## Search found 61 matches

Fri Mar 15, 2019 2:54 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Replies: 3
Views: 133

The rate constant of the reaction between CO2 and OH in aqueous solution to give the HCO3- ion is 1.5 *10^10 L/mol*s at 25 C. Determine the rate constant at blood temperature (37 C), given that the activation energy for the reaction is 38 kJmol-1.
Fri Mar 15, 2019 2:50 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Replies: 3
Views: 114

The rate constant of the first-order reaction 2 N2O(g)--->2 N2(g) + O2(g) is 0.76 1/s at 1000. K and 0.87 1/s at 1030. K.
Calculate the activation energy of the reaction.
How do you use Arrhenius here?
Fri Mar 15, 2019 2:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial Pressure
Replies: 4
Views: 329

### Re: Partial Pressure

Is the value for Kp given at a different temperature? Maybe use Van't Hoff? Because we don't include solids in our equilibrium constant equations, right?
Mon Mar 04, 2019 11:37 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate determining step
Replies: 2
Views: 137

### Re: Rate determining step

I'm confused about this too. I think in elementary steps, we can use the coefficients as the exponents for the rate law equation or maybe experimental data?
Mon Mar 04, 2019 11:35 pm
Forum: General Rate Laws
Topic: Order Reaction/Rate Law
Replies: 3
Views: 141

### Re: Order Reaction/Rate Law

i think adding up the exponents in the rate law equation gives us the order of the reaction, or we could look at the way concentration changes as time increases (on a graph) ?
Mon Mar 04, 2019 5:10 pm
Forum: General Rate Laws
Topic: K
Replies: 3
Views: 138

### Re: K

doesn't k change in response to changes in the rate of a reaction (so anything that increases or slows down the reaction including temperature, concentration, etc) ?
Mon Mar 04, 2019 5:08 pm
Forum: General Rate Laws
Topic: Rate Law
Replies: 2
Views: 135

### Rate Law

How do we determine the Rate Law for a reaction when the experimental data isn't clear on what is doubled?
Mon Mar 04, 2019 12:53 pm
Forum: First Order Reactions
Topic: First Order Reactions
Replies: 6
Views: 194

### Re: First Order Reactions

I think the derived ln formula for first order will always be a straight line but I don't think the actual rate law for first order reactions are first order, i'm not totally sure though.
Mon Mar 04, 2019 12:51 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test #2
Replies: 2
Views: 162

### Re: Test #2

I think for that one you had to solve for the Kw value at the lower temperature and then take the square root of that value to find the H+ concentration. If that value was lower than 10^-7 (which is the H+ concentration at pH of 7) then I think your solution was acidic because you had more H+ than O...
Wed Feb 20, 2019 9:23 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cells
Replies: 7
Views: 172

### Re: Galvanic Cells

A battery is just a collection of galvanic cells joined in a series and each galvanic cell has an anode and a cathode.
Wed Feb 20, 2019 9:20 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Midterm Question
Replies: 5
Views: 402

### Re: Midterm Question

yes, because the K value was large so product formation was favored so products are clearly more stable.
Wed Feb 20, 2019 9:19 pm
Forum: Balancing Redox Reactions
Topic: H+ vs H3O+
Replies: 10
Views: 327

### Re: H+ vs H3O+

I think we're supposed to use H+ when balancing acidic redox reactions for simplicity.
Wed Feb 20, 2019 9:18 pm
Forum: Calculating Work of Expansion
Topic: expansion
Replies: 2
Views: 126

### Re: expansion

there's usually a volume change or a change in the number of moles between reactants and products, I think.
Wed Feb 20, 2019 9:17 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: entropy
Replies: 4
Views: 294

### Re: entropy

entropy is the measure of disorder or random activity in a system, whereas enthalpy is a measure of the overall energy is a system
Wed Feb 20, 2019 8:03 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: stoichiometric coefficients for calculating Gibbs free energy
Replies: 2
Views: 138

### Re: stoichiometric coefficients for calculating Gibbs free energy

I think this is when you are calculating the enthalpy of formation of the standard molar entropy for 1 mole of NH3 because then you just want to produce one mole of that product. I'm not totally sure though.
Wed Feb 06, 2019 11:58 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: U= 3/2nRT
Replies: 2
Views: 187

### Re: U= 3/2nRT

i think this is used when you have to calculate the heat capacity of an ideal gas at a constant volume
Wed Feb 06, 2019 11:56 pm
Forum: Calculating Work of Expansion
Topic: Temperature in Work Equations
Replies: 3
Views: 160

### Re: Temperature in Work Equations

in the second equation the pressure is constant and the volume is changing in response so everything on the other side of the ideal gas law equation stays constant, i'm not sure why we don't include it though.
Wed Feb 06, 2019 11:55 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: Calculate degeneracy
Replies: 1
Views: 94

### Re: Calculate degeneracy

degeneracy is the number of positions a molecule can have raised to the number of molecules/particles in the object you're looking at. the ratio of the change in volume is equal to the change in degeneracy, so if you double the volume the ratio of degeneracy would be 2:1 (final degeneracy over initi...
Thu Jan 31, 2019 10:48 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Thermo Test/Midterm
Replies: 9
Views: 282

### Re: Thermo Test/Midterm

I think he'll expect us to know how to do it because we went through it in chem 14a. I'm not totally sure though.
Thu Jan 31, 2019 10:46 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Change in internal energy equation
Replies: 2
Views: 142

### Re: Change in internal energy equation

I think that's the equation for calculating heat. The equations for specific heat capacity and molar heat capacity include moles and grams I think?
Thu Jan 31, 2019 10:45 pm
Forum: Phase Changes & Related Calculations
Topic: 8.1 (6th Edition)
Replies: 1
Views: 78

### 8.1 (6th Edition)

Identify the following systems as open, closed, or isolated: (a) coffee in a very-high-quality thermos bottle; (b) coolant in a refrigerator coil; (c) a bomb calorimeter in which benzene is burned; (d) gasoline burning in an automobile engine; (e) mercury in a thermometer; (f) a living plant. Does a...
Sat Jan 26, 2019 10:44 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess’s Law
Replies: 2
Views: 96

### Re: Hess’s Law

I would put each equation on top of each other, then cancel out the products that are used up as reactants in the next step (you may have to multiply to cancel them out exactly), then just add up all the enthalpy changes when you are left with your desired chemical reaction.
Sat Jan 26, 2019 10:38 am
Forum: Phase Changes & Related Calculations
Topic: Severe burn from steam clarification
Replies: 5
Views: 1605

### Re: Severe burn from steam clarification

when steam hits your skin, a lot of energy will be released as it condenses into a liquid, undergoing a phase change (because your skin temperature is a lot cooler in temperature), this energy release causes a much worse burn than if the same amount of boiling water were to hit your skin where it wo...
Sat Jan 26, 2019 10:35 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: State Properties
Replies: 6
Views: 147

### Re: State Properties

work can't be a state function because it is proportional to the distance an object is moved, which depends on the path used to go from the initial to the final state and thus if work isn't a state function, then heat can't be a state function either because according to the first law of thermodynam...
Sat Jan 26, 2019 10:33 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 11
Views: 927

### Re: Le Chatelier's Principle

if they increase pressure by adding an inert gas, it doesn't shift the chemical reaction either way (regardless of the moles of gas on each side of the chemical reaction)
Wed Jan 16, 2019 11:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Endothermic Reaction
Replies: 4
Views: 148

### Re: Endothermic Reaction

I think K would decrease since in an endothermic reaction is like having heat as a reactant but it will push the reaction forward so i'm not totally sure.
Wed Jan 16, 2019 11:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pH
Replies: 5
Views: 158

### Re: pH

and then if you're given pH and you need to find the H30+ concentration you just do the antilog: 10^(-pH)
Wed Jan 16, 2019 11:46 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 11
Views: 927

### Re: Le Chatelier's Principle

If you focus on the inverse relationship pressure has with volume, that tends to help.
It will go to the side with fewer moles when volume decreases or pressure increases, and vice versa.
Tue Jan 08, 2019 7:48 pm
Forum: Ideal Gases
Topic: Activity
Replies: 3
Views: 145

### Re: Activity

I think thats supposed to be a representation of the units, bars, thats used when solving the equilibrium constant using pressure. I'm not sure though.
Tue Jan 08, 2019 7:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.41
Replies: 1
Views: 75

### 11.41

A 25.0-g sample of ammonium carbamate, NH4(NH2CO2), was placed in an evacuated 0.250-L fl ask and kept at 25 C. At equilibrium, 17.4 mg of CO2 was present. What is the value of Kc for the decomposition of ammonium carbamate into ammonia and carbon dioxide? The reaction is NH4(NH2CO2)(s)-->2 NH3(g) ...
Tue Jan 08, 2019 7:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.43
Replies: 2
Views: 139

### 11.43

Consider the reaction 2 NO(g) --> N2(g) O2(g). If the initial partial pressure of NO(g) is 1.0 bar, and x is the equilibrium concentration of N2(g), what is the correct equilibrium relation?
How do you find the equilibrium constant formula?
Fri Nov 30, 2018 7:41 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Equilibrium Constants
Replies: 2
Views: 141

### Equilibrium Constants

How do we find the equilibrium constants for weak acids/bases? Is it different from strong acids/bases?
Fri Nov 30, 2018 7:40 pm
Forum: Naming
Topic: Naming Coordination Compounds
Replies: 1
Views: 120

### Naming Coordination Compounds

Does anyone have any advice on how to memorize all the different ligands?
Fri Nov 30, 2018 7:38 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 17.31
Replies: 2
Views: 111

### 17.31

Use the information in Table 17.4 to write the formula for each of the following coordination compounds: (a) potassium hexacyanidochromate(III) (b) pentaamminesulfatocobalt(III) chloride (c) tetraamminediaquacobalt(III) bromide (d) sodium bisoxalato(diaqua)ferrate(III) Does anyone have the answers f...
Fri Nov 30, 2018 7:34 pm
Forum: Sigma & Pi Bonds
Topic: Triple bond?
Replies: 18
Views: 788

### Re: Triple bond?

it has one sigma and two pi bonds but it has the same electron density as a single or triple bond, I think.
Fri Nov 30, 2018 7:34 pm
Forum: Naming
Topic: Coordination Number
Replies: 3
Views: 175

### Re: Coordination Number

A coordination number is the number of atoms or ions immediately surrounding a central atom in a complex.
Fri Nov 30, 2018 7:33 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 17.33
Replies: 1
Views: 111

### 17.33

Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center: (a) HN(CH2CH2NH2)2; (b) CO3 2; (c) H2O;(d) oxalate.
What does 'polydentate' mean?
Sun Nov 18, 2018 3:15 pm
Forum: Resonance Structures
Topic: Polar
Replies: 8
Views: 496

### Re: Polar

polarity shouldn't affect the resonance structure, focus on the formal charge when determining resonance.
Sun Nov 18, 2018 3:13 pm
Forum: Sigma & Pi Bonds
Topic: Amount of sigma bonds
Replies: 6
Views: 517

### Re: Amount of sigma bonds

a single bond is representative of one sigma bond; a double bond is representative of a sigma bond and a pi bond; a triple bond is representative of one sigma and two pi bonds.
Sun Nov 18, 2018 3:09 pm
Forum: Lewis Structures
Topic: Polar vs Nonpolar molecules
Replies: 7
Views: 382

### Re: Polar vs Nonpolar molecules

if the molecule is asymmetric, the bond dipole moments won't "cancel out" and the molecule will have a net dipole moment and the molecule is therefore polar, but if the molecule is symmetric, dipole moments will usually cancel out. hope this helps.
Sat Nov 10, 2018 12:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Naming the shape
Replies: 6
Views: 360

### Re: Naming the shape

There are images online that are seriously helpful in identifying the different shapes, I use them all the time to make sure I'm doing it right.
Sat Nov 10, 2018 12:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity and Molecular Shape
Replies: 1
Views: 165

### Polarity and Molecular Shape

How does polarity affect the molecular shape of molecules? Does it change their VSEPR model at all?
Sat Nov 10, 2018 12:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape
Replies: 2
Views: 129

### Molecular Shape

When we draw molecules with more than one lone pair around the central atom, how do we depict that that is a trigonal planar or a tetrahedral since its not as obvious as those with atoms attached?
Fri Nov 02, 2018 11:30 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum Numbers related to Orbitals
Replies: 4
Views: 183

### Re: Quantum Numbers related to Orbitals

I don't think it matters whether you make it positive or negative as long as you don't use the same four quantum numbers for two different elements.
Fri Nov 02, 2018 11:28 am
Forum: Properties of Electrons
Topic: De Broglie Formula vs. Speed of Light Formula
Replies: 5
Views: 409

### Re: De Broglie Formula vs. Speed of Light Formula

the speed of light formula is only used on wavelengths in the electromagnetic radiation spectrum, you can't use it when particle has mass (you have to use de broglie for that).
Fri Nov 02, 2018 11:27 am
Forum: Ionic & Covalent Bonds
Topic: Dipole
Replies: 4
Views: 130

### Re: Dipole

I think one will always be at least slightly more electronegative than the other; if they're the same element (like N2) then there wouldn't be any dipole moments because they would have equal electronegativity, i'm not totally sure though.
Wed Oct 24, 2018 7:16 pm
Forum: Properties of Electrons
Topic: Degeneracy
Replies: 11
Views: 616

### Re: Degeneracy

do you have any other examples that might make it a bit more clear? thanks so much.
Wed Oct 24, 2018 7:15 pm
Forum: Properties of Light
Topic: Quantum Test
Replies: 11
Views: 587

### Re: Quantum Test

Review his notes a couple times because he talks about everything during class, and then I do practice problems from the book because it exposes you to different ways he might ask a question on the exam. Good luck!
Wed Oct 24, 2018 7:14 pm
Forum: Quantum Numbers and The H-Atom
Topic: spin
Replies: 4
Views: 170

### Re: spin

I think so. I don't think it matters too much as long as you don't assign the same four quantum numbers to any two elements.
Wed Oct 24, 2018 7:12 pm
Forum: Sigma & Pi Bonds
Topic: 3.9 (sixth edition)
Replies: 1
Views: 168

### 3.9 (sixth edition)

Which M2 ions (where M is a metal) are predicted to have the following ground-state electron configurations: (a) [Ar]3d7; (b) [Ar]3d6; (c) [Kr]4d4; (d) [Kr]4d3? Where do you start when you approach this problem?
Fri Oct 19, 2018 6:48 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Delta x
Replies: 2
Views: 60

### Re: Delta x

I think it has something to do with the particle in the box analogy, like the electron has to be found somewhere inside this diameter which is the box. I'm not sure though.
Fri Oct 19, 2018 6:46 pm
Forum: Properties of Light
Topic: Atomic Spectrum Module #27
Replies: 1
Views: 99

### Atomic Spectrum Module #27

The meter was defined in 1963 as 1,650,763.73 wavelengths of radiation emitted by krypton-86 (it has since been redefined). What is the wavelength of this krypton-86 radiation? To what region of the electromagnetic spectrum does this wavelength correspond (i.e. infrared, ultraviolet, x-ray, etc.)? W...
Fri Oct 19, 2018 6:43 pm
Forum: Properties of Light
Topic: Atomic Spectrum Module #28
Replies: 1
Views: 71

### Atomic Spectrum Module #28

In 1.0 s, a 60 W bulb emits 11 J of energy in the form of infrared radiation (heat) of wavelength 1850 nm. What is the energy per photon of light emitted? How many photons of infrared radiation does the lamp generate in 1.0 s?

Thu Oct 11, 2018 10:41 pm
Forum: Properties of Light
Replies: 4
Views: 140

I think he also talked about how it was a theoretical concept used to explain other things? I'm a little unclear about that part.
Thu Oct 11, 2018 10:38 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 2
Views: 92

### Re: Orbitals

do you have to know how to get from l to n to figure that out or is it just something you have to know?
Thu Oct 11, 2018 10:36 pm
Forum: SI Units, Unit Conversions
Topic: Conversion
Replies: 6
Views: 286

### Re: Conversion

The unit joules is equal to kg*m^2*s^-2 but I'm not totally sure how that would work in a conversion.
Thu Oct 11, 2018 10:27 pm
Forum: Photoelectric Effect
Topic: Confused conceptually with photoelectric effect
Replies: 3
Views: 115

### Re: Confused conceptually with photoelectric effect

I think he was just trying to get the fact that the length of the wavelength is inversely related to the frequency of the photons, so long wavelengths didn't have enough energy to allow electrons to escape the metal but short wavelengths had high frequency so they were able to excite the electrons i...
Thu Oct 04, 2018 6:32 pm
Forum: Empirical & Molecular Formulas
Topic: Molecular Formula
Replies: 12
Views: 243

### Re: Molecular Formula

In that question they tell you that the diagram shown is the molecular structure, so I think you could just count out each of the atoms and that would give you the molecular formula. That one confused me too.
Thu Oct 04, 2018 6:29 pm
Forum: Limiting Reactant Calculations
Topic: multiple limiting reactants
Replies: 9
Views: 350

### Re: multiple limiting reactants

I think it can have more than one limiting reactant but the mole ratio has to be the same between them and the quantities used have to have to match that mole ratio, so that both are used up simultaneously. But i'm pretty sure that this is a very hypothetical situation and is not seen in chemical re...
Thu Oct 04, 2018 6:14 pm
Forum: Limiting Reactant Calculations
Topic: Competing Reactions
Replies: 2
Views: 346

### Re: Competing Reactions

I believe that it is a seperate chemical equation that is happening using the same reactants, so they would probably make that distinction in the question. I think what they were trying to get across with the concept of "competing reactions" though is just that the actual yield might be le...
Thu Oct 04, 2018 6:10 pm
Forum: Molarity, Solutions, Dilutions
Topic: Q E27
Replies: 4
Views: 204

### Re: Q E27

If you start off with one molecule of water, you have to divide by Avogadro's number to convert the molecule to moles, and then you can multiply the mole by the molar mass of water to get grams. So you should end up with 2.991 x 10^-23 g/molecule. Does that make sense?