## Search found 108 matches

Thu Jan 21, 2021 7:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Strong acids & bases
Replies: 1
Views: 8

### Strong acids & bases

Hi! Just to confirm, do strong acids/bases not have equilibrium constants because they dissociate completely?
Thu Jan 21, 2021 7:18 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Textbook 6.B.3
Replies: 3
Views: 7

### Re: Textbook 6.B.3

Hi! So, the first part asks you to solve for the pH of the desired solution, which is 200.0 mL of a 0.025 M HCl solution. HCl is a strong acid, so it completely dissociates into H+ and Cl-, and so you can calculate the pH by taking the negative log of [H+] or [0.025]. For part b, to find the actual ...
Wed Jan 20, 2021 1:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Percent ionization
Replies: 8
Views: 30

### Re: Percent ionization

MHarrold_1E wrote:[ionized amount]/[initial amount] x100 = percent ionized.

But would you divide the [H3O+] ionized or the [CB] ionized by the initial amount?
Tue Jan 19, 2021 8:27 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Relevance of equilibrium constant
Replies: 5
Views: 18

### Relevance of equilibrium constant

Hi! I was just thinking, and I'm not really sure what an equilibrium constant actually means. What exactly does it tell us?
Tue Jan 19, 2021 8:25 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm 1
Replies: 24
Views: 121

### Re: Midterm 1

Anna Yang 1A wrote:On the syllabus it says that the midterm is on a Friday during class time. Is this true because for 14A last quarter, it was during our respective discussion sections?

Hi! Yes this is true. Midterms this quarter will be held during our class lecture time on Friday.
Mon Jan 18, 2021 10:32 am
Forum: Phase Changes & Related Calculations
Topic: ionization percentage
Replies: 10
Views: 35

### Re: ionization percentage

To add on, for strong acids/bases, they ionize or dissociate completely, and therefore their percent ionization is 100%. For weak acids and bases (which don't ionize completely), you take the equilibrium [OH-] (for bases) or the [H3O+] (for acids) and divide it by the initial concentration of the we...
Fri Jan 15, 2021 7:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Percent ionization
Replies: 6
Views: 18

### Re: Percent ionization

To add on to the above response, percent ionization is just how much of the acid dissociates into H3O+.
Wed Jan 13, 2021 9:01 am
Forum: Student Social/Study Group
Replies: 25
Views: 62

Hi! I would definitely attend some UA sessions if you can. I find the worksheets they give really helpful. I would also suggest doing textbook problems as we go through each unit, as it gives you good practice.
Wed Jan 13, 2021 8:58 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: K in endo and exo when temp. decreases
Replies: 11
Views: 47

### Re: K in endo and exo when temp. decreases

According to Le Chatelier's principle, chemical reactions adjust so as to minimize the effect of changes. Therefore, I believe decreasing the temperature will increase the K value (more products) for an exothermic reaction and decrease the K value for an endothermic reaction. Please correct me if I...
Tue Jan 12, 2021 1:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Simplifying Expressions: K<10^?
Replies: 6
Views: 42

### Re: Simplifying Expressions: K<10^?

Hi! I would just go with anything smaller than 10^-3, because that is what the textbook goes by too. Dr. Lavelle also mentioned for anything smaller than 10^-4, the value of x is DEFINITELY negligible. It's just more certain, but I would still stick to anything smaller than 10^-3.
Mon Jan 11, 2021 1:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium constant for water
Replies: 4
Views: 24

### Equilibrium constant for water

Hi! In the equilibrium constant of water, why are the concentrations of H3O+ and OH- the same (1x10^-7 for both)? I didn't really understand the reasoning.
Mon Jan 11, 2021 8:28 am
Forum: Administrative Questions and Class Announcements
Topic: Sapling Homework
Replies: 7
Views: 48

### Re: Sapling Homework

Hi! I was sent to a page where it asked me to pay again or to "use credit". The "use credit" is the option you should choose, but this option will only be there if you purchased a full year access to sapling or more than one term.
Mon Jan 11, 2021 8:25 am
Forum: Ideal Gases
Topic: Ice method
Replies: 14
Views: 64

### Re: Ice method

Using ICE as a method is a bit more involved than what explanation allows, but a brief overview is what follows. ICE is an acronym standing for Initial, Change, and Equilibrium. When given a chemical equation and their initial concentrations, you can input their initial concentrations into Initial ...
Fri Jan 08, 2021 9:20 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Sapling Week 1&2 Homework Question
Replies: 8
Views: 74

### Re: Sapling Week 1&2 Homework Question

Hi! As far as I know, temperature is one of the only things that affect the equilibrium constant (K). The way I look at how temperature affects a reaction is by whether it's exothermic or endothermic. If the reaction is endothermic, heat would technically be on the reactants side, and if you increas...
Wed Jan 06, 2021 9:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium constant dependence on concentrations
Replies: 3
Views: 30

### Equilibrium constant dependence on concentrations

Hi! Is the equilibrium constant for a certain reaction the same every time regardless of the initial concentrations of reactants and products. In other words, do the concentrations of reactants and products affect the equilibrium constant if it's for the same reaction? Hopefully this makes sense
Wed Jan 06, 2021 9:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Stability of reactants vs products
Replies: 5
Views: 24

### Re: Stability of reactants vs products

Hi! In general, whichever reaction (forward or reverse) is more favored is the one leading to more stability. So if the forward reaction is favored (large K value), the products are favored - more products are produced. This means that products have higher stability, because reactions tend to move i...
Tue Jan 05, 2021 4:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: chemical equilibrium pt 2 module #19
Replies: 1
Views: 14

### Re: chemical equilibrium pt 2 module #19

Hi! So your first 2 steps are correct regarding the balanced chemical equation and the setup for the reaction quotient. However, the concentrations that you're plugging in are incorrect. Notice how the moles are given, but not mol/L (which is your concentration and what you need to find the reaction...
Mon Jan 04, 2021 6:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium favoring one side over the other
Replies: 2
Views: 18

### Equilibrium favoring one side over the other

Hi! If a reaction is at equilibrium with a given equilibrium constant, why is it that one side is favored over the other? In other words, why are the products sometimes favored over the reactants and vice versa if the reaction is at equilibrium (forward and reverse reactions have equal rates)?
Mon Jan 04, 2021 6:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Finding Concentrations at Equilibrium
Replies: 5
Views: 37

### Re: Finding Concentrations at Equilibrium

Hi! To add on to the above responses, if the equilibrium concentration for a reactant or a product isn't given, the equilibrium constant (Kc) would be given instead. This way, using the products/reactants formula, you could set it equal to the equilibrium constant and solve for the unknown reactant ...
Wed Dec 16, 2020 11:38 am
Forum: Student Social/Study Group
Topic: Winter Break Plans
Replies: 32
Views: 138

### Re: Winter Break Plans

Hi! Like many of us, I will be spending time at home with just my family this winter. I'll probably catch up on netflix, and just relax before winter quarter begins!
Fri Dec 11, 2020 8:14 am
Forum: Naming
Topic: 9C.1
Replies: 1
Views: 13

### Re: 9C.1

Hi! You add 'ate' to the end of the TM cation when the overall charge on the complex is negative. For example, in this case, [Co (NH3)6] 3+ is just hexaammine cobalt (III) because the overall charge of the coordination sphere (complex) is positive. However, for [Co (CN)5 (OH2)] 2- you add 'ate' to t...
Thu Dec 10, 2020 10:12 pm
Forum: Balancing Chemical Reactions
Topic: Diatomic Molecules
Replies: 7
Views: 85

### Re: Diatomic Molecules

Also, one thing to know about diatomic molecules are that they are NOT polar.
Thu Dec 10, 2020 3:00 pm
Forum: Sigma & Pi Bonds
Topic: Sapling Week 7/8 #18
Replies: 2
Views: 17

### Sapling Week 7/8 #18

Hi! For Week 8 Sapling Number 18, why is it that the hydrogen atoms are in the same plane for H2CCH2 and H2CCCCH2 but not for H2CCCH2?
Thu Dec 10, 2020 1:30 pm
Forum: Conjugate Acids & Bases
Topic: Textbook question 6.21
Replies: 2
Views: 32

### Textbook question 6.21

Hi! The question here is how many protons could this base (thymine) accept? I thought we needed to count the lone pairs (2 on each oxygen and 1 on each nitrogen), giving a total of 6 sites to accept protons. However, the solutions manual said only the lone pairs on the nitrogen could accept protons....
Wed Dec 09, 2020 7:13 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Question
Replies: 6
Views: 72

### Re: Final Question

Hi! If you go on his website and go to the acid and base outline, there's a list of points we should know for the final.
Wed Dec 09, 2020 6:58 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: CO2 and H2O
Replies: 3
Views: 41

### CO2 and H2O

Hi! What intermolecular forces are present between CO2 and H2O?

I know CO2 is a nonpolar molecule, and H2O is a polar molecule, so is there still hydrogen bonding present?
Wed Dec 09, 2020 3:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AX2E3 shape
Replies: 3
Views: 38

### AX2E3 shape

Hi! Could someone explain why AX2E3 (the trigonal bipyramidal electron arrangement) is linear? What effect do the equatorial lone pairs have on the central atom in this case?
Wed Dec 09, 2020 3:05 pm
Forum: Identifying Acidic & Basic Salts
Topic: Titration
Replies: 2
Views: 24

### Re: Titration

Hi! Yes, if it was a titration involving a weak acid and a weak base, the equivalence or stoichiometric point is where moles acid = moles base.
Tue Dec 08, 2020 8:38 am
Forum: Hybridization
Topic: Why is Hybridization necessary?
Replies: 4
Views: 63

### Why is Hybridization necessary?

Hi! Why is hybridization needed for compounds like NH3? I understand why it’s necessary for carbon (because carbon makes 4 bonds, but there are only two unpaired electrons if unhybridized) but not for elements like nitrogen. Could someone please explain this?
Mon Dec 07, 2020 8:43 pm
Forum: Naming
Topic: 9C.3d
Replies: 2
Views: 29

### Re: 9C.3d

Hi! Oxalate is a polydentate ligand, and therefore the prefix 'bis' is used instead 'di'. Other examples of polydentate ligands to watch out for are ethylenediamine (en), diethylenetriamine (dien), and ethylenediaminetetraacetato (edta). Bis, tris, tetrakis, etc. prefixes would be used for these.
Mon Dec 07, 2020 4:11 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Energy of orbitals
Replies: 2
Views: 34

### Energy of orbitals

Hi! Do different orbitals in the same atomic subshell (s,p,d,f) have the same energy or different? For example, does the orbital 2px have the same energy as 2py and 2pz orbitals?
Mon Dec 07, 2020 2:26 pm
Forum: Amphoteric Compounds
Topic: Recognizing Amphoteric Compounds
Replies: 9
Views: 154

### Re: Recognizing Amphoteric Compounds

You can determine if a species is acidic or basic by looking at whether it donates a proton or accepts a proton. If it donates a proton, then it’s acidic. If it accepts a proton, then it’s basic. Amphoteric species are ones that can react with both acids and bases depending on what other species th...
Sun Dec 06, 2020 7:24 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelates
Replies: 3
Views: 26

### Re: Chelates

A chelate is formed when the ligand is polydentate. In addition to this, chelates are formed when more than one atom in the ligand have a lone pair and sigma bond on them, so that they can rotate and form a ring structure to bind to the metal cation in more than one place. Common examples of chelat...
Sun Dec 06, 2020 10:44 am
Forum: Bronsted Acids & Bases
Topic: Difference between Bronsted Acid and Lewis acid?
Replies: 4
Views: 12

### Re: Difference between Bronsted Acid and Lewis acid?

In simple terms, a Bronstead acid is a proton donor (gives off a H+), and a lewis acid is an electron pair acceptor.
Fri Dec 04, 2020 11:55 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelating ligands and polydentate compounds
Replies: 3
Views: 21

### Re: Chelating ligands and polydentate compounds

Hi! The way I look at it is if the polydentate ligand has more than one atoms with a lone pair AND a single bond, it can form a chelate.
Thu Dec 03, 2020 12:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Textbook question 2E. 1
Replies: 3
Views: 25

### Textbook question 2E. 1

Hi! In the image below, question 2E 1, could someone please explain why the 2nd model may have lone pairs?
Thu Dec 03, 2020 9:19 am
Forum: Naming
Topic: Writing it out
Replies: 4
Views: 29

### Re: Writing it out

I agree. Sodium is a cation that comes before the coordination complex (the bracket)
Wed Dec 02, 2020 10:03 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination numbers and shapes
Replies: 3
Views: 44

### Re: Coordination numbers and shapes

Hey! Just to add on, the coordination number represents the number of bonds that are formed by a specific cation, or transition metal. With this, we can use this information and the information we know about the shapes of molecules (i.e. coordination # of 6 being octahedral, # 4 being square planar...
Wed Dec 02, 2020 9:59 am
Forum: Biological Examples
Topic: Enzyme Function
Replies: 8
Views: 83

### Re: Enzyme Function

Hi! These particular transition metals interact and bind with amino acids or other solutions in the active site of an enzyme. Hope this helps :)
Tue Dec 01, 2020 3:20 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Sapling Number 3
Replies: 8
Views: 60

### Re: Sapling Number 3

Natallie K 3B wrote:But then why is trigonal bipyramidal not an answer?

This is because there are 5 bonds involved in trigonal bipyramidal. Hope this helps :)
Mon Nov 30, 2020 7:44 pm
Forum: Biological Examples
Topic: Biological Functions of Transition Metals
Replies: 5
Views: 62

### Re: Biological Functions of Transition Metals

I believe that the order of transition metals does not matter, but what's important is that the first row transition metals have unique biological functions.
Mon Nov 30, 2020 7:35 pm
Forum: Naming
Topic: formula for coordination compounds
Replies: 2
Views: 28

### Re: formula for coordination compounds

Hi! When there is more than one ligand, you place them in alphabetical order. In today's lecture for example, [Co(NH3)5Cl], it would be penta ammine chloro cobalt (II) with ammine being before chloro.
Hope this helps :)
Fri Nov 27, 2020 4:33 pm
Forum: Lewis Structures
Topic: Ring structures
Replies: 4
Views: 49

### Ring structures

Hi! In the sapling homework, there was a question asking to draw structures of a compound/molecule, one of them being a ring structure.

How do we know when molecules have ring structures?
Thu Nov 26, 2020 10:05 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Coordination Compounds
Replies: 5
Views: 31

### Re: Coordination Compounds

Like above, there is no difference in OH2 and H2O. They are just written like that in order to show which atom is actually bonding to the cation. In this case, O (the negatively charged atom) is what's binding to the cation. Therefore, for the purpose of showing which cation and atom are bonding, H2...
Wed Nov 25, 2020 9:22 am
Forum: Determining Molecular Shape (VSEPR)
Topic: What does delocalized π bond mean?
Replies: 18
Views: 143

### Re: What does delocalized π bond mean?

In general, molecules that have resonance, would have delocalized pi bonds. Hope this makes sense :)
Wed Nov 25, 2020 9:21 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Electron vs. Molecular Geometry
Replies: 3
Views: 12

### Re: Electron vs. Molecular Geometry

Hi! The electron geometry refers to the arrangement of electron density around the central atom. So, for example, if there are 3 bonding pairs and 2 lone pairs around the central atom, there are 5 regions of electron density around the central atom. This makes the electron geometry trigonal bipyrami...
Mon Nov 23, 2020 2:05 pm
Forum: Sigma & Pi Bonds
Topic: Delocalized pi bond
Replies: 4
Views: 39

### Delocalized pi bond

Hi! What exactly are delocalized pi bonds?

I was doing the sapling homework, and the question was

Which of the species contains a delocalized π bond?
- CO2−3
- H2O
- O3
- HCN

Could someone please explain what they are?
Mon Nov 23, 2020 11:59 am
Forum: Octet Exceptions
Replies: 5
Views: 88

### Re: Where to place radicals

Hi! I believe when given a radical, the atom which is the most electronegative gets the full octet. So if you are deciding between giving one electron to which atom, go with the most electronegative one. This is because their pulling power of electrons is stronger, so therefore, the more electronega...
Mon Nov 23, 2020 11:54 am
Forum: Administrative Questions and Class Announcements
Topic: Thanksgiving Discussion
Replies: 7
Views: 62

### Re: Thanksgiving Discussion

I believe discussions on Thursday and Friday will be cancelled this week.
Sat Nov 21, 2020 9:27 pm
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi Bond Strength
Replies: 4
Views: 44

### Re: Sigma and Pi Bond Strength

To my understanding, pi bonds can't rotate or they will break. Sigma bonds, however, are able to rotate without breaking, so that may be another reason/example of sigma bonds being stronger. I agree with this statement. To add on, sigma bonds are stronger than pi bonds, because there is a bigger ov...
Thu Nov 19, 2020 12:41 pm
Forum: Lewis Structures
Topic: Textbook 2B.1
Replies: 4
Views: 19

### Re: Textbook 2B.1

Hi! Like all the answers above, we leave the lone pair of electrons on N to minimize formal charge. When nitrogen is bonded to 3 atoms and has 1 lone pair of e-, the formal charge is zero. This makes the molecule more stable by minimizing energy.
Tue Nov 17, 2020 6:37 pm
Forum: Student Social/Study Group
Topic: Midterm 2
Replies: 3
Views: 56

### Re: Midterm 2

Hi! The VSPER model is not on midterm 2. It goes till the end of outline 3 - chemical bonds. In the textbook, it's sections 1D to 1F, 2A-2D, and 3F.4 - 3F.5.
Tue Nov 17, 2020 6:32 pm
Forum: Dipole Moments
Topic: Textbook question 3F.5
Replies: 2
Views: 43

### Textbook question 3F.5

Hi! In the homework question below, I don't understand why the answer is CHI3. Could someone please explain?

3F5 - Suggest, giving reasons, which substance in each of the following pairs is likely to have the higher normal melting point (Lewis structures may help your arguments): c) CHI3 or CHF3
Mon Nov 16, 2020 8:36 pm
Forum: Lewis Structures
Topic: Textbook Problem 2B.15
Replies: 2
Views: 20

### Re: Textbook Problem 2B.15

Hi! The double bond can be from Cl to the N atom, but this is unfavorable. If you double bond the N to the Cl, there are more formal charges present in the molecule ClNO2: Cl would have a +1 charge, N +1, and both O's would have a -1 charge. However, when double bonded to the oxygen, Cl has no charg...
Mon Nov 16, 2020 11:37 am
Forum: Lewis Structures
Topic: Identifying lewis acids and bases
Replies: 5
Views: 50

### Identifying lewis acids and bases

Hi! I came across a problem where it asked me to identify which reactant is a lewis acid and which reactant is a lewis base.

CH3NH2 + CH3Br → Br- + (CH3)2NH2+

From this equation, how do we know which reactant is a lewis acid/base?
Mon Nov 16, 2020 7:54 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing Power Practice Problem
Replies: 3
Views: 55

### Re: Polarizing Power Practice Problem

Hi! Polarizing power is an atom's ability to pull electrons (distort e- in other atoms), so cations are the ones that tend to have high polarizing power because their positive charge attracts negative electrons. There are two factors to remember when it comes to polarizing power: charge and size. Th...
Sat Nov 14, 2020 8:34 am
Forum: Formal Charge and Oxidation Numbers
Topic: Clarification
Replies: 8
Views: 37

### Re: Clarification

Yes! The sum of all formal charges should equal the overall charge of that compound.
Thu Nov 12, 2020 12:06 pm
Forum: Octet Exceptions
Topic: Expanded Octets
Replies: 1
Views: 18

### Expanded Octets

Hi! When it comes to expanded octets, do only central atoms have expanded octets, or can the surrounding atoms have expanded octets too? What I mean is, for example, ICl5 (iodine pentachloride) has 42e-. When drawing the structure, can the Cl's surrounding the central atom (I) have expanded octets l...
Thu Nov 12, 2020 11:53 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: Hydrogen bonding why it works?
Replies: 4
Views: 24

### Re: Hydrogen bonding why it works?

Adding on to what Megan said, the hydrogen in hydrogen bonds are only covalently bonded to an N, O, F, and that creates a dipole-dipole interaction with another electronegative atom. So really, there's only 1 bond, and the other is an attraction. Hope this helps!
Wed Nov 11, 2020 10:22 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Writing ground-state e- configurations
Replies: 3
Views: 30

### Writing ground-state e- configurations

Hi! When asked to write the ground-state electron configuration for an atom, do we write the noble gas configuration, or the full configuration? What I mean is, for example, the e- configuration for carbon is 1s^2 2s^2 2p^2, but can also be written as [He]2s^2 2p^2. Which one are we supposed to write?
Wed Nov 11, 2020 9:04 am
Forum: Lewis Structures
Topic: C Valence Electrons
Replies: 5
Views: 38

### Re: C Valence Electrons

Hi! Going off of what everyone said above, to determine the value of valence electrons, the e- present in the outermost shell, I look at the group numbers. While counting groups, I skip the group of transition metals, so Li is in group 1, Be in 2, B in 3, and C in group 4. Since carbon is present in...
Mon Nov 09, 2020 8:05 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals and probability
Replies: 2
Views: 37

### Orbitals and probability

Hi! While looking through the outline of the Quantum World unit, I came across this point: • Describe the interpretation of atomic orbitals in terms of probability. I am not sure what this means and what it is referring to. Could someone please explain? I am confused on how orbitals are related to p...
Mon Nov 09, 2020 12:06 pm
Forum: Ionic & Covalent Bonds
Topic: The ionic model
Replies: 7
Views: 28

### Re: The ionic model

Hi! All ionic bonds have some covalent character, because in reality, the electron density around the two atoms is shared. And sharing = covalent.
Mon Nov 09, 2020 12:03 pm
Forum: Octet Exceptions
Topic: Expanded Octets
Replies: 6
Views: 27

### Re: Expanded Octets

To add on to all the answers above, usually, the elements P, S, and Cl have expanded octets. Also, I asked a TA about the limit to expanded octets, and she said we would usually see up to 14 electrons in total within an expanded octet.
Sun Nov 08, 2020 8:19 am
Forum: Ionic & Covalent Bonds
Topic: Salts and molecules
Replies: 4
Views: 45

### Re: Salts and molecules

Hi!
Yes. In general, ionic bonds are referred to as salts, and covalent bonds are referred to as molecules.
Sat Nov 07, 2020 7:40 am
Forum: Ionic & Covalent Bonds
Topic: Electronegativity
Replies: 16
Views: 90

### Re: Electronegativity

Also, since fluorine only requires one more electron to make it stable (a noble gas configuration), it is highly reactive, and therefore attracts electrons very easily.
Fri Nov 06, 2020 9:20 am
Forum: Lewis Structures
Topic: Sapling Question #3
Replies: 2
Views: 36

### Re: Sapling Question #3

I believe the chemical formulas will be given to you usually, but like above, anything ending with 'ate' suggests 3 oxygens (nitrate: NO3-), and anything ending with 'ite' suggests 2 oxygens (Nitrite: NO2-). Hope this helps!
Thu Nov 05, 2020 3:53 pm
Forum: Resonance Structures
Topic: Delocalized electrons and stability
Replies: 2
Views: 44

### Delocalized electrons and stability

Why do delocalized electrons (from resonance structures) lead to an increase in stability of atoms?
Wed Nov 04, 2020 6:20 pm
Forum: Lewis Structures
Topic: Central atom
Replies: 4
Views: 34

### Central atom

Why is the atom with the lower ionization energy the central atom? And are all other atoms bonded to the central atom?
Wed Nov 04, 2020 1:26 pm
Forum: Lewis Structures
Topic: ionization energy vs. electronegativity
Replies: 5
Views: 23

### Re: ionization energy vs. electronegativity

Ionization energy and electronegativity are synonymous, so they have the same periodic trends, so I believe you can use either The above statement is true - they are synonymous. If you think about it, oxygen is very electronegative (high tendency to attract electrons), and therefore it has a higher...
Wed Nov 04, 2020 1:20 pm
Forum: Resonance Structures
Topic: Delocalized e-
Replies: 5
Views: 50

### Delocalized e-

What are delocalized electrons? Dr. Lavelle mentions it in his lecture when he explains resonance, and how those structures have delocalized electrons, but I'm not really sure what they mean.
Tue Nov 03, 2020 7:26 am
Forum: Trends in The Periodic Table
Topic: # of electrons
Replies: 23
Views: 118

### Re: # of electrons

Like the statements above, the number of electrons for an element is equivalent to its atomic number. To find the number of valence electrons, however, you would need to count the number of electrons in an elements' outermost shell. For example, in Magnesium, the number of electrons is = to its atom...
Tue Nov 03, 2020 7:21 am
Forum: Lewis Structures
Topic: sides
Replies: 12
Views: 129

### Re: sides

Hi! The side doesn't matter as long as you have the correct number of electrons for each element.
Mon Nov 02, 2020 8:36 am
Forum: Lewis Structures
Topic: Brackets for Anions
Replies: 6
Views: 45

### Re: Brackets for Anions

You use brackets for structures that have an overall charge. Therefore, you will see them when drawing cations and anions' lewis structures.
Sat Oct 31, 2020 10:21 am
Forum: Trends in The Periodic Table
Topic: Periodic Table & Electron Affinity
Replies: 11
Views: 81

### Re: Periodic Table & Electron Affinity

Hi! Electron affinity is basically the opposite of ionization energy. It's the energy released when electrons are added to a gas phase atom. It's not as periodic, but there's usually high e- affinity for elements in the top right of the periodic table. Halogens (group 17) have high e- affinities. In...
Fri Oct 30, 2020 8:44 am
Forum: Quantum Numbers and The H-Atom
Topic: Sampling week 2,3,4, Q8
Replies: 3
Views: 30

### Re: Sampling week 2,3,4, Q8

Once given the wavelength, you should be able to figure out whether it belongs to the Lyman or Balmer series. For example, if the wavelength belongs to one from the visible light spectrum, then it is the Balmer series, meaning n2 should be 2. If in Lyman's series, n2 is 1 After doing what was menti...
Fri Oct 30, 2020 8:40 am
Forum: Ionic & Covalent Bonds
Topic: Nonpolar and polar
Replies: 16
Views: 273

### Re: Nonpolar and polar

Polar molecules have an unequal sharing of electrons. For example, in the molecule H2O, O is more electronegative than H, making it attract more electrons. This gives them a partial negative charge, and hydrogen (H) a partial positive charge. The e- sharing is unequal, and therefore the molecule is ...
Tue Oct 27, 2020 6:34 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect
Replies: 13
Views: 119

### Re: Photoelectric Effect

The energy does not get absorbed if it's less than the work function - it just passes through the metal
Mon Oct 26, 2020 10:02 pm
Forum: Photoelectric Effect
Topic: Moles of atoms/photons
Replies: 3
Views: 39

### Moles of atoms/photons

In general, when the question asks to calculate the number of moles of atoms or moles of photons, do you multiply by Avagadro's constant or divide by it?
Mon Oct 26, 2020 10:13 am
Forum: Molarity, Solutions, Dilutions
Topic: Textbook question G25
Replies: 2
Views: 54

### Textbook question G25

Could someone please explain this question? Practitioners of the branch of alternative medicine known as homeopathy claim that very dilute solutions of substances can have an effect. Is the claim plausible? To explore this question, suppose that you prepare a solution of a supposedly active substanc...
Thu Oct 22, 2020 7:59 pm
Forum: Empirical & Molecular Formulas
Topic: workshop question emp formula
Replies: 3
Views: 68

### Re: workshop question emp formula

Hi! So first, I would write the combustion reaction out: CxHyOz + O2 --> CO2 + H2O Once you have this, you're given the mass of CO2 and H2O produced, so the first thing you should always do is convert to moles. For CO2, it will be 1.2073g divided by its molar mass (44.01g/mol), which will give you t...
Thu Oct 22, 2020 9:35 am
Forum: Einstein Equation
Topic: Sapling
Replies: 2
Views: 48

### Re: Sapling

Hi! So once you got the work function - the energy to remove an electron - you take the total energy of photons, and divide it by the work function value: 7.4e-7/2.726e-19

This gives you the answer of 2.71e12 electrons ejected. Hope this helped!
Wed Oct 21, 2020 8:38 am
Forum: Photoelectric Effect
Topic: Absorption of a photon
Replies: 4
Views: 35

### Absorption of a photon

In the photoelectric effect, if the energy of the photon is less than the threshold energy (work function), no electrons are ejected. Does that mean the photon just passes through the metal or does it still get absorbed with no electron ejection?
Tue Oct 20, 2020 3:15 pm
Forum: Photoelectric Effect
Topic: Spectral Lines
Replies: 4
Views: 52

### Re: Spectral Lines

Hi! Spectral lines are basically showing electron energy levels - each line represents an energy transition of an electron. Hope this helps!
Tue Oct 20, 2020 10:46 am
Forum: Student Social/Study Group
Topic: Electron mass
Replies: 3
Views: 26

### Re: Electron mass

I believe the mass of electrons will be given on the formula sheet, and the same goes for the mass of protons and neutrons (if not on the formula sheet, it will be given with the question)!
Mon Oct 19, 2020 10:54 am
Forum: DeBroglie Equation
Topic: QM description of electrons
Replies: 4
Views: 47

### QM description of electrons

In his lecture, Dr. Lavelle mentions that electrons have discrete energies with only certain wavelengths allowed inside an atom. What exactly does this mean?
Mon Oct 19, 2020 10:28 am
Forum: DeBroglie Equation
Topic: measurable wave-like properties
Replies: 3
Views: 23

### Re: measurable wave-like properties

I would say anything smaller than the wavelength 10^-15 would be hard to detect, making the wavelike properties unmeasurable.
Fri Oct 16, 2020 6:57 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Sapling week 2/3 question 5
Replies: 2
Views: 33

### Re: Sapling week 2/3 question 5

Just like said above, you count the number of lines the electron can be de-excited to. So in this case, for example, from n= 5 to n = 4 is 1 line. However, since it doesn't give you a specific energy level to which the electron drops, count till the lowest energy level, which is n=1. n =5 to n =4 is...
Wed Oct 14, 2020 4:45 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Bohr Frequency Condition frequency equation
Replies: 2
Views: 28

### Bohr Frequency Condition frequency equation

For the frequency equation, v = -R [(1/n1^2)-(1/n2^2)], I was confused as to what n1 and n2 were.

So, for example, if an electron is emitting energy from energy level n= 5 to n= 2, what is n1 and n2 respectively in the frequency equation above? Which energy level is n1 and which energy is n2?
Wed Oct 14, 2020 12:16 pm
Forum: Photoelectric Effect
Topic: Sapling #4
Replies: 2
Views: 26

### Re: Sapling #4

Hi! So the first part of the problem, you're given the frequency of the photons, and therefore, you can find the energy of the photons using the E = hv equation. Once you have the e(photon), and since you're given the kinetic energy, you can solve for the energy to remove an electron using the equat...
Tue Oct 13, 2020 7:05 pm
Forum: Empirical & Molecular Formulas
Topic: Compounds can Have the Same Molecular Formulas
Replies: 4
Views: 47

### Re: Compounds can Have the Same Molecular Formulas

Hi! I'm not fully sure if this is right, but I think the only way different compounds can have the same molecular formulas is by being an isomer. Isomers have the same molecular formula but different structural formulas, so the atoms are the same, but the order they're in are arranged differently. T...
Mon Oct 12, 2020 1:26 pm
Forum: Photoelectric Effect
Topic: Focus-Topics Photoelectric Effect Assessment Question #34
Replies: 2
Views: 19

### Re: Focus-Topics Photoelectric Effect Assessment Question #34

Hi! So we know the equation E(photon) - E(energy to remove e-) = kinetic energy of emitted e-. Therefore, if we solve for the energy of the photon and the energy required to remove the electron, we can find the kinetic energy. To solve for the energy needed to emit/remove an electron, you can use th...
Mon Oct 12, 2020 11:06 am
Forum: Photoelectric Effect
Topic: Photon Energy in Photoelectric Experiment
Replies: 6
Views: 44

### Re: Photon Energy in Photoelectric Experiment

Hi! I believe if light doesn't have enough energy to eject an electron, it just passes through the metal and is not absorbed.
Mon Oct 12, 2020 10:26 am
Forum: Properties of Light
Topic: Light Intensity and Frequency
Replies: 7
Views: 82

### Re: Light Intensity and Frequency

Hi! An increase in light intensity doesn't increase the energy of light, but it increases the number of photons ejected. It is relative to the amplitude of the wave. And increasing the frequency indeed increases the energy of light, and this can be seen through the equation - E = hv, h being Planck'...
Sun Oct 11, 2020 5:54 pm
Forum: Properties of Light
Topic: Calculating Properties of Incident Light Problems
Replies: 1
Views: 26

### Re: Calculating Properties of Incident Light Problems

Hi! So for part B, there's no formula specific to incident light. Rather, you just manipulate the E = hv formula: E = hv = hc/wavelength

This way, once you find the energy of the incident light, you can use the formula above to find its wavelength.

Hope this helps!
Fri Oct 09, 2020 8:42 am
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Reactions Order
Replies: 31
Views: 241

### Re: Balancing Chemical Reactions Order

I've heard that strategy too, and it typically always works. For me, in general, I find it the easiest to start with an element that's not H and O - I would balance all the other elements first. That being said, there's no specific order, but some people find it easier to leave O and H for last.
Thu Oct 08, 2020 9:03 am
Forum: Limiting Reactant Calculations
Topic: Textbook Question M.5
Replies: 7
Views: 64

### Re: Textbook Question M.5

Hi! So to find the moles of each product, you need to first find the limiting reactant. Once you find the limiting reactant, you use its (the limiting reactant's) number of moles and the molar ratio to determine the number of moles of each product. To find the moles remaining from the excess reactan...
Wed Oct 07, 2020 10:25 am
Forum: Limiting Reactant Calculations
Topic: Limiting reactants
Replies: 8
Views: 80

### Limiting reactants

When looking for limiting reactants, what happens if the ratio of calculated moles is equal to the molar ratio in the balanced equation? Would that mean there's no limiting reactant? And if that were the case, which reactant would determine the amount of product formed?
Wed Oct 07, 2020 9:55 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Review of Chemical and Physical Principles Fundamentals E.15
Replies: 7
Views: 44

### Re: Review of Chemical and Physical Principles Fundamentals E.15

In this question, it's asking you to find the molar mass of the sulfide (of the metal) if it had one. So first, you would find the molar mass of (OH)2, and subtract it from the molar mass of M(OH)2 (74.10 g/mol). This will give you the molar mass of M, and then using the periodic table, you find tha...
Tue Oct 06, 2020 8:36 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Fundamentals Review problems question
Replies: 5
Views: 38

### Fundamentals Review problems question

In the Fundamental review problems hw E9, the question starts with

"Epsom salts consist of magnesium sulfate heptahydrate. Write its formula."

I'm not sure how to write a formula with heptahydrate added. I know it's first MgSO4, but I don't know what comes next.