Search found 71 matches

by Janine Chan 2K
Thu Mar 15, 2018 10:42 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 16.69: Pre exponential factor in catalysis
Replies: 1
Views: 153

Re: 16.69: Pre exponential factor in catalysis

I think it's just that when doing the problems, we can assume A is the same and that they cancel out, but in real life A is actually different.
by Janine Chan 2K
Thu Mar 15, 2018 10:35 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.17 [ENDORSED]
Replies: 3
Views: 255

Re: 14.17 [ENDORSED]

David Zhou 1L wrote:For this though, couldn't the Fe be oxidized into Fe2+? Why does it have to be Fe2+ oxidized into Fe3+?


I believe it's because we have FeCl2 as a reactant, which would imply the iron on the reactants side must be Fe2+.
by Janine Chan 2K
Thu Mar 15, 2018 10:33 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: 14.55
Replies: 3
Views: 538

Re: 14.55

The +1.23 volts is for the oxidation reaction. The standard reduction potential is actually -1.23 V so the solution manual is correct. And you want to get the most negative value of E because in an electrolytic cell, the reaction is non spontaneous. Thanks, I see what you mean. But if the +1.23 vol...
by Janine Chan 2K
Thu Mar 15, 2018 9:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.91
Replies: 1
Views: 153

Re: 14.91

I was confused at this too, but I think it's asking about more about the salt bridge. The external circuit is where the flow of electrons happens, but we need electrolytes to complete the circuit. Since e- go from anode to cathode, electrolytes will then go from cathode to anode. https://www.chem.wi...
by Janine Chan 2K
Thu Mar 15, 2018 9:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.57
Replies: 1
Views: 211

Re: 8.57

Did you mean standard enthalpy? We aren't able to directly do Hfproducts-Hfreactants because the question gives values for heat of combustion (not formation).
by Janine Chan 2K
Thu Mar 15, 2018 12:38 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.13 c
Replies: 1
Views: 113

Re: 14.13 c

The anode should be written on the left and the cathode should be on the right. In this reaction, Cl2 is being reduced, so the half reaction with Cl2 and Cl- is on the right.
by Janine Chan 2K
Thu Mar 15, 2018 2:35 am
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: 14.55
Replies: 3
Views: 538

14.55

The solution manual states that the cathode should have the least negative E and the anode should have the most negative E. However, it then says that the cathode, which is Ni2+, has a E of -0.23 V while the anode has a E of +1.23 V. Isn't this contradictory? Also, if the point is to make a cell wit...
by Janine Chan 2K
Wed Mar 14, 2018 10:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.17 [ENDORSED]
Replies: 3
Views: 255

14.17 [ENDORSED]

"Write balanced half-reactions for the redox reaction of an acidified solution of potassium permanganate and iron(II) chloride." How do we know to use Fe3+ + e- --> Fe2+ as the half rxn? Why not Fe2+ + 2e- --> Fe or something else?
by Janine Chan 2K
Wed Mar 14, 2018 12:34 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.73 b and 8.75 c
Replies: 1
Views: 129

Re: 8.73 b and 8.75 c

In 8.75c, 4 C-H bonds are still broken. It's just written as 1 in the answer key because it cancels with the 3 C-H bonds formed in CH3Cl in the products.
by Janine Chan 2K
Tue Mar 13, 2018 10:44 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: elementary reaction
Replies: 1
Views: 129

Re: elementary reaction

We can assume the rate law using the coefficients in an elementary reaction only when proposing a reaction mechanism.
by Janine Chan 2K
Tue Mar 13, 2018 10:41 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalyst
Replies: 2
Views: 183

Re: Catalyst

Catalysts increase the rate of reaction by providing a new pathway for the reaction with a lower activation energy.
by Janine Chan 2K
Wed Mar 07, 2018 7:54 pm
Forum: First Order Reactions
Topic: 15.37C
Replies: 5
Views: 635

Re: 15.37C

Nope you're good, if you divide both the initial and final mass by liters to find the concentrations of each, the liters will cancel out when you plug into [A]t=[A]0e-ktanyway.
by Janine Chan 2K
Wed Mar 07, 2018 2:55 pm
Forum: First Order Reactions
Topic: 15.27 C & D
Replies: 1
Views: 157

Re: 15.27 C & D

Since 15% isn't a multiple of 1/2, we have to do more calculations. We first solve for k using the 1st-order equation t 1/2 =0.693/k. If we end up with 15% of the initial concentration, we can say that [A] t =.15, and [A] 0 =1. By rearranging the equation ln[A] t = -kt + ln[A] 0 , we can solve for t...
by Janine Chan 2K
Tue Mar 06, 2018 5:01 pm
Forum: Second Order Reactions
Topic: 15.19 Part C
Replies: 3
Views: 330

Re: 15.19 Part C

So we have rate=k[A][B] 2 [C] 2 . The initial rate is given in units (mmolA)*L -1 *s -1 . Each of the concentrations are given in units mmol*L -1 . When we multiply all the concentrations of reactants together, we end up with units mmol*L -5 . By dividing (mmolA)*L -1 *s -1 by mmol 5 *L -5 to find u...
by Janine Chan 2K
Tue Mar 06, 2018 4:52 pm
Forum: General Rate Laws
Topic: 15.3
Replies: 4
Views: 237

Re: 15.3

I think the reaction rate is always written as positive. In the solutions manual, it makes up for the decreasing concentration by adding a negative sign in the equation (-∆conc/∆time). So, you would just say that the reactant concentration is decreasing at (input rate here).
by Janine Chan 2K
Tue Mar 06, 2018 3:34 pm
Forum: General Rate Laws
Topic: Coefficients affecting order & molecularity
Replies: 2
Views: 136

Coefficients affecting order & molecularity

Are the coefficients of the reactants correlated to the order/rate law of a reaction? Or is the rate law only dependent on the concentrations and rate constant given? I guess in other words, can we determine the order/rate law solely by looking at an equation and the coefficients? For example, in 15...
by Janine Chan 2K
Thu Mar 01, 2018 10:20 am
Forum: General Rate Laws
Topic: 15.9
Replies: 5
Views: 289

Re: 15.9

The reaction rate = ∆concentration of reactants or products/∆time, which would give you units of molarity/time, which is usually mol*L -1 seconds -1 . If you look at the the general equation for the differential rate law, it is rate = k[R] -1 . For example, for a first order reaction, the rate = k[A...
by Janine Chan 2K
Wed Feb 28, 2018 10:17 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.9
Replies: 3
Views: 237

Re: 15.9

So to calculate the reaction rate, we usually do reaction rate = ∆concentration of reactants or products/∆time. This would give you Molarity/Time, which is usually mol*L -1 seconds -1 . If you look at the the general equation for the differential rate law, it is rate = k[R] n . Part a of this questi...
by Janine Chan 2K
Wed Feb 28, 2018 9:34 pm
Forum: First Order Reactions
Topic: 15.15
Replies: 4
Views: 248

Re: 15.15

Doesn't ln[A] vs. time have to be linear to assume it's first order? Or in this case we're just saying that in this question, we can see that multiplying by a factor of 1.2 will increase the rate by a factor of 1.2, which aligns with the first order differential rate law rate = k[A].
by Janine Chan 2K
Thu Feb 22, 2018 11:34 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.57
Replies: 2
Views: 157

Re: 14.57

The values are given to you for pH=7 at the beginning of the problem set!
by Janine Chan 2K
Thu Feb 22, 2018 11:30 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: 14.55 homework
Replies: 1
Views: 270

14.55 homework

In this question, how do we know one of the half reactions should include water?
by Janine Chan 2K
Thu Feb 22, 2018 2:16 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.33b homework
Replies: 3
Views: 242

14.33b homework

Where do we get the equation 3Tl+ --> 2Tl + Tl 3+ from? Wouldn't Tl+ e- --> Tl also be Tl+ "disproportionating" in solution?
by Janine Chan 2K
Wed Feb 21, 2018 9:54 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.15a cell drawing
Replies: 1
Views: 137

14.15a cell drawing

For the anode, why is it written in the order Ag(s)|AgBr(s)|Br-(aq)? Is this because Br- is an ion/aqueous so it's written closest to the salt bridge? If solids are written on the outside, why is Ag(s) written before AgBr? Is this because it's written from reactants to products? But if it's written ...
by Janine Chan 2K
Wed Feb 21, 2018 8:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.13B
Replies: 3
Views: 196

Re: 14.13B

How do we know I2 isn't conducting?
by Janine Chan 2K
Wed Feb 14, 2018 10:11 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: Zero Degeneracy
Replies: 2
Views: 291

Re: Zero Degeneracy

Degeneracy can't be 0, but entropy can be 0 if it's a perfect crystal (aka when W=1 because there is only one state for it to exist in). When W=1, ln(1)=0, making S equal to 0.
by Janine Chan 2K
Wed Feb 14, 2018 9:48 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.101 sign?
Replies: 1
Views: 137

Re: 9.101 sign?

I believe the signs don't change due to the way the question is worded. We don't assign the interior or the exterior to be the "system," so we don't say the ∆S of the "surroundings" is -∆S of the "system." The question simply asks which is greater: the change in entropy...
by Janine Chan 2K
Wed Feb 14, 2018 9:12 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.47 Isothermal Irreversible Free Expansion
Replies: 3
Views: 268

Re: 9.47 Isothermal Irreversible Free Expansion

Since entropy is a state function, the pathway taken from final to initial doesn't matter. ∆Ssys for irreversible and reversible should be the same.
by Janine Chan 2K
Wed Feb 07, 2018 7:13 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.63
Replies: 4
Views: 224

Re: 9.63

In order for decomposition of compounds into their elements to be stable, ∆G of decomposition would have to be (+) aka it won't spontaneously break down. Since decomposition is the opposite of formation, ∆G f would have to be (-). In other words, the formation is spontaneous and the decomposition is...
by Janine Chan 2K
Wed Feb 07, 2018 4:39 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.35 solution manual errors [ENDORSED]
Replies: 1
Views: 95

9.35 solution manual errors [ENDORSED]

In the solution manual error doc, a different value of Cv is used for each gas. Why is this?
by Janine Chan 2K
Tue Feb 06, 2018 9:44 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: How to approach 9.53
Replies: 1
Views: 260

Re: How to approach 9.53

Yes, we are supposed to use the equation ∆G = ∆Hvap - T∆Svap. We use the vaporation values because NH3 is going from a liquid to a gas.
by Janine Chan 2K
Tue Feb 06, 2018 9:42 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13
Replies: 6
Views: 303

Re: 9.13

The solution manual error says Cv but uses 5/2 R, which is the value for Cp. Maybe the doc has a typo too?
by Janine Chan 2K
Tue Feb 06, 2018 12:01 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.25
Replies: 5
Views: 276

Re: 9.25

There are 6 different states the molecule can exist in (you can switch the Os and the Fs around the S atom 6 different ways).
by Janine Chan 2K
Mon Feb 05, 2018 11:51 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: HW 9.13 Cp vs Cv
Replies: 2
Views: 84

Re: HW 9.13 Cp vs Cv

In the solution manual errors PDF, the equation ∆S=nCvln(T2/T1) is used, with Cv being 5/2 R
by Janine Chan 2K
Mon Feb 05, 2018 10:47 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: HW 9.13 Cp vs Cv
Replies: 2
Views: 84

HW 9.13 Cp vs Cv

In 9.13, why is Cv used instead of Cp when finding the change in entropy resulting from the increase in temperature? Cv is the heat capacity at constant volume, and volume in this question isn't constant
by Janine Chan 2K
Fri Feb 02, 2018 1:37 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Micro states
Replies: 5
Views: 266

Re: Micro states

Also, the more microstates there are, the higher the entropy.
by Janine Chan 2K
Tue Jan 30, 2018 11:15 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Question 9.89
Replies: 1
Views: 119

Re: Question 9.89

I believe it stands for standard molar entropy, the entropy of 1 mol of substance at standard state
by Janine Chan 2K
Tue Jan 30, 2018 11:01 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.27a
Replies: 4
Views: 189

Re: 9.27a

In general, more complex molecules will have higher entropy. Since HBr is larger than HF, it is more complex, has more particles (and thus more possible states it can exist in), and higher entropy.
by Janine Chan 2K
Tue Jan 30, 2018 10:56 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 9.33 (a)
Replies: 3
Views: 403

Re: 9.33 (a)

The way I thought about it was that when we first look at the equation, there are 2 mols on the left and 2 mols on the right. However, the reactants side has a mol of gas, which has more entropy than liquids are solids. Aqueous just means it's dissolved in water. A gas would have more entropy than a...
by Janine Chan 2K
Wed Jan 24, 2018 1:56 pm
Forum: Calculating Work of Expansion
Topic: 8.93
Replies: 3
Views: 160

8.93

When writing the chemical equation, how do you know water is in the liquid state?
by Janine Chan 2K
Tue Jan 23, 2018 12:11 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Work, reversible and irreversible
Replies: 2
Views: 113

Re: Work, reversible and irreversible

Also, in reversible expansion, the external pressure always matches the internal pressure. If there is any increase in pressure, external and internal energy will match each other. So, reversible reactions are always doing the maximum possible amount of work. In a reversible reaction, the process is...
by Janine Chan 2K
Tue Jan 23, 2018 12:04 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW #41 vs #21
Replies: 3
Views: 195

Re: HW #41 vs #21

In lecture, we discussed how in a perfect system, q system + q surroundings = 0. If this is the case, q system = - q surroundings . In this sense, you could say it's true that the negative sign can go on either one, because q system = - q surr is the same as q surroundings = - q system . If you assi...
by Janine Chan 2K
Mon Jan 22, 2018 10:28 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.91
Replies: 1
Views: 128

8.91

In the textbook, the question states that it takes 10.5 hours to reach 5C, but the solution manual uses 10 h. Is this a typo or am I missing something? I used these equations (4.184)(150 g)(5C - 0C)= 3135 J for 150 g and then I did ( \frac{3135 J}{150 g}*\frac{18.02 g}{1 mol}*\frac{1 kJ}{1000 J}*\fr...
by Janine Chan 2K
Wed Jan 17, 2018 9:48 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.19(b)
Replies: 1
Views: 111

Re: 8.19(b)

1.30*105 J is the amount of energy it takes to raise the temperature of water which is calculated by (400.0 g)(4.18)(100.0-22.0). 1.45*105 is the total amount of energy it takes to raise the temperature of both the water and the kettle itself.
by Janine Chan 2K
Wed Jan 17, 2018 9:43 pm
Forum: Phase Changes & Related Calculations
Topic: 8.17
Replies: 3
Views: 228

Re: 8.17

When going from a solid to liquid, aka melting, heat is required without a change in temperature because it is a phase change. So, q is positive. For work, say ice is the solid. Ice, the system, gains energy, while the surroundings lose energy. This implies work is negative (because the system loses...
by Janine Chan 2K
Wed Jan 17, 2018 8:56 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: system and surroundings [ENDORSED]
Replies: 3
Views: 256

Re: system and surroundings [ENDORSED]

The kettle should be part of the system, which is why the kettle is included when calculating the heat that must be supplied. I guess if you think about it, the kettle must be heated first before the water can be heated.
by Janine Chan 2K
Wed Jan 17, 2018 8:49 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Transfer at Constant Volume/Pressure
Replies: 4
Views: 176

Re: Heat Transfer at Constant Volume/Pressure

Here is a mathematical approach in addition to the responses above... At constant volume, the heat transfer is interpreted as ∆U. This is true because ∆U = q + w, and w = -P ex ∆V, where P is external pressure and V is volume. If the volume is constant, ∆V=0, which implies w=0, and thus ∆U=q. At con...
by Janine Chan 2K
Thu Jan 11, 2018 9:44 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Relating energy and heat [ENDORSED]
Replies: 2
Views: 169

Re: Relating energy and heat [ENDORSED]

The terms energy and heat are also related in the equation ∆U = q + w, with ∆U being the change in internal energy, q being heat, and w being work. In other words, heat and work are both means of transferring energy.
by Janine Chan 2K
Thu Jan 11, 2018 9:38 pm
Forum: Calculating Work of Expansion
Topic: Reversible vs. Irreversible Reaction
Replies: 2
Views: 200

Re: Reversible vs. Irreversible Reaction

Also, reversible reactions occur slowly, while irreversible reactions occur quickly. So, if the process is reversible (done slowly), minimal energy is lost to the surrounding as heat, allowing for maximum expansion work.
by Janine Chan 2K
Wed Jan 10, 2018 12:07 pm
Forum: Calculating Work of Expansion
Topic: Work for reversible vs irreversible process
Replies: 3
Views: 222

Re: Work for reversible vs irreversible process

Reversible processes are very slow. Because it is done slowly, less energy is lost to the surrounding as heat. In the gas and piston example, an extremely small increase in external pressure would cause the gas to be compressed and the piston to move in. If the process were to be done quickly (aka i...
by Janine Chan 2K
Fri Dec 08, 2017 5:48 pm
Forum: Bronsted Acids & Bases
Topic: Determining acidity
Replies: 3
Views: 290

Re: Determining acidity

The example given in class compared HClO with HBrO and HIO and said that HClO is more acidic. Since Cl is more electronegative, it takes e- density away from O, thus stabilizing it (a stable resulting anion would drive the reaction forward). Taking e- density away from O makes the compound a stronge...
by Janine Chan 2K
Tue Dec 05, 2017 12:40 am
Forum: Bronsted Acids & Bases
Topic: Ch 12 #27
Replies: 2
Views: 212

Re: Ch 12 #27

We multiply 200 ml by .025 M to find the number of moles that were actually made. Then divide by 250 ml to get the molarity of the actual solution.
by Janine Chan 2K
Tue Dec 05, 2017 12:13 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endothermic v. Exothermic Reactions
Replies: 9
Views: 1551

Re: Endothermic v. Exothermic Reactions

Reactions that include bond breaking are generally endothermic. EX: Cl2 <--> 2Cl. Combustion reactions are almost always exothermic.
by Janine Chan 2K
Mon Dec 04, 2017 3:46 pm
Forum: Naming
Topic: Using ion in names
Replies: 2
Views: 213

Re: Using ion in names

Yes, I believe if it just asks you to name the compound and there is no charge, you don't need to write "ion." If it's a complex ion (aka has a + or - charge), you'll need to write ion at the end of the name.
by Janine Chan 2K
Sat Dec 02, 2017 12:17 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Delocalized Pi Bonds [ENDORSED]
Replies: 2
Views: 322

Re: Delocalized Pi Bonds [ENDORSED]

Pi bonds in benzene would be delocalized. When you draw the Lewis structure, it alternates between single and double bonds. In reality, there are no alternating bonds, which is why benzene is usually drawn with a circle inside a hexagon. The p-orbitals overlap side-to-side and electrons are delocali...
by Janine Chan 2K
Sat Dec 02, 2017 12:12 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 11.57 [ENDORSED]
Replies: 1
Views: 447

Re: 11.57 [ENDORSED]

If you're given moles and liters, you'll have to convert to molarity. K can only be found with concentrations (molarity) or partial pressure (where the units will be something like atm, bar).
by Janine Chan 2K
Thu Nov 23, 2017 1:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: HW 4.43
Replies: 1
Views: 126

Re: HW 4.43

The s-character in sp2 is more than that in sp3. The way I see it is in sp2, the ratio of s:p is 1:2, while the ratio in sp3 is 1:3. If the bond angle in sp2 is larger, that would mean an increased s-character would result in a larger bond angle.
by Janine Chan 2K
Thu Nov 23, 2017 11:15 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Shifted VS Lie
Replies: 2
Views: 172

Re: Shifted VS Lie

When the reaction lies to left, there are more reactants than products. If the equilibrium is shifted to the left, there are more products than reactants. Equilibrium will shift to the side with fewer moles, so if there are products, equilibrium will shift to the reactant side (left side).
by Janine Chan 2K
Sun Nov 12, 2017 11:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Drawing VSEPR Models
Replies: 2
Views: 231

Re: Drawing VSEPR Models

I believe the lines and triangles you are referring too are just bonds between two atoms. The lines and triangles symbolize depth. If you imagine your paper to be the plane you're drawing the VSEPR structure on, the lines fading out would indicate an atom that is going into your paper, and the trian...
by Janine Chan 2K
Sun Nov 12, 2017 5:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 3
Views: 256

Re: Bond Angles

When molecules have lone pairs around the central atom, other bond angles are forced closer together (we won't know the exact angle, but you can see that the bond angles would be a little less than those in a structure without lone pairs). This applies to O3, which has 1 lone pair around the central...
by Janine Chan 2K
Sun Nov 12, 2017 5:30 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Thiosulfate ion shape
Replies: 2
Views: 487

Re: Thiosulfate ion shape

There actually is no lone pair around the S. I believe the Lewis structure is just a sulfur atom in the middle, surrounded by 3 oxygen atoms and 1 other sulfur atom. Since there are 4 bonding pairs around the central atom, it would be a tetrahedral shape.
by Janine Chan 2K
Sun Nov 12, 2017 4:11 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Textbook Problem Chp 4 #9
Replies: 3
Views: 197

Re: Textbook Problem Chp 4 #9

In a trigonal planar shape, there are only 3 bonding pairs surrounding the central atom. As you drew in your Lewis structure, ICl3 has 3 bonding pairs and 2 lone pairs, which would make it T-shaped.
by Janine Chan 2K
Tue Oct 31, 2017 11:49 pm
Forum: Trends in The Periodic Table
Topic: 2.81 – Oxygen Anomaly
Replies: 2
Views: 243

Re: 2.81 – Oxygen Anomaly

Nitrogen also has a half-filled sub shell, which means it has lower energy and is more stable. Since it would be more difficult to take away an electron from a more stable subshell (aka higher ionization energy), Oxygen has the lower ionization energy.
by Janine Chan 2K
Tue Oct 31, 2017 11:40 pm
Forum: Trends in The Periodic Table
Topic: Writing Electron Config for Chromium after being ionized once?
Replies: 2
Views: 237

Re: Writing Electron Config for Chromium after being ionized once?

It should be (1). Higher energy electrons are removed first. In this case, the 4s electrons have a higher energy than 3d.
by Janine Chan 2K
Wed Oct 25, 2017 2:49 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: HW Question 2.37
Replies: 2
Views: 148

Re: HW Question 2.37

I believe in this case "penetrate" just means how close the electron can get to the atom. So since it "penetrates" more, it is more attracted to the nucleus and therefore more effective at shielding other electrons than orbitals that are further out from the nucleus.
by Janine Chan 2K
Wed Oct 25, 2017 1:51 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Helium block
Replies: 2
Views: 329

Re: Helium block

^ The electron configuration of Helium is 1s^2, so yes, it is part of the s-block.
by Janine Chan 2K
Tue Oct 17, 2017 8:15 pm
Forum: DeBroglie Equation
Topic: 1.39 Help
Replies: 5
Views: 370

Re: 1.39 Help

I think the only thing you're missing is that 41 should be in m * s^-1, not just meters.
by Janine Chan 2K
Tue Oct 17, 2017 7:23 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: ch1 question 43
Replies: 8
Views: 686

Re: ch1 question 43

I also had a question on this^
The solution manual uses a different character for Planck's constant, and it uses the equation ∆p∆x= h/2, whereas in lecture we learned the equation ∆p∆x=h/4pi.
by Janine Chan 2K
Thu Oct 12, 2017 12:29 am
Forum: Properties of Light
Topic: Question 1.15 Rydberg Equation Math Problem
Replies: 1
Views: 152

Re: Question 1.15 Rydberg Equation Math Problem

So I used the equation was c/wavelength=R(1/n_1^2 - 1/n_2^2). Essentially, you're using the given wavelength and using c=v*wavelength to find the frequency, and then using v=R((1/n_1^2 - 1/n_2^2) to find n_2. (We also already know n_1 = 1 because a wavelength of 102.6nm is Lyman series
by Janine Chan 2K
Wed Oct 11, 2017 2:51 pm
Forum: Properties of Light
Topic: Rydberg's Formula
Replies: 4
Views: 358

Re: Rydberg's Formula

The formula basically relates the wavelength to the initial and final states of an electron. We can find the inverse of the wavelength by multiplying Rydberg's constant by the change in energy of the electron.
by Janine Chan 2K
Wed Oct 04, 2017 3:05 pm
Forum: Significant Figures
Topic: Sig Figs in 0.0380 [ENDORSED]
Replies: 5
Views: 471

Re: Sig Figs in 0.0380 [ENDORSED]

Leading zeroes are not significant (in 0.032, the zeroes before 3 aren't significant so there would be 2sf). Trailing zeroes ARE significant (in 0.03000, all the zeroes after 3 are significant so there would be 4sf).
by Janine Chan 2K
Tue Oct 03, 2017 1:41 pm
Forum: Empirical & Molecular Formulas
Topic: F.1 textbook exercise
Replies: 3
Views: 335

Re: F.1 textbook exercise

If the compound includes carbon atoms, C will be written first. If it includes hydrogen atoms, H will come second. Any other elements should follow in alphabetical order. Hope that helps!

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