## Search found 131 matches

Tue Jan 14, 2020 10:55 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 5I.13
Replies: 3
Views: 20

### Re: 5I.13

The equilibrium constant tells us the relative stability of the reactants and the products. If K is more than one or exceeds one by a lot (K>1 or K>>1), then the reaction favors products, implying that products are more stable. If K is less than one or is very very small (K<10^-3), that means the re...
Tue Jan 14, 2020 10:53 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Autoprolysis
Replies: 8
Views: 32

### Re: Autoprolysis

There are other examples of molecules beside water than can do autoprotolysis due to them being amphiprotic. Examples include ammonia, acetic acid, and H2SO4. These aren't really significant; the autoprotolysis of water is the important one you have to know for acid/base equilibria.
Tue Jan 14, 2020 10:50 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Percentage deprotonation
Replies: 1
Views: 11

### Re: Percentage deprotonation

A high percent deprotonation means that a weak acid was able to produce a sizeable amount of hydronium ions compared to other weak acids. A high percent protonation means that a weak base was able to produce a sizeable amount of hydroxide ions compared to other weak bases. Reminder: Percent Deproton...
Mon Jan 13, 2020 4:34 pm
Forum: Ideal Gases
Topic: Dividing by volume
Replies: 3
Views: 15

### Re: Dividing by volume

It really doesn't matter which value: n, R, or T, that you divide by the volume. Communitive rule of multiplication and division. Just make sure you divide by the volume only once, don't divide each value n, R, and T by volume and then multiply those together; that would be nRT/(v^3). You want P = n...
Mon Jan 13, 2020 4:30 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changing Pressure
Replies: 3
Views: 16

### Re: Changing Pressure

How does increasing or decreasing the partial pressure of a reactant affect the partial pressure of the product, and vice versa for a change in product and its effect on the reactant? Think of equilibrium as an unbalanced see-saw where one side is supposed to have a different "weight" tha...
Mon Jan 13, 2020 4:26 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Homework 5J.5b
Replies: 2
Views: 16

### Re: Homework 5J.5b

Question 5J.5b in the homework gives the following reaction: H20(aq) + C(s) = H2(g) + CO(g). Will the reactants or products be favored by an increase in total pressure due to compression, and why? Writing the value for K gives us K= P_CO*P_H2/P_H2O. This means partial pressure, I'm not sure of any ...
Mon Jan 13, 2020 4:19 pm
Forum: Ideal Gases
Topic: "omitting" the units
Replies: 5
Views: 42

### Re: "omitting" the units

We omit the units because in actuality we are supposed to be calculating equilibrium constants and reaction quotients using the activities of each reactant or product of a reaction. Activities are unitless, only scalar values, so it makes sense that calculating a value K with unitless values produce...
Mon Jan 13, 2020 4:16 pm
Forum: Ideal Gases
Topic: Partial Pressure
Replies: 7
Views: 31

### Re: Partial Pressure

It is called partial pressure instead of just pressure because there are several gases in a given volume at once. Each gas has a certain amount of moles that occupies part of the total pressure. The sum of all the partial pressures of the gases present equals the total pressure. If only one gas was ...
Mon Jan 13, 2020 4:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: lecture 1/13 topic
Replies: 1
Views: 25

### Re: lecture 1/13 topic

What did Dr. Lavelle mean in lecture 1 today when he said that 10^-12 is actually and would be correct if it were written as 10^-7 for the concentration of H3O+? Correct me if I misinterpreted your question; this is my best explanation for what you're asking. If Hydronium concentrations were 10^-12...
Mon Jan 13, 2020 4:08 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH range
Replies: 3
Views: 20

### pH range

Is it possible for a pH level to go under 0 or above 14? Is it possible for hydronium concentrations to be above 1M (for pH less than 0) or hydroxide concentrations more than 1M (for pH greater than 14)?
Mon Jan 13, 2020 4:02 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier
Replies: 3
Views: 19

### Le Chatelier

In class, we've gone over how changes to pressure and to concentration may shift the direction of the reaction and how changing the temperature actually changes the equilibrium constant of a certain reaction. Is there possibly another way to change the value of K? Is there another parameter not disc...
Mon Jan 13, 2020 4:00 pm
Forum: Student Social/Study Group
Topic: F19 Final
Replies: 3
Views: 17

### Re: F19 Final

This is something that I would ask Professor Lavelle about, considering he is the one who was in charge of administering it with the help of last quarter's TA's. Our current TA's may have whereabouts as to where/when to pick up your final but speaking with Prof. Lavelle is definitely the best course...
Fri Jan 10, 2020 6:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Difference between lies, sits, and shifts
Replies: 4
Views: 16

### Re: Difference between lies, sits, and shifts

They essentially mean the same thing, and another one you might see is that it "favors" one side. Okay, I see thank you! However, for the "favors" part I remember seeing in his module (the first module I believe) where K>1 means that there is a "slight" favoring of pro...
Fri Jan 10, 2020 5:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Small "x" approximations for cubic equations
Replies: 3
Views: 18

### Small "x" approximations for cubic equations

I know that for cubic equations, we can make an assumption that x is small so that the equation is much easier to solve. I can't seem to remember what the threshold is for K that allows for that assumption. Was it K<10^-3 or K<10^-4?
Fri Jan 10, 2020 5:42 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Response of Equilibria to Change
Replies: 3
Views: 27

### Re: Response of Equilibria to Change

Think of the real reason as using algebra to compare two values Q and K. I would use arbitrary values for concentrations (something easy like 10) and calculate an arbitrary K value. You can use 1 as an arbitrary initial volume. With the new volume increased or decreased, you can use 0.5 for the new ...
Fri Jan 10, 2020 5:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Difference between lies, sits, and shifts
Replies: 4
Views: 16

### Re: Difference between lies, sits, and shifts

They essentially mean the same thing, and another one you might see is that it "favors" one side.
Wed Jan 08, 2020 2:57 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Clarification on Q<K and R&P concentrations
Replies: 2
Views: 27

### Re: Clarification on Q<K and R&P concentrations

Yes, just because Q<K doesn't necessarily mean that [R]>[P]. It just means that more product is favored. For instance, Q can be 10^2 and K can be 10^5. There's a lot more product than reactant, but the K requires even more product.
Tue Jan 07, 2020 11:55 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Effects of Concentration on Equilibrium
Replies: 6
Views: 40

### Re: Effects of Concentration on Equilibrium

Yes, by altering the concentrations of either reactants or products or both while the reaction is at equilibrium, it will be temporarily thrown out of balance. However, Le Chatelier's principle states that a reaction thrown out of equilibrium will try to minimize the effect of changing the concentra...
Tue Jan 07, 2020 11:05 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc versus K
Replies: 4
Views: 30

### Re: Kc versus K

Kc is the equilibrium constant calculated using the concentrations (molarities) of the products and reactants raised to their respective coefficients. K is just the equilibrium constant in general, and K can be represented as Kc or Kp, depending on the information a problem may give you.
Tue Jan 07, 2020 11:03 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Homework 5I.23
Replies: 3
Views: 29

### Re: Homework 5I.23

For number 5I.23 in the homework, why is the initial concentration (in moles) for CH4(g) 0 instead of 0.478? The initial concentration of CH4 is zero because we started off with ONLY moles of CO and H2. The 0.478 moles of CH4 is after you wait long enough for the system to reach equilibrium. Theref...
Tue Jan 07, 2020 10:43 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G11
Replies: 5
Views: 56

### Re: 5G11

The answers written with P are the expressions of the ratio of the reactants and products' partial pressures whereas those with brackets represent concentrations of the reactants and products. K values or Q values written with P are usually used for equations with gases while those written with conc...
Tue Jan 07, 2020 10:14 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Heterogenous vs. Homogenous equations
Replies: 6
Views: 30

### Re: Heterogenous vs. Homogenous equations

Another important thing to note is that when a heterogeneous reaction has reactants or products indicated as solids or pure solvents (like H2O), we must write them as "1" when we are writing an expression for K or Q. For instance, in a heterogeneous reaction with an acid HA and H2O as reac...
Tue Jan 07, 2020 10:11 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reaction quotient (Q)
Replies: 3
Views: 29

### Re: Reaction quotient (Q)

When Q<K, it means that the current amount of reactants/products wants more products. This is because when Q<K, it is saying that the ratio of product/ratio isn't high enough to reach K, so it needs more product to increase the value of Q to reach K. For Q>K, the reaction favors creation of more rea...
Mon Jan 06, 2020 10:51 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure's Effect on Equilibrium
Replies: 6
Views: 56

### Re: Pressure's Effect on Equilibrium

Inert gases do no side reactions because they're inert. Although they changed the pressure (PV = nRT), they don't change the volume of the container used and thusly the concentrations (n/V) are still the same. This is true for partial pressures as well, since the volume is constant and the moles of ...
Mon Jan 06, 2020 10:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook question 5G.11
Replies: 2
Views: 21

### Re: Textbook question 5G.11

It is possible to do problem 5G.11 without reading that particular section. For this class, the reaction quotient is calculated the same way you calculate the equilibrium constant K, either using partial pressures or concentrations. Just remember that the reaction quotient captures pressures/concent...
Mon Dec 02, 2019 4:57 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pKa calculations
Replies: 1
Views: 21

### Re: pKa calculations

Use the equation pH = -log[H3O+], from which you calculate the hydronium concentration by taking the anti-log. Then use the hydronium concentration along with the concentrations of [HA] and [A-] to evaluate Ka = [H3O+][A-]/[HA]. Once you have Ka, use the formula pKa = -log Ka.
Mon Dec 02, 2019 4:54 pm
Forum: Naming
Topic: Roman numerals
Replies: 7
Views: 48

### Re: Roman numerals

The sum of each oxidation number in the coordination compound should add up to the total charge of the complex, which in this case is -4. Each CN is a -1 and there's 6 of them, so those are a total of -6. To have a sum of -4, the charge of the cation must be +2.
Mon Dec 02, 2019 4:53 pm
Forum: Bond Lengths & Energies
Topic: Boiling Point and bonds
Replies: 5
Views: 38

### Re: Boiling Point and bonds

Boiling points and other phase changes where entropy increases is due to the intermolecular forces weakening so that the attraction between each molecule is weaker and thus there is more space between each molecule. Boiling doesn't break intramolecular bonds, but it does break intermolecular attract...
Mon Dec 02, 2019 4:50 pm
Forum: Identifying Acidic & Basic Salts
Topic: Bronsted Acids vs Lewis Acids
Replies: 2
Views: 27

### Re: Bronsted Acids vs Lewis Acids

In most cases bronsted acids = lewis acids and bronsted bases = bronsted bases, it's just the definitions that can be a bit confusing. Lewis acids are lone pair acceptors and Lewis bases are lone pair donors.
Bronsted acids are proton donors and bronsted bases are proton acceptors.
Mon Dec 02, 2019 4:48 pm
Forum: Lewis Acids & Bases
Topic: Lewis vs. Bronsted
Replies: 3
Views: 27

### Re: Lewis vs. Bronsted

Most of the time, the definitions will overlap and a lewis acid is also a bronsted acid b/c the acid satisfies both definitions. For instance, HCl is both a bronsted/lewis acid because it loses a proton to form Cl-, and when it forms Cl-, it "receives" a lone pair due to the fact that Cl- ...
Mon Dec 02, 2019 4:44 pm
Forum: Calculating the pH of Salt Solutions
Topic: Change in pH of a solution
Replies: 2
Views: 20

### Re: Change in pH of a solution

Why do some molecules have a stronger affect on pH than others? I know that all conjugate bases of a strong acid do not change the pH (from lecture on 12/2) but why is this and does it have to do with how much hydroxide or hydronium is produced and the amount of dissociation? Conjugate bases of str...
Mon Dec 02, 2019 4:41 pm
Forum: Bronsted Acids & Bases
Topic: pH and pka
Replies: 1
Views: 24

### Re: pH and pka

To get pH from pKa, use pKa to solve for Ka; using Ka, which is equal to [H3O+][A-]/[HA], if given the other variables, you can solve for [H3O+], and then solve for pH by computing -log[Hydronium]. To get pKa from pH, do the exact same process but this time, you are solving for Ka so that you can pl...
Mon Dec 02, 2019 4:35 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Bonding angles
Replies: 1
Views: 26

### Re: Bonding angles

Bonding angles, especially in long chained ligands like NH2-CH2-CH2-NH2 allow for a geometric configuration that allows the ligand to bind to the TM cation at two places, forming a chelate. Another important factor is the fact that the ligand is only sigma bonds, so the ligand is allowed rotation at...
Mon Dec 02, 2019 4:30 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: little a meaning
Replies: 2
Views: 29

### Re: little a meaning

I don't recall any "little a" in the log equation for pKa or pH or pOH; the "a" may be referring to "acid" but in each of the equations for pKa, pH, pOH, the equation is the same: p(something) = - log(something), where the log is base 10. Might be some Mandela Effect go...
Mon Dec 02, 2019 4:23 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: lecture example pKa Ka
Replies: 2
Views: 24

### Re: lecture example pKa Ka

If Ka is provided as some number, then it is most likely a weak acid. Strong acids have Ka values that tend towards infinity because strong acids are COMPLETELY deprotonated while weak acids are partially deprotonated, so Ka values are concrete values that are not towards infinity.
Mon Dec 02, 2019 4:21 pm
Forum: Calculating the pH of Salt Solutions
Topic: 6C.19
Replies: 3
Views: 44

### Re: 6C.19

Decide which acid in each of the following pairs is the stronger and explain why: (a) HF or HCl; (b) HClO or HClO2; (c) HBrO2 or HClO2; (d) HClO4 or H3PO4; (e) HNO3 or HNO2; (f) H2CO3 or H2GeO3. a) HCl because Cl is bigger, so the bond length is longer and thus the bond is weaker. Acids with easier...
Mon Dec 02, 2019 4:14 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6B.7
Replies: 1
Views: 17

### Re: 6B.7

In order to solve this problem, use the equation for the pH of any solution with a hydronium concentration. pH = -log [H3O+], and remember that this is log base 10. To solve for [H3O+], multiply both sides by the negative one, so that log[H3O+] = -pH. Then you raise 10 to the power of (-pH) in order...
Mon Nov 25, 2019 12:03 pm
Forum: Student Social/Study Group
Topic: HW Week 9 & 10
Replies: 4
Views: 44

### Re: HW Week 9 & 10

I would recommend week 9 hw cover the recently covered material on coordination compounds (there's only 5 assigned problems on those) and week 10 hw cover primarily acids and bases. HW 9 could be half coordination compounds and half acids and bases, as long as it is relevant to recently covered mate...
Mon Nov 25, 2019 12:00 pm
Forum: Bronsted Acids & Bases
Topic: Protonation
Replies: 1
Views: 27

### Re: Protonation

Can someone explain the concept of protonation? What exactly is it that determines how protonated a base is, or how deprotonated an acid is? It sounds like, "the number of molecules that have gained/lost a proton" (respectively) but in the example the textbook provides it seems like how p...
Mon Nov 25, 2019 11:53 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Focus 2.61
Replies: 1
Views: 22

### Re: Focus 2.61

The lewis structure for HOCO is a chain of H, O, C, and O (respectively) with two bends: one at the first O and one at C. There is a single bond between H-O, then a single bond between O-C, and a double bond between C-O. There is a lone electron on the C, making it a radical.
Mon Nov 25, 2019 11:47 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Dimagnetism & Paramagnetism
Replies: 6
Views: 41

### Re: Dimagnetism & Paramagnetism

We did not go over dimagnetism or paramagnetism in lecture. Those topics are not included in the 14A curriculum, last I checked.
Mon Nov 25, 2019 11:45 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: What type of concentrations can be part of the eq constant equation?
Replies: 1
Views: 17

### Re: What type of concentrations can be part of the eq constant equation?

You have to include all reactants and products that are NOT precipitates (solids) or pure liquids. We include all the components with the (aq) symbol.
Mon Nov 25, 2019 11:43 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Distinction regarding Interionic and Intermolecular forces
Replies: 1
Views: 22

### Re: Distinction regarding Interionic and Intermolecular forces

Interionic forces such as ion-ion or ion-dipole are between individual +/- ions themselves. For instance, when we refer to the forces between NaCl, we are describing the interactions between Na+ and Cl- because unlike covalent compounds, ionic compounds are arranged in a manner where cations and ani...
Mon Nov 25, 2019 11:40 am
Forum: Lewis Acids & Bases
Topic: 6A.3
Replies: 1
Views: 32

### Re: 6A.3

The overall idea of 6A.3 is that the metals from group 1 and 2 form very strong bases when they react to form metal oxides or metal hydroxides (eg. NaOH, CaO) and that nonmetals, especially halogens, can form very strong acids when combined with oxygen (eg. H2SO4, H2CO3). There are elements near the...
Mon Nov 25, 2019 11:35 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: chelating complexes
Replies: 2
Views: 27

### Re: chelating complexes

We can predict if a polydentate ligand has the ability to form chelates based on the bonds it has within itself. For example, the NH2-CH2-CH2-NH2 ligand was able to form a chelate with a cation metal because the bonds within that ligand composed of only sigma bonds, which allow rotation into a ring ...
Mon Nov 25, 2019 11:31 am
Forum: Hybridization
Topic: Question 2F.15
Replies: 2
Views: 19

### Re: Question 2F.15

If the hybridization increases in s-character, it means that there's less p and less d character. For instance, sp has more s character than sp2 or sp3. sp3 has bond angles of 109.5, sp2 is 120, and sp is 180. As you can see, the less p character there is, aka more s character, the bond angles are g...
Wed Nov 20, 2019 5:32 pm
Forum: General Science Questions
Topic: Test 2: IMF
Replies: 4
Views: 78

### Re: Test 2: IMF

It is a great idea to review those specific intermolecular forces. The test will definitely cover IMF, and it is necessary to know the hierarchy of the strengths of the IMFs. The hierarchy is LDF < Dipole-induced dipole < dipole-dipole < h-bonding or ion-dipole (ask TA's or Prof. Lavelle for clarifi...
Wed Nov 20, 2019 5:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: XA2E2
Replies: 9
Views: 58

### Re: XA2E2

AX2E2 is bent because the electron regions arrange themselves in a tetrahedral manner, but since there are only two actual bonds on the central atom, the geometry is bent. The angle is less than 109.5 degrees, however, because of the repulsion of the two lone pairs.
Wed Nov 20, 2019 5:26 pm
Forum: Biological Examples
Topic: Cisplatin
Replies: 2
Views: 32

### Cisplatin

Can someone explain to me briefly how the chlorine atoms on one side of the cisplatin attaches to the DNA? Why does this occur in terms of chemistry?
Wed Nov 20, 2019 5:16 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Covalent Bonds
Replies: 4
Views: 28

### Coordination Covalent Bonds

I understand that standard covalent bonds between nonmetals are composed of sigma and pi bonds, but how exactly does a covalent bond form between a TM cation and a nonmetal? Does it have something to do with the d-orbitals?
Wed Nov 20, 2019 5:10 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate
Replies: 2
Views: 31

### Re: Polydentate

Can someone explain how to determine whether or not a ligand is polydentate? Does it always involve drawing out the full compound to see where lone pairs are present? A ligand is considered polydentate if it has two or more lone pairs that it is able to donate to the lewis acid/TM cation. The easie...
Wed Nov 20, 2019 5:07 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 part c)
Replies: 2
Views: 24

### Re: 3F.5 part c)

Yes, the difference in the relative strengths of their LDF is due to their differences in polarizability. Because iodine is larger and has more electrons, it's more polarizable than chlorine, which is why the LDF in the compound with iodine is stronger and thus has a higher boiling point.
Wed Nov 20, 2019 5:04 pm
Forum: Dipole Moments
Topic: Hydrogen Bonds
Replies: 2
Views: 29

### Re: Hydrogen Bonds

I am a bit confused on determining whether a molecule forms hydrogen bonds. I know it only occurs when the hydrogen is attached to either N, O, or F. What are the other requirements? For example, hydrogen bonds between different molecules. Can the H only bond to N,O,F on other molecules? Or can it ...
Wed Nov 20, 2019 4:54 pm
Forum: Hybridization
Topic: 2F15
Replies: 4
Views: 28

### Re: 2F15

As the hybridized orbital has more s character (meaning less p character), the less regions of electron density are around a particular atom. For instance, if we compare sp3 to sp2, the s character increased (25% to 33%) and there is one less region of electron density, so the shape went from a tetr...
Wed Nov 20, 2019 4:51 pm
Forum: Dipole Moments
Topic: 3F.5
Replies: 2
Views: 36

### Re: 3F.5

Suggest, giving reasons, which substance in each of the following pairs is likely to have the higher normal melting point: CHI3 or CHF3. The solution says CHI3 will have the higher melting point since it has larger london forces. However, I am unsure why. How do you determine which has the stronger...
Thu Nov 14, 2019 12:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Homework 2E.5
Replies: 2
Views: 22

### Re: Homework 2E.5

Can someone help me with this problem? It states, " (a) What is the shape of a ClO2+ ion? (b) What is the expected OClO bond angle?" To start, we will draw the lewis structure of this molecule. The total number of valence electrons is 18, and since Cl isn't as electronegative as the oxyge...
Thu Nov 14, 2019 12:41 pm
Forum: *Liquid Structure (Viscosity, Surface Tension, Liquid Crystals, Ionic Liquids)
Topic: Viscosity/Surface Tension
Replies: 4
Views: 48

### Re: Viscosity/Surface Tension

Viscosity is the quality of being "sticky" or very dense. A great example of this is syrup, or honey, which are fluid but very dense. The reason that these viscous liquids are the way they are is because the bonds between the molecules are very strong. Stronger IMF means that liquids are m...
Thu Nov 14, 2019 12:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Trigonal Bipyramidal angles
Replies: 2
Views: 29

### Re: Trigonal Bipyramidal angles

For the trigonal bipyramidal angles, the angles between the horizontal, non-axial bonds of the trigonal atoms are 120 degrees. This is because the horizontal atoms form a figure analogous to the trigonal planar shape. The axial angles are 90 degrees and 180 degrees, depending on which angle between ...
Thu Nov 14, 2019 12:31 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: Ion-Dipole
Replies: 2
Views: 19

### Re: Ion-Dipole

Ion-dipole interactions are IMF between ions and molecules with dipole moments. For example, putting NaCl (ionic bond) in a pool of water (contains H-bonding but is also considered having a strong dipole moment) causes the salt and water to form very strong intermolecular forces. This is because bot...
Thu Nov 14, 2019 12:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: difference between trigonal planar and tetrahedral
Replies: 4
Views: 24

### Re: difference between trigonal planar and tetrahedral

Trigonal planar involves three areas of electron density around the central atom. With three areas of electron density, the best way to put them as far away from each other as possible is to form 120 degree angles from atom-central atom-atom. Therefore, the three areas of electron density form three...
Thu Nov 14, 2019 12:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion strength
Replies: 1
Views: 18

### Re: Repulsion strength

Recall that we are talking about areas of electron density around the central atom in the molecule. These areas want to repel each other due to coloumbic forces (negative <--> negative). Bonds repulse each other as much as they can so that electron densities are far from each other. However, lone pa...
Mon Nov 04, 2019 12:39 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7741
Views: 1058271

### Re: Post All Chemistry Jokes Here

Carbon dioxide to his therapist: "It was a horrible experience. I had to travel up some human's disgusting, mucus riddled trachea. Life sucks." *Therapist puts down his clipboard revealing that he is methane*: "Buddy, you think your life was hard? You're lucky to have traveled through...
Mon Nov 04, 2019 12:31 pm
Topic: Midterm 1
Replies: 1
Views: 43

### Midterm 1

Does anyone know if we have to know about Black Body radiation for the test? I know it's unlikely but I just want to make sure.
Mon Nov 04, 2019 12:23 pm
Forum: Lewis Structures
Topic: Line structures
Replies: 2
Views: 28

### Re: Line structures

We will not have to be familiar with complex line structures like those used in O-chem to convey depth or those used in O-chem to shorthand draw long alkynes. The exam will only go over the simple, two dimensional lewis structures which we went over in class and had lots of examples on.
Mon Nov 04, 2019 12:17 pm
Forum: Properties of Light
Topic: General Concept
Replies: 3
Views: 45

### Re: General Concept

Using classical Newtonian mechanics, we describe light as the intersection of two orthogonal waves: electric waves and magnetic waves. As a wave, the energy of the light depends on the magnitude of the amplitude. The formula c = lambda x frequency applies to light as a wave. Using quantum mechanics,...
Mon Nov 04, 2019 12:13 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent and Ionic Bonds
Replies: 6
Views: 37

### Re: Covalent and Ionic Bonds

Whenever a molecule or compound has at least two atoms of different elements, that molecule is said to have BOTH ionic and covalent character. The best way to determine if the bond between two atoms is more ionic or covalent is to compare their electronegativity values (which would be given on a tes...
Mon Nov 04, 2019 12:10 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge/Lewis structures
Replies: 5
Views: 32

### Re: Formal Charge/Lewis structures

Yes, and if there are any negative formal charges, they are ideally on the outer atoms to delocalize the negative charge.
Mon Nov 04, 2019 12:09 pm
Forum: Dipole Moments
Topic: Magnetic Dipole Moment and Electric Dipole Moment
Replies: 2
Views: 22

### Re: Magnetic Dipole Moment and Electric Dipole Moment

Magnetic dipole moments is a more physics-based concept which doesn't translate to visual representations on molecules well; electric dipole moment is the measure of difference in partial charges on one end of a polar molecule to another. It is calculated by the formula EDM = Charge (coloumbs) x dis...
Mon Nov 04, 2019 12:03 pm
Forum: Dipole Moments
Topic: Ion and Molecule Interactions
Replies: 2
Views: 23

### Re: Ion and Molecule Interactions

Will we have to memorize each kJ.mol^-1 value for the interactions that give rise to attractive forces? We will not have to memorize those values, but know the hierarchy of intermolecular/interionic force strength, which goes from 1. Ion-ion (strongest) 2. Hydrogen bonding 3. Ion-dipole 4. dipole-d...
Mon Nov 04, 2019 12:00 pm
Forum: Coordinate Covalent Bonds
Topic: Dissociation energy
Replies: 3
Views: 54

### Re: Dissociation energy

Explain how covalent bond dissociation energy is related to covalent bond multiplicity, atomic radius, and the presence of unpaired electrons. Am mostly confused on the reference to the presence of unpaired electrons. Covalent Bond multiplicity: more bonds between two atoms means higher dissociatio...
Mon Nov 04, 2019 11:56 am
Forum: Formal Charge and Oxidation Numbers
Topic: Chlorine in center: electronegativity vs. formal charge
Replies: 4
Views: 47

### Re: Chlorine in center: electronegativity vs. formal charge

What if the central atom is the most electronegative atom? (Ex. chlorine in the center in ClO4-) Would you want chlorine to be 0 or more negative than the oxygens since chlorine is more electronegative? What would the correct structure be for Cl04-? I've seen two different answers - one with 3 doub...
Mon Nov 04, 2019 11:53 am
Forum: Ionic & Covalent Bonds
Topic: C, N, O, and F
Replies: 13
Views: 89

### Re: C, N, O, and F

Do C, N, O, and F always follow the octet guideline even if their formal charge is not 0? Because they're located in period 2, where n=2, those atoms do not have access to an empty d-block where they can form bonds transcending the octet rule; therefore, they will pretty much always follow the octe...
Mon Nov 04, 2019 11:51 am
Forum: Lewis Structures
Topic: Steps of drawing lewis structures
Replies: 1
Views: 22

### Re: Steps of drawing lewis structures

What are the least to most important steps for drawing Lewis structures? For example, is it more important to do formal charges first, or moving electrons first, etc. The most important steps in general to draw lewis structures is to count how many electrons there are and make sure you draw that am...
Mon Oct 28, 2019 2:07 pm
Forum: Ionic & Covalent Bonds
Topic: Number of Chemistry Community Posts
Replies: 3
Views: 45

### Re: Number of Chemistry Community Posts

I think I've been overdoing it
Mon Oct 28, 2019 2:06 pm
Forum: Resonance Structures
Topic: Resonance
Replies: 3
Views: 27

### Re: Resonance

Resonance is the ability of chemical compounds or molecules to have different but valid lewis structures. In each resonant structure, the position of the atoms themselves are the same, but the lone pairs as well as covalent bonds may be moved around. For instance, https://www.google.com/url?sa=i&...
Mon Oct 28, 2019 1:39 pm
Forum: Bond Lengths & Energies
Topic: Electron-Electron Repulsion
Replies: 2
Views: 23

### Re: Electron-Electron Repulsion

I was wondering if someone could explain to me more about the electron-electron repulsion that makes the atomic radii bigger (I think). Does it matter that much and which one has a bigger impact, the pull from the protons or that repulsion? Electron shielding occurs when there many orbitals or shel...
Mon Oct 28, 2019 1:35 pm
Forum: Ionic & Covalent Bonds
Topic: Ground-State electron configuration
Replies: 3
Views: 29

### Re: Ground-State electron configuration

Ground state electron configurations correctly follow all of the rules listed by Aufbau's principle (correct order of subshells according to increasing energy), Pauli Exclusion principle (two electrons per orbital; each electron has a unique set of four quantum numbers), and Hund's rule (fill orbita...
Mon Oct 28, 2019 1:32 pm
Forum: Ionic & Covalent Bonds
Topic: Electron Configuration: 2A.5B
Replies: 1
Views: 17

### Re: Electron Configuration: 2A.5B

Recall how for the d-block, we subtracted 1 from the period number that it was actually in. For f-block, subtract 2 from the period number that the atom appears to fall in. Remember to use Aufbau's principle to figure out which subshell comes after which. For Bi, it is [Xe] 4f14 5d10 6s2 6p3.
Mon Oct 28, 2019 1:29 pm
Forum: Ionic & Covalent Bonds
Topic: likely charge of atoms
Replies: 3
Views: 20

### Re: likely charge of atoms

Because Gallium is a metal, it is more likely to form a cation by removing three of its electron in order to obtain the nearest full shell. Since it has three valence electrons (its configuration is [Ar] 3d10 4s2 4p1) Gallium's cation would be Ga3+.
Mon Oct 28, 2019 1:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Midterm
Replies: 6
Views: 80

### Re: Midterm

Considering how important VSEPR is in chemistry overall as well as this class and likely further classes you'll take, I wouldn't be surprised if we were tested on VSEPR. It is a good idea to read over the section on VSEPR, which is 2E I believe. Also, I don't think we were going to go over VSEPR tod...
Mon Oct 28, 2019 1:20 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: 1B.15
Replies: 1
Views: 34

### Re: 1B.15

This question was very detailed and I was hoping someone could break it down conceptually. Thank you! The velocity of an electron that is emitted from a metallic surface by a photon is 3.6x10^3 km/s. What is the wavelength of the radiation that caused photoejection of the electron?" (b) No ele...
Mon Oct 28, 2019 1:10 pm
Forum: Ionic & Covalent Bonds
Topic: valence electrons
Replies: 6
Views: 36

### Re: valence electrons

Remember that valence electrons are the amount of electrons in the outermost shell, or the highest n-value. For an atom configuration with say, [Ar] 3d10 4s2 4p3, the outermost shell is 4, so the electrons with the n=4 are the valence electrons. So that particular atom has 5 valence electrons. For m...
Mon Oct 28, 2019 1:02 pm
Forum: Trends in The Periodic Table
Topic: reactivity
Replies: 3
Views: 25

### Re: reactivity

S-block metals are much more reactive because they have less electrons to remove in order to reduce their electron cloud to a full valence shell. For example, magnesium has 2 valence electrons to remove to become a cation whereas p-block metals have more. Because the p-block metals have many electro...
Mon Oct 28, 2019 12:58 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E.9
Replies: 1
Views: 19

### Re: 1E.9

The problem gives the following three sets: a. [4, 2, -1, +1/2] b. [5, 0, -1, +1/2] c. [4, 4, -1, +1/2] Set a is valid. Set b is invalid because l=0 and ml can only be numbers where the absolute value of ml is less than or equal to l. Therefore, ml in this case can only be 0. Set c is incorrect beca...
Mon Oct 21, 2019 5:01 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: exceptions
Replies: 2
Views: 16

### Re: exceptions

[quote][/quote]
Chromium and Copper are the exceptions that were mentioned in class. Their configurations are [Ar] 3d5 4s1 and [Ar] 3d10 4s1, respectively.
Mon Oct 21, 2019 4:59 pm
Forum: Quantum Numbers and The H-Atom
Topic: f- orbitals?
Replies: 4
Views: 26

### Re: f- orbitals?

It is definitely a useful thing to know, and it's good to practice it so that you are aware of it, even though it may not appear in class or on a test. However, if you ever study radioactivity in chemistry, then knowing how to determine figurations of the f-block may come in handy. For f-block, take...
Mon Oct 21, 2019 4:56 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: determining the number of orbitals
Replies: 1
Views: 26

### Re: determining the number of orbitals

Depending on how well you know the periodic table, you would only need to know the first number "n" in order to determine how many orbitals are in that shell number. For instance, n=1 has 1 orbital, n=2 has 4 orbitals, n=3 has 9 orbitals (s, p, d), and n=4 has 16 orbitals (s, p, d, f). If ...
Mon Oct 21, 2019 4:53 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: example in class
Replies: 6
Views: 45

### Re: example in class

The subscripts for p-orbitals are completely arbitrary since all the p-orbitals are symmetrical to each other in an atom. It's just conventional to write the first p-orbital as px and the second as py and so on.
Mon Oct 21, 2019 4:51 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration
Replies: 4
Views: 36

### Re: Electron Configuration

The reason we do that is to specify which exact orbitals the electrons are occupying. Because of Hund's Rule, the electrons individually occupy each p orbital before having to share an orbital with another electron (this is to maximize stability). For the homework, it is okay to write it as 2p3 inst...
Mon Oct 21, 2019 1:38 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Exceptions (Cr and Cu)
Replies: 3
Views: 41

### Re: Exceptions (Cr and Cu)

The pattern only happens again in the 4d row; it doesn't exactly replicate in the 6th or 7th rows. However, there are some changes in the 4d row that are different than the 3d row. Luckily, we won't really have to worry about those periods as all of this class will be centered on the main group elem...
Mon Oct 21, 2019 1:30 pm
Forum: Quantum Numbers and The H-Atom
Topic: Ionization Energy
Replies: 4
Views: 22

### Re: Ionization Energy

To add on to what the others have said, it also has to do with stability in terms of whether the orbitals or subshells are full or not. For instance the reason that the second ionization energy for Na is so high is because it would have to remove an electron from its inner core, which would be its n...
Mon Oct 21, 2019 12:58 pm
Forum: *Shrodinger Equation
Topic: Shrodinger Eq. and second derivation
Replies: 1
Views: 44

### Re: Shrodinger Eq. and second derivation

The second derivative* of the wave function with respect to position (x) is an important component of the Schrodinger equation. If you want an in depth explanation on why that is then I would recommend you go to office hours with Prof. Lavelle or perhaps the TA's because the math behind the schrodin...
Mon Oct 21, 2019 12:52 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration
Replies: 2
Views: 50

### Re: Electron Configuration

How are electrons added to a configuration? I know that whether electrons are added to an atom can change the spin type but what are some scenarios in which electrons will be added? Electrons can be "added" to orbitals when an atom becomes an anion or when, in the coming unit, atoms take ...
Mon Oct 21, 2019 12:48 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum Mechanics and Computers
Replies: 1
Views: 28

### Re: Quantum Mechanics and Computers

Modern computers rely on electronics, with electrons being a fundamental aspect. As you know, most to all electronics, especially the one you used to type this question, rely on electricity, which is the movement of electrons from one place to another. Many components of technology nowadays uses the...
Mon Oct 21, 2019 12:31 pm
Forum: Trends in The Periodic Table
Topic: Isoelectronic Atoms
Replies: 6
Views: 50

### Re: Isoelectronic Atoms

When explaining isoelectronic atoms in class today he kept mentioning the electrons in terms of OF electrons. What are OF electrons? I'm not entirely sure what is meant by "of electrons", however, I can try my best to explain the concept of isoelectronic atoms without using confusing term...
Mon Oct 21, 2019 12:25 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Minimum uncertainty?
Replies: 2
Views: 35

### Re: Minimum uncertainty?

If the HBI Equation gives us the minimum uncertainty, what does this mean in context? Does this imply that the object could actually have a greater uncertainty in its position/momentum? The equation is saying that there is a limit to how much we can know about position and momentum simulataneously....
Mon Oct 21, 2019 12:18 pm
Forum: Trends in The Periodic Table
Topic: 1st and 2nd Ionization
Replies: 5
Views: 44

### Re: 1st and 2nd Ionization

The first ionization energy is the amount of energy required to remove an electron from an atom in a gaseous state. The second ionization energy is the energy required to remove another electron in addition to the electron that is already removed. The second ionization energy is always greater that ...
Mon Oct 21, 2019 12:16 pm
Forum: *Shrodinger Equation
Topic: Parts of the Schrodinger Equation
Replies: 1
Views: 29

### Re: Parts of the Schrodinger Equation

Hi all! I understand that we will not need to calculate the equation itself, but I am still confused on how the equation works. I understand that the hamiltonian is the double derivative, but what is it the double derivative of? Can someone please explain the parts of this equation? The hamiltonian...
Mon Oct 14, 2019 12:11 pm
Forum: DeBroglie Equation
Topic: 1B.15
Replies: 2
Views: 50

### Re: 1B.15

1B.15 The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 3 103 km?s21. (a) What is the wavelength of the ejected electron? (b) No electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50 3 1016 Hz. How much energy is r...
Mon Oct 14, 2019 12:05 pm
Forum: Properties of Electrons
Topic: 1A.11 Question about Lyman series
Replies: 2
Views: 44

### Re: 1A.11 Question about Lyman series

Balmer series refers to the different wavelengths of photons absorbed/emitted for the electron to transition from/to energy levels n=2 and n=3, 4, 5, etc. Lyman series refers to the different wavelengths of photons absorbed/emitted for the electron to transition from/to energy levels n=1 to n=2, 3, ...