Search found 30 matches

by Sarah Noorani 3L
Wed Mar 09, 2016 2:50 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode Sign
Replies: 1
Views: 304

Re: Anode Sign

If you want to add both reactions rather than subtract, then yes you flip the anode sign. This is because you are using reduction potentials, but oxidation is occurring at the anode, which is the reverse reaction of reduction. Therefore, you would have to flip the sign for the reaction occurring at ...
by Sarah Noorani 3L
Wed Mar 09, 2016 2:44 am
Forum: *Alkenes
Topic: Bonds As functional groups
Replies: 2
Views: 484

Re: Bonds As functional groups

Double and triple bonds are considered functional groups because just like any other functional group, they would get priority in naming (for example, if the numbers 1 and 2 were to be assigned to a double bond and a methyl substituent, then the 1 would be assigned to the double bond because it has ...
by Sarah Noorani 3L
Fri Mar 04, 2016 10:12 am
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Cyclohexane problem
Replies: 1
Views: 302

Re: Cyclohexane problem

The first thing to look at is which option will give the lowest numbers. In this case, you have two options: you can either use 1,1,2 or 1,2,2. Since it is better to use two 1s rather than two 2s, we go with the first option. The only time you put the lower number with the substituent that comes fir...
by Sarah Noorani 3L
Thu Mar 03, 2016 1:23 am
Forum: *Organic Reaction Mechanisms in General
Topic: The position of nucleophile and elctrophile
Replies: 1
Views: 361

Re: The position of nucleophile and elctrophile

In this case, yes. The Br must attach to the carbon in the center because it is bound to more carbons, so it is more stable than the carbons on the sides.
by Sarah Noorani 3L
Tue Feb 23, 2016 1:29 pm
Forum: *Alkanes
Topic: Naming Clarification
Replies: 3
Views: 556

Re: Naming Clarification

The rule that we must use the lowest number to specify which carbon the substituent is attached to is to ensure that there is a uniform way to specify which carbon we are referring to, but the substituents should always be in alphabetical order, regardless of the numbers or prefixes in front of the ...
by Sarah Noorani 3L
Tue Feb 16, 2016 9:56 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Catalyst
Replies: 1
Views: 361

Re: Catalyst

A catalyst is a substance that increases the rate of a reaction by lowering the activation energy of a reaction. It does this by binding to the reactants and making it easier for the product to form (by bringing reactants together, orienting the reactants in the correct position to react, or providi...
by Sarah Noorani 3L
Tue Feb 09, 2016 1:04 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Q 14.21
Replies: 1
Views: 339

Re: Q 14.21

The first half reaction should be reversed because the Cu^(2+) is being reduced to Cu, and Cr^(2+) should be oxidized to Cr^(3+), which has a reduction potential of -0.41 V (this value can be found in the table). Subtracting the reduction potential of the anode from that of the anode gives 0.34 v -(...
by Sarah Noorani 3L
Thu Feb 04, 2016 8:52 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Reactions with e-
Replies: 1
Views: 263

Re: Balancing Redox Reactions with e-

After you add all the H2O (and H+ or OH-), find the charge on both sides of the reaction. For example, consider the reaction Cl2 + 2H2O --> 2HClO + 2H+ The reactant side has a total charge of 0 (because the Cl2 and H2O are neutral) while the product side has an overall charge of +2 (because of the 2...
by Sarah Noorani 3L
Tue Feb 02, 2016 1:55 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Ecell calculations
Replies: 2
Views: 406

Re: Ecell calculations

Changing the stoichiometric coefficients would not change the value for Ecellstandard because it is an intensive property, so it doesn't depend on the amount of substance present. However, if you reverse the chemical equation, then you would have to reverse the sign for Ecellstandard.
by Sarah Noorani 3L
Tue Jan 26, 2016 9:44 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal and delta U
Replies: 3
Views: 693

Re: Isothermal and delta U


Since the temperature does not change, delta T is 0, which makes delta U also equal to 0. This is because if the temperature does not change, the kinetic energy of the molecules doesn't change, so there is no change in internal energy.
by Sarah Noorani 3L
Fri Jan 22, 2016 1:04 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Definition of degeneracy and relationship to entropy
Replies: 6
Views: 2365

Re: Definition of degeneracy and relationship to entropy

The equation S=klnW is used to calculate statistical entropy (the entropy associated with large numbers of atoms and molecules). The equation delta S=q/T is used to calculate the thermodynamic entropy. In both cases, increasing the temperature or volume causes an increase in entropy because it would...
by Sarah Noorani 3L
Wed Jan 20, 2016 10:31 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Equations
Replies: 2
Views: 422

Re: Entropy Equations

\Delta S=nRln(V_{2}/V_{1}) is the equation that should be used when there is a change in volume. When there is a change in temperature, use the equation \Delta S=nRln(T_{2}/T_{1}) . The equation \Delta S=q/T should be used when you know the q (or can calculate it) for a reversible p...
by Sarah Noorani 3L
Thu Jan 14, 2016 10:12 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Work
Replies: 4
Views: 729

Re: Work

The negative sign in -PdeltaV must always be used when calculating work (even when work is done on the system). When work is done on the system, the gas will be compressed. This means that the final volume will be less than the initial volume, so the change in volume will be negative. A negative val...
by Sarah Noorani 3L
Fri Jan 08, 2016 12:46 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Using Bond Enthalpies in Calculations
Replies: 3
Views: 483

Re: Using Bond Enthalpies in Calculations

The process for calculating the enthalpy change of a reaction using bond enthalpies should not be thought of as enthalpy of reactants - enthalpy of products. Rather, it is the enthalpy needed to break the bonds in the reactants (a positive value) plus the enthalpy released when new bonds are formed ...
by Sarah Noorani 3L
Sat Dec 05, 2015 1:19 am
Forum: Calculating the pH of Salt Solutions
Topic: Why is H-H Equation an approximation
Replies: 2
Views: 784

Re: Why is H-H Equation an approximation

When we use the Henderson-Hasselach equation, we assume that the concentration of the acid, [HA] is the initial acid concentration. This is an approximation because a small percentage of the acid is converted to its conjugate base in the reaction HA + H2O --> A- + H3O+. Since we do not use the conce...
by Sarah Noorani 3L
Sun Nov 29, 2015 11:14 pm
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: Inductive Effect
Replies: 2
Views: 870

Re: Inductive Effect

The inductive effect can be useful in determining relative acid strength because if there are acids in which the same type of bond is broken when donating the H atom, then the acid that results in the most stable anion is the strongest acid. For example, when comparing CLOH and IOH, the O-H bond is ...
by Sarah Noorani 3L
Tue Nov 24, 2015 11:41 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Why is trichloroacetic acid stronger than acetic acid?
Replies: 1
Views: 7849

Re: Why is trichloroacetic acid stronger than acetic acid?

Since the Cl atoms in CCl4COOH are more electronegative than H atoms (in CH3COOH), they pull electron density away from the central carbon atom. This causes the carbon atom to pull electron density from the oxygen in the O-H bond, which weakens the O-H bond. Because the O-H bond is weaker in trichlo...
by Sarah Noorani 3L
Mon Nov 16, 2015 6:02 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework 11.89 balanced equation
Replies: 1
Views: 325

Re: Homework 11.89 balanced equation

If you look at the changes in the partial pressures of A, B, and C, then you can see that A and C changed by 10 kPa while B changed by 5 kPa, so the molar ratio of A:B:C is 2:1:2.
by Sarah Noorani 3L
Mon Nov 16, 2015 5:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: stability of atoms/molecules at equilibrium
Replies: 1
Views: 314

Re: stability of atoms/molecules at equilibrium

Decomposition reactions that have a small equilibrium constant have reactants that are more thermodynamically stable as compared to molecules with a higher K value for their decomposition reaction. This is because a small K value means that reactants are favored over the products, so it is difficult...
by Sarah Noorani 3L
Sun Nov 15, 2015 12:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: #10 from Quiz 3 Prep Fall 2014
Replies: 1
Views: 356

Re: #10 from Quiz 3 Prep Fall 2014

Since you are given Kp rather than Kc, you need to find the initial partial pressure of H2O. Use the number of moles of H2O (0.100 mol) and the volume (4.00 L) to solve for the partial pressure of H2O by using the equation PV=nRT. When you do this, the partial pressure of H2O is 2.05 atm, which is a...
by Sarah Noorani 3L
Sun Nov 15, 2015 11:45 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constant for Partial Pressure
Replies: 1
Views: 342

Re: Equilibrium Constant for Partial Pressure

The partial pressures given in the problem are in kPa. When finding the equilibrium constant, the partial pressures should be in bar. To convert from kPa to bar, you have to divide the partial pressures by 100.
by Sarah Noorani 3L
Thu Nov 12, 2015 5:01 pm
Forum: Naming
Topic: Writing formulas from compounds with "bis"
Replies: 1
Views: 375

Re: Writing formulas from compounds with "bis"

The prefixes di, tri, tetra, etc. are used to indicate how many molecules of a specific compound is in the coordinate compound. For example, diamine would mean there are two NH3 molecules present. However, alternate prefixes are used when the molecule already has a prefix (such as in ethylenediamine...
by Sarah Noorani 3L
Thu Nov 12, 2015 11:52 am
Forum: Naming
Topic: Naming of Oxalate
Replies: 1
Views: 541

Re: Naming of Oxalate

The alternative prefixes must also be used for polydentate ligands. Since oxalato can form a bond with the metal in two places (the two oxygen atoms with the negative formal charges), it is a bidentate and uses the alternative prefixes.
by Sarah Noorani 3L
Sat Nov 07, 2015 4:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Difference between Q and K
Replies: 3
Views: 620

Re: Difference between Q and K

If Q is less than K, then the ratio of the molar concentration of products to that of reactants is less than what it is at equilibrium, so the reaction will proceed in the forward reaction in order to increase the molar concentration of products to approach the value of K. If Q is greater than K, th...
by Sarah Noorani 3L
Wed Nov 04, 2015 1:52 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty in position
Replies: 5
Views: 827

Re: Uncertainty in position

The electron confined to an atom with a radius greater than 150 pm would have a larger uncertainty in position, and, because of this, it would have a lower uncertainty in velocity. Therefore, the velocity of the electron in the atom with a larger radius could be more precisely known as compared to t...
by Sarah Noorani 3L
Tue Oct 27, 2015 11:48 am
Forum: Octet Exceptions
Topic: How to draw Lewis Structures for incomplete octets?
Replies: 1
Views: 1152

Re: How to draw Lewis Structures for incomplete octets?

H, Li, and Be are exceptions to the octet rule because they do not have complete octets. In the case of BF3, B is also an exception because it has 6 valence electrons rather than 8 (it will eventually form a coordinate covalent bond with another atom or molecule that has a lone pair in order to acqu...
by Sarah Noorani 3L
Thu Oct 22, 2015 1:45 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Sigma bonds and Pi Bonds
Replies: 8
Views: 941

Re: Sigma bonds and Pi Bonds

No, there can only be one sigma bond between two atoms because when the orbitals from two atoms overlap end-to-end (in a sigma bond), in order to form another bond to share more electrons, it is only possible for their orbitals to overlap side-to-side (which forms a pi bond). This is why double bond...
by Sarah Noorani 3L
Fri Oct 16, 2015 1:32 am
Forum: Octet Exceptions
Topic: Radical Octets
Replies: 1
Views: 459

Re: Radical Octets

Radicals are atoms with an unpaired electron. They are highly reactive because they are most stable when they gain an electron from another atom. Any element in the p-block starting with the third row of the periodic table can have an expanded octet. This is because atoms with orbitals in the n=3 le...
by Sarah Noorani 3L
Thu Oct 08, 2015 11:23 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration for Chromium
Replies: 1
Views: 535

Re: Electron Configuration for Chromium

If Cr were to form a bond with another atom, then yes, it would be best to remove an electron from the 4s orbital so that the configuration would be 3d^5. However, when the Cr atom is not bonding, there is no way for it to just "lose" an electron, so it has to have the electron in an orbit...
by Sarah Noorani 3L
Fri Oct 02, 2015 4:09 pm
Forum: Photoelectric Effect
Topic: Wavelengths of photons
Replies: 3
Views: 411

Re: Wavelengths of photons

In the photoelectric effect, the photons released by the atom were not measured; the detector only detected the ejected electrons. The wavelengths of the electromagnetic radiation emitted by atoms to form the emission spectrum depends on the element because the atoms release different wavelengths of...

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