## Search found 103 matches

Sat Mar 14, 2020 10:09 am
Forum: Administrative Questions and Class Announcements
Topic: UA Final Review - Kate, Riya, Matthew
Replies: 13
Views: 1165

### Re: UA Final Review - Kate, Riya, Matthew

For Q4. a), how do you know that 5.00 x 10^-3 mol H2C2O4 = 1.00 x 10^-2 mol H+?
Sat Mar 14, 2020 8:56 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7C.11 c)
Replies: 2
Views: 17

### 7C.11 c)

If you increase the concentration of the reactants, I understand that this increases the rate of the reaction, but why doesn't this have an effect on the rate constant?
Sat Mar 14, 2020 8:38 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Fast Step
Replies: 1
Views: 15

### Fast Step

Why doesn't the fast step have an effect on the overall reaction?
Mon Mar 09, 2020 11:08 am
Forum: First Order Reactions
Topic: Deriving First Order Half Life Equation
Replies: 3
Views: 28

### Deriving First Order Half Life Equation

When deriving the half life equation for a first order reaction, why do you set [A] equal to .5[A]0 when t = t(1/2)?
Mon Mar 09, 2020 10:52 am
Forum: First Order Reactions
Topic: Pseudo-First Order Reaction
Replies: 4
Views: 60

### Pseudo-First Order Reaction

If a reaction is in second order, when can you assume that it will be a pseudo-first-order reaction?
Sun Mar 08, 2020 7:33 pm
Forum: General Rate Laws
Topic: 7A.3
Replies: 4
Views: 51

### 7A.3

The combustion reaction C2H4 (g) + 3O2 (g) --> 2CO2 (g) + 2H2O (g) has a unique rate of .44 mol.L^-1.s^-1 When finding the rate at which oxygen reacts and the rate at which water forms, why do both of these rates have positive values? Shouldn't they be opposite values since one is used up in the rea...
Sun Mar 08, 2020 7:20 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: k
Replies: 10
Views: 96

### Re: k

k is unit-less because it is a ration of concentrations of products and reactants thanks for all the answers everyone but i forgot to clarify in my original question that i'm referring to the k that is in rate laws. i thought that k in the context of kinetics had units? In terms of kinetics, the un...
Mon Mar 02, 2020 9:14 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 6.45
Replies: 1
Views: 25

### 6.45

Is a "strongly reducing metal" the same thing as a reducing agent?
Mon Mar 02, 2020 4:46 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Dilution in Concentration Cell
Replies: 1
Views: 34

### Dilution in Concentration Cell

If the anode in a concentration cell is diluted, why does this increase the cell potential?
Mon Mar 02, 2020 4:18 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6.43 a)
Replies: 1
Views: 24

### 6.43 a)

Why does E cell decrease as the cell reaction progresses but Eºcell does not decrease?
Sun Mar 01, 2020 3:09 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N. 3b)
Replies: 3
Views: 63

### 6N. 3b)

How come when you flip the reaction at the anode to make it an oxidation reaction, you don't have to flip the sign of the electrode potential at the anode? For example, for Zn (s) -->Zn^2+ (aq) + 2e-, the solution manual says that the electrode potential in this for is -.76 V. Why wouldn't it be +.7...
Sun Mar 01, 2020 9:01 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Stronger Reducing Agent
Replies: 2
Views: 26

### Stronger Reducing Agent

When you have to find which metal is the stronger reducing agent, how do you know which reduction potential to use? For example, if the question just asks about Fe, how would you know whether to use the reduction potential using Fe2+ or Fe3+?
Sat Feb 29, 2020 8:22 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L. 7 a)
Replies: 2
Views: 38

### 6L. 7 a)

For the reaction AgBr (s) <--> Ag+ (aq) + Br- (aq), how are you supposed to know which half reaction will be the anode/cathode once you have the balanced half reactions? The oxidation numbers also stay the same, so I'm also confused on how to balance these half reactions.
Sat Feb 29, 2020 6:45 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L. 5 c)
Replies: 1
Views: 15

### 6L. 5 c)

For the given reaction, Cl2 (g) + H2 (g) --> HCl (aq), when writing the half reactions, why is the product 2Cl- for the reduction of Cl2 and the product for the oxidation of H2 is 2H+? Why aren't the products HCl like how it's given in the question?
Sat Feb 29, 2020 10:50 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Product in Concentration Cells
Replies: 1
Views: 29

### Product in Concentration Cells

Why is the solution with lower concentration the product in a concentration cell?
Sat Feb 29, 2020 10:34 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation at 25ºC
Replies: 2
Views: 27

### Nernst Equation at 25ºC

When deriving the Nernst equation at 25ºC, why is lnQ changed to logQ in the ending equation?
Sat Feb 29, 2020 9:29 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: No Salt Bridge
Replies: 7
Views: 69

### No Salt Bridge

In the case when there's no salt bridge (and there's a build up of charges in the anode and cathode), why does the left side (anode) build up in positive charge while the right side (cathode) build up in negative charge?
Mon Feb 24, 2020 7:29 am
Forum: Van't Hoff Equation
Topic: deltaS/R
Replies: 7
Views: 97

### Re: deltaS/R

Sydney Pell 2E wrote:When comparing temperatures, deltaS and deltaH are assumed to stay constant for both temperatures which could be why deltaS/R seems to be ignored.

Why can you assume that delta S is constant when you're using the van't Hoff equation to compare temperatures?
Sun Feb 23, 2020 5:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L. 3
Replies: 4
Views: 49

### 6L. 3

When you're given the cell diagram of a galvanic cell, how do you know which side will be the anode and which will be the cathode? Is the left side always the anode and the right side always the cathode?
Sun Feb 23, 2020 11:54 am
Forum: Balancing Redox Reactions
Topic: 6K. 5a)
Replies: 5
Views: 57

### Re: 6K. 5a)

Section 6K has a useful table that explains how to balance reactions in acidic and basic solutions. When it comes to balancing a reaction in a basic solution, you balance oxygen first with water on either side and then to balance hydrogens, you add water to the side that needs more hydrogens and ad...
Sat Feb 22, 2020 9:24 pm
Forum: Balancing Redox Reactions
Topic: 6K. 5a)
Replies: 5
Views: 57

### 6K. 5a)

I need help trying the balance the half reaction Br-(aq) --> BrO3-(aq) in a basic solution. I've balanced the reaction so then the O's are balanced on both sides: Br-(aq) + 3H2O (l) --> BrO3- But I don't understand what to do after this part, especially where you're supposed to put more H2O molecule...
Sat Feb 22, 2020 6:32 pm
Forum: Balancing Redox Reactions
Topic: Identifying Acidic/Basic Solutions
Replies: 2
Views: 58

### Identifying Acidic/Basic Solutions

Would there ever be a case where a question doesn't specify whether the redox reaction is in an acidic/basic solution? If so, how would you know if it's in an acidic/basic solution?
Sun Feb 16, 2020 11:26 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: When to Use Certain Equations
Replies: 2
Views: 32

### When to Use Certain Equations

What's the difference between the equations ΔGr = ΔG° + RTlnQ and ΔGr = -RTlnK? To elaborate, when are you supposed to use one over the other?
Sun Feb 16, 2020 10:31 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 5G. 13
Replies: 6
Views: 103

### Re: 5G. 13

I'm confused on what value of K you're supposed to use for delta G = -RTlnK. The problem gives you the partial pressures, so are you supposed to find Kp? But at the same time, it says that K = 6.8, so which one are you supposed to use?
Tue Feb 11, 2020 8:54 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Extensive and Intensive Properties
Replies: 12
Views: 210

### Extensive and Intensive Properties

Why is heat capacity considered to be an extensive property whereas specific heat capacity and molar heat capacities are intensive properties?
Tue Feb 11, 2020 5:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5 Percent Rule
Replies: 1
Views: 33

### 5 Percent Rule

When you're doing the 5 percent rule, are you checking to see if the x value that you solved for is 5% of the initial concentration of your reactant? What if there's multiple reactants with initial concentrations?
Tue Feb 11, 2020 2:38 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Replies: 20
Views: 290

What's the effect of adding an inert gas to a reaction at equilibrium? I know it has something to do with the pressure and volume, but I don't remember which of these are affected.
Sun Feb 09, 2020 6:30 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Residual Entropy
Replies: 5
Views: 29

### Re: Residual Entropy

What causes there to still be some energy, allowing it to have some disorder? I thought that at 0 Kelvin, all particles stop moving, therefore there wouldn't be any disorder. At 0 K, there is no contribution to entropy from rotational/thermal motion. However, there is, for most molecules, residual ...
Sun Feb 09, 2020 6:24 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Boltzmann Entropy Equation Clarificaiton
Replies: 3
Views: 22

### Re: Boltzmann Entropy Equation Clarificaiton

Also, in what conditions are you supposed to use this equation? Is it only if the problem states what the degeneracy value is or if it says what the number of microstates and particles are?
Sun Feb 09, 2020 6:20 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Boltzmann Entropy Equation Clarificaiton
Replies: 3
Views: 22

### Boltzmann Entropy Equation Clarificaiton

Conceptually, is this equation just saying that if you have a higher W, the W value means that you have more microstates/particles, which causes there to be more disorder (S, or entropy)?
Sun Feb 09, 2020 6:08 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Residual Entropy
Replies: 5
Views: 29

### Re: Residual Entropy

I believe residual entropy is the energy that remains even when a sample is brought to 0 Kelvin caused by disorder in the sample. What causes there to still be some energy, allowing it to have some disorder? I thought that at 0 Kelvin, all particles stop moving, therefore there wouldn't be any diso...
Sun Feb 09, 2020 6:06 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Residual Entropy
Replies: 5
Views: 29

### Re: Residual Entropy

How is residual entropy different from the regular entropy that we've been using for any other problem (for example, like delta S)?
Sun Feb 02, 2020 4:10 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4C. 9
Replies: 1
Views: 27

### 4C. 9

(a) Calculate the heat that must be supplied to a copper kettle of mass 500.0 g containing 400.0 g of water to raise its temperature from 22.0°C to the boiling point of water, 100.0°C.

For part a, why does the q value of the metal have to be added to the q value of the water?
Sun Feb 02, 2020 3:50 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4B 11
Replies: 2
Views: 20

### 4B 11

In an adiabatic process, no energy is transferred as heat. Indicate whether each of the following statements about an adiabatic process in a closed system is always true, always false, or true in certain conditions (specify the conditions): (a) delta U = 0; (b) q = 0; (c) q < 0; delta U = q; (e) del...
Sun Feb 02, 2020 2:42 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Finding Work with Pressure
Replies: 2
Views: 15

### Finding Work with Pressure

When you're trying to find the value of work, when would pressure be negative when calculating -P*deltaV, making the work positive?
Sat Feb 01, 2020 6:03 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Enthalpy vs. Heat
Replies: 6
Views: 51

### Enthalpy vs. Heat

Can someone explain what the difference is between enthalpy and heat? I'm a little confused between the two.
Sat Feb 01, 2020 12:54 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: q and delta H
Replies: 2
Views: 26

### q and delta H

What's the difference between q and delta H? To elaborate, how do you know if a problem is talking about q vs a problem talking about delta H?
Sun Jan 26, 2020 10:35 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpy vs. Standard Enthalpy of Formation
Replies: 2
Views: 26

### Bond Enthalpy vs. Standard Enthalpy of Formation

What's the difference between between bond enthalpies and standard enthalpies of formation? Bond enthalpies are the amount of energy in a bond, but how is that different from standard enthalpies of formation?
Sun Jan 26, 2020 10:30 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Using Bond Enthalpies
Replies: 2
Views: 11

### Using Bond Enthalpies

When trying to find the change in enthalpy of the reaction by using bond enthalpies, do you always have to manipulate the given bond enthalpies? For example, if that bond enthalpy is given as positive, do you have to make it negative if this bond is broken?
Sun Jan 26, 2020 9:53 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: L.atm to Joules
Replies: 2
Views: 29

### L.atm to Joules

When converting from L.atm to joules, I saw both the constants (101.325 J / L.atm) and (8.314 J.K.mol^-1 / .08206 L.atm.K^-1.mol^-1). Is either fine to use when you're trying to convert to joules?
Sun Jan 26, 2020 9:13 am
Forum: Calculating Work of Expansion
Topic: Calculating Work
Replies: 1
Views: 17

### Calculating Work

After you calculate the value for work, does this value represent the work done by the system or the work done on the system? I'm confused on what it means when work is positive as opposed to when work is negative.
Sun Jan 26, 2020 8:42 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 4A.1
Replies: 12
Views: 69

### 4A.1

What's the difference between a closed and an isolated system?
Sun Jan 19, 2020 1:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6B. 11a)
Replies: 2
Views: 27

### 6B. 11a)

A student added solid Na2O to a volumetric flask of volume 200.0 mL, which was then filled with water, resulting in 200.0 mL of NaOH solution. Then 5.00 mL of the solution was transferred to another volumetric flask and diluted to 500.0 mL. The pH of the diluted solution is 13.25." For the seco...
Sun Jan 19, 2020 11:55 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6B.9
Replies: 3
Views: 30

### Re: 6B.9

505316964 wrote:I also got a negative number.

Can ph be negative?

It's definitely possible to calculate a negative value for pH. It's just a little hard to accurately verify it when working in a lab.
Sat Jan 18, 2020 2:35 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.1 a)
Replies: 5
Views: 43

### 5J.1 a)

CO (g) + H2O (g) <--> CO2 (g) + H2
Question: If the partial pressure of CO2 is increased, what happens to the partial pressure of H2?

I understand that when the partial pressure of CO2 is increased, the reaction will make more reactants. But why does this decrease the partial pressure of H2?
Sat Jan 18, 2020 1:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I 25
Replies: 4
Views: 38

### Re: 5I 25

So for example, if Q > K instead, would the K equation be [SO2][NO2] / [NO][SO3]?
Sat Jan 18, 2020 11:44 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q < K
Replies: 16
Views: 129

### Q < K

When Q < K, is saying "the reaction proceeds to the right" the same thing as saying "the reaction proceeds to form products"?
Sat Jan 18, 2020 11:21 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I 25
Replies: 4
Views: 38

### 5I 25

For the reaction SO2 (g) + NO2 (g) <--> NO (g) + SO3, you're given the initial amount of moles for both the products and reactants. For this problem, why is it necessary to find Q first, and then find K?
Sun Jan 12, 2020 12:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Comparing K Values
Replies: 4
Views: 53

### Comparing K Values

When you're comparing two different K values, what does it mean by which reaction would be "thermodynamically more stable"?
Sun Jan 12, 2020 11:17 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q<K
Replies: 4
Views: 25

### Q<K

Can someone explain the relationship of why when Q<K, it means that more products are formed?
Sun Jan 12, 2020 10:02 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K and Q
Replies: 3
Views: 32

### Re: K and Q

It's because the concentration of solids and liquids don't change since they are pure substances, so they don't affect the value of K.
Wed Jan 08, 2020 6:03 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K for Gases
Replies: 12
Views: 96

### K for Gases

When a question asks you to find K for a reaction that involves gases and it doesn't specify whether to find Kc or Kp, should you just find Kp? Or should you put down both Kc and Kp?
Mon Jan 06, 2020 6:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.3
Replies: 8
Views: 106

### 5G.3

Why is K written in terms of the partial pressures of the reactants and products rather than the concentrations of the reactants and products for both parts 5G.3 a) and b)?
Sat Dec 07, 2019 8:51 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 5006

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

For 20, why is the expected geometry tetrahedral and square planar?
Sat Dec 07, 2019 11:38 am
Forum: Calculating the pH of Salt Solutions
Topic: [OH-] & pOH
Replies: 2
Views: 93

### [OH-] & pOH

Can someone please explain conceptually why decreasing [OH-] makes the pOH increase?
Sat Dec 07, 2019 9:41 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: London Dispersion vs. Dipole-Dipole
Replies: 2
Views: 99

### London Dispersion vs. Dipole-Dipole

When do you know that a molecule with London dispersion forces will have stronger intermolecular forces than a molecule with dipole-dipole interactions? More specifically, why aren't the dipole-dipole interactions stronger than the London dispersion forces? An example can be H2S (LDF's) vs. H2Se (di...
Sat Dec 07, 2019 9:25 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Finding pH From Strong Acids/Bases
Replies: 1
Views: 19

### Finding pH From Strong Acids/Bases

When you have a reaction of a strong acid and a strong base, after finding how many moles H+ the strong acid makes and how many moles OH- the strong base makes, why do you have to subtract the moles of H+ from the moles of OH- to get the resulting concentration of H+?
Sat Dec 07, 2019 8:55 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentates and Chelates
Replies: 4
Views: 101

### Polydentates and Chelates

Are all polydentates considered to be chelating ligands?
Sat Nov 30, 2019 12:22 pm
Forum: Hybridization
Topic: Hybridized Orbitals
Replies: 1
Views: 33

### Hybridized Orbitals

Can someone please explain the concept behind hybridized orbitals and how orbitals are mixed together to create these hybridized orbitals?
Sat Nov 30, 2019 12:16 pm
Forum: Bronsted Acids & Bases
Topic: Water as Acid or Base
Replies: 2
Views: 34

### Water as Acid or Base

When H2O is a reactant in an acid-base reaction, how do you know whether it will act as an acid or base? Do you first look at the other reactant and determine whether that other reactant will be an acid/base?
Sat Nov 30, 2019 12:05 pm
Forum: Bronsted Acids & Bases
Topic: Net Ionic Equations
Replies: 5
Views: 62

### Re: Net Ionic Equations

For example, in 17b) under Fundamentals J, it asks to write the chemical reaction for when KClO reacts with H2O. The reaction looks like...
ClO- + H2O --> HClO + OH-
In this example, why are H2O and HClO not written as ions?
Sat Nov 30, 2019 11:45 am
Forum: Bronsted Acids & Bases
Topic: Net Ionic Equations
Replies: 5
Views: 62

### Net Ionic Equations

When writing net ionic equations, how do you know which molecules will be written as ions and which molecule(s) will be written together (not as ions)?
Thu Nov 28, 2019 4:01 pm
Forum: Bronsted Acids & Bases
Topic: Writing Equations
Replies: 1
Views: 25

### Writing Equations

When you're writing out the equations for acid-base reactions, how do you know whether the molecules (for both products and reactants) will be an aqueous solution or a liquid if the question doesn't specify?
Sat Nov 23, 2019 12:11 pm
Forum: Naming
Topic: Naming Order
Replies: 6
Views: 78

### Naming Order

When you're writing out the formula for compounds, does the order of the ligands matter? For example, for 9C. #3d), would it be wrong to write Na[Fe(C2O4)2 (OH2)2] instead of Na[Fe(OH2)2 (C2O4)2 ]?
Tue Nov 19, 2019 9:29 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Atomic Size & LDF's
Replies: 2
Views: 44

### Atomic Size & LDF's

Why does a bigger atomic size have stronger London dispersion forces?
Mon Nov 18, 2019 9:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs & Polarity
Replies: 3
Views: 42

### Lone Pairs & Polarity

Except for a molecule that has the VSEPR formula AX2E3 (linear shape), would all molecules with lone pairs be polar?
Mon Nov 18, 2019 8:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: XeF2 Bond Angle and Shape
Replies: 2
Views: 33

### XeF2 Bond Angle and Shape

When drawing the Lewis structure for XeF2, Xe has three lone pairs around it, but why is its molecular shape linear with a bond angle of 180 degrees instead of the lone pairs pushing down on the bonded atoms? Why isn't this shape similar to a bent molecule, like H2O, where it has two lone pairs arou...
Mon Nov 18, 2019 6:31 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability
Replies: 2
Views: 122

### Polarizability

I know that the bigger the size of an atom/molecule is, the more polarizable it is, but how do atoms/molecules with higher polarizability have stronger attractions?
Sun Nov 17, 2019 3:38 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Dipole-Induced Dipole
Replies: 2
Views: 75

### Dipole-Induced Dipole

When do dipole-induced dipole interactions occur? Is it when a molecule with dipole-dipole gets close to/interacts with a molecule that doesn't have dipole-dipole interactions? What would be an indicator of dipole-induced dipole interactions ?
Sat Nov 16, 2019 9:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E 11 b)
Replies: 4
Views: 35

### 2E 11 b)

When drawing the Lewis structure for ICl3, how do you know that iodine will have 2 lone pairs around it? Why can't you add multiple bonds, making the atoms have an expanded octet?
Sat Nov 16, 2019 6:16 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: 3F.5 c)
Replies: 3
Views: 36

### Re: 3F.5 c)

If that's the case, when would you look at London dispersion forces rather than dipole-dipole interactions to determine which molecule is stronger? Would you only do this when both of molecules have dipole-dipole interactions?
Sat Nov 16, 2019 6:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E 1 b)
Replies: 2
Views: 35

### 2E 1 b)

The question has a ball-and-stick model of a linear molecule (bond angle of 180 degrees) and asks whether there must, may be, or can't be one or more lone pairs on the central atom. Why may this specific molecule have lone pairs on the central atom? I thought if it was linear, it wouldn't have any l...
Sat Nov 16, 2019 5:57 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: 3F.5 c)
Replies: 3
Views: 36

### 3F.5 c)

The solutions manual says that between CHI3 and CHF3, CHI3 has a higher normal melting point because it has stronger London dispersion forces, but don't they both have dipole-dipole interactions and then determine which has stronger attractions from there?
Wed Nov 06, 2019 9:59 am
Forum: Octet Exceptions
Topic: Expanded Octet
Replies: 2
Views: 39

### Expanded Octet

Can someone please explain the process of drawing Lewis structures for atoms with an expanded octet? I really don't understand how to draw the structures for these molecules. Do you just put all the single bonds in and lone pairs on the outside atoms, and then draw double bonds until you've used up ...
Tue Nov 05, 2019 9:54 am
Forum: Lewis Structures
Topic: Drawing Double Bonds
Replies: 2
Views: 60

### Drawing Double Bonds

When you have to draw double bonds by using taking away the lone pairs on certain atoms, how do you know which atoms' lone pairs you should take away to form these double bonds?
Tue Nov 05, 2019 9:37 am
Forum: Lewis Structures
Topic: 2B 19 a)
Replies: 1
Views: 45

### 2B 19 a)

In 2B 19 a), when drawing the Lewis structure for NO+, why is it drawn so then the formal charge on O is +1? I thought you had to draw structures so then the most electronegative atoms have a negative charge.

The same goes for c) for CO, where C has a -1 charge and O has a +1 charge.
Tue Nov 05, 2019 9:25 am
Forum: Resonance Structures
Topic: Resonance Hybrids
Replies: 3
Views: 40

### Resonance Hybrids

Are all resonance structures considered to be resonance hybrids? If so, when we draw resonance structures, can we just draw all the resonance structures and just say it's a hybrid?
Mon Nov 04, 2019 10:02 pm
Forum: Lewis Structures
Topic: 2B 9
Replies: 1
Views: 46

### 2B 9

Why are all three molecules (ammonium chloride, potassium phosphide, and sodium hypochlorite) in #5 under 2B drawn as ions for their Lewis structures rather than the traditional connected Lewis structures that we've typically been doing?
Sun Nov 03, 2019 3:06 pm
Forum: Trends in The Periodic Table
Topic: Effective Nuclear Charge and Nuclear Charge
Replies: 6
Views: 81

### Effective Nuclear Charge and Nuclear Charge

Why is the effective nuclear charge (Z_eff_e) less than the nuclear charge (Ze)?
Sun Nov 03, 2019 3:03 pm
Forum: Trends in The Periodic Table
Topic: Electronegativity vs. Electron Affinity
Replies: 3
Views: 40

### Electronegativity vs. Electron Affinity

What's the difference between electronegativity and electron affinity? Also, why does electron affinity increase across and up the periodic table?
Sat Nov 02, 2019 5:13 pm
Forum: Lewis Structures
Topic: Double Bonds vs. Lone Pairs
Replies: 2
Views: 28

### Double Bonds vs. Lone Pairs

After drawing the Lewis structure with single bonds and the lone pairs each atom but you have left over valence electrons you need to fit into the Lewis structure, how do you know whether these left over electrons will be made into a double bond or lone pairs?
Sat Nov 02, 2019 12:30 pm
Forum: Resonance Structures
Topic: Delocalized Electrons
Replies: 2
Views: 31

### Delocalized Electrons

How do you know which electrons are delocalized in resonance structures?
Sat Nov 02, 2019 10:38 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodal Planes
Replies: 1
Views: 34

### Nodal Planes

When referring to the shapes of atomic orbitals, what are nodal planes and electron density?
Sat Oct 26, 2019 11:37 am
Forum: Trends in The Periodic Table
Topic: Exceptions to Octet Rule
Replies: 2
Views: 29

### Re: Exceptions to Octet Rule

Are there other elements that are also exceptions to the octet rule, or is there a trend we need to remember that helps us know which atoms are exceptions of the octet rule?
Sat Oct 26, 2019 11:35 am
Forum: Trends in The Periodic Table
Topic: Exceptions to Octet Rule
Replies: 2
Views: 29

### Exceptions to Octet Rule

Why are P, Cl, and S exceptions to the octet rule?
Sat Oct 26, 2019 11:32 am
Forum: Trends in The Periodic Table
Topic: Effective Nuclear Charge and Ionization Energy
Replies: 2
Views: 30

### Effective Nuclear Charge and Ionization Energy

What's the correlation between effective nuclear charge and ionization energy? Is it that the higher the effective nuclear charge is, the higher the ionization energy will be since it will be harder to remove the electron?
Sat Oct 26, 2019 11:12 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E 13.e
Replies: 1
Views: 28

### 1E 13.e

Tungsten's ground-electron configuration is [Xe] 4f^14 5d^4 6s^2. Why doesn't this follow the exception rule like chromium and copper? As in, why wouldn't the electron configuration be [Xe] 4f^14 5d^5 6s^1?
Sat Oct 26, 2019 10:33 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Effective Nuclear Charge
Replies: 2
Views: 35

### Re: Effective Nuclear Charge

What's the trend for effective nuclear charge on the periodic table, and can someone explain it conceptually in terms of the other electrons in the atom?
Sat Oct 19, 2019 8:53 pm
Forum: Quantum Numbers and The H-Atom
Topic: Ml values
Replies: 2
Views: 54

### Ml values

How do you find the values of ml, and what do those values specifically signify?
Sat Oct 19, 2019 8:46 pm
Forum: Quantum Numbers and The H-Atom
Topic: Values of l
Replies: 2
Views: 61

### Values of l

What does it mean if l has multiple possible values? Specifically, what does each number represent? For example, if l = 2, then its possible values are -1, 0, 1, or if l =3, then its possible values are -2, -1, 0, 1, 2.
Sat Oct 19, 2019 7:42 pm
Forum: Quantum Numbers and The H-Atom
Topic: n, l, m
Replies: 4
Views: 56

### Re: n, l, m

Also, how do you translate it to each other (like finding how many subshells are in a given n or how many orbitals are in subshells with l equal to a certain number)?
Sat Oct 19, 2019 7:42 pm
Forum: Quantum Numbers and The H-Atom
Topic: n, l, m
Replies: 4
Views: 56

### n, l, m

Can someone please explain the differences between n, l, and m conceptually?
Sat Oct 19, 2019 3:59 pm
Forum: Quantum Numbers and The H-Atom
Topic: Correlation Between n and l
Replies: 6
Views: 87

### Correlation Between n and l

In the book, it gives an example where if n = 3, l can have any three values (0,1, and 2), but what do these three numbers indicate?
Sun Oct 13, 2019 12:02 pm
Forum: Einstein Equation
Topic: 1B.15 c)
Replies: 3
Views: 114

### 1B.15 c)

The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 x 10^km s^-1. (a) What is the wavelength of the ejected electron? ... (c) What is the wavelength of the radiation that caused photoejection of the electron? What's the difference between the wavelengths in parts (...
Sun Oct 13, 2019 11:37 am
Forum: Einstein Equation
Topic: 1B.15
Replies: 2
Views: 73

### Re: 1B.15

For part b, since you want to find the energy and it gives you the frequency (2.50 x 10^16 Hz or 2.50 x 10^16 s^-1), use Planck's constant to evaluate E from E=hv.
Sun Oct 13, 2019 11:21 am
Forum: Einstein Equation
Topic: Units for E [ENDORSED]
Replies: 4
Views: 150

### Units for E[ENDORSED]

Is the unit for E always implied as being J/atoms or J/photons?
Sun Oct 13, 2019 10:59 am
Forum: Einstein Equation
Topic: 1B.7 b)
Replies: 1
Views: 53

### 1B.7 b)

Sodium vapor lamps emit yellow light of wavelength 589 nm. How much energy is emitted by b) 5.00mg of Na atoms emitting light at this wavelength? From a) I found that the energy emitted by an excited sodium atom is 3.37 x 10^-19 J. Then for part b, I found that 5.00mg of Na atoms = 1.31 x 10^20 Na a...
Sun Oct 13, 2019 10:17 am
Forum: Limiting Reactant Calculations
Replies: 7
Views: 275

When you're trying to find the limiting reactant and see which reactant makes the least amount of product, do you have to convert the moles of product to grams or can you just leave it as moles?
Fri Oct 04, 2019 12:03 pm
Forum: Limiting Reactant Calculations
Topic: General Limiting Reactant Question
Replies: 4
Views: 58

### General Limiting Reactant Question

When finding the percent yield, how do you know whether or not you have to find the limiting reactant (because there were questions like M.3 where you don't need to find the limiting reactant)? Do you find the limiting reactant only if the both/all the masses of the limiting reactants are given as o...
Fri Oct 04, 2019 8:27 am
Forum: Limiting Reactant Calculations
Topic: M5
Replies: 2
Views: 60

### M5

In question M.5 b), the reaction 6ClO2 (g) + 2BrF3 (l) --> 6ClO2 (s) + Br2 (l) is carried out with 12 mol ClO2 and 5 mol BrF3. It asks to estimate how many moles of each product will be made and how many moles of the excess reactant will remain. From a) I understand that the excess reactant will be ...