## Search found 66 matches

Fri Mar 16, 2018 12:57 pm
Forum: Experimental Details
Topic: Rate Unit Conversion
Replies: 4
Views: 438

### Re: Rate Unit Conversion

It will vary from question to question. sometimes the question will specify which units it wants it in. sometimes you can just leave it in the units they give you to begin with.
Fri Mar 16, 2018 12:54 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: Homework Problem 9.25
Replies: 1
Views: 232

### Re: Homework Problem 9.25

you can make 1.38 x 10^-23 ln(6^6.02 x 10^23) into (1.38 x 10^-23)(6.02 x 10^23) ln(6) because properties of ln. basically if theres an exponent like ln3^2 you can bring the exponent down and multiply it so it becomes 2 x ln3.
Fri Mar 16, 2018 12:50 pm
Forum: *Alkanes
Topic: Final
Replies: 13
Views: 1134

### Re: Final

Yes, but only to the extent of which he went over in class so probably just identifying functional groups and stuff like that
Sat Mar 10, 2018 12:14 pm
Forum: General Rate Laws
Topic: Fractional Rate Law [ENDORSED]
Replies: 4
Views: 191

### Re: Fractional Rate Law[ENDORSED]

I believe that you would add the exponents together 2+(-1)=1
Sat Mar 10, 2018 12:02 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: reactant concentration [ENDORSED]
Replies: 4
Views: 193

### Re: reactant concentration[ENDORSED]

I'm not sure, but I believe it's like the analogy he gives when you have a million dollars and you give away a dollar but you would just say you still have a million dollars. So if you have a large concentration you can just say it's "constant."
Sat Mar 10, 2018 11:58 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Transition States [ENDORSED]
Replies: 2
Views: 83

### Re: Transition States[ENDORSED]

Yes because they are more unstable
Wed Feb 28, 2018 12:11 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Rate constant
Replies: 2
Views: 124

### Re: Rate constant

to add on, the rate constant depends on the energy barrier and temperature while I believe the equilibrium constant depends on concentration
Wed Feb 28, 2018 12:07 pm
Forum: General Rate Laws
Topic: Negative 1/a
Replies: 8
Views: 305

### Re: Negative 1/a

Since products is decreasing, the slope will be negative when you take the tangent to the curve. (that means that the slope of the products is positive because products is increasing)
Wed Feb 28, 2018 11:56 am
Forum: First Order Reactions
Topic: Derivation
Replies: 8
Views: 300

### Re: Derivation

He probably won't but there's always a small chance that he might incorporate it in a question.
Fri Feb 23, 2018 4:54 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Spontaneous Directions [ENDORSED]
Replies: 7
Views: 248

### Re: Spontaneous Directions[ENDORSED]

Because of the equation deltaG= -nFE, E (standard reduction potential) must be positive in order for the reaction to be spontaneous. When E is positive, deltaG is negative (when deltaG is negative the reaction is spontaneous).
Fri Feb 23, 2018 3:55 pm
Forum: Balancing Redox Reactions
Topic: Identifying Oxi/Red Agents [ENDORSED]
Replies: 6
Views: 316

### Re: Identifying Oxi/Red Agents[ENDORSED]

the whole thing S2O3 2- is the reducing agent or is oxidized
Fri Feb 23, 2018 3:50 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cells
Replies: 5
Views: 200

### Re: Galvanic Cells

yes, because they're spontaneous
Tue Feb 13, 2018 8:34 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta G for Phase Changes
Replies: 1
Views: 121

### Re: delta G for Phase Changes

I believe that at phase changes, it is at equilibrium. And at equilibrium deltaG=0
Tue Feb 13, 2018 8:32 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Winter 2011 Midterm #1
Replies: 2
Views: 306

### Re: Winter 2011 Midterm #1

In calorimeter problems you use the equation q=C(calorimeter)deltaT because C ,or heat capacity, is different for every calorimeter
Tue Feb 13, 2018 8:29 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cp or Cv in temperature change
Replies: 3
Views: 329

### Re: Cp or Cv in temperature change

When there are two variables changing like Temperature and Pressure, you would hold the other constant when solving for Delta S when theres change in temp (using equation deltaS=nCpln(T2/T1)
If the two variables are Temperature and Volume you would use the equation deltaS=nCvln(T2/T1)
Sat Feb 10, 2018 11:32 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: closed vs isolated
Replies: 11
Views: 533

### Re: closed vs isolated

I don't think they are unless it says otherwise. I do know that if it's a bomb calorimeter volume stays constant
Wed Feb 07, 2018 5:40 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
Replies: 2
Views: 117

### 9.25

since the question doesn't give you the amount of molecules, do you just assume that it's avogadro's constant?
Wed Feb 07, 2018 5:04 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.19
Replies: 1
Views: 88

### 9.19

How come for the 3rd step you have to cool the water back to 85 degrees Celsius? Will it always be like that for all questions like this one?
Sun Feb 04, 2018 3:46 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: How do we find out if a system is favorable? [ENDORSED]
Replies: 7
Views: 1725

### Re: How do we find out if a system is favorable?[ENDORSED]

A system is favorable when it is spontaneous. Spontaneity depends on wether deltaG is negative (giving off heat) or positive (requiring heat).
Sun Feb 04, 2018 3:45 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Deriving Equations
Replies: 2
Views: 102

### Re: Deriving Equations

I'm not 100% about this but in my discussion someone said that we won't need to know how to derive equations on our tests, but they are fair game on the midterm/final. I'm thinking that they may be conceptual questions? I'm pretty sure he wouldn't make us derive it.
Sun Feb 04, 2018 3:43 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible systems
Replies: 7
Views: 284

### Re: Reversible systems

Yes since both change in volume and change in pressure increase entropy, you would would calculate the entropy from volume and pressure, then add them together.
Tue Jan 23, 2018 11:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.73 part C
Replies: 3
Views: 135

### Re: 8.73 part C

the reaction enthalpy of the whole equation is the bond enthalpy of reactants - bond enthalpy of products. This is because breaking bonds is endothermic (+) and requires energy while forming bonds releases energy and is exothermic (-). For me, I draw out the lewis structures and count how many diffe...
Tue Jan 23, 2018 11:08 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.25
Replies: 1
Views: 102

### Re: 8.25

The first part of the question gives you enough information to find the heat capacity of the calorimeter which is -0.478 KJ/C. This information is needed for the second part of the question (use the equation deltaU=CdeltaT) Since it's a constant volume calorimeter, there is no change in volume and s...
Tue Jan 23, 2018 10:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Assuming Temperature
Replies: 3
Views: 118

### Re: Assuming Temperature

I'm pretty sure if the temperature isn't given you assume its standard temp which is 25 degrees C aka 298K
Fri Jan 19, 2018 4:58 pm
Forum: Phase Changes & Related Calculations
Topic: 8.23
Replies: 5
Views: 361

### 8.23

I'm not sure if this question would go under this topic but how come the question uses the formula q=CdealtT? I thought that the equation is q=mCdeltaT?
Wed Jan 17, 2018 11:21 pm
Forum: Calculating Work of Expansion
Topic: 8.3 Homework
Replies: 4
Views: 211

### Re: 8.3 Homework

In chemistry, work is negative when it is done by the system. When work is done on the system it is positive. (In physics it is the opposite) So since work is being on the system (air) it is positive.
Wed Jan 17, 2018 11:17 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: U and H
Replies: 3
Views: 181

### Re: U and H

deltaU is the change in internal energy. deltaH is the change in enthalpy. Enthalpy is the amount of heat released at constant pressure. So the change in internal energy equals the change in enthalpy minus the product of pressure times change in volume.
Fri Jan 12, 2018 8:54 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Specific Heat Capacity vs Heat Capacity
Replies: 5
Views: 233

### Re: Specific Heat Capacity vs Heat Capacity

Heat capacity is the amount of heat required to raise the temperature of an object by 1 degrees Celsius. However, the amount of heat required depends on the amount of substance. This means that heat capacity is an extensive property and would change based on how much of the substance you have. Speci...
Fri Jan 12, 2018 8:49 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 8.1 part c [ENDORSED]
Replies: 8
Views: 416

### Re: 8.1 part c[ENDORSED]

A bomb calorimeter would be an isolated system because it has no contact with its surroundings. It can't release energy or mass and the outside also doesn't affect the system.
Fri Jan 12, 2018 8:47 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Type of system for mercury in thermometer
Replies: 5
Views: 336

### Re: Type of system for mercury in thermometer

It would be a closed system because the mass (mercury) is fixed but it can still exchange energy with its surroundings
Sat Dec 09, 2017 10:20 pm
Forum: Photoelectric Effect
Topic: nm to m
Replies: 4
Views: 230

### Re: nm to m

When given the wavelength in nm, how do we convert it to m?
the conversion is 1 nm= 1x10^-9 m. So if you're given 1nm you multiply 1nm by (1m / 1x10^9nm). Or, you can do 1nm x 1x10^-9 m/nm. basically you want to cancel out nm to get m
Sat Dec 09, 2017 10:03 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Question in adding H20 in equilibrium reaction
Replies: 2
Views: 298

### Re: Question in adding H20 in equilibrium reaction

i think it's because C6H12O6(aq) is aqueous which means it's dissolved in water and adding water would change the concentration, changing the equilibrium constant
Sat Dec 09, 2017 9:59 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Adding Water
Replies: 2
Views: 244

### Re: Adding Water

I'm not entirely sure, but to my understanding if products and reactants are aqueous then they are dissolved in water. So adding water would affect the concentration of products and reactants that are aqueous
Sat Dec 09, 2017 9:55 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Last Minute question
Replies: 2
Views: 176

### Re: Last Minute question

No I'm pretty they won't be
Fri Dec 08, 2017 11:35 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pKa and Ka
Replies: 3
Views: 302

### pKa and Ka

The smaller the pKa, the stronger the acid. Does this also mean the smaller the Ka, the stronger the acid?
Fri Dec 08, 2017 10:11 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Pd electron configuration
Replies: 2
Views: 279

### Re: Pd electron configuration

We didn't learn it in class but I'm pretty sure that's just another exception you just have to memorize (since it doesn't apply to Ni which should be in the same situation but is not an exception)
Fri Dec 08, 2017 8:53 pm
Forum: Properties of Light
Topic: Atomic Spectra
Replies: 1
Views: 147

### Re: Atomic Spectra

I'm not sure what your question is, but because it says "in the ultraviolet spectrum of atomic hydrogen" that refers to the Lynman series where n=1. Then you can convert the wavelength (102.6 nm) to energy and find the n final value. (I think) since energy is positive, you know that it's g...
Fri Dec 08, 2017 11:20 am
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: Base Strength
Replies: 2
Views: 277

### Re: Base Strength

I think you can look at its conjugate acid. If its conjugate acid is weaker then the base if stronger. So if you had two bases, look at both its conjugate acids and whichever conjugate acid is weaker, that base is stronger.
Tue Dec 05, 2017 11:59 pm
Forum: Lewis Acids & Bases
Topic: 12.53
Replies: 2
Views: 184

### 12.53

The question is "suggest an explanation for the different strengths of (a) acetic acid and trichloroacetic acid; (b) acetic acid and formic acid."
Will we need to memorize what acetic acid and all the other acids are?
Tue Dec 05, 2017 11:58 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted Acids and Bases versus Lewis Acids and Bases
Replies: 3
Views: 271

### Re: Bronsted Acids and Bases versus Lewis Acids and Bases

The difference between the two definitions are- Bronsted acid: donates a proton Bronsted base: accepts a proton Lewis acid: species that accepts an electron pair Lewis base: species that donates an elctrion pair The bronsted definition is more strict and while the lewis definition is more general. T...
Tue Dec 05, 2017 11:39 pm
Forum: Hybridization
Topic: sp3 hybridization
Replies: 6
Views: 346

### Re: sp3 hybridization

It's based on how many areas of electron density there are. So since trigonal planar are 3 areas of electron density it would be sp2, seesaw has 5 areas of electron density and would be sp3d
Tue Dec 05, 2017 4:09 pm
Forum: Naming
Topic: Determining Linking Atom
Replies: 2
Views: 110

### Re: Determining Linking Atom

I'm pretty sure he will always make it clear which atom is linked. Otherwise, I'm not sure.
Tue Dec 05, 2017 4:08 pm
Forum: Bronsted Acids & Bases
Topic: J.11 part c
Replies: 1
Views: 108

### Re: J.11 part c

Since the HI is donating its H, a proton, you know that's the acid. I'm pretty sure when you talk about acids you're referring to the hydronium ion (H+) so that's another reason why I would think HI is the acid.
Tue Dec 05, 2017 10:23 am
Forum: Lewis Acids & Bases
Topic: Memorizing Acids and Bases
Replies: 7
Views: 332

### Re: Memorizing Acids and Bases

We will need to memorize which acids and bases are strong. I would assume other bases and acids that aren't "strong" are weak
Tue Dec 05, 2017 10:21 am
Forum: Lewis Acids & Bases
Topic: Writing equations with acids and bases
Replies: 5
Views: 216

### Re: Writing equations with acids and bases

Yeah we'll need to memorize which acids and bases are strong
Tue Dec 05, 2017 10:18 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: 12.57
Replies: 3
Views: 210

### Re: 12.57

Since the sigfigs in the question is all 2 or 4, i assume that your answer would be correct. I'm assuming it's just an error in the solution manual.
Mon Dec 04, 2017 11:00 pm
Forum: Conjugate Acids & Bases
Topic: HW 12.7
Replies: 3
Views: 190

### Re: HW 12.7

I'm pretty sure you just have to look it up/memorize the name because there's no other way to really figure it out.
Thu Nov 30, 2017 9:23 am
Forum: Naming
Topic: Order of Ligands
Replies: 8
Views: 362

### Order of Ligands

When you're writing, for example in 17.31, Na [Fe (OH2)2 (C2O4)2] does it matter if (C2O4)2 is written before (OH2)2 or is also alphabetical?
Thu Nov 30, 2017 9:16 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changes in K
Replies: 4
Views: 198

### Re: Changes in K

Yes. K is the equilibrium constant (or reaction quotient at equilibrium) which is unaffected by changes in concentration. Q is the reaction quotient at anytime.
Thu Nov 30, 2017 9:14 am
Forum: Ideal Gases
Topic: Temperature in PV=nRT
Replies: 9
Views: 521

### Re: Temperature in PV=nRT

Temperature is in Kelvin (K)
Sat Nov 25, 2017 2:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles
Replies: 1
Views: 89

### Bond angles

does "bond angle" refer to the angle between a bonded molecule and the angle between an electron pair and a bonded molecule (or an electron pair and an electron pair) ?
Sat Nov 25, 2017 2:29 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs vs. Bonding Pairs
Replies: 6
Views: 313

### Re: Lone Pairs vs. Bonding Pairs

Lone electrons take up more space so it has greater repulsion
Tue Nov 21, 2017 10:00 pm
Forum: Ideal Gases
Topic: R in PV=nRT [ENDORSED]
Replies: 7
Views: 385

### Re: R in PV=nRT[ENDORSED]

R is the ideal gas constant and R= 0.08206 (L atm)/(K mol)
Tue Nov 21, 2017 9:54 pm
Forum: Naming
Topic: Naming
Replies: 1
Views: 97

### Re: Naming

yes
Tue Nov 21, 2017 2:56 pm
Forum: Naming
Topic: Ligand Names
Replies: 6
Views: 239

### Re: Ligand Names

I don't think we would since he never said anything about memorizing them. For the midterm we didn't and I'm assuming we won't need to know for the final but I'm not 100% sure.
Mon Nov 20, 2017 4:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Question 4.13 a
Replies: 3
Views: 177

### Re: Question 4.13 a

if you check VESPR theory diagrams online you can see that if the VESPR notation is AX2E3 (or if it has 2 bonds and 3 lone pairs), the shape is linear.
this is the diagram I'm referring to. http://mrbeckschemistry.weebly.com/uplo ... 79.png?464
Thu Nov 09, 2017 10:41 am
Forum: Limiting Reactant Calculations
Topic: Two-step reactions [ENDORSED]
Replies: 2
Views: 231

### Re: Two-step reactions[ENDORSED]

If they give you the amount of the reactants in equation 1, you find the limiting reactant of that equation and calculate how much product is created. Then you use the amount of product, found in equation 1, in the second equation. Many times the excess reactant in step 1 is used in step 2, so now y...
Sun Nov 05, 2017 7:56 pm
Forum: Octet Exceptions
Topic: Expanded Octet Max
Replies: 2
Views: 192

### Re: Expanded Octet Max

There's not necessarily a max expanded octet but it can go very high like in Cl04^- the Cl has 7 bonds. If you continue doing more problems you'll get more intuition for drawing Lewis structures. You can try drawing the Lewis structures according to formal charge to make the central atom's formal ch...
Fri Nov 03, 2017 2:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Formal Charge
Replies: 1
Views: 109

### Re: Formal Charge

yes the most stable structure is when the central atom has a formal charge of 0
Sun Oct 29, 2017 10:42 pm
Forum: Trends in The Periodic Table
Topic: Electron affinity versus ionization energy [ENDORSED]
Replies: 3
Views: 218

### Re: Electron affinity versus ionization energy[ENDORSED]

Electron affinity and ionization are different. Ionization energy is the energy NEEDED to remove an electron from an atom in the gas state while electron affinity is the energy RELEASED when an election is added to a gas-phase atom. Ionization energy increases up and to the right because the smaller...
Sun Oct 29, 2017 1:53 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.81
Replies: 1
Views: 123

### 2.81

Can someone explain why the ionization energy for oxygen would be lower than that of nitrogen or fluorine?
Wed Oct 18, 2017 9:03 pm
Forum: DeBroglie Equation
Topic: De Broglie's and Photoelectric Effect
Replies: 2
Views: 172

### Re: De Broglie's and Photoelectric Effect

You use DeBroglie's equation in part a when finding the wavelength of the ejected electron You would use the kinetic energy formula in part C to help you find the energy of the photon. E(photon) - threshold energy = E(kinetic) You plug in mass of an election and the velocity into the kinetic energy ...
Sat Oct 14, 2017 9:05 pm
Forum: Properties of Light
Topic: 1.15 [ENDORSED]
Replies: 2
Views: 204

### 1.15[ENDORSED]

Why does n=1? Do you just always assume of not given that the initial energy is n=1?
Thu Oct 12, 2017 11:41 pm
Forum: Properties of Light
Topic: Speed of Light Constant
Replies: 18
Views: 687

### Re: Speed of Light Constant

I would use 2.998x10^8 to be more accurate but when you round it probably won't make a big difference. Also on the test I'm sure they'll give us the constants they'd want us to use.
Thu Oct 05, 2017 8:06 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E.15 [ENDORSED]
Replies: 10
Views: 677

### Re: E.15[ENDORSED]

when they say that the molar mass of M(OH)2 is 74.10gmol-1 they're giving you two known elements O and H and one unknown M. To find what M is you subtract the molar mass of M(OH)2 by the molar mass of (OH)2. What you're left is the molar mass of M. You can then match that number with an element on t...
Thu Oct 05, 2017 7:30 pm
Forum: Limiting Reactant Calculations
Topic: Avogadros Number
Replies: 6
Views: 736

### Re: Avogadros Number

Avogadro's number is 6.022x10^23. A mole is a unit used to describe an amount of chemical substances (like a mole of Carbon or a mole of H20). 1 mole = 6.022x10^23. Moles is comparable to using the world "dozen" which means 12. If I say I have two dozen eggs I would have 24 eggs. If I say ...

Go to advanced search