## Search found 60 matches

Sun Mar 17, 2019 5:48 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Catalyst in rate law?
Replies: 6
Views: 933

### Re: Catalyst in rate law?

A catalyst can be present in the rate law if it is a reactant in the rate determining step. Because it is a reactant in that step, it is included in the rate law.
Sun Mar 17, 2019 5:45 pm
Forum: Balancing Redox Reactions
Topic: How to balance half reaction
Replies: 5
Views: 386

### Re: How to balance half reaction

I agree with Henry's answer except instead of adding OH- equal to double the amount of H2O initially added, find how many H one side needs to make it balanced and and add twice that amount of H2O to that side and that amount of OH- to the other side. Also don't forget to balance all the other reacta...
Sun Mar 17, 2019 5:39 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: k' vs k'
Replies: 3
Views: 331

### Re: k' vs k'

They are not related, they just happen to be written the same.
Sun Mar 10, 2019 2:26 pm
Forum: General Rate Laws
Topic: Problem
Replies: 1
Views: 100

### Re: Problem

t1/2 = 0.693/k
to get to 1/64 the original power, just do it 6 times because 2^6=64
Sun Mar 10, 2019 2:24 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Order
Replies: 2
Views: 140

### Re: Order

Use experimental data to calculate the order of reactants in a reaction. Divide one experiment by another as shown in class on March 1st. The order shows how many of that molecule interact in the rate determining step.
Sun Mar 10, 2019 2:23 pm
Forum: General Rate Laws
Topic: Unique rates
Replies: 1
Views: 72

### Re: Unique rates

The two are equivalent, but typically when referring to the unique rate you would be referring to the equation that describes the rate with respect to one reactant or product while the rate law describes it in terms of all reactants. Eg. Unique rate = -\frac{1}{a}\frac{d[A]}{dt} for a as a reactant ...
Sun Mar 03, 2019 8:27 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: concentration cell
Replies: 2
Views: 94

### Re: concentration cell

A concentration cell is a galvanic cell with both sides containing the same solutions at different molarities. The Eo is always zero because it is calculated using the standard reduction potentials of both sides which are the same because the solutions contain the same components.
Sun Mar 03, 2019 8:20 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Cell Diagram
Replies: 4
Views: 161

### Re: Cell Diagram

Everything that is added to the solutions that participates in the redox reaction is put into the cell diagram except for water and the acid/base that is added to the solution to allow the reaction to happen. This means that the electrode, and oxidized/reduced materials are added, as well as other m...
Sun Mar 03, 2019 8:16 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration Cell
Replies: 2
Views: 122

### Re: Concentration Cell

E o is always 0 for a concentration cell because E o refers to the potential of a solution at 1M concentration. For the concentration cell, E o would be calculated using 1M solutions of the solutions on each side, and since in a concentration cell, both solutions have the same components, the differ...
Mon Feb 25, 2019 12:24 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating cell potential using cathode and anode values
Replies: 2
Views: 90

### Re: Calculating cell potential using cathode and anode values

Expanding on Aili's answer, the standard potential for the anode should be negative already because it is oxidized so it will be subtracted when you add them.
Mon Feb 25, 2019 12:22 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Conductors and Cell Diagrams
Replies: 1
Views: 71

### Re: Conductors and Cell Diagrams

An inert conductor is used when the ions on the cathode side will not form a solid on their own. This should be given I don't think we need to know when to use it and when not to.
Mon Feb 25, 2019 12:17 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Hydrogen Electrode
Replies: 1
Views: 65

### Re: Hydrogen Electrode

Comparing the half reactions is just one method for calculating the overall cell potential. The standard hydrogen electrode is an electrode that is used to measure the potentials of substances and to standardize them. A galvanic cell is set up and potential is measured between the cell of interest a...
Tue Feb 19, 2019 1:08 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Molar Gibbs free energy
Replies: 3
Views: 201

### Re: Molar Gibbs free energy

The molar Gibbs free energy refers to the amount of Gibbs free energy per mole of a substance.
Standard Gibbs free energy is the total amount of energy, not just the amount of energy in each mole of the substance.
Tue Feb 19, 2019 1:05 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Van't Hoff Equation
Replies: 3
Views: 117

### Re: Van't Hoff Equation

K is just a constant in the equation that relates entropy and enthalpy in a system.
If you want to know more I suggest you look at the section in the thermodynamics tab called Van't Hoff Equation.
Tue Feb 19, 2019 1:02 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs free energy
Replies: 7
Views: 229

### Re: Gibbs free energy

Gibbs free energy is a measure of energy contained within a system. More specifically, this energy is the energy in the system that can be accessed to do work. Enthalpy is the measure of energy due to temperature. Entropy is a measure of the number of quantum states that a system can occupy. Heat is...
Sun Feb 10, 2019 1:32 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: 9.25 6th edition
Replies: 1
Views: 89

### Re: 9.25 6th edition

Each SO2F2 can be in 1 of 6 configurations. Since we are calculating the molar entropy or entropy per mole, use the Boltzmann equation with n=6.022x1023
So, $S=k_{b}lnW=1.38\times 10^{-23}ln6^{6.022\times 10^{23}}=14.9J\cdot K^{-1}$
Sun Feb 10, 2019 1:26 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Calculation Help
Replies: 1
Views: 85

### Re: Calculation Help

5/2 R should be used when pressure is constant and 3/2 R when volume is constant. They are derived from ideal gas equations not discussed in class.
Sun Feb 10, 2019 1:23 pm
Forum: Calculating Work of Expansion
Topic: Using Derivative/Integral Equations
Replies: 5
Views: 195

### Re: Using Derivative/Integral Equations

You won't have to integrate to solve any problems. They were just used to derive others from class.
As for knowing which equations to use when certain values are constant, you just have to remember which to use in which scenario.
Sun Feb 03, 2019 4:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of Complicated Molecule
Replies: 1
Views: 85

### Re: Enthalpy of Complicated Molecule

The way that you would find out the enthalpy of a molecule would be by using the enthalpies of the other molecules in the reaction which should be given. You could also add up the bond enthalpies if those are given.
Sun Feb 03, 2019 1:16 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW problem 4A.11
Replies: 1
Views: 82

### Re: HW problem 4A.11

$C=\frac{22.5 kJ}{23.97^{O}C-22.45^{O}C}$
Sat Feb 02, 2019 4:05 pm
Forum: Calculating Work of Expansion
Topic: SI unit for P
Replies: 6
Views: 225

### Re: SI unit for P

In this class, use atm when reporting pressures.
Fri Jan 25, 2019 10:55 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Energy of raising water temp, Adams Disc 1A
Replies: 1
Views: 77

### Re: Energy of raising water temp, Adams Disc 1A

You should memorize the general pattern of rises and plateaus but not the specific numbers.
Fri Jan 25, 2019 10:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: State properties
Replies: 3
Views: 123

### Re: State properties

Adding on to that, because enthalpy is a state function, you can calculate it by adding the enthalpies of multiple reactions to find the enthalpy of the overall reaction.
Fri Jan 25, 2019 10:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: methods
Replies: 2
Views: 93

### Re: methods

You should know all three methods because you will need to choose one according to what you are given in each problem.
Sat Jan 19, 2019 6:01 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: strong acids and bases
Replies: 2
Views: 134

### Re: strong acids and bases

If you are given a K value, an acid with a Ka < $1\times 10^{-3}$ or a base with Kb less than that value will be a weak acid/base respectively.
(This is also a general rule but works in the majority of situations)
Sat Jan 19, 2019 5:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Stability of reactions using equilibrium constant
Replies: 1
Views: 193

### Re: Stability of reactions using equilibrium constant

The dissociation of F2 is more stable. The K value is larger meaning there is a higher ratio of products to reactants. The dissociated molecule is the product so there should be more products made in the F2 dissociation than the Cl2 dissociation.
Sat Jan 19, 2019 5:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th Edit 5I.23
Replies: 1
Views: 38

### Re: 7th Edit 5I.23

Did you make sure to use concentrations instead of moles of each chemical? (convert using moles / liters)
Also, in the Kc value don't forget to put the proper exponents on the terms that have coefficients in the balanced equation.
Thu Jan 10, 2019 11:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5H3 from 7th edition
Replies: 2
Views: 64

### Re: 5H3 from 7th edition

When the two equations are combined in full, the result will be: 2BrCl + H 2 + Cl 2 <--> Br 2 + 2HCl + Cl 2 To write the full equilibrium constant equation for this, we would get: K = \frac{[Br_{2}][2HCl][Cl_{2}]}{[2BrCl][H_{2}][Cl_{2}]} This is the same as both K values multiplied together. The Cl ...
Thu Jan 10, 2019 11:24 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th Edition 5H.3
Replies: 1
Views: 47

### 7th Edition 5H.3

In this problem, both reactions were combined and their K values were multiplied together. Is this the case for all problems of this type or are there other factors to consider when combining the two K factors?
Wed Jan 09, 2019 1:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc for Gases
Replies: 2
Views: 43

### Re: Kc for Gases

You are correct in saying that we use Kp for gases, but if necessary, you can convert using the ideal gas law: PV=nRT or P=(Concentration)RT
Sun Dec 09, 2018 12:14 am
Forum: Bronsted Acids & Bases
Topic: 7th edition fundamentals J.9
Replies: 1
Views: 87

### Re: 7th edition fundamentals J.9

The phosphoric acid will donate a H+ to each of 3 ammonia molecules. This will result in PO43- and 3NH4+. They come together to form the salt (NH4)3PO4.
Sun Dec 09, 2018 12:12 am
Forum: Bronsted Acids & Bases
Topic: Fundamentals J.17 (7th Edition)
Replies: 1
Views: 125

### Re: Fundamentals J.17 (7th Edition)

If the molecule dissociates into an ion that doesn't affect the pH such as Na+, it can be left out of the net ionic equation.
Sun Dec 09, 2018 12:10 am
Forum: Lewis Acids & Bases
Topic: 12.25
Replies: 1
Views: 285

### Re: 12.25

First calculate the amount of moles of Ba(OH) 2 using the molar mass. Then remember that it completely dissociates into that number of moles of Ba and twice the number of moles of OH. Divide by .1L to get the molarity of Ba and OH. Then calculate the pOH using the molarity of OH and subtract it from...
Sun Dec 02, 2018 10:02 pm
Forum: Hybridization
Topic: Hybridization Application
Replies: 2
Views: 124

### Re: Hybridization Application

Yes, whenever an atom is bonded to another atom, its regions of electron density are hybridized into sp, sp2, etc. orbitals.
Sun Dec 02, 2018 9:55 pm
Forum: Bronsted Acids & Bases
Topic: Fundamentals J.1 Bronsted Acids and Bases
Replies: 2
Views: 193

### Re: Fundamentals J.1 Bronsted Acids and Bases

There are certain characteristics to acids and bases that are good to remember. For example, a compound consisting of one hydrogen and one halogen will always be a strong acid. Molecules with group 1 or 2 metals and an OH group will be basic. Also, any compound with an N atom that has a lone pair wi...
Sun Dec 02, 2018 9:42 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate ligand geometry
Replies: 1
Views: 109

### Re: Polydentate ligand geometry

Polydentate ligand lone pairs are in the same orientation as atoms in the VSEPR model. For example, if there are 6 lone pairs from ligands bonding to the transition metal, they will be in an octahedral shape. The lone pairs should be the correct distance apart to form these shapes.
Sun Nov 25, 2018 2:42 pm
Forum: Hybridization
Topic: BrF3
Replies: 2
Views: 531

### Re: BrF3

If you draw the Lewis structure, there should be 28 e - (21 from the 3 fluorine, 7 from bromine). The bromine is bonded to each of the 3 fluorine atoms by a single bond. That leaves 4 electrons which are put around the bromine atom as 2 lone pairs. This gives a total of 5 regions of electron density...
Sun Nov 25, 2018 2:38 pm
Forum: Hybridization
Topic: Hybridization Orbitals
Replies: 2
Views: 193

### Re: Hybridization Orbitals

The 1 and 2 after the H and C represent the 1 in 1s or 2 in 2sp shell respectively. This is to distinguish between other shells such as 2s, 3s, 4s, etc. or a 3sp hybrid orbital. The hydrogen has 1s because a H atom has a valence electron in the 1s shell. The C has 2sp because the orbitals are a hybr...
Sun Nov 25, 2018 2:34 pm
Forum: Hybridization
Topic: Resonance and hybridization
Replies: 1
Views: 106

### Re: Resonance and hybridization

In a resonance structure, the hybridization is found the same way as a non resonant structure. That is, by looking at the regions of electron density around the atom. If a lone pair in one resonance structure is a bonding pair in another resonance structure, the lone pair is considered to be in the ...
Sun Nov 18, 2018 10:59 pm
Forum: Bond Lengths & Energies
Topic: Electrostatic Energy and Energy Density
Replies: 1
Views: 129

### Re: Electrostatic Energy and Energy Density

I believe that we do not need to know these concepts for class.
Sun Nov 18, 2018 10:36 pm
Forum: Electronegativity
Topic: Question about what makes something ionic
Replies: 5
Views: 180

### Re: Question about what makes something ionic

Because the difference in their electronegativities is only about .76, the bond has mostly covalent character. Only bonds with a difference in electronegativity of 2 or greater are said to have mostly ionic character.
Sun Nov 18, 2018 10:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles in 7E 2E.13.b
Replies: 4
Views: 155

### Bond Angles in 7E 2E.13.b

In this problem, the POCl 3 molecule has a tetrahedral shape. In class we learned that tetrahedral molecules always have bond angles of 109.5 o and this is the correct answer in the solutions manual. However, the bond angles are not exactly 109.5 because (I assume) of the double bond that the oxygen...
Fri Nov 09, 2018 1:06 am
Forum: Dipole Moments
Topic: Dipole Equation- Units
Replies: 1
Views: 96

### Re: Dipole Equation- Units

The unit for dipole moments is the debye which is 3.336x10-30 coulomb meter.

charge (coulombs) x distance (meters) = debye (coulomb meter)
Fri Nov 09, 2018 1:02 am
Forum: Ionic & Covalent Bonds
Topic: Bond strength and state of matter
Replies: 2
Views: 145

### Re: Bond strength and state of matter

What determines if a substance is a solid, liquid, or gas is not necessarily bonds but interactions between the atoms/molecules. These can be hydrogen bonds, Van der Waals' interactions, etc. If these interactions are stronger, then the atoms/molecules will be held more tightly together so it will t...
Thu Nov 08, 2018 9:11 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic Solubility
Replies: 2
Views: 73

### Re: Ionic Solubility

It has to do with the difference in electromagnetically between the two elements. Ag and F have very different electromagnetically so their bond has a high ionic character. This means that it will be soluble in water. As you go down the group, Cl, Br... the electronegativities get closer to that of ...
Sun Nov 04, 2018 6:47 pm
Forum: Electronegativity
Topic: Problem 2D #11 (7th edition)
Replies: 2
Views: 136

### Re: Problem 2D #11 (7th edition)

The polarizability gets bigger as the ion gets larger. The radius of O2- is less that the radius of N3-. Thus, it has a smaller polarizability. Also, N3- is less electronegative which also contributes.
Sun Nov 04, 2018 6:44 pm
Forum: Lewis Structures
Topic: B9 in 7th Edition
Replies: 1
Views: 44

### Re: B9 in 7th Edition

A) The brackets are just to distinguish between the Cl and NH4. B) The Molecule is K 3 P. The three K + ions surrounding the P 3- ion show that there are 3 potassium ions per phosphorous ion in this salt. The arrangement of K + ions around the phosphorous is arbitrary. C) Again here the brackets are...
Sun Nov 04, 2018 6:38 pm
Forum: Ionic & Covalent Bonds
Topic: bond order
Replies: 2
Views: 2070

### Re: bond order

The bond order is simply the number of bonds between two atoms.

For a single bond, the bond order is 1.
For a double bond, the bond order is 2.
etc.
Sun Oct 28, 2018 9:19 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 3d before 4s for Z > 10
Replies: 3
Views: 161

### Re: 3d before 4s for Z > 10

This rule only comes into effect for elements above argon (Z=18). You are correct that 3d is written before 4s, etc. when writing electron configurations However the 4s shell will fill before the 3d shell. This can be seen for the elements Potassium and Calcium (19 & 20). K: [Ar] 4s 1 , Ca: [Ar]...
Sun Oct 28, 2018 5:01 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: when 4s goes after 3d??
Replies: 2
Views: 136

### Re: when 4s goes after 3d??

The 4s orbital is always written after the 3d orbitals because it has higher energy. Remember higher n means higher energy. However, The 4s orbital will fill before the 3d orbital which is why potassium and calcium have electrons in the 4s orbital but not the 3d orbital. Keep in mind the exceptions ...
Sun Oct 28, 2018 4:36 pm
Forum: Lewis Structures
Topic: Lewis Dot Order
Replies: 10
Views: 236

### Re: Lewis Dot Order

It is generally best to choose the atom with the lowest ionization energy as the central atom. Start with this atom and arrange the others symmetrically around it.
Sun Oct 21, 2018 4:50 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post Module #13
Replies: 1
Views: 61

### Re: Atomic Spectra Post Module #13

Since the absorbed wavelengths are detected, the spectrometer can produce a spectrum with absorbed lines, hence the name absorption line spectrum. Because it is measuring absorbed lines, the experiment is called absorption spectroscopy.
Sun Oct 21, 2018 4:47 pm
Forum: Properties of Electrons
Topic: Electrons - Wave Properties
Replies: 4
Views: 159

### Re: Electrons - Wave Properties

All particles have particle and wave-like properties.
Electrons do have a wavelength and since they are small enough, the wavelength can usually be measured.
Larger objects such as a baseball have wavelengths that cannot be measured.
Sun Oct 21, 2018 4:42 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Hw 1D.9 - radial nodes and angular nodal surfaces differences
Replies: 1
Views: 95

### Re: Hw 1D.9 - radial nodes and angular nodal surfaces differences

We do not need to know radial nodes.
Angular nodal surfaces and nodal planes are the same so the question is asking for how many nodal planes in each.
Calculating them would involve the schrodinger equation which we are not using in class so just memorize them.
Sun Oct 14, 2018 9:06 pm
Forum: Photoelectric Effect
Topic: 1B.15 Part C
Replies: 2
Views: 96

### Re: 1B.15 Part C

Use the equation to find the energy of the incoming radiation: E_{photon}=E_{K}+\phi . The velocity of the ejected electron is given and the mass of the electron is in the list of constants, so you can calculate E_{K} (kinetic energy of electron) using \frac{1}{2}mv^2 . In part (b) you calculated th...
Fri Oct 12, 2018 11:23 pm
Forum: Photoelectric Effect
Topic: Properties of Light
Replies: 5
Views: 182

### Re: Properties of Light

The intensity of a source of light is the number of protons that come from the source. This is different from the energy of the light wave, which is dependent on the frequency of the wave, hence the equation: E=hv.
Tue Oct 09, 2018 4:04 pm
Forum: Properties of Light
Topic: Problem 1B.5: Units KeV
Replies: 2
Views: 68

### Re: Problem 1B.5: Units KeV

keV is a kilo-electron Volt, or 1000 electron volts. 1 Joule is equal to $6.24*10^{18}$ electron volts. So 1 Joule = $6.24*10^{15}$ keV.
Thu Oct 04, 2018 4:06 pm
Forum: Significant Figures
Topic: Molar Mass
Replies: 5
Views: 211

### Re: Molar Mass

Use the most accurate molar mass given to you. If the periodic table you are using gives the molar mass of carbon as 12.011 g/mol, then use that. Because the problem you gave an example of starts with 3.45g carbon (3 sig figs), the final result should be rounded to 3 significant figures. In other wo...
Wed Oct 03, 2018 1:38 pm
Forum: Empirical & Molecular Formulas
Topic: Writing formula from diagram
Replies: 2
Views: 152

### Re: Writing formula from diagram

Look at how many atoms of each color there are and write the formula based off of the key it gives you.
Eg. F1 (7th edition). Dark grey = C, White = H, Red = O
10 Dark grey atoms
16 white atoms
1 red atom
Molecular formula - C10H16O
The order in which you put the atoms doesn't really matter.
Mon Oct 01, 2018 2:38 pm
Forum: SI Units, Unit Conversions
Topic: Fundamental Exercises E3 [ENDORSED]
Replies: 3
Views: 136

### Re: Fundamental Exercises E3[ENDORSED]

I agree with Matthew. Because the question says that the lab can manipulate individual atoms, it is safe to assume that each circle on the scale represents a single atom. Therefore, the answer will be 3 atoms of astatine rather than 3 moles of astatine.