## Search found 51 matches

Fri Mar 16, 2018 2:41 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 16.65 part b
Replies: 1
Views: 135

### Re: 16.65 part b

I'm assuming this is for 15.65 part b. For an endothermic reaction, the activation energy of the forward reaction will be higher than the activation energy of the reverse reaction. For an exothermic reaction, the activation energy of the reverse reaction will be higher than the activation energy of ...
Fri Mar 16, 2018 2:39 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.49
Replies: 2
Views: 175

### Re: 15.49

Intermediates cannot be included in the rate law of the overall reaction.
In Step 2, the rate law is just for that reaction and for that reaction, the concentration of HOBr plays a role in its rate law.
Fri Mar 16, 2018 2:34 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: q under non-constant pressure
Replies: 1
Views: 267

### Re: q under non-constant pressure

It would ultimately be dependant on the question: on which variables they ask us to solve and the given info.
Fri Mar 16, 2018 2:31 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.93.a
Replies: 1
Views: 133

### Re: 14.93.a

The reaction is trying to reach equilibrium. In order to do that, the concentrations must be the same. When the electrode with the higher concentration starts to get reduced, the amount of substance available for reduction decreases. Eventually, this will lead the reaction to equilibrium.
Fri Mar 16, 2018 2:24 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: H2 Cell Potential
Replies: 1
Views: 138

### Re: H2 Cell Potential

In order to define standard potentials of electrodes, we need a reference. Therefore, we defined the standard potential of a hydrogen electrode to be 0 and then used it to define the standard potentials of all other electrodes.
Fri Mar 16, 2018 2:19 am
Forum: First Order Reactions
Topic: integrated rate
Replies: 1
Views: 242

### Re: integrated rate

An Integrated Rate Law gives the concentration of reactants or products after a reaction begins.
Fri Mar 16, 2018 2:17 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic vs Concentration Cells
Replies: 1
Views: 130

### Re: Galvanic vs Concentration Cells

A Concentration Cell is an example of a Galvanic Cell.
Thu Mar 15, 2018 12:05 am
Forum: Balancing Redox Reactions
Topic: 14. 93 a
Replies: 1
Views: 143

### Re: 14. 93 a

Reduction means that a given substance is gaining electrons, thus becoming more neutral. This would cause the amount of the substance available at the electrode to decrease, thus lowering the concentration. Since the reaction is trying to achieve equilibrium, the reduction would occur at the electro...
Wed Mar 14, 2018 11:46 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: electro motive force
Replies: 1
Views: 139

### Re: electro motive force

Electromotive Force is another name for the cell potential. The cell potential is at its maximum when the pushing power of the cell is balanced against an external matching source of potential.
Wed Mar 14, 2018 11:37 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: endothermic reaction.
Replies: 5
Views: 356

### Re: endothermic reaction.

In an endothermic reaction, the activation energy barrier is higher for the forward reaction than the reverse reaction.
Wed Mar 14, 2018 11:36 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 16.65
Replies: 1
Views: 126

### Re: 16.65

In an endothermic reaction, the activation energy of the forward reaction would be higher than the activation energy of the reverse reaction.

In an exothermic reaction, the activation energy of the reverse reaction would be higher than the activation energy of the forward reaction.
Wed Mar 14, 2018 10:44 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: isolated system after time
Replies: 2
Views: 290

### Re: isolated system after time

The change in internal energy would be zero for it is an isolated system.
Wed Mar 14, 2018 10:17 pm
Forum: General Rate Laws
Topic: rate law vs integrated rate law
Replies: 2
Views: 723

### Re: rate law vs integrated rate law

Rate Law is an expression that gives the reaction rate in terms of the concentration of species at any time.

An Integrated Rate Law gives the concentration at any time after the start of the reaction.
Sun Mar 11, 2018 11:42 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Collision Theory
Replies: 3
Views: 241

### Re: Collision Theory

In a chemical reaction, we need to break or form bonds. If we look at the gases, we need molecules to meet (or collide) in order to break/ form new bonds. Hense, we have the collision theory. Two factors that affect the whether bonds are broken or formed within a collision are relative speed and kin...
Sun Mar 11, 2018 11:34 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Heterogeneous vs Homogeneous
Replies: 1
Views: 93

### Re: Heterogeneous vs Homogeneous

A homogeneous catalyst is a catalyst that is the same phase as the reactants. For example, if the reactants in a reaction are composed of gases and the catalyst is also a gas, then the catalyst is classified as a homogeneous catalyst. A heterogeneous catalyst is a catalyst that is present in a diffe...
Sun Mar 11, 2018 11:32 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 3
Views: 203

### Re: Catalysts

A catalyst operates by lowering the activation energy of a certain reaction. Therefore, it affects the overall rate of the reaction. It does not, however, affect the equilibrium composition. Both the forward and reverse reactions are accelerated due to the catalyzed path. Therefore the equilibrium c...
Sun Mar 04, 2018 11:52 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.23 c) HW
Replies: 2
Views: 153

### Re: 15.23 c) HW

Oh and here is 15.3, To calculate the unique rate of formation for the reaction with reactants aA and bB and cC and dD, where a,b,c, and d are coefficients, calculate one the following -1/a * delta [A]/delta t. (both a and A can be switched to b and B or c and C respectively) the formula is on page ...
Sun Mar 04, 2018 11:50 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.23 c) HW
Replies: 2
Views: 153

### Re: 15.23 c) HW

I'm not sure if you are referring to 15.23 or 15.3, but here is 15.23. In order to find the rate constant, we will use the formula ln( \frac{[A][sub]0]}{[A][sub]t]} ) =kt, and solve for k. We know the initial concentration of A, but we need to find the concentration of A at time 115s. This final con...
Sun Mar 04, 2018 11:30 pm
Forum: First Order Reactions
Topic: 15.23 c
Replies: 2
Views: 213

### Re: 15.23 c

We know that two moles of A are consumed to produce 1 mole of B. Therefore, we can calculate the resulting concentration by multiplying the concentration of B by two. Since we are given the initial concentration of A, the concentration of A at time t, would be the initial concentration minus the res...
Sun Feb 11, 2018 9:04 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: H2(g) --> H2(g) Entropy
Replies: 1
Views: 149

### Re: H2(g) --> H2(g) Entropy

The Molar Entropy of H2(g) is 130.68 Joules(K-1)(mol-1).

Gibbs Free Energy of Formation is 0 kilojoules per mol.
Sun Feb 11, 2018 8:50 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: When does C = 5/2 R or 6/2 R?
Replies: 2
Views: 194

### Re: When does C = 5/2 R or 6/2 R?

C=5/2 R when you are dealing with an ideal gas that has linear molecules.
C=3R when you are dealing with an ideal gas that has non-linear molecules.
Sun Feb 11, 2018 8:48 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Irreversible vs Reversible
Replies: 3
Views: 258

### Re: Irreversible vs Reversible

A reversible process is one that can be reversed by an infinitely small change. For example, assume we have a system where the External Pressure matches the pressure of a gas in the system. In this case, the piston won't move. If we increase or decrease the external pressure by an infinitely small n...
Wed Jan 31, 2018 6:25 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.43
Replies: 5
Views: 196

### Re: 9.43

Appendix 2: Experimental Data of Inorganic Substances. Page A12 (for me) in the textbook. It's also on the formula sheet.
Sun Jan 28, 2018 10:34 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: example 9.2
Replies: 2
Views: 163

### Re: example 9.2

For that example, you would use pressure to calculate moles of the substance. Also, I don't think there was any change in pressure.
Sun Jan 28, 2018 10:30 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13
Replies: 3
Views: 200

### Re: 9.13

As a substance enters gas phase, the molecules are so far apart that their interactions are basically insignificant; their intermolecular interactions are negligible. Therefore under ideal behavior, we can assume that it is one mole of a gas.
Sun Jan 28, 2018 10:10 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.3
Replies: 5
Views: 333

### Re: 9.3

Heat is being transferred from one reservoir to another. In the first one, q is negative for heat is leaving the system. In the second one, q is positive for heat is being supplied to the system.
Sun Jan 21, 2018 10:17 pm
Forum: Phase Changes & Related Calculations
Topic: Carbon as graphite [ENDORSED]
Replies: 7
Views: 484

### Re: Carbon as graphite[ENDORSED]

In 67b, C(gr) means that we are looking at Carbon in graphite form. I'm not too sure on why Carbon is more stable as graphite.
Sun Jan 21, 2018 10:11 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Negative Specific Heat Capacities
Replies: 1
Views: 546

### Re: Negative Specific Heat Capacities

We know that C=q divided by Delta T, where C is the heat capacity, q is the heat supplied, and Delta T is the change in temperature.

If a system loses energy, it can result in a negative delta T, therefore negative heat capacity.
Sun Jan 21, 2018 10:08 pm
Forum: Administrative Questions and Class Announcements
Topic: test week 3
Replies: 1
Views: 143

### Re: test week 3

One way would be:

If a system does -40 J of work and no other transfer of energy took place, what is the value of Delta U?

Question 8.15 is a pretty good example as well.
Sun Jan 14, 2018 9:57 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: molar heat capacity of a gas
Replies: 1
Views: 101

### Re: molar heat capacity of a gas

I think you are referring to C v and C p . C v is the proportionality between the heat supplied to a system and the temperature rise under constant volume and C p is the same thing under constant pressure. Gas can be compressed to create a difference in pressure and volume. Under constant pressure, ...
Sun Jan 14, 2018 9:46 pm
Forum: Phase Changes & Related Calculations
Replies: 5
Views: 337

### Re: Question about Problem 8.41

Yeah. The heat from the water is transferred to the ice.
Sun Jan 14, 2018 9:43 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Units when calculating reaction enthalpy
Replies: 1
Views: 61

### Re: Units when calculating reaction enthalpy

So, Standard Reaction Enthalpy of a reaction (for example, combustion) is often kJ. If they ask you for the Reaction Enthalpy of one mole of a substance, then it is kJ/mol. Standard Enthalpy of Formation is always kJ/mol.
Sat Dec 09, 2017 10:41 pm
Forum: Quantum Numbers and The H-Atom
Topic: Spin Quantum Number: Test 3
Replies: 3
Views: 312

### Re: Spin Quantum Number: Test 3

Technically, the first electron can either spin up or spin down. There's no way of identifying which comes first. When drawing the orbital diagram, we typically start off with spin up. We could start with spin down on the orbital diagram and it diagram would follow Pauli's exclusion principle and Hu...
Sat Dec 09, 2017 10:31 pm
Forum: Electronegativity
Topic: Carbon and Sulfur electronegativity?
Replies: 4
Views: 4631

### Re: Carbon and Sulfur electronegativity?

One way of identifying which element is more electronegative is by looking at which element is the closest to Fluorine. In this case, it is Sulfur.
Sat Dec 02, 2017 8:23 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted Acid and Base Reaction
Replies: 2
Views: 250

### Re: Bronsted Acid and Base Reaction

A Bronsted Acid is a proton donor and a Bronsted Base is a proton acceptor.

A proton in these definitions refers to the hydrogen ion.

So if a reaction involves the transfer of a proton, then the reaction could be classified as a Bronsted Acid and Base Reaction.
Sat Dec 02, 2017 8:09 pm
Forum: Bronsted Acids & Bases
Topic: Lewis Acids and Bases Vs. Bronsted Acids and Bases
Replies: 4
Views: 334

### Re: Lewis Acids and Bases Vs. Bronsted Acids and Bases

So a Bronsted acid is a proton donor and a Bronsted base is a proton acceptor. A Lewis acid is an electron pair acceptor and a Lewis base is an electron pair donor. On pg. 467 in TB, it says: "In the Lewis theory, the proton is an acid; in the Bronsted theory, the species that supplies the prot...
Sat Nov 25, 2017 8:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium
Replies: 2
Views: 145

### Re: Equilibrium

The reactants don't completely react with each other and form products because the products are also reacting and decomposing into their "reactants." The rate of both reactions are the same, therefore there is no net change. If we were to alter the temperature, pressure or the concentratio...
Sat Nov 25, 2017 8:18 pm
Forum: Naming
Topic: Finding Coordination Number
Replies: 6
Views: 455

### Re: Finding Coordination Number

Coordination number is the number of bonds in a coordination sphere.
Sat Nov 25, 2017 8:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ch 11 #47
Replies: 1
Views: 136

### Re: Ch 11 #47

Since, x=.01 M, the final concentration at Equilibrium for PCl 5 is .009 M. This means that .01M of PCl 5 has decomposed. Initial Concentration- Final Concentration= Concentration decomposed (.019M) - (.009 M) = .010M Therefore, it would be .01M divided by .019M (Concentration decomposed Divided by ...
Sat Nov 25, 2017 8:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Problem 11.47
Replies: 1
Views: 191

### Re: Textbook Problem 11.47

For part a for 11.47 I got x=.01 mol per Liter. For part b, the question is asking what percentage of the PCL 5 has decomposed at equilibrium. Since x=.01 mol per Liter, we know that at equilibrium the concentration of PCl 5 is .009 mol per Liter. That means .01 M of PCl 5 has decomposed. .01 M divi...
Sat Nov 25, 2017 7:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Equitorial vs. Axial Lone Pair
Replies: 2
Views: 347

### Re: Equitorial vs. Axial Lone Pair

I believe it depends on the molecule. For example, IF 4 + has an VSEPR Formula for AX 4 E. The shape is trigonal bipyramidal and there are two possible locations for the lone pair. If the lone pair takes the axial position, then it would strongly repel the electron pairs in the three equatorial posi...
Tue Nov 07, 2017 8:03 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Trends of Polarizing Power
Replies: 4
Views: 7118

### Re: Trends of Polarizing Power

Atoms and ions are considered polarizable if they readily undergo a large distortion with their electron clouds. An anion is said to be highly polarizable if it is large. In the large anion, the nucleus exerts a weak force on the electrons in the outermost shell. So, the electron cloud can become ea...
Tue Nov 07, 2017 7:49 pm
Forum: Ionic & Covalent Bonds
Topic: Homework 3.39
Replies: 3
Views: 262

### Re: Homework 3.39

I'm pretty sure he is going to give us the chemical formulas during the exam. However, he might expect us to know the formulas for common compounds such as water and carbon dioxide.
Sat Nov 04, 2017 10:45 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Aufbau principle
Replies: 4
Views: 370

### Re: Aufbau principle

They're related. Pauli's Exclusion Principle and Hund's Rule deals with the arrangement of electrons within an orbital. Aufbau's Principle deals with the arrangement of the orbitals (which orbitals are filled first).
Sat Nov 04, 2017 10:40 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Replies: 2
Views: 246

### Re: Position: Radius vs. Diameter

Yes. The uncertainty in the position pertains to the diameter. The radius would only cover half of the distance of the atom and the electron could be in the other half.
Sat Oct 28, 2017 11:43 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Removing an Electron [ENDORSED]
Replies: 5
Views: 440

### Re: Removing an Electron[ENDORSED]

Yep. The electrons in the outer shell (valence electrons) are the ones that will be removed. The outer most shell is the last part of the electron configuration.
Sat Oct 28, 2017 11:35 pm
Forum: Properties of Light
Topic: The uncertainty principle [ENDORSED]
Replies: 5
Views: 528

### Re: The uncertainty principle[ENDORSED]

Certain forces have more of an influence on subatomic particles than a larger object. For example, if a photon were to hit both an electron and a basketball, the impact of the photon would greatly influence an electron and would have basically no effect on the basketball. The uncertainties of large ...
Sat Oct 21, 2017 10:38 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electric Spin
Replies: 5
Views: 302

### Re: Electric Spin

Does that mean that when doing configurations it doesn't matter if we choose clockwise or counterclockwise spin for single electrons? Or is there a preference? Usually, you fill the electron configurations by starting with "spin up." However, you can also start with "spin down" ...
Sat Oct 21, 2017 10:29 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Principle Quantum Number [ENDORSED]
Replies: 3
Views: 243

### Re: Principle Quantum Number[ENDORSED]

Hey,

The principal quantum number is one of the four quantum number often denoted as n. The principal quantum number is used to describe the energy and size (shell).
Fri Oct 13, 2017 9:25 pm
Forum: Properties of Light
Topic: Balmer vs Lyman Series [ENDORSED]
Replies: 3
Views: 313

### Re: Balmer vs Lyman Series[ENDORSED]

The Balmer Series corresponds to the visible light section of the spectrum and the Lyman Series corresponds to the Ultraviolet section of the spectrum. Lyman Series: When an electron travels from any energy level to the energy level of 1 (i.e, n=3 to n=1, n=10 to n=1), the electron emits energy with...
Fri Oct 13, 2017 9:16 pm
Forum: Properties of Light
Topic: Rydberg's Formula
Replies: 3
Views: 474

### Re: Rydberg's Formula

We use the formula with the negative to calculate ΔE. For example, if we were to calculate the energy emitted from an electron from the energy level of 4 to an energy level of 2, ΔE would be negative. However, if we were to use the formula with the negative to calculate the energy absorbed from a ph...