## Search found 101 matches

Sat Mar 14, 2020 8:36 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Qc vs Kc
Replies: 15
Views: 586

### Re: Qc vs Kc

If Q>K, then the products are greater and the reverse reaction is favored. If Q<K, then reactants are greater and the forward reaction is favored.
Sat Mar 14, 2020 8:26 pm
Forum: Zero Order Reactions
Topic: Units
Replies: 9
Views: 192

### Re: Units

The units for k in a zero order reaction is M/s.
Fri Mar 13, 2020 1:27 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: how to find k
Replies: 4
Views: 67

### Re: how to find k

To find K, Ecell would equal 0 since the reaction is at equilibrium, so you would use the equation E naught = RT/nF lnK.
Fri Mar 13, 2020 1:21 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Week 10 Review Problems
Replies: 4
Views: 71

### Re: Week 10 Review Problems

You need to have Pt(s) for the cathode because there is no solid metal on that side.
Fri Mar 13, 2020 1:11 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: endgame q 1d and 1e
Replies: 1
Views: 48

### Re: endgame q 1d and 1e

For 1d, the size of the anode has no effect on the cell potential. For 1e, more Ag+ is reduced to solid Ag on the cathode side, so the overall cell potential increases.
Sun Mar 08, 2020 9:48 pm
Forum: General Rate Laws
Topic: 7A.11 part b
Replies: 1
Views: 34

### Re: 7A.11 part b

Since the reaction is first-order, the rate increases in direct proportion to the concentrations of both reactants, so doubling the concentration of reactants will double the reaction rate.
Sun Mar 08, 2020 9:34 pm
Forum: General Rate Laws
Topic: Integrated vs Differential Rate Laws?
Replies: 1
Views: 66

### Re: Integrated vs Differential Rate Laws?

Integrated rate law provides an equation of the initial concentration and the measured concentration of one or more reactants after a given amount of time. Differential rate law provides an expression of the rate of concentration change over a specific time period.
Fri Mar 06, 2020 12:19 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Favoring reactions
Replies: 7
Views: 159

### Re: Favoring reactions

The reaction will favor the reactants if the anode has a larger value than the cathode, because the overall cell potential will be negative, so delta G will be positive.
Fri Mar 06, 2020 12:16 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: galvanic cells
Replies: 8
Views: 157

### Re: galvanic cells

The cathode has the more positive cell potential, the anode has the more negative cell potential.
Fri Mar 06, 2020 12:15 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E° vs E
Replies: 7
Views: 134

### Re: E° vs E

E°is the cell potential under standard conditions, while E is under non-standard conditions.
Sun Mar 01, 2020 11:43 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst equation and K
Replies: 3
Views: 75

### Re: Nernst equation and K

You use K when the concentrations of products and reactants are at equilibrium. Electron flow stops at equilibrium because the voltage drops down to 0.
Sun Mar 01, 2020 11:36 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E of concentration cell
Replies: 1
Views: 26

### Re: E of concentration cell

The E value for concentration cells will always be 0 because the standard cell potential for the cathode and the anode will cancel each other out.
Sun Mar 01, 2020 11:32 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Determining n
Replies: 5
Views: 129

### Re: Determining n

n is the moles of electrons transferred in the reaction, which is determined from writing the oxidation and reduction half-reactions.
Sun Mar 01, 2020 11:19 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electromotive force
Replies: 3
Views: 68

### Re: Electromotive force

Electron flow can go in any direction.
Sun Mar 01, 2020 11:08 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Delta G and Electrochemistry
Replies: 2
Views: 43

### Re: Delta G and Electrochemistry

Max cell potential is related to gibbs free energy through the equation deltaG = -nFE
Sun Feb 23, 2020 11:18 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff Equation
Replies: 3
Views: 97

### Re: Van't Hoff Equation

The Van't hoff equation relates the change in the equilibrium constant K of a chemical reaction to the change in temperature. It is derived from combining the equations deltaG = deltaH - TdeltaS and delta G = -RTlnK.
Sun Feb 23, 2020 11:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Difference in phases
Replies: 5
Views: 70

### Re: Difference in phases

A comma used when the ions are in the same phase, and a line is used when they are not.
Sun Feb 23, 2020 11:09 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Gibbs free energy and max work
Replies: 2
Views: 43

### Gibbs free energy and max work

Why is gibbs free energy equal to maximum work?
Sun Feb 23, 2020 11:03 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 5J.11 b
Replies: 2
Views: 87

### Re: 5J.11 b

When the halogen is split, heat is required to break the bond, so it is an endothermic reaction.
Sun Feb 23, 2020 10:59 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: applying gibbs free energy
Replies: 5
Views: 94

### Re: applying gibbs free energy

Gibbs free energy also represents the maximum work from the energy that is released.
Sun Feb 16, 2020 11:55 pm
Forum: Van't Hoff Equation
Topic: When to Use Vant Hoff
Replies: 5
Views: 111

### Re: When to Use Vant Hoff

We use the equation to relate the change in the equilibrium constant K in a chemical reaction to the change in temperature, given a standard enthalpy change.
Sun Feb 16, 2020 11:31 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff Equation
Replies: 3
Views: 88

### Re: Van't Hoff Equation

The equation is derived from the two equations deltaG = deltaH - TdeltaS and deltaG = -RTlnK set equal to each other. The equation is used to find out how the change in K of a chemical reaction relates to the change in temperature, given a standard enthalpy change.
Sun Feb 16, 2020 8:49 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: K equation with Gibbs free energy
Replies: 3
Views: 48

### Re: K equation with Gibbs free energy

When the problem asks for G at any stage of the reaction, we use G = G* + RTlnQ. However, at equilibrium G = 0 and Q = K, so then we would use G* = -RTlnK.
Wed Feb 12, 2020 2:45 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Example 4I.3
Replies: 3
Views: 136

### Re: Example 4I.3

Entropy is a state function, so the change in entropy of the system is the same regardless of whether the path is reversible or irreversible.
Wed Feb 12, 2020 2:40 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 4j.3
Replies: 1
Views: 30

### Re: 4j.3

The value is given in Table 4C.1 in the textbook.
Sun Feb 09, 2020 11:41 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: extensive vs intensive
Replies: 4
Views: 77

### Re: extensive vs intensive

An extensive property depends on the amount of substance, such as heat capacity. An intensive property doesn't depend on the amount of substance, such as specific heat or molar heat capacity.
Sun Feb 09, 2020 8:08 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Gas Constant
Replies: 3
Views: 48

### Re: Gas Constant

Based on the units given in the problem, it will determine which value of R to use.
Sun Feb 09, 2020 8:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4E.5
Replies: 1
Views: 38

### Re: 4E.5

C-H bonds cancel out on both sides of the reactions in parts a and b, so you don't consider them when calculating the rxn enthalpy.
Sat Feb 08, 2020 11:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.7
Replies: 4
Views: 50

### Re: 4D.7

298K is the most common temperature used in data for reaction enthalpies, so we just have to assume that when no temperature is stated.
Sat Feb 08, 2020 11:30 pm
Forum: Phase Changes & Related Calculations
Topic: Difference in energy needed for the different phases
Replies: 3
Views: 45

### Re: Difference in energy needed for the different phases

It requires much more energy to completely break the hydrogen bonding in water molecules to convert to the gas phase.
Sun Feb 02, 2020 4:23 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4C. 9
Replies: 1
Views: 29

### Re: 4C. 9

The heat supplied will raise the temperature of copper and the temperature of water, so both values of q must be added together.
Sun Feb 02, 2020 4:16 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4B 11
Replies: 2
Views: 22

### Re: 4B 11

This is more of a conceptual question that is based on the equation for internal energy, delta U = q + w. Given that this is an adiabatic process, this would mean that q, energy transferred as heat, equals 0. Delta U would also equal 0, but only under the conditions that no work is done.
Sun Feb 02, 2020 4:00 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Question 4C.11
Replies: 4
Views: 83

### Re: Question 4C.11

Use Table 4C.1 to find the enthalpy of fusion of water. Convert 80.0 grams of ice to moles and multiply by the enthalpy of fusion to get the heat needed to melt the ice. Then, use 80.0 g in the equation q= mCΔT to find the heat needed to raise the temperature from 0 to 25 degrees C.
Sat Feb 01, 2020 4:33 pm
Forum: Calculating Work of Expansion
Topic: Reversible vs Irreversible process
Replies: 2
Views: 33

### Reversible vs Irreversible process

What is the difference between a reversible and irreversible process? How does it relate to the work of expansion?
Fri Jan 31, 2020 4:58 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.9
Replies: 2
Views: 37

### Re: 4D.9

Table 4D.2 in the textbook gives the standard enthalpies of formation for each compound. O2 and N2 are in their most stable form so their enthalpy of formation is 0. The rxn releases 1/4 amount of energy per mole of TNT consumed.
Sun Jan 26, 2020 9:58 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy
Replies: 5
Views: 71

### Re: Enthalpy

Enthalpy only depends on the initial and final values of heat in a reaction, not the path it takes to get to the current state.
Sun Jan 26, 2020 9:48 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpies of Formation
Replies: 4
Views: 31

### Re: Standard Enthalpies of Formation

The standard rxn enthalpy can be calculated by using the standard enthalpy of formation of all products and subtracting it by the standard enthalpy of formation of all reactants.
Sun Jan 26, 2020 8:43 pm
Forum: Phase Changes & Related Calculations
Topic: Heat v Enthalpy
Replies: 3
Views: 50

### Re: Heat v Enthalpy

Heat depends on the path taken to obtain the current state. Enthalpy is a state function because it only depends on the initial and final values of heat, so it doesn't depend on the path taken.
Fri Jan 24, 2020 12:35 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Partial Pressure
Replies: 5
Views: 55

### Re: Partial Pressure

Increasing the partial pressure of one element causes an increase in partial pressure on the other side of the reaction in order to minimize the effect of the change. This also applies when increasing the overall pressure, where the equilibrium shifts in the direction that decreases the number of mo...
Fri Jan 24, 2020 12:14 am
Forum: Ideal Gases
Topic: R Constant
Replies: 26
Views: 392

### Re: R Constant

It depends on the units for pressure and volume given in the problem.
Sun Jan 19, 2020 8:25 pm
Forum: Ideal Gases
Topic: Using PV=nRT
Replies: 7
Views: 74

### Re: Using PV=nRT

Yes, you would use the equation to convert between concentration and partial pressure, depending on what the problem asks for.
Fri Jan 17, 2020 10:38 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Change in Pressure
Replies: 5
Views: 52

### Re: Change in Pressure

According to Le Chatelier's principle, when the amount of reactant or product is changed in a reaction, the equilibrium will shift to minimize the effect
Thu Jan 16, 2020 7:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solids and Equilibrium
Replies: 9
Views: 110

### Re: Solids and Equilibrium

Solids and liquids do not affect equilibrium or the equilibrium constant because they are pure substances that don't change in a reaction.
Thu Jan 16, 2020 7:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.13 c
Replies: 2
Views: 40

### 5I.13 c

(c) Use your results from parts (a) and (b) to determine which is thermodynamically more stable relative to its atoms at 1000. K, Cl2 or F2.

Why is Cl2 more stable than F2?
Thu Jan 16, 2020 7:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Bar and atm
Replies: 1
Views: 22

### Re: Bar and atm

Yes, the partial pressures should always be in bar.
Sun Jan 12, 2020 12:46 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial pressure
Replies: 4
Views: 44

### Re: Partial pressure

The total pressure is the sum of the partial pressures of each gas in a mixture.
Sat Jan 11, 2020 1:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Which Constant to use
Replies: 4
Views: 61

### Re: Which Constant to use

You would convert the partial pressures to concentration using the ideal gas law equation.
Sat Jan 11, 2020 1:37 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Change in pressure
Replies: 5
Views: 50

### Re: Change in pressure

Increasing pressure results from decreasing volume, so there are more moles of gas in the reactants and the reaction shifts to the right.
Fri Jan 10, 2020 5:46 pm
Forum: Ideal Gases
Topic: Ideal Gas Law
Replies: 6
Views: 50

### Re: Ideal Gas Law

For reactions that have homogeneous equilibrium for a gas, we can use the ideal gas law to convert between partial pressure and concentration.
Fri Jan 10, 2020 5:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G1
Replies: 2
Views: 49

### Re: 5G1

Equilibrium rxns are affected by the amount of products and reactants. The equilibrium constant represents the P/R ratio at equilibrium, which is not affected by the higher pressure of reactant since the temperature is constant.
Sun Dec 08, 2019 1:22 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR and polarity
Replies: 8
Views: 242

### Re: VSEPR and polarity

A molecule is polar when the central atom has lone pairs and the atoms attached aren’t the same, so the dipoles don’t cancel.
Sun Dec 08, 2019 1:10 am
Forum: Bronsted Acids & Bases
Topic: arrhenius bases
Replies: 1
Views: 109

### Re: arrhenius bases

We won’t need to know Arrhenius acids and bases for the final, just know the Lewis/Bronsted definitions.
Sat Dec 07, 2019 4:24 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 115
Views: 6397

### Re: MARSHMALLOW- FINAL REVIEW SESSION[ENDORSED]

For mini marshmallow 2c, why is the coordination number for K[Cu(en)2(CN)2] 6?
Sat Dec 07, 2019 4:18 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 115
Views: 6397

### Re: MARSHMALLOW- FINAL REVIEW SESSION[ENDORSED]

Nikki Razal 4E wrote:for question 40c, how do you know whether o2 or o3 has the stronger bond and why?

o2 has double bonds that are shorter and therefore stronger than the o3 bonds, which is between a single and double bond due to resonance.
Sat Dec 07, 2019 4:00 pm
Forum: Identifying Acidic & Basic Salts
Topic: 6.21 c
Replies: 1
Views: 50

### 6.21 c

Why do the nitrogens in thymine show amphiprotic behavior? I understand that it accepts protons due to the lone pairs, but how can it donate protons?
Fri Dec 06, 2019 12:22 am
Forum: Bronsted Acids & Bases
Topic: Acidic Strength
Replies: 3
Views: 85

### Re: Acidic Strength

Cl is more electronegative than Br, so it can withdraw electrons from the O-H bond and it becomes easier to remove H+.
Sun Dec 01, 2019 11:23 pm
Forum: Naming
Topic: Naming
Replies: 1
Views: 31

### Re: Naming

There would be no suffix, so the metal name would just be iron. The suffix -ate is added when the compound has a negative charge.
Sun Dec 01, 2019 11:03 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate ligands
Replies: 2
Views: 67

### Re: Polydentate ligands

Drawing out the lewis structure would help in determining which atoms on the ligand have lone pairs and can bind to the transition metal.
Sun Dec 01, 2019 12:05 pm
Forum: Naming
Topic: Coordination Compounds Formula
Replies: 1
Views: 44

### Coordination Compounds Formula

When writing the formula from a coordination compound, does the order of the ligands matter?
Sat Nov 30, 2019 5:14 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9C.5
Replies: 1
Views: 37

### 9C.5

Why can CO3 2- be monodentate or bidentate? And why is oxalate bidentate? I'm confused because all the oxygens have lone pairs, so how do you determine which places on the ligand bind to a single metal center?
Sat Nov 30, 2019 4:45 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Square-Planar Complex vs. Tetrahedral Complex
Replies: 2
Views: 76

### Re: Square-Planar Complex vs. Tetrahedral Complex

You won't know which complex it is, since you don't know if the central transition metal atom has lone pairs or not.
Sun Nov 24, 2019 11:57 pm
Forum: Hybridization
Topic: Hybridization number
Replies: 3
Views: 64

### Re: Hybridization number

The number of hybrid orbitals is equal to the number of bonds and lone pairs around the central atom.
Sun Nov 24, 2019 11:48 pm
Forum: Hybridization
Topic: Sigma and Pi bonds
Replies: 3
Views: 59

### Sigma and Pi bonds

Why are sigma bonds stronger than pi bonds?
Sun Nov 24, 2019 8:19 pm
Forum: Hybridization
Topic: Hybridization
Replies: 1
Views: 46

### Hybridization

Can someone please explain the hybridization concept and why it occurs?
Sun Nov 24, 2019 8:11 pm
Forum: Hybridization
Topic: Hybridization and lone pairs
Replies: 2
Views: 64

### Re: Hybridization and lone pairs

Lone pairs on the central atom count toward the number of hybrid orbitals in a molecule, which then determines the hybridization.
Thu Nov 21, 2019 2:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: electron-pair geometry vs molecular geometry
Replies: 3
Views: 61

### Re: electron-pair geometry vs molecular geometry

The electron pair geometry is based on the number of regions of electron density around the atom (parent shape), while molecular geometry is the actual shape that includes bonding pairs and lone pairs.
Sun Nov 17, 2019 11:53 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape vs Electron Geometry
Replies: 4
Views: 91

### Molecular Shape vs Electron Geometry

What is the difference between molecular shape and electron geometry?
Sun Nov 17, 2019 11:24 pm
Forum: Determining Molecular Shape (VSEPR)
Replies: 5
Views: 104

### Re: Radicals and molecular shape

The single unpaired electron on the central atom is treated as a region of high electron density, so it acts like a lone pair when determining the molecular shape.
Fri Nov 15, 2019 12:40 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Homework Problem 2E.11
Replies: 1
Views: 32

### Re: Homework Problem 2E.11

The square planar shape minimizes repulsion, so it has the lowest energy. The lone pairs on either side are farthest from each other and farthest from the atoms bonded to the central atom.
Thu Nov 14, 2019 11:49 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angle of OClO
Replies: 1
Views: 37

### Re: bond angle of OClO

The lone pair on Cl exerts strong repulsion on the O atoms, causing them to move closer together, which slightly decreases the bond angle.
Thu Nov 14, 2019 11:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Textbook question 2E.1
Replies: 4
Views: 90

### Re: Textbook question 2E.1

The lone pair on the central atom has a stronger repelling effect, pushing the bonding pairs closer together to create a bent shape.
Sat Nov 09, 2019 10:37 pm
Forum: Dipole Moments
Topic: Van Der Waals
Replies: 5
Views: 91

### Re: Van Der Waals

All molecules have van der Waals forces because their electrons are constantly moving around and creating temporary dipoles.
Sat Nov 09, 2019 9:14 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: hydrogen vs london
Replies: 2
Views: 45

### Re: hydrogen vs london

Hydrogen bonds are always stronger because they have dipole-dipole interactions between a hydrogen atom and an electronegative atom, whereas london forces only have temporary dipoles that form weak attractions.
Wed Nov 06, 2019 3:51 pm
Forum: Octet Exceptions
Topic: Xenon and Expanded Octets
Replies: 2
Views: 59

### Re: Xenon and Expanded Octets

The Xenon in the expanded lewis structures has a formal charge of 0 when you follow the equation FC = V - (L + S/2). It can't have a negative charge because it is a noble gas and its outer shell is full, so it can't attract more electrons.
Wed Nov 06, 2019 3:38 pm
Forum: Bond Lengths & Energies
Topic: de Broglie threshold
Replies: 4
Views: 134

### Re: de Broglie threshold

Particles with wavelengths less than 10^-15 m have mass that is too large for there to be detectable wavelike properties.
Mon Nov 04, 2019 3:37 pm
Forum: Quantum Numbers and The H-Atom
Topic: Orbital vs Subshells
Replies: 3
Views: 78

### Re: Orbital vs Subshells

Each value of l is a subshell, and within each subshell are orbitals. The magnetic quantum number ml labels individual orbitals.
For example, when l=2, ml= -2,-1,0,1,2 meaning there are 5 d-orbitals.
Mon Nov 04, 2019 3:25 pm
Forum: Trends in The Periodic Table
Topic: Effective Nuclear Charge
Replies: 5
Views: 240

### Effective Nuclear Charge

Can someone please explain the concept of effective nuclear charge and how it relates to periodic trends?
Mon Nov 04, 2019 12:26 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electron Configurations
Replies: 2
Views: 149

### Re: Electron Configurations

3p^3 is fine, I don't think we'll need to specify px, py, pz.
Sat Nov 02, 2019 7:05 pm
Forum: Octet Exceptions
Replies: 3
Views: 96

Radicals are compounds with unpaired electrons. They have an odd number of valence electrons, so one of their atoms cannot form an octet.
Fri Nov 01, 2019 11:23 pm
Forum: Bond Lengths & Energies
Topic: Bond strength and electronegativity
Replies: 2
Views: 59

### Bond strength and electronegativity

What is the relationship between bond strength and electronegativity?
Fri Nov 01, 2019 11:04 pm
Forum: Bond Lengths & Energies
Topic: Test?
Replies: 8
Views: 229

### Re: Test?

The midterm will cover bond lengths and energies, up to the end of Focus 2D in the textbook.
Sun Oct 27, 2019 7:41 pm
Forum: Octet Exceptions
Topic: Valence electrons for atomic numbers after 20
Replies: 2
Views: 44

### Re: Valence electrons for atomic numbers after 20

You would count the valence electrons on the outermost shell, which in this case are the s and p orbitals. The d orbital has a lower energy level.
Fri Oct 25, 2019 6:19 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E. 7 Ground state vs. Excited State
Replies: 2
Views: 41

### Re: 1E. 7 Ground state vs. Excited State

The ground-state electron configuration is the arrangement of electrons with the lowest energy state possible.
Thu Oct 24, 2019 5:22 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Question 2A #5 part c
Replies: 2
Views: 39

### Re: Question 2A #5 part c

Ga loses 3 electrons to form Ga^3+, meaning it loses its valence 4s and 4p electrons on the outermost shell.
Thu Oct 24, 2019 5:08 pm
Forum: Electronegativity
Topic: The dipole moment
Replies: 2
Views: 60

### Re: The dipole moment

The dipole moment refers to the difference between partial charges across a molecule. The atom with higher electronegativity in a covalent bond pulls electrons away from the other atom, creating a partial negative charge, and the other atom is surrounded by a partial positive charge.
Thu Oct 24, 2019 2:48 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: HW 1D.23
Replies: 4
Views: 176

### Re: HW 1D.23

Do you mean part C? When n=2, it can have values of 0 and 1 for l, which translate to one s-orbital and three p-orbitals respectively.
Sun Oct 20, 2019 7:32 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s orbitals and 3d orbitals
Replies: 2
Views: 51

### Re: 4s orbitals and 3d orbitals

As Dr. Lavelle explained in lecture, the 4s state is higher in energy than 3d once the 4s state becomes occupied and the electron enters the 3d state.
Sat Oct 19, 2019 7:07 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Using the equation
Replies: 1
Views: 46

### Re: Using the equation

The problem will usually ask directly for the minimum uncertainty in the speed or position of an object.
Thu Oct 17, 2019 8:11 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Equations
Replies: 3
Views: 52

### Re: Photoelectric Effect Equations

h/mv is used to find the wavelength of one moving particle with momentum p, in this case an electron. hc/E calculates the wavelength of the light needed to eject an electron.
Thu Oct 17, 2019 2:45 pm
Forum: DeBroglie Equation
Topic: DeBroglie Equation Use
Replies: 5
Views: 97

### Re: DeBroglie Equation Use

DeBroglie equation is used to calculate the wavelength of any moving particle with linear momentum p. All matter has wavelike properties, but it is only noticed for objects of extremely small mass such as electrons.
Mon Oct 14, 2019 7:39 pm
Forum: Einstein Equation
Topic: 1B.9
Replies: 5
Views: 270

### 1B.9

A lamp rated at 32 W (1W = 1 J.s-1) emits violet light of wavelength 420 nm. How many photons of violet light can the lamp generate in 2.0 s? How many moles of photons are emitted in that time interval?

I'm not sure how to go about solving this problem. Can someone please explain?
Thu Oct 10, 2019 10:39 pm
Forum: Properties of Light
Topic: Wavelength help
Replies: 3
Views: 47

### Re: Wavelength help

Increasing the wavelength of a light source will lower the frequency, which decreases the energy of each photon. If it goes below the threshold frequency, the light cannot eject electrons.
Thu Oct 10, 2019 10:31 pm
Forum: Photoelectric Effect
Topic: Photons and electrons
Replies: 5
Views: 96

### Re: Photons and electrons

We would use the equation λ = hc/E, which is derived from taking λv = c and rearranging it in terms of v, then plugging it into the Einstein equation E = hv.
Thu Oct 10, 2019 1:01 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Conserved in Chem Rxn
Replies: 5
Views: 273

### Re: Conserved in Chem Rxn

Yes, electrons and protons must be conserved because they contribute to the atomic mass. According to the law of conservation of mass, the mass of the left side of the equation must equal the mass on the right.
Tue Oct 08, 2019 4:37 pm
Forum: Significant Figures
Replies: 8
Views: 361

I think you will be docked off a little since it is off in the 0.1 decimal place, which is far off and probably a result of rounding too early on in the problem. We need to be as precise as possible when solving chemistry problems, so only round to the correct number of sig figs when you reach the f...
Tue Oct 08, 2019 4:15 pm
Forum: Empirical & Molecular Formulas
Topic: F 17
Replies: 2
Views: 81

### Re: F 17

After you find the empirical formula of OsC4O4 in part a, find the molar mass of the empirical formula unit to get 302.27 g/mol. Divide the given molar mass of 907 g/mol by 302.27 g/mol to get a value of 3. Then multiply the coefficients in the empirical formula by the factor 3 to get the molecular ...
Thu Oct 03, 2019 2:43 pm
Forum: SI Units, Unit Conversions
Topic: knowing how many sig figs to use
Replies: 17
Views: 343

### Re: knowing how many sig figs to use

I would suggest rounding to the correct amount of sig figs for the final answer and trying to keep the precise values on your calculator as you work through the problem, that way there is more accuracy.
Thu Oct 03, 2019 11:37 am
Forum: Ionic & Covalent Bonds
Topic: Ionic vs Covalent
Replies: 32
Views: 14648

### Re: Ionic vs Covalent

Ionic bonds are stronger than covalent bonds, but when dissolved in water, they become much weaker because ions separate and are surrounded by water molecules.
Thu Oct 03, 2019 11:14 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: F.13 homework problem
Replies: 4
Views: 158

### Re: F.13 homework problem

I don't think naming compounds is something we will be tested on or actually have to know. However, you should be expected to remember the formulas of common compounds such as hydrochloric acid and calcium carbonate. In this case, PCL5 is a molecular compound, so the rule for this is replacing the e...
Tue Oct 01, 2019 7:24 pm
Forum: Empirical & Molecular Formulas
Topic: E.25 Parts (b) & (c)
Replies: 2
Views: 52

### Re: E.25 Parts (b) & (c)

For a, you would convert the given number of moles, 0.750 mol KNO3, into the number of molecules.
0.750 mol * 6.022*10^23 = 4.52*10^23 formula units.