Search found 55 matches

by Kyra Dingle 1B
Sun Mar 18, 2018 6:06 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7609
Views: 1019594

Re: Post All Chemistry Jokes Here

What is the chemical formula for the molecules in candy?

Carbon-Holmium-Cobalt-Lanthanum-Tellurium

or CHoCoLaTe
by Kyra Dingle 1B
Sun Mar 18, 2018 5:52 pm
Forum: Calculating Work of Expansion
Topic: Final Question W18: Reversible vs. Irreversible External Pressure
Replies: 4
Views: 240

Re: Final Question W18: Reversible vs. Irreversible External Pressure

In irreversible expansion, external pressure is held constant, while for reversible expansion, external pressure is changing. You can tell by the equations that are used under each condition as irreversible expansion uses -P(deltaV) and reversible expansion uses -nRTln(V2/V1).
by Kyra Dingle 1B
Sun Mar 18, 2018 5:43 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: State Functions
Replies: 4
Views: 313

State Functions

How many state functions should we have gotten as an answer for the question on the final?
by Kyra Dingle 1B
Sat Mar 10, 2018 4:10 pm
Forum: Zero Order Reactions
Topic: Zero Order and Catalysts [ENDORSED]
Replies: 2
Views: 482

Zero Order and Catalysts [ENDORSED]

What is connection between a zero order reaction and the presence of a catalyst?
by Kyra Dingle 1B
Sat Mar 10, 2018 4:06 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Substitution Reactions [ENDORSED]
Replies: 1
Views: 103

Substitution Reactions [ENDORSED]

On Friday, Lavelle explained a bit about substitution reactions and nucleophiles. Do we need to understand this concept for the final? If so can someone explain how these reactions connect to reaction profiles that are based on Gibbs Free Energy rather than Activation energy?
by Kyra Dingle 1B
Sat Mar 10, 2018 12:34 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Methods to approach proposed reaction mechanisms
Replies: 1
Views: 67

Methods to approach proposed reaction mechanisms

Can someone explain the difference between the steady-state and the pre-equilibrium approach?
by Kyra Dingle 1B
Sun Mar 04, 2018 9:11 pm
Forum: First Order Reactions
Topic: Order Reactions
Replies: 3
Views: 171

Order Reactions

Will we need to derive each of the different order reactions from the differential rate law for any future tests?
by Kyra Dingle 1B
Wed Feb 28, 2018 12:51 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Rate constant
Replies: 2
Views: 131

Rate constant

What is the difference between a rate constant and an equilibrium constant?
by Kyra Dingle 1B
Tue Feb 27, 2018 11:48 pm
Forum: Second Order Reactions
Topic: 15.35
Replies: 1
Views: 89

15.35

For this question, we are meant to calculate the time needed for a concentration to decrease to a) 1/16th b) 1/4th c) 1/5th the original value. We are given the half-life of the second-order reaction and the initial concentration. In the solution manual we use the second-order half life equation to ...
by Kyra Dingle 1B
Tue Feb 27, 2018 12:29 am
Forum: First Order Reactions
Topic: First Order Reaction Equations
Replies: 3
Views: 136

First Order Reaction Equations

How do you know when to use
or when to use ?
Are there specific instances when we use each?
by Kyra Dingle 1B
Mon Feb 26, 2018 1:08 am
Forum: First Order Reactions
Topic: Direct Proportions and First Order
Replies: 5
Views: 187

Direct Proportions and First Order

Why does a directly proportional relationship between the rate of the reaction and the concentration of the reactants indicate a first order?
by Kyra Dingle 1B
Mon Feb 26, 2018 12:38 am
Forum: General Rate Laws
Topic: Unique Rate of Reactions
Replies: 3
Views: 146

Unique Rate of Reactions

What is the unique rate of reactions? How would you calculate it?
by Kyra Dingle 1B
Mon Feb 26, 2018 12:37 am
Forum: General Rate Laws
Topic: rate of reaction vs rate law
Replies: 2
Views: 118

Re: rate of reaction vs rate law

The rate of the reaction can be found as the change in concentration of product or reactant over the change in time. The rate law (aka differential rate law) is found using the equation k[R]^n in which n is the order of the reactant, [R] represents the concentration of the reactant, and k is the rat...
by Kyra Dingle 1B
Mon Feb 19, 2018 12:31 am
Forum: Balancing Redox Reactions
Topic: Standard Reduction Potential
Replies: 3
Views: 148

Standard Reduction Potential

How come the standard reduction potentials stay the same when half reactions are balanced?
by Kyra Dingle 1B
Sun Feb 18, 2018 7:17 pm
Forum: Balancing Redox Reactions
Topic: Balancing
Replies: 3
Views: 149

Re: Balancing

I believe you can determine how many electrons to add to a half reaction based on the change in oxidation number of the element being reduced or oxidized. The number of electrons added would then make up for the difference to make both sides of the reaction balanced
by Kyra Dingle 1B
Sun Feb 18, 2018 6:56 pm
Forum: Balancing Redox Reactions
Topic: Half Reaction
Replies: 3
Views: 147

Half Reaction

When giving a full redox reaction and asked to write either the oxidation or reduction half-reactions, can we use the elements alone with an oxidation number for each half reaction? or are we expected to utilize the full compound when writing the half reaction? For example, in 14.1 we are asked to w...
by Kyra Dingle 1B
Sat Feb 10, 2018 9:31 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Molar entropy v standard entropy of formation
Replies: 3
Views: 791

Molar entropy v standard entropy of formation

What is the difference between molar entropies and standard entropy of formation? Why do we use molar entropies to find the standard reaction entropies and not standard entropies of formation?
by Kyra Dingle 1B
Sat Feb 10, 2018 9:14 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Stability
Replies: 2
Views: 124

Stability

Why can we look at the Gibbs Free Energies of Formation to determine stability? Why would a positive free energy of formation indicate an unstable compound while negative ones indicate stable compounds?
by Kyra Dingle 1B
Sat Feb 10, 2018 8:16 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Calculating Gibbs Free Energy [ENDORSED]
Replies: 2
Views: 147

Calculating Gibbs Free Energy [ENDORSED]

When asked to calculate Gibbs Free Energy when should you use the equation deltaH - T*deltaS compared to using the standard formation values and subtract the sum of the products from the sum of the reactants?
by Kyra Dingle 1B
Sun Feb 04, 2018 11:05 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 9.31
Replies: 2
Views: 144

9.31

For future exams will we be required to know the states of substances like in 9.31 in which we needed to know the states of ethene and polyethylene to determine which has the higher molar entropy?
by Kyra Dingle 1B
Sun Feb 04, 2018 10:35 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Higher Molar Entropy
Replies: 4
Views: 181

Higher Molar Entropy

How would you define molar entropy? What are some good ways to determine if a substance or compound has a higher or lower molar entropy?
by Kyra Dingle 1B
Sun Feb 04, 2018 10:19 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.19 Finding standard entropy of water
Replies: 1
Views: 90

9.19 Finding standard entropy of water

Can someone explain further why when determining the standard entropy of water at 85 degrees C you need to find the entropy change when heating the reactants to boiling point and the change when cooling the products back down to 85 and then finally add those changes with the standard entropy at 100 ...
by Kyra Dingle 1B
Sun Jan 28, 2018 9:41 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Deriving the equation for changes in pressure
Replies: 1
Views: 116

Deriving the equation for changes in pressure

How would you derive the equation you would use for entropy changes due to changes in pressure?
by Kyra Dingle 1B
Sun Jan 28, 2018 9:28 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal Reversible
Replies: 3
Views: 253

Isothermal Reversible

When a problem mentions that an entropy change occurred isothermally do we assume that the process was also reversible? Why or why not?
by Kyra Dingle 1B
Sun Jan 28, 2018 9:03 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Calculating Entropy Change [ENDORSED]
Replies: 2
Views: 95

Calculating Entropy Change [ENDORSED]

When using the Second Law of Thermodynamics, how do we know when q will be negative? Does it depends on whether q is referring to the system or surroundings? or when q is referring to heat lost or gain?
by Kyra Dingle 1B
Thu Jan 18, 2018 2:42 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Homework 8.15
Replies: 3
Views: 173

Homework 8.15

Why is part c, q<0, always false in adiabatic processes, in which no energy is transferred as heat? Is this because in these processes, q is simply 0 and would not be negative for the situation? What is an example of a situation in which q would be negative?
by Kyra Dingle 1B
Thu Jan 18, 2018 1:54 pm
Forum: Administrative Questions and Class Announcements
Topic: Test
Replies: 1
Views: 139

Test

For our test would we be provided with the standard enthalpies of formation, if given a question asking to calculate the standard reaction enthalpy for a reaction?
by Kyra Dingle 1B
Thu Jan 18, 2018 1:51 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Extensive v Intensive Properties
Replies: 2
Views: 147

Extensive v Intensive Properties

What is the difference between an extensive and an intensive property, and how do they relate to heat capacity?
by Kyra Dingle 1B
Thu Jan 18, 2018 1:48 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Internal Energy
Replies: 4
Views: 183

Internal Energy

What is the difference between internal energy and enthalpy?
by Kyra Dingle 1B
Sun Jan 14, 2018 8:47 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Molar Heat Capacity
Replies: 4
Views: 109

Re: Molar Heat Capacity

Yes as the molecule becomes more complex the heat capacity will increase as a result. Homework problem #29 in the textbook deals with this concept as NO2 is seen to have a higher molar heat capacity compared to NO due to the additional oxygen allowing for a greater absorption of added energy.
by Kyra Dingle 1B
Sat Jan 13, 2018 11:35 pm
Forum: Phase Changes & Related Calculations
Topic: Steam Burning
Replies: 7
Views: 304

Steam Burning

Can someone give again the explanation Lavelle shared last Monday about why steam burns a lot more and how that relates to phase changes?
by Kyra Dingle 1B
Thu Jan 11, 2018 12:19 pm
Forum: Calculating Work of Expansion
Topic: Work conversion [ENDORSED]
Replies: 1
Views: 123

Work conversion [ENDORSED]

Do we need to know the conversion of liter-atmospheres to joules?
by Kyra Dingle 1B
Sat Dec 09, 2017 8:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Adding a compound to reaction
Replies: 2
Views: 280

Re: Adding a compound to reaction

If a solid is added, it should have not effect since it is not included in the equilibrium constant. May I ask which specific problem you are referring to in his practice test?
by Kyra Dingle 1B
Sat Dec 09, 2017 8:13 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: X in ICE table
Replies: 3
Views: 1028

Re: X in ICE table

One way to determine is through what the problem gives you. If only the amount of the initial reactant is given, then the initial concentration of the products would be 0. This then means that the reactants will be consumed to make products until the reaction reaches equilibrium. Since the reactants...
by Kyra Dingle 1B
Sat Dec 09, 2017 3:33 pm
Forum: Lewis Structures
Topic: NO2 Lewis Structure
Replies: 2
Views: 369

Re: NO2 Lewis Structure

NO2 cannot be drawn with two double bonds and one lone pair on the N central atom because it violates the octet rule. N cannot have exceed the octet rule because it does not have empty d orbitals unlike many of the third period elements, which uses their empty d orbitals to accommodate more electrons.
by Kyra Dingle 1B
Sat Dec 09, 2017 3:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Changing Kc
Replies: 2
Views: 365

Re: Changing Kc

The value of Kc can change when stoichiometric coefficients are halved because when calculating Kc itself it requires the stoichiometric coefficients used in the chemical equation as exponents of the reactants or products. To demonstrate using an equation that had A + 2B = 4C and assuming they are a...
by Kyra Dingle 1B
Sat Dec 09, 2017 11:29 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sits vs shifts left/right
Replies: 1
Views: 215

Re: Sits vs shifts left/right

I believe the term "sits to the left" means there are more reactants at equilibrium, which can be seen through determining if K is small (K<10^-3). The term "sits to the right" then refers to a larger amount of products, which can be seen through determining that K is large (K> 1...
by Kyra Dingle 1B
Sat Dec 09, 2017 4:05 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 12.39
Replies: 1
Views: 114

12.39

Can someone explain how to find the pKa of NH3OH and (CH3)2NH2? I understand the need to subtract the pKb from 14 to find the pKa, but how do you find the pKb in the first place?
by Kyra Dingle 1B
Fri Dec 08, 2017 11:15 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Conductivity of Acids and Bases [ENDORSED]
Replies: 1
Views: 240

Conductivity of Acids and Bases [ENDORSED]

Do we need to know the conductivity of certain acids and bases for the final?
by Kyra Dingle 1B
Fri Dec 08, 2017 10:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: XeO2F2
Replies: 3
Views: 1758

Re: XeO2F2

XeO2F2 is polar and it helps to identify this through drawing out the lewis structure. In doing so, you can see that Xe has 5 electron densities with 4 bonded pairs and one lone pair. The single lone pair gives the compound a seesaw shape which then would be polar
by Kyra Dingle 1B
Fri Dec 08, 2017 8:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 1
Views: 142

Re: Polarity

The molecular shape can be used to determine polarity through observing the lone pairs and the resulting shape of the compound. If there are no lone pairs the compound should be nonpolar, but once there are lone pairs it is important to observe the shape to see if any dipole moments exists and if th...
by Kyra Dingle 1B
Fri Dec 08, 2017 8:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: #45 in Lyndon's Practice Exam
Replies: 1
Views: 117

#45 in Lyndon's Practice Exam

Can someone explain again the concept behind why the fact that electron withdrawing atoms can stabilize anions by delocalizing the negative charge is true?
by Kyra Dingle 1B
Fri Dec 08, 2017 8:08 pm
Forum: Biological Examples
Topic: Biological Importance
Replies: 2
Views: 261

Biological Importance

What are some important things we need to know regarding the biological aspects/importance of coordination complexes? For example, we need to know 4 myoglobins form hemoglobins.
by Kyra Dingle 1B
Mon Nov 27, 2017 5:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Writing reaction quotient or equilibrium expression
Replies: 5
Views: 192

Writing reaction quotient or equilibrium expression

For writing the reaction quotient, Q, or equilibrium expression, K, when do we write it as partial pressure with the capital P then the molecule as a subscript in contrast to as a concentration with the molecule surrounded in brackets? For example in 11.3, it asks to write the equilibrium expression...
by Kyra Dingle 1B
Tue Nov 21, 2017 10:54 pm
Forum: Hybridization
Topic: 4.95 composition of the pi bond
Replies: 2
Views: 139

4.95 composition of the pi bond

Can someone elaborate why the pi bonds for the structure in 4.95 have only the 2p hybridization in contrast to the sigma bonds with the sp2 hybridization and perhaps how you would come to this conclusion through observing the lewis structure?
by Kyra Dingle 1B
Tue Nov 21, 2017 2:35 pm
Forum: Naming
Topic: Ligand Names
Replies: 6
Views: 247

Ligand Names

There is a table in the book that includes a list of common ligands and their corresponding formulas. Are we required to know all of these for the test or final?
by Kyra Dingle 1B
Tue Nov 21, 2017 2:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: CH2CL2 4.25
Replies: 2
Views: 107

CH2CL2 4.25

In the problem 4.25, why is CH2CL2 polar? I understand the Cl is more electronegative and thus there is a stronger pull of the electrons/negative charge towards the Cl. However, when drawing the lewis structure couldn't the Cl be draw opposite to each other to make these charges cancel?
by Kyra Dingle 1B
Sat Nov 18, 2017 5:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lewis Structures and VSEPR Shape
Replies: 4
Views: 213

Lewis Structures and VSEPR Shape

When drawing lewis structures, do we need to draw them in a way that reflect the molecular shape? For example in sulfur tetrafluoride (SF4), during lecture we drew it with the lone pair on the left side of the sulfur (the equatorial plane). I believe this reflects the most stable shape with the leas...
by Kyra Dingle 1B
Wed Nov 08, 2017 11:46 pm
Forum: Lewis Structures
Topic: Lewis Structure [ENDORSED]
Replies: 4
Views: 232

Lewis Structure [ENDORSED]

When asked to find the lewis structure, do you automatically write the structure with the lowest energy?
by Kyra Dingle 1B
Sun Nov 05, 2017 7:35 pm
Forum: Lewis Structures
Topic: 3.39
Replies: 1
Views: 112

3.39

Would someone be able to explain why the lewis structures for the compounds are written separately and not with any connecting bonds? For example in part a, the chlorine anion is not bonded to the NH3 and stands alone with 4 lone pairs. How would you also be able to recognize that you need do this f...
by Kyra Dingle 1B
Wed Nov 01, 2017 7:37 pm
Forum: Quantum Numbers and The H-Atom
Topic: Multiple Electron Atoms
Replies: 2
Views: 191

Multiple Electron Atoms

Can someone elaborate further on the effective nuclear charge and how it relates to electron shielding in multiple electron atoms?
by Kyra Dingle 1B
Sun Oct 29, 2017 10:28 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Speed of light [ENDORSED]
Replies: 1
Views: 136

Re: Speed of light [ENDORSED]

Both values are correct. However, the specific value you would use for a problem is all dependent on the number of significant figures required for the problem. For example if only 2 sig figs are required, 3.0* 10^8 m*s^-1 would be used in the problem.
by Kyra Dingle 1B
Fri Oct 20, 2017 10:51 pm
Forum: SI Units, Unit Conversions
Topic: Quantum Mechanics
Replies: 4
Views: 330

Re: Quantum Mechanics

I believe to determine which has a higher electron affinity, you would need to refer to the periodic table. Electron affinities tend to be the highest towards the right of the periodic table. You would apply this electron affinity trend by comparing where each element is locating in relation to each...
by Kyra Dingle 1B
Fri Oct 13, 2017 4:49 pm
Forum: Photoelectric Effect
Topic: Lyman Series v Balmer series
Replies: 2
Views: 224

Re: Lyman Series v Balmer series

The main difference between the Lyman and Balmer series is the energy level in which electrons come to rest. For the Lyman series n=1, while for the Balmer series n=2. Another important characteristic to note is that the Lyman series is found within the ultraviolet spectrum, while the Balmer series ...
by Kyra Dingle 1B
Fri Oct 06, 2017 9:36 am
Forum: Balancing Chemical Reactions
Topic: L35
Replies: 2
Views: 280

Re: L35

Before doing anything it is important to check that all the equations are balanced! 1. Convert the 2.50 t to grams. This is best done by converting first to kilograms and then converting that value to grams. 2. Convert the g of NaBr to moles by dividing by the molar mass of NaBr. 3. Once you found t...

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