer and then round the final answer to the number of sig figs that are in the numbers given in the problem.

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