Search found 110 matches
- Fri Mar 13, 2020 11:55 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Week 10 Review Problems (pg.7)
- Replies: 2
- Views: 221
Week 10 Review Problems (pg.7)
I thought different species in the same state are separated by , not | ? Since Ag and AgBr are both solids, shouldn't it be |Ag(s), AgBr(s)| ?
- Wed Mar 11, 2020 1:25 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activation Energy vs. Free Energy of Activation
- Replies: 3
- Views: 293
Re: Activation Energy vs. Free Energy of Activation
Kassidy Ford 1I wrote:^^^ does this mean that it is literally Gibbs free energy??
Yes, free energy of activation refers to Gibbs free energy.
- Wed Mar 11, 2020 1:21 pm
- Forum: General Rate Laws
- Topic: intermediates
- Replies: 12
- Views: 661
Re: intermediates
Reaction intermediates are formed in one step and then consumed in a later step of the reaction mechanism. Therefore, intermediates are not listed in rate laws.
- Wed Mar 11, 2020 1:13 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: E cell
- Replies: 9
- Views: 584
Re: E cell
E cell is the cell potential at non-standard state conditions. You would use the Nernst Equation to find E cell.
E standard cell is the standard cell potential, which means concentrations are 1 M and pressures are 1 bar.
E standard cell is the standard cell potential, which means concentrations are 1 M and pressures are 1 bar.
- Wed Mar 11, 2020 12:58 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Reaction orders
- Replies: 3
- Views: 246
Re: Reaction orders
No, that is not always the case. A good example is homework problem 7A.15. The given reaction is 2A(g) + 2B(g) + C(g) ---> 2G(g) + 4F(g). Even though A has a coefficient of 2, the data shows that reactant A is first order.
- Mon Mar 09, 2020 2:06 pm
- Forum: General Rate Laws
- Topic: 7A.17
- Replies: 5
- Views: 353
Re: 7A.17
You can compare experiments 1 and 3 since the concentration of B is changing and the concentration of C is constant.
- Tue Mar 03, 2020 2:08 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6N 9: anode v cathode
- Replies: 2
- Views: 170
Re: 6N 9: anode v cathode
The standard reduction potential for Sn2+ + 2e- ---> Sn is -0.14V
The standard reduction potential for 2H+ + 2e- ---> H2 is 0.0V
Therefore, tin would be the anode because you would flip the sign to get a positive standard cell potential (+0.14V).
The standard reduction potential for 2H+ + 2e- ---> H2 is 0.0V
Therefore, tin would be the anode because you would flip the sign to get a positive standard cell potential (+0.14V).
- Tue Mar 03, 2020 2:00 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Platinum
- Replies: 6
- Views: 366
Re: Platinum
You include Pt(s) when there is no solid metal conductor. For example, for problem 6M.11 (part a), the cell diagram would be:
| Pt(s) | Ti3+(aq), Ti2+(aq) || Co2+(aq) | Co(s)
| Pt(s) | Ti3+(aq), Ti2+(aq) || Co2+(aq) | Co(s)
- Tue Mar 03, 2020 1:52 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: n
- Replies: 4
- Views: 350
Re: n
The number of electrons transferred is determined by your half-reactions. n is equal to the same number of electrons needed (in both the oxidation and reduction reactions) to balance out the charge between the reactants and products.
- Tue Mar 03, 2020 1:45 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L.5
- Replies: 5
- Views: 372
Re: 6L.5
Pt(s) is necessary because the oxidized and reduced species are in the same solution.
- Mon Mar 02, 2020 3:50 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6M.7
- Replies: 5
- Views: 358
Re: 6M.7
Chem_Mod wrote:Can you please post the question.
6M.7 Arrange the following metals in order of increasing strength as reducing agents for species in aqueous solution:
(a) Cu, Zn, Cr, Fe
- Mon Mar 02, 2020 3:48 pm
- Forum: Balancing Redox Reactions
- Topic: 6L.5 (part d)
- Replies: 2
- Views: 222
6L.5 (part d)
6L.5 (d)
Au+(aq) ---> Au(s) + Au3+(aq)
Can someone please explain how to write the oxidation half-reaction? The solutions manual says the oxidation reaction should be:
Au3+(aq) + 3e- ---> Au(s)
But why isn't it Au3+(aq) + 2e- ---> Au+(aq) ?
Au+(aq) ---> Au(s) + Au3+(aq)
Can someone please explain how to write the oxidation half-reaction? The solutions manual says the oxidation reaction should be:
Au3+(aq) + 3e- ---> Au(s)
But why isn't it Au3+(aq) + 2e- ---> Au+(aq) ?
- Wed Feb 26, 2020 8:35 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Writing half reactions from cell diagrams
- Replies: 1
- Views: 143
Writing half reactions from cell diagrams
Pt(s)|O2(g)|H+(aq)||Cr2O7^-2(aq),H+(aq),Cr^3+(aq)|Pt(s)
How would you write the half reaction for the anode?
How would you write the half reaction for the anode?
- Wed Feb 26, 2020 8:20 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6N.13
- Replies: 2
- Views: 266
6N.13
6N.13 Calculate the reaction quotient, Q, for the following cell reactions, given the measured values of the cell potential. a) Pt(s)|Sn^4+(aq),Sn^2+(aq)||Pb^4+(aq), Pb^2+(aq)|C(gr) When I tried to calculate Q, I got 2.68 x 10^6, but the solutions manual says the answer is 10^6. Can someone please e...
- Tue Feb 25, 2020 2:28 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6N.7b
- Replies: 2
- Views: 232
Re: 6N.7b
If you use n=2, make sure you square the concentrations of your products and reactants for your value of Q (due to the coefficient of 2 in the H+). E should equal 0.06 V.
- Tue Feb 25, 2020 1:58 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 7th edition 6N.1
- Replies: 5
- Views: 765
Re: 7th edition 6N.1
For part b, why does the solutions manual use n=2 instead of n=1 since there is only 1 mol of e- transfer? For K, I got 1x10^2 instead of 1x10^4.
- Tue Feb 25, 2020 1:31 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6M.7
- Replies: 5
- Views: 358
6M.7
For homework problem 6M.7 part a, how do you know which standard reduction potential you should use for Cr? When Cr loses 2 e-, the standard reduction potential is -0.91, but when it loses 3 e-, it is -0.74. The one I use will determine if Cr is a stronger reducing agent than Zn.
- Thu Feb 20, 2020 5:29 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: gas constant for gibbs free energy
- Replies: 5
- Views: 390
Re: gas constant for gibbs free energy
Gibbs free energy is in J/mol and temperature is in Kelvins. Therefore, you would use 8.314 J/mol.K in order to cancel out all the units and find a value for K (which does not have any units).
- Thu Feb 20, 2020 5:25 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation numbers
- Replies: 6
- Views: 395
Re: Oxidation numbers
H2 has a neutral charge because it is the most stable form of hydrogen. Other then that, the oxidation number of hydrogen is +1.
- Thu Feb 20, 2020 5:15 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Spontaneous
- Replies: 20
- Views: 1101
Re: Spontaneous
A reaction is spontaneous when Delta(G) is greater than 0, or a negative value. When Delta(G) is a positive value, the reaction is not spontaneous, and the reverse reaction is favored. Finally, when Delta(G) is equal to 0, the reaction is at equilibrium.
- Thu Feb 20, 2020 5:07 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Extensive and Intensive Properties
- Replies: 12
- Views: 1008
Re: Extensive and Intensive Properties
Since the heat required depends on the amount of the substance, heat capacity is an extensive property. Specific heat capacity and molar heat capacity are intensive properties because they are the heat required to raise the temperature of 1 g or 1 mol by 1 degree Celsius.
- Thu Feb 20, 2020 4:49 pm
- Forum: Balancing Redox Reactions
- Topic: redox reactions in acidic and basic solutions
- Replies: 1
- Views: 144
Re: redox reactions in acidic and basic solutions
Under acidic conditions, we are allowed to add H+ or H20 and under basic conditions, we are allowed to add OH- or H20. We do this to balance the number of atoms in the chemical equation. For example, in an acidic solution, if there is an oxygen atom in the given equation, you would have to add the a...
- Wed Feb 12, 2020 12:28 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Pizza Rolls 6 (pt.1)
- Replies: 10
- Views: 657
Re: Pizza Rolls 6 (pt.1)
Since internal energy (U) and entropy (S) are state functions, you can look at their initial and final values. Since they are the same (the system goes back to its original volume and pressure), the change of internal energy/entropy is 0.
- Wed Feb 12, 2020 12:25 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: using the first law
- Replies: 3
- Views: 264
Re: using the first law
When the volume is constant, w=0. If the problem gives you the amount of energy that increased/decreased (q) after doing a certain amount of work (w) is when you can incorporate both q and w for the change in internal energy.
- Tue Feb 11, 2020 3:13 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 4I.5
- Replies: 4
- Views: 122
Re: 4I.5
Sartaj Bal 1J wrote:Why is the value of Cp,m 75.3 J K^-1 mol^-1 in this problem?
In this problem, H2O is a liquid, not a gas. Cp(liquid)=75.3 J/K*mol, which is given on our equations sheet.
- Tue Feb 11, 2020 10:38 am
- Forum: Administrative Questions and Class Announcements
- Topic: Pizza Rolls REVIEW Session DOWNLOAD HERE
- Replies: 67
- Views: 5250
Re: Pizza Rolls REVIEW Session DOWNLOAD HERE
Can someone help explain why and how the equation for 3b includes (1/2)(m)(delta H of fusion)? I get what you would isolate to get the answer but I'm not sure how they got that part of the equation. For problem 3B, you have to use the equation q=mC(Delta T) but also the phase change equation q=m(de...
- Tue Feb 11, 2020 10:35 am
- Forum: Administrative Questions and Class Announcements
- Topic: Pizza Rolls REVIEW Session DOWNLOAD HERE
- Replies: 67
- Views: 5250
Re: Pizza Rolls REVIEW Session DOWNLOAD HERE
Can someone show me step by step on how to solve for number 10. I did not understand why q(ice)=q(water). CHEM MOD: q(ice) = -q(water) DO NOT forget the negative sign. The heat released from one material in a system is absorbed by the other material in the system. For #10, why do we have to convert...
- Sat Feb 08, 2020 9:08 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Negative Heat Capacity
- Replies: 4
- Views: 270
Negative Heat Capacity
Can heat capacities be negative for simple molecules?
- Sat Feb 08, 2020 2:37 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Equation for Cv and Cp
- Replies: 3
- Views: 160
Re: Equation for Cv and Cp
Since the equations for Cv and Cp are given on the equation sheet for monatomic gases, I would try to memorize the equation for linear and non-linear. For linear: Cv=(5/2)R, Cp=(7/2)R For nonlinear: Cv=3R, Cp=4R However, if you memorize the equation Cp=Cv+R, then you can use this equation to figure ...
- Sat Feb 08, 2020 2:33 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Calorimeters
- Replies: 17
- Views: 913
Re: Calorimeters
A bomb calorimeter measures specific heat at a constant volume.
- Sat Feb 08, 2020 2:31 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Delta H and qp
- Replies: 8
- Views: 134
Re: Delta H and qp
Delta H is equal to q when the heat released or absorbed is at a constant pressure.
- Thu Feb 06, 2020 10:52 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Sessions in covel
- Replies: 2
- Views: 83
Re: Sessions in covel
I tried to go to this review session also and when I got there the door was locked and the lights were turned off. I ran into the UA there and he also seemed confused as to why the room was not open.
- Thu Feb 06, 2020 9:03 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Help on 9.5
- Replies: 4
- Views: 289
Re: Help on 9.5
When calculating the first entropy change, heat is transferred FROM the reservoir at 800 K (meaning that heat is lost), which is why q is negative.
- Thu Jan 30, 2020 8:11 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: 4A.1
- Replies: 12
- Views: 450
Re: 4A.1
In a closed system, energy can be exchanged with its surroundings. For example, if you put a lid on a pot, matter cannot be exchanged, but energy can still be transferred. In an isolated system, nothing is exchanged with its surroundings. An example of this is a thermos; however, it is not 100% perf...
- Thu Jan 30, 2020 8:07 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Closed and Isolated
- Replies: 5
- Views: 221
Re: Closed and Isolated
No system is ever 100% isolated.
- Thu Jan 30, 2020 8:03 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: 4A.3 part c
- Replies: 4
- Views: 227
Re: 4A.3 part c
The change in internal energy is equal to the work (which was calculated in part A) in absence of other changes. My solution manual also said the answer was 28 J.
- Thu Jan 30, 2020 7:57 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: qp and qv
- Replies: 8
- Views: 331
Re: qp and qv
Enthalpy, which is represented by delta(h), is heat at a constant pressure. Heat is represented by "q", and because the pressure is constant, it will have the subscript "p" for pressure, rather than "v" for volume.
- Thu Jan 30, 2020 7:51 pm
- Forum: Phase Changes & Related Calculations
- Topic: internal energy
- Replies: 11
- Views: 552
Re: internal energy
The change in internal energy is represented by delta(U). Delta(U) is equal to the energy transferred by heating (q) + the energy transferred by compression (w).
delta U = q + w
delta U = q + w
- Wed Jan 22, 2020 9:58 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Values for pKb and pKa
- Replies: 3
- Views: 203
Re: Values for pKb and pKa
The lower the pKa, the stronger the acid. The lower the pKb, the stronger the base. An easy way to check to see if you have the correct values is to add pKa and pKb and make sure the sum is equal to 14.
- Wed Jan 22, 2020 9:54 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Best Way To Study?
- Replies: 13
- Views: 561
Re: Best Way To Study?
I found the UA learning sessions to be the most helpful to prepare for the tests. It is also beneficial to do as many of the homework problems as you can.
- Wed Jan 22, 2020 9:52 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 1 Study Guide/Worksheet
- Replies: 5
- Views: 789
Re: Test 1 Study Guide/Worksheet
Megan Kirschner wrote:I also don't understand why that one is 2 sig figs. Is there a place I could get good review on sig figs?
I went to another review session and the TA said that there are only two sig figs because when dealing with pH, you look at the number of sig figs AFTER the decimal.
- Wed Jan 22, 2020 9:48 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ice Box
- Replies: 9
- Views: 168
Re: Ice Box
Matt Sanruk 2H wrote:Do we get points off for not doing ICE boxes?
I would make an ICE box just to be safe. This way, you can show all your work and less likely to make errors.
- Tue Jan 21, 2020 5:11 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 1 Study Guide/Worksheet
- Replies: 5
- Views: 789
Re: Test 1 Study Guide/Worksheet
Can you please explain why for #2, the answers only have two sig figs?
- Tue Jan 21, 2020 5:06 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5% approximation rule
- Replies: 5
- Views: 161
Re: 5% approximation rule
As a general rule of thumb, can we assume the approximation rule whenever K < 10^-5 or K < 10^-3? Which value of K is it? (assuming that you always check if the approximation is valid after solving for x) How do you check if the approximation is valid? Do you look at what you solved for x and see i...
- Thu Jan 16, 2020 6:43 pm
- Forum: Ideal Gases
- Topic: ph
- Replies: 10
- Views: 448
Re: ph
Yes, the pH can be less than 0 and greater than 14; however, is it more likely for the pH to fall in the 0-14 range.
- Thu Jan 16, 2020 6:40 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Acids and Bases
- Replies: 2
- Views: 109
Re: Acids and Bases
The pH increases as the solution becomes more basic (which means a higher concentration of OH- ions and a lower concentration of H+ ions) and decreases as the solution becomes more acidic (which means a lower concentration of OH- ions and a higher concentration of H+ ions).
- Thu Jan 16, 2020 6:37 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert gas
- Replies: 4
- Views: 91
Re: Inert gas
An inert gas does not chemically react, which means it does not change under given conditions. Noble gases are inert gases (examples include helium, argon, and neon).
- Thu Jan 16, 2020 6:31 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Negative pH
- Replies: 6
- Views: 213
Re: Negative pH
If a pH is less than 0 or greater than 14, that means the concentrations of H30+ or OH- are larger than one molar. However, the concentration of hydrogen ions are usually between 1 M or 10^-14 M.
- Thu Jan 16, 2020 6:26 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: change in temp
- Replies: 4
- Views: 89
Re: change in temp
If a reaction is endothermic, that means it absorbs heat and heat is used as a reactant. In endothermic reactions, an increase in temperature (heat) leads to an increase in reactants. According to Le Chatelier's Principle, the reaction would then shift to the products to reach equilibrium.
- Mon Jan 13, 2020 3:57 pm
- Forum: Student Social/Study Group
- Topic: F19 Final
- Replies: 4
- Views: 139
F19 Final
When/where can we pick up our Chem 14a final from last quarter?
- Wed Jan 08, 2020 8:53 pm
- Forum: Ideal Gases
- Topic: Equilibrium
- Replies: 7
- Views: 180
Re: Equilibrium
K is the equilibrium constant, while Q is the reaction quotient. They are calculated the same way but you can compare Q and K to determine if the forward reaction or the reverse reaction is favored. If Q<K at some time during the reaction, then reactants are favored. If Q>K at some time during the r...
- Wed Jan 08, 2020 8:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Finding K without aq
- Replies: 4
- Views: 129
Re: Finding K without aq
The value of K would be 1. However, it is very rare.
- Wed Jan 08, 2020 8:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K vs Kp vs Kc
- Replies: 9
- Views: 311
Re: K vs Kp vs Kc
Madeline Phan 1J wrote:when writing the expression for k, how do you know when to use brackets or to write p in front?
You use brackets to represent concentration and you use P to represent partial pressure. For a gas, we use its partial pressure and the equilibrium constant is denoted by Kp.
- Wed Jan 08, 2020 8:29 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 6
- Views: 615
Re: Le Chatelier's Principle
Le Chatelier's Principle states that chemical reactions adjust so as to minimize the effect of any changes (such as the change in concentration, pressure, or temperature). When a reaction undergoes these changes, the equilibrium will shift and favor either the formation of products or reactants (dep...
- Wed Jan 08, 2020 8:20 pm
- Forum: Ideal Gases
- Topic: Gas Law
- Replies: 6
- Views: 208
Re: Gas Law
The ideal gas law allows you to be able to convert between partial pressure and concentration.
PV=nRT
P=(n/v)RT
P=(conc)RT
PV=nRT
P=(n/v)RT
P=(conc)RT
- Wed Dec 04, 2019 11:32 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Square Planar Polarity
- Replies: 2
- Views: 532
Re: Square Planar Polarity
There would be a dipole moment so it would be polar.
- Wed Dec 04, 2019 11:22 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Acid Strength
- Replies: 5
- Views: 347
Re: Acid Strength
You would look at the bond strength. For part a, HCl has a weaker bond strength than HF, which means it is a stronger acid. However, for part b, you would base the strength of the acid on the amount of oxygen atoms. HClO2 has more O atoms than HClO, which is why it is the stronger acid.
- Wed Dec 04, 2019 11:16 pm
- Forum: Naming
- Topic: Naming Compounds
- Replies: 2
- Views: 123
Re: Naming Compounds
I think it would be safe to write out the whole name.
- Wed Dec 04, 2019 11:15 pm
- Forum: Biological Examples
- Topic: Biological Significance
- Replies: 2
- Views: 167
Biological Significance
What are some important coordination compounds that we should know their biological significance for?
- Wed Dec 04, 2019 11:10 pm
- Forum: Lewis Acids & Bases
- Topic: Characteristics of Lewis acids
- Replies: 2
- Views: 181
Re: Characteristics of Lewis acids
Lewis acids would have the same qualities as Bronsted acids. However, a Bronsted acid donates H+, so there would have to be a proton transfer if a chemical reaction wants to be classified as a reaction between a Bronsted acid and base.
- Mon Dec 02, 2019 9:06 pm
- Forum: Lewis Acids & Bases
- Topic: Acidic or Basic
- Replies: 3
- Views: 543
Acidic or Basic
What are some common drinks, food, or household items that we should be able to identify as acidic or basic for the final?
- Wed Nov 27, 2019 3:48 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polarity and dipole moments
- Replies: 8
- Views: 569
Re: Polarity and dipole moments
Dipole moments cancel out in non-polar molecules. This means that the molecule is symmetrical. Polar molecules have dipole moments because there is a separation of charge. Tetrahedral molecules are only non-polar when all four atoms bonded to the central atom are the same element.
- Wed Nov 27, 2019 3:44 pm
- Forum: Bronsted Acids & Bases
- Topic: Relative Acidity
- Replies: 3
- Views: 224
Re: Relative Acidity
The stronger the bond, the weaker the acid. For example, HF is a very weak acid because it has a very strong bond (it is also a large molecule). The higher the electronegativity, the greater the attraction. Increasing electronegativity decrease basicity (which means an increase in acidity) because t...
- Wed Nov 27, 2019 3:36 pm
- Forum: Lewis Acids & Bases
- Topic: Bronsted and Lewis Acids
- Replies: 4
- Views: 225
Re: Bronsted and Lewis Acids
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.
- Wed Nov 27, 2019 2:53 pm
- Forum: Bronsted Acids & Bases
- Topic: Bronsted acid
- Replies: 9
- Views: 957
Re: Bronsted acid
A Bronsted acid is a species that is capable of donating a proton. HBr classifies as a Bronsted acid because it donates a H+ to water (the Bronsted base). HBr donates its proton to become Br-.
- Wed Nov 27, 2019 2:42 pm
- Forum: Bronsted Acids & Bases
- Topic: Acids vs Bases
- Replies: 5
- Views: 359
Re: Acids vs Bases
Acids increase the concentration of H+ ions when dissolved in water, are proton donors, have a pH less than 7, and are sour in taste. Bases increase the concentration of OH- ions when dissolved in water, are proton acceptors, have a pH greater than 7, and are bitter in taste.
- Tue Nov 19, 2019 3:28 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Types of forces
- Replies: 4
- Views: 193
Re: Types of forces
The question is asking what type of force can occur for a certain molecule if it is paired up with that same molecule. So for SO2, since it is polar, it has dipole-dipole forces and London Dispersion forces. Dipole-induced dipole or ion-dipole forces would only occur if SO2 was paired with a differe...
- Tue Nov 19, 2019 3:21 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Are London Dispersion and Induced-Dipole-Induced-Dipole Interactions the same?
- Replies: 2
- Views: 83
Re: Are London Dispersion and Induced-Dipole-Induced-Dipole Interactions the same?
London Dispersion forces are also known as dipole-induced dipole interactions.
- Tue Nov 19, 2019 3:18 pm
- Forum: Dipole Moments
- Topic: Dipole moment
- Replies: 1
- Views: 154
Re: Dipole moment
The most electronegative elements are located in the upper right-hand corner of the periodic table. So as you move across a row from left to right, electronegativity increases. As you move down a group, electronegativity decreases. When drawing the lewis structure of a molecule, if it is symmetrical...
- Tue Nov 19, 2019 3:12 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Hydrogen Bonding
- Replies: 2
- Views: 122
Re: Hydrogen Bonding
Hydrogen bonding will ONLY occur is hydrogen is bonded to a nitrogen, oxygen, or fluorine atom.
- Tue Nov 19, 2019 3:11 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Seesaw Shape
- Replies: 12
- Views: 571
Re: Seesaw Shape
The lone pair in the seesaw shaped molecule affects all angles in the molecule. So the bond angles will be <90 degrees and <120 degrees.
- Sat Nov 16, 2019 12:16 pm
- Forum: Ionic & Covalent Bonds
- Topic: Polarity
- Replies: 6
- Views: 382
Re: Polarity
An easy way to determine if a molecule is polar or non-polar is to draw the Lewis Structure and see if it is symmetric or non-symmetric. If the Lewis Structure is symmetric, the molecule is non-polar, which also means it only has non-polar bonds. If the Lewis Structure is non-symmetric, the molecule...
- Wed Nov 13, 2019 8:24 pm
- Forum: Properties of Light
- Topic: Midterm Solution Q2B
- Replies: 2
- Views: 344
Midterm Solution Q2B
Q2B. A beam of light at constant intensity and increasing frequency is shown on a metal surface. A detector reads the number of electrons ejected from the sheet of metal. The graph below has a frequency of the incoming light on the X axis and the number of the ejected electrons on the Y axis. Draw t...
- Wed Nov 13, 2019 7:35 pm
- Forum: Properties of Light
- Topic: Midterm Solution Q2.A
- Replies: 2
- Views: 176
Midterm Solution Q2.A
For the midterm Q2A, I understand we need to convert 492 kJ.mol^-1 to J, but why do we first have to divide it by Avogadro’s number? When do we use Avogadro’s number?
- Tue Nov 12, 2019 9:07 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: 3F.5 (b)
- Replies: 4
- Views: 531
Re: 3F.5 (b)
It helps if you draw out the Lewis Structure for both molecules. In diethyl ether, there is no hydrogen bonding, while in butanol, there is hydrogen bonding. Hydrogen bonding is the strongest intermolecular force, which means it has a higher boiling point.
- Tue Nov 12, 2019 9:02 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: 3F5C
- Replies: 3
- Views: 205
Re: 3F5C
Both CHI3 and CHF3 are polar and have London Dispersion forces. However, CHI3 has a stronger London Dispersion force because CHI3 is a much bigger molecule than CHF3. Iodine has a greater molar mass than fluorine, and the bigger the atom, the stronger the intermolecular force. This would then requir...
- Fri Nov 08, 2019 8:13 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Monday Lecture
- Replies: 2
- Views: 137
Re: Monday Lecture
I don't believe so. I would only worry about the homework due in your discussion class.
- Fri Nov 08, 2019 8:07 pm
- Forum: Student Social/Study Group
- Topic: Class Grading
- Replies: 44
- Views: 3425
Re: Class Grading
Madeline Phan 4H wrote:So for our midterm, we will just get a raw score for now?
Yes. Today in lecture, Professor Lavelle said that midterm scores will be released next Wednesday.
- Fri Nov 08, 2019 8:04 pm
- Forum: General Science Questions
- Topic: Test 2
- Replies: 20
- Views: 767
Re: Test 2
When is test 2?
- Wed Nov 06, 2019 1:12 pm
- Forum: Properties of Light
- Topic: 1A.15
- Replies: 3
- Views: 268
Re: 1A.15
How do you know that n1=1?
- Tue Nov 05, 2019 6:21 pm
- Forum: Administrative Questions and Class Announcements
- Topic: DINO NUGGETS Review Session! Download Problems HERE [ENDORSED]
- Replies: 52
- Views: 6420
Re: DINO NUGGETS Review Session! Download Problems HERE [ENDORSED]
for dino nuggets #4 why is the answer 2 sig figs and not 3? is it because 250 mL has only 2 sig figs? i'm a bit confused if that's the reason or if it's something else - if someone could clarify that would be great! thanks so much Yes, for #4, the answer only has 2 sig figs because 250 mL has only ...
- Mon Oct 28, 2019 5:53 pm
- Forum: Octet Exceptions
- Topic: Unpaired Electrons
- Replies: 1
- Views: 178
Unpaired Electrons
If you have a compound like ClO, which has 13 valence electrons, why would chlorine have the unpaired electron and not oxygen? What determines which atom gets the unpaired electron?
- Mon Oct 28, 2019 3:55 pm
- Forum: Lewis Structures
- Topic: Resonance Structures
- Replies: 2
- Views: 139
Resonance Structures
When drawing the possible Lewis Structures for ClNO2, why can only the oxygens be double bonded, and not the chlorine?
- Mon Oct 28, 2019 3:51 pm
- Forum: Ionic & Covalent Bonds
- Topic: 2A.11
- Replies: 4
- Views: 215
Re: 2A.11
For part a, [Ar]3d^6 has a total of 24 electrons, which is chromium. However, since the unknown metal has an additional 3 electrons, you would find the element that has 27 electrons, which is cobalt. The answer to part a would be Co^3+. You can apply the same process to parts b, c, and d.
- Mon Oct 28, 2019 10:57 am
- Forum: Lewis Structures
- Topic: Exceptions to the Octet Rule
- Replies: 3
- Views: 113
Exceptions to the Octet Rule
How do you know if an element can exceed the octet rule?
- Mon Oct 28, 2019 10:55 am
- Forum: Lewis Structures
- Topic: Lewis Structure
- Replies: 2
- Views: 113
Re: Lewis Structure
Yes. Odd-electron molecules, electron-deficient molecules, and hypervalent molecules are all exceptions to the octet rule. An odd number of valence electrons can lead to unpaired electrons, as well as the central atom having more or less electrons needed.
- Mon Oct 28, 2019 10:46 am
- Forum: Lewis Structures
- Topic: BrF3
- Replies: 2
- Views: 102
BrF3
How do you draw the lewis structure for bromine trifluoride? I know it has 28 valence electrons, but when I draw the lewis structure I can't figure out how to draw the bonds in a way to complete the octet.
- Mon Oct 28, 2019 10:34 am
- Forum: Lewis Structures
- Topic: Central Atoms
- Replies: 2
- Views: 81
Central Atoms
When drawing lewis structures, how do you know which atom is the central atom? I understand that for CCl4 the central atom would be carbon, but what about for compounds like NHF2?
- Sun Oct 27, 2019 10:02 pm
- Forum: Lewis Structures
- Topic: 2A.11
- Replies: 1
- Views: 91
2A.11
Which M^3+ ions (where M is metal) are predicted to have the following ground-state electron configurations:
a) [Ar]3d^6
b) [Ar]3d^5
c) [Kr]4d^5
d) [Kr]4d^3
I'm super confused on how to go about this problem.
a) [Ar]3d^6
b) [Ar]3d^5
c) [Kr]4d^5
d) [Kr]4d^3
I'm super confused on how to go about this problem.
- Sun Oct 27, 2019 9:52 pm
- Forum: Lewis Structures
- Topic: Electron Configuration
- Replies: 3
- Views: 159
Electron Configuration
In row 5 on the periodic table, why does the electron configuration for Niobium (Nb) have "5s1" and not"5s2"?
- Fri Oct 25, 2019 4:17 pm
- Forum: Lewis Structures
- Topic: Video Modules
- Replies: 11
- Views: 379
Video Modules
Does anyone know if Professor Lavelle is planning on uploading more video modules on to his website? Or is the "Heisenberg Uncertainty Principle" going to be the last video?
- Fri Oct 25, 2019 4:13 pm
- Forum: Lewis Structures
- Topic: Transition Elements
- Replies: 2
- Views: 109
Transition Elements
How do you find the number of valence electrons a transition element has by using the periodic table?
- Fri Oct 25, 2019 4:12 pm
- Forum: Lewis Structures
- Topic: Finding Valence Electrons
- Replies: 8
- Views: 377
Re: Finding Valence Electrons
An easy way to find the number of valence electrons an element has is to use the periodic table. The group number (column) represents the number of valence electrons, excluding the transition elements in groups 3-12. Group 1 = 1 e- Group 2 = 2 e- Group 13 = 3 e- Group 14 = 4 e- Group 15 = 5 e- and s...
- Fri Oct 25, 2019 4:07 pm
- Forum: Lewis Structures
- Topic: Single or Double Bonds
- Replies: 4
- Views: 118
Single or Double Bonds
When drawing Lewis Structures, how do you know when you're supposed to use a single or double bond?
- Fri Oct 25, 2019 4:02 pm
- Forum: Lewis Structures
- Topic: Expanded Valence Shells Example
- Replies: 2
- Views: 100
Re: Expanded Valence Shells Example
Yes. During my lecture class, Professor Lavelle worked the problems out on the board.
- Sat Oct 19, 2019 1:29 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Same spin
- Replies: 10
- Views: 468
Re: Same spin
When drawing spin, is there a reason why only half of the arrow point is used? I've seen it done both ways. In high school, I was taught to only draw half of the arrow point but Professor Lavelle draws the whole arrow point. I don't think it really matters as long as the arrow is pointing in the ri...
- Sat Oct 19, 2019 1:26 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Tips for the Midterm
- Replies: 10
- Views: 316
Tips for the Midterm
Does anyone have any helpful study tips to prepare for the upcoming midterm? What topics should I review?
- Sat Oct 19, 2019 1:21 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Hund's rule
- Replies: 5
- Views: 124
Re: Hund's rule
Hund's rule states that due to e- repulsion, e- in the same subshell occupy different orbitals with parallel spin. This allows for the lowest energy state. All orbital shells must be occupied by one e- before an orbital can be paired up with two.
- Sat Oct 19, 2019 1:15 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Quantum Numbers
- Replies: 3
- Views: 145
Re: Quantum Numbers
If n=4, there would be four subshells: s, p, d, f.
- Sat Oct 19, 2019 1:10 pm
- Forum: General Science Questions
- Topic: Homework for week 4
- Replies: 1
- Views: 89
Re: Homework for week 4
Homework for week 4 should be from the problems listed under the Quantum World since we are still covering topics from that unit.