Search found 50 matches

by Nicole Nikolov 1K
Sun Mar 18, 2018 9:25 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cp and Cv
Replies: 5
Views: 283

Cp and Cv

Is there a way to convert between the molar heat capacity at constant pressure and constant volume, Cp and Cv? Or would we have to be provided this information on an exam? Also, is there a way to convert between the specific heat capacity and the molar heat capacity?
by Nicole Nikolov 1K
Sun Mar 18, 2018 9:20 am
Forum: General Rate Laws
Topic: Rate constant units
Replies: 6
Views: 427

Rate constant units

What is a general rule of thumb to figure out the units of the rate constant and the initial rate? I'm having trouble figuring them out once we get past fourth order reactions...
by Nicole Nikolov 1K
Sun Mar 18, 2018 9:16 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Relation between cell potential and concentration
Replies: 1
Views: 166

Re: Relation between cell potential and concentration

You can use Le Chatelier's principle to help figure this out... If you decreased the concentration of one of the reactants Ecell would shift toward the reactants; if you increased the concentration of one of the reactants Ecell would shift toward the products. If you increased the concentration of o...
by Nicole Nikolov 1K
Sun Mar 18, 2018 5:16 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Max work at constant T & P [ENDORSED]
Replies: 1
Views: 194

Max work at constant T & P [ENDORSED]

When solving for Gibbs free energy, you find the maximum work that could be done at constant pressure and temperature. Is it possible to calculate deltaG for a process at constant volume?
by Nicole Nikolov 1K
Sat Mar 17, 2018 4:11 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated Systems
Replies: 3
Views: 231

Isolated Systems

In an isolated system, are we assuming that it is constant volume? In class, Lavelle simply defined an isolated system as one that does exchange energy or matter with the surroundings...but if we change its volume, that means we are doing work on it and therefore changing the amount of energy it con...
by Nicole Nikolov 1K
Sat Mar 17, 2018 3:39 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Enthalpy
Replies: 1
Views: 207

Standard Reaction Enthalpy

What if you're trying to solve for the standard reaction enthalpy (using any of the three methods we learned in class), but one of the reactants or products in the reaction aren't in their most stable form? What would you have to do to solve for the standard reaction enthalpy in this case?
by Nicole Nikolov 1K
Sat Mar 17, 2018 3:28 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: H+
Replies: 3
Views: 246

Re: H+

I'm not 100% sure either but my guess is that the solution would have to be 1M... in lecture he said that the standard state for a solution is 1M at 1atm.
by Nicole Nikolov 1K
Thu Mar 15, 2018 9:22 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: PV Diagrams
Replies: 1
Views: 201

PV Diagrams

By looking at a PV diagram, can you distinguish between reversible and irreversible reactions? Or are PV diagrams only useful for distinguishing between isothermal, adiabatic, isobaric, and isovolumetric processes?
by Nicole Nikolov 1K
Thu Mar 15, 2018 8:48 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Work in Isolated System
Replies: 1
Views: 208

Work in Isolated System

In class and early in chapter 8, an isolated system was defined as a system that cannot exchange energy or matter with its surroundings. However, the book defines the first law of thermodynamics as "the internal energy of an isolated system is constant." I thought you were allowed to chang...
by Nicole Nikolov 1K
Thu Mar 15, 2018 8:38 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Calculating Work
Replies: 2
Views: 123

Re: Calculating Work

Not only is it being done against constant external pressure, but the fact that the temperature is "suddenly" increased means is it an irreversible process which indicates the use of w = -P(deltaV).
by Nicole Nikolov 1K
Thu Mar 15, 2018 5:14 pm
Forum: Phase Changes & Related Calculations
Topic: Internal Pressure in Reversible vs Irreversible Processes
Replies: 1
Views: 191

Internal Pressure in Reversible vs Irreversible Processes

In an reversible process, you can basically say that external and internal pressure are changing so slow and so little that they are changing together. However, in an irreversible process, does the internal pressure have any effect on the work done? w=-Pex(deltaV) takes into consideration only exter...
by Nicole Nikolov 1K
Thu Mar 15, 2018 4:59 pm
Forum: Phase Changes & Related Calculations
Topic: Reversible Expansions
Replies: 3
Views: 276

Reversible Expansions

I understand that the work a system can do is greatest in a reversible process. For example, if you look at a PV diagram you can see that the area under a curve is greatest for a reversible process. However, I am having trouble understanding it from more of a mathematical viewpoint. Can someone plea...
by Nicole Nikolov 1K
Mon Feb 12, 2018 11:29 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Test 1, Question 7
Replies: 2
Views: 146

Re: Test 1, Question 7

The heat that is leaving the ice cube will go directly into the tea/water, so q(ice)=-q(tea). Because the ice cube is already at 0*C that means it doesn't have to cool down before it starts melting, meaning that it's going to start melting immediately. You will first want to determine if the entire ...
by Nicole Nikolov 1K
Mon Feb 12, 2018 11:11 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: comparing entropies
Replies: 1
Views: 93

Re: comparing entropies

1. gas
2. assuming that all other parameters such as temperature are the same, then the two will have the same amount of entropy since both are considered incompressible.
3. same answer as #2.
by Nicole Nikolov 1K
Mon Feb 12, 2018 11:05 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Laws of Thermodynamics
Replies: 2
Views: 161

Re: Laws of Thermodynamics

It could be an okay way of reminding yourself what each law has to do with but it doesn't necessarily define each one. The first law of thermodynamics has to do with the conservation of energy. It says that energy can neither be created nor destroyed; it is only transformed. The second law of thermo...
by Nicole Nikolov 1K
Mon Feb 12, 2018 12:03 am
Forum: Balancing Redox Reactions
Topic: redox reactions and salts
Replies: 2
Views: 105

Re: redox reactions and salts

There are many redox reactions that do not result in a salt product. The use of redox reactions in electrochemistry is only one example. For example, cellular respiration and photosynthesis are redox reactions that do not result in the production of a salt. Redox reactions are reactions in which one...
by Nicole Nikolov 1K
Sun Feb 11, 2018 11:58 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: heat capacity sign
Replies: 2
Views: 135

Re: heat capacity sign

Heat capacities can never be negative because that would mean that the substance is creating and giving off energy from thin air and this violates the first law of thermodynamics.
by Nicole Nikolov 1K
Sun Feb 11, 2018 11:47 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta H
Replies: 4
Views: 134

Re: delta H

Forming a bond releases energy, thus reducing the energy of the molecule. The molecule will therefore be more stable since it is at a lower energy state.
by Nicole Nikolov 1K
Sun Feb 11, 2018 11:31 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Revsersible vs. Irreversible reactions
Replies: 3
Views: 136

Re: Revsersible vs. Irreversible reactions

In a reversible reaction, we are assuming that it is happening so slowly that no heat is lost to the surroundings. Therefore, the total change in entropy of the universe for a reversible reaction will be equal to zero, whereas the total change in entropy of the universe for an irreversible reaction ...
by Nicole Nikolov 1K
Sun Feb 11, 2018 5:10 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: avogadro's number
Replies: 1
Views: 90

Re: avogadro's number

To solve for W, you need to find X^N, with X being the number of possible orientations and N being the total number of molecules. You would use Avogadro's number to solve for N only if you are provided a value in grams or moles, because your goal is to find the number of molecules.
by Nicole Nikolov 1K
Sun Feb 11, 2018 5:04 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: entropy and moles
Replies: 2
Views: 222

Re: entropy and moles

The entropy of a reaction only changes if there is a change in the number of moles of gas. This is because the number of micro states of the molecules in a solid or liquid is going to be the same regardless of how many molecules there are. However, since the molecules in a gas are moving around and ...
by Nicole Nikolov 1K
Sun Feb 11, 2018 4:52 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Using q reversible
Replies: 1
Views: 77

Re: Using q reversible

When calculating the change in entropy of the system, you need to take heat transfer, q, into account regardless of whether it is a reversible or irreversible process. Because entropy is a state variable, the change in entropy will be the same for both reversible and irreversible processes. However,...
by Nicole Nikolov 1K
Mon Feb 05, 2018 7:29 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: "Favorability"
Replies: 5
Views: 234

Re: "Favorability"

Favorability can be determined based on whether delta G is positive or negative; therefore, whether a reaction is spontaneous (favorable) is determined based on the changes in enthalpy and entropy values of the reaction. So you would need to look at the relative values of delta H and delta S to dete...
by Nicole Nikolov 1K
Sun Feb 04, 2018 11:29 pm
Forum: Phase Changes & Related Calculations
Topic: Determining if reversible or irreversible
Replies: 2
Views: 105

Re: Determining if reversible or irreversible

One way to determine whether a reaction is reversible or irreversible is to look at the delta S. If delta S is equal to zero, the reaction is reversible (this is an ideal process). If delta S is greater than zero (all real processes), then the reaction is irreversible because heat/energy is lost to ...
by Nicole Nikolov 1K
Sun Feb 04, 2018 11:24 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: requirements for reversible reactions
Replies: 1
Views: 60

Re: requirements for reversible reactions

Delta S would have to be zero because otherwise heat would be lost to the surroundings. If heat is lost to the surroundings, the reaction cannot be reversed. Delta G would have to be negative, indicating a release in energy. This means that the products will have lower energy than the reactants, the...
by Nicole Nikolov 1K
Sun Feb 04, 2018 11:20 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Test 1 Question
Replies: 4
Views: 224

Re: Test 1 Question

This is an isolated system because the whole point of a cooler is to keep the contents inside cold. Therefore, no heat/energy is being exchanged between the inside and the outside. An "ideal" cooler would 100% prevent the flow of heat between the system and the surroundings.
by Nicole Nikolov 1K
Mon Jan 22, 2018 2:55 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Concepts for Chapter 8 [ENDORSED]
Replies: 5
Views: 237

Re: Concepts for Chapter 8 [ENDORSED]

I would definitely recommend reading the textbook chapters we cover in class. Also doing all of the homework problems will help to solidify the concepts behind them. Hope this helps!
by Nicole Nikolov 1K
Mon Jan 22, 2018 2:09 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: N: number of particle [ENDORSED]
Replies: 4
Views: 160

Re: N: number of particle [ENDORSED]

In the carbon monoxide example today, he put N=4 instead of N=2 because he was referring to four CO molecules, not the number of atoms within each molecule.
by Nicole Nikolov 1K
Sat Jan 13, 2018 8:19 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Differences between properties
Replies: 1
Views: 64

Re: Differences between properties

An intensive property has to do with the element in and of itself, not the size or amount of the sample (color, temperature, solubility are examples). An extensive property is one that depends on the amount of the substance (mass and volume are examples).
by Nicole Nikolov 1K
Sat Jan 13, 2018 8:15 pm
Forum: Phase Changes & Related Calculations
Topic: Most stable phases for halogens
Replies: 3
Views: 162

Re: Most stable phases for halogens

The most stable phase for any element can be looked up from the periodic table. For the halogens, fluorine will be a gas, chlorine a gas, bromine, a liquid, iodine a solid, and astatine a solid.
by Nicole Nikolov 1K
Sat Dec 09, 2017 10:42 pm
Forum: Conjugate Acids & Bases
Topic: % Ionization [ENDORSED]
Replies: 3
Views: 432

Re: % Ionization [ENDORSED]

To find percent ionization, you should divide the hydrogen concentration at equilibrium by the initial concentration of the acid, and multiply by 100.
by Nicole Nikolov 1K
Sat Dec 09, 2017 10:39 pm
Forum: Quantum Numbers and The H-Atom
Topic: Spin Quantum Number: Test 3
Replies: 3
Views: 207

Re: Spin Quantum Number: Test 3

There is no way of predicting whether the electron will be spin up or spin down. That is why we should always write +/- 0.5. In addition, question #8 is asking for ALL the possible values for the spin quantum number, so that would include both the positive and negative value.
by Nicole Nikolov 1K
Sun Dec 03, 2017 11:15 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Do net dipole charges affect bases and acids?
Replies: 2
Views: 297

Re: Do net dipole charges affect bases and acids?

The greater the net dipole moment in a molecule, the stronger the acid/base, so the more it dissociates. That means that strong acids/bases have the highest electronegativity differences.
by Nicole Nikolov 1K
Sun Dec 03, 2017 10:52 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Weak Acids / Strong Acids
Replies: 5
Views: 240

Re: Weak Acids / Strong Acids

It turns out that most acids and bases are weak, so not that many acids and bases are strong. The best way to go about it would be to memorize all of the strong acids and bases and just to assume that the others are weak.
by Nicole Nikolov 1K
Sun Nov 26, 2017 11:54 pm
Forum: Biological Examples
Topic: Memorization of compounds
Replies: 5
Views: 386

Re: Memorization of compounds

I think it might be helpful to memorize the names of certain compounds; however, I think it would be a lot more helpful to have a general understanding of how to name coordination compounds.
by Nicole Nikolov 1K
Sun Nov 26, 2017 11:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Symmetrical Molecules
Replies: 3
Views: 211

Re: Symmetrical Molecules

If a molecule is completely symmetrical, then it will be nonpolar. However, when it comes to 3D molecules and more complex molecules it can get a bit more tricky. Even if these molecules look symmetrical at first glance based on their shape, you have to make sure that all of the dipole moments betwe...
by Nicole Nikolov 1K
Mon Nov 20, 2017 12:01 am
Forum: Hybridization
Topic: Hybrid orbitals
Replies: 3
Views: 157

Re: Hybrid orbitals

You should always fill orbitals from lowest energy to highest energy. You can use Hund's rule, the Aufbau principle, and the Pauli exclusion principle to determine the placement and spin of the electrons.
by Nicole Nikolov 1K
Mon Nov 13, 2017 12:45 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Extent of memorization [ENDORSED]
Replies: 2
Views: 100

Re: Extent of memorization [ENDORSED]

We will definitely have to know the nomenclature for VSEPR, and I'm pretty sure we will have to know the common bond angles. We will probably have to know the angles for linear, trigonal planar, tetrahedral, trigonal bipyramidal, and octahedral. We won't have to know bond angles for things like trig...
by Nicole Nikolov 1K
Mon Nov 13, 2017 12:40 pm
Forum: Dipole Moments
Topic: dipole moment arrows [ENDORSED]
Replies: 2
Views: 181

Re: dipole moment arrows [ENDORSED]

Yes, the arrow will always point to the most electronegative atom because the electrons are being pulled in that direction. To figure out whether a molecule is polar or non polar you need to figure out whether the dipole moments cancel. It is possible that the dipole moments will be in the same dire...
by Nicole Nikolov 1K
Mon Nov 13, 2017 12:30 pm
Forum: Sigma & Pi Bonds
Topic: # of sigma and pi bonds [ENDORSED]
Replies: 4
Views: 276

Re: # of sigma and pi bonds [ENDORSED]

Yes. This is true because a bond can only have one head-on overlap. For double and triple bonds, the additional bonds will be pi bonds and will form perpendicular to the sigma bond.
by Nicole Nikolov 1K
Sun Nov 05, 2017 11:28 pm
Forum: Dipole Moments
Topic: Dipole Moments and Electronegativity [ENDORSED]
Replies: 2
Views: 163

Re: Dipole Moments and Electronegativity [ENDORSED]

Yes, so the greater the difference is electronegativities of two atoms, the greater the dipole moments. Basically, the greater the electronegativity of one atom, the more likely it is to pull the electrons in the bond towards it.
by Nicole Nikolov 1K
Sun Nov 05, 2017 11:03 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shell, subshell, and orbital
Replies: 5
Views: 297

Re: Shell, subshell, and orbital

The principal quantum number n simply tells us what energy level the electron is found in. The angular momentum number l describes the shape of the orbital and it can range from 0 to n-1. The magnetic quantum number tells us the orientation of the orbital and ranges from -l to l.
by Nicole Nikolov 1K
Sun Oct 29, 2017 11:59 pm
Forum: Resonance Structures
Topic: HOW [ENDORSED]
Replies: 1
Views: 160

Re: HOW [ENDORSED]

To determine the most stable structure you would have to determine the formal charge of each possible structure. The most stable one will be the one with the least overall formal charge.
by Nicole Nikolov 1K
Sun Oct 29, 2017 11:44 pm
Forum: Electronegativity
Topic: Electronegativity [ENDORSED]
Replies: 3
Views: 273

Re: Electronegativity [ENDORSED]

Another way to think about it is as you move to the right of the periodic table you are adding more positive charge to the nucleus but the electrons are being added to the same orbital; therefore, the electrons are attracted more strongly to the nucleus. As you move down a period, even though you ar...
by Nicole Nikolov 1K
Tue Oct 24, 2017 10:29 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 3d and 4s
Replies: 5
Views: 284

Re: 3d and 4s

Generally, the 4s orbital will be filled before the 3d orbital, because 4s is of lower energy than 3d. If you follow the fourth period of the periodic table from left to right, you see that 4s gets filled before 3d. However, two exceptions to this in the fourth period are chromium and copper: these ...
by Nicole Nikolov 1K
Tue Oct 24, 2017 9:32 am
Forum: Ionic & Covalent Bonds
Topic: Ionization Energy [ENDORSED]
Replies: 5
Views: 245

Re: Ionization Energy [ENDORSED]

Yes, ionization energy is the energy required to remove an electron from an atom. Ionization energies differ for each element, generally increasing across a period and decreasing down a group. The ionization energy for an element will always be the same if, for example, it is the first electron you ...
by Nicole Nikolov 1K
Sun Oct 15, 2017 10:59 am
Forum: DeBroglie Equation
Topic: Units for Mass [ENDORSED]
Replies: 3
Views: 182

Re: Units for Mass [ENDORSED]

From my experience, you will almost always use kilograms when plugging numbers into equations. But to be 100% sure, you should make sure to look at the units for any constants you're using in your calculations and at the units of other values you are plugging in. Make sure that these units cancel ou...
by Nicole Nikolov 1K
Sun Oct 15, 2017 10:35 am
Forum: Properties of Electrons
Topic: Speed/Energy of Electrons
Replies: 4
Views: 239

Re: Speed/Energy of Electrons

I think I'm also kind of confused between speed and frequency. If light has a higher frequency doesn't that mean that it's going to be faster?
by Nicole Nikolov 1K
Sun Oct 08, 2017 3:36 pm
Forum: Limiting Reactant Calculations
Topic: Calculating how much of the excess remains [ENDORSED]
Replies: 4
Views: 286

Re: Calculating how much of the excess remains [ENDORSED]

Wouldn't you see how much of the excess product is consumed by comparing the molar ratios of the two (or more) reactants? You can never compare the masses of two different reactants; you would have to use moles, right?
by Nicole Nikolov 1K
Sun Oct 08, 2017 3:11 pm
Forum: Significant Figures
Topic: Sig Fig in final answer [ENDORSED]
Replies: 3
Views: 259

Re: Sig Fig in final answer [ENDORSED]

Your final answer in this case would only have two significant figures. This is because your final answer can only be as precise as the least precise value you used in your calculations.

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