## Search found 55 matches

Sat Dec 07, 2019 5:32 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 115
Views: 6397

### Re: MARSHMALLOW- FINAL REVIEW SESSION[ENDORSED]

Can someone please explain how to do #34. I know that you find the moles then use the excess moles and find the pH using that, but my math doesn't add up. When HCl and CaO are accidentally mixed in the flask, they will react to form salt and water making the following equation: 2HCl + CaO ---> CaCl...
Sat Dec 07, 2019 5:13 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 115
Views: 6397

### Re: MARSHMALLOW- FINAL REVIEW SESSION[ENDORSED]

Can someone please explain how to do #34. I know that you find the moles then use the excess moles and find the pH using that, but my math doesn't add up. When HCl and CaO are accidentally mixed in the flask, they will react to form salt and water making the following equation: 2HCl + CaO ---> CaCl...
Sat Dec 07, 2019 5:06 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 115
Views: 6397

### Re: MARSHMALLOW- FINAL REVIEW SESSION[ENDORSED]

for question 41d) Doesn't thymine have 10 atoms that could form hydrogen bonds? all 6 hydrogens, both nitrogens, and both oxygens. Technically if the question was asking for how many HYDROGEN BONDS can form not just how many ATOMS, wouldn't it be 12 h-bonds because each oxygen can for 2 h-bonds?
Sat Dec 07, 2019 3:01 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 115
Views: 6397

### Re: MARSHMALLOW- FINAL REVIEW SESSION[ENDORSED]

when are the answers for marshmallows being posted???
Fri Dec 06, 2019 10:37 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 115
Views: 6397

### Re: MARSHMALLOW- FINAL REVIEW SESSION[ENDORSED]

for 2b of mini marshmallows is the name spelt correctly? shouldnt it be Dihydroxo and not Dihydroxy ? maybe im just confused lol.
Tue Dec 03, 2019 10:41 am
Forum: Ionic & Covalent Bonds
Topic: bond lengths
Replies: 4
Views: 252

### Re: bond lengths

I don't think the specific bond lengths will need to be known. However, it is good to know that single bonds are the longest, then double bonds, then triple bonds.
Tue Dec 03, 2019 10:39 am
Forum: Amphoteric Compounds
Topic: water
Replies: 4
Views: 87

### Re: water

If water is added to an acidic solution it will act as a base, if water is added to a basic solution it will act as an acid.
Tue Dec 03, 2019 10:35 am
Forum: Student Social/Study Group
Topic: Test Banks
Replies: 2
Views: 99

### Re: Test Banks

I'm not sure about test banks but it you look up "marshmallow" on Chem Community there are practice questions there.
Tue Dec 03, 2019 10:32 am
Forum: Student Social/Study Group
Topic: Practice Final
Replies: 17
Views: 665

### Re: Practice Final

It looks like the review sessions begin at early quantum. Does this mean that fundamentals isn't on the final?
Tue Dec 03, 2019 10:24 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentates
Replies: 9
Views: 246

### Re: Polydentates

A ligand is polydentate if it can bond to a central metal atom in multiple coordinate bonding cites.
Sun Dec 01, 2019 10:46 pm
Forum: Ionic & Covalent Bonds
Topic: Carbon
Replies: 4
Views: 212

### Re: Carbon

I don't think a bond order beyond triple bond can exist between atoms. I believe the bond length may be too short and the nuclei of the two atoms may begin to repel each other making it a less stable structure than a triple bond.
Sun Dec 01, 2019 10:40 pm
Forum: General Science Questions
Topic: test taking nervousness
Replies: 19
Views: 418

### Re: test taking nervousness

Doing as many practice problems as possible may help you be more confident in your skills knowing that you've already attempted almost every problem style that could possibly be on the final.
Sun Dec 01, 2019 10:39 pm
Forum: General Science Questions
Topic: Bruincasts
Replies: 9
Views: 322

### Re: Bruincasts

I don't think this class has any recorded lectures, sorry.
Sun Dec 01, 2019 10:23 pm
Forum: Biological Examples
Topic: Cisplatin
Replies: 12
Views: 196

### Re: Cisplatin

cisplatin works to shut down cell division because it binds to the DNA at two nearby guanines such that the DNA cannot be "unzipped" for DNA replication. If the DNA can't replicate then cell division can no longer occur and the cell will just eventually die.
Sun Dec 01, 2019 10:05 pm
Forum: Lewis Acids & Bases
Topic: Strong versus weak
Replies: 5
Views: 101

### Re: Strong versus weak

strong acids and bases will completely dissociate in water while weak acids and bases will only partially dissociate.
Mon Nov 25, 2019 2:33 pm
Forum: *Molecular Orbital Theory Applied To Transition Metals
Topic: Ligands
Replies: 5
Views: 205

### Re: Ligands

Debora Fernandez Clemente_ 4H wrote:Can a ligand be a whole compound attached to a TM?

Yes, compounds may bond to transition metals and be ligands. Depending on the shape of the compound may be polydentate and bond to more than one ligand bonding cite.
Mon Nov 25, 2019 2:20 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: polydentate
Replies: 3
Views: 64

### Re: polydentate

A polydentate molecule can bind to a central metal atom at more than just one ligand bonding cite as a result of a specific shape that allows it to.
Mon Nov 25, 2019 2:17 pm
Forum: Bronsted Acids & Bases
Topic: Why do acids and bases react?
Replies: 3
Views: 68

### Re: Why do acids and bases react?

Because KOH and HBr are soluble, they will dissociate to K+, OH-, H+. and Br-. Then the ions will react with one another to form the products.
Mon Nov 25, 2019 2:11 pm
Forum: Biological Examples
Topic: Cisplatin
Replies: 17
Views: 452

### Re: Cisplatin

Cisplatin will bond to two nearby Guanine molecules on the DNA and prevent the DNA from being able to "unzip" for DNA replication. Thus without DNA replication a cell cannot divide will eventually die.
Mon Nov 25, 2019 2:06 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: acids
Replies: 4
Views: 86

### Re: acids

All acids will have hydrogen atoms so that they can dissociate and release Hydronium (H+) ions in solution to bond with OH- or proton acceptor Lewis bases.
Sat Nov 16, 2019 2:46 pm
Forum: Sigma & Pi Bonds
Topic: Sigma & Pi Bonds
Replies: 4
Views: 100

### Re: Sigma & Pi Bonds

A sigma bond is the first bond between atoms. Pi bonds are the second or third bonds. In the example that was introduced in lecture, the sigma and pi bonds are relevant in biological molecules which have cis and trans isomers. This means that the molecules have the same molecular formula but a diffe...
Sat Nov 16, 2019 2:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Symmetry and Polarity
Replies: 13
Views: 193

### Re: Symmetry and Polarity

Lewis structures can be deceiving of the actual molecular shape. It is best to use the VSEPR model to se the symmetry of the molecular shape. Then the dipole moments of polar bonds can create partially charged vectors. If, when considering the molecular symmetry and charge of each bond, the vectors ...
Sat Nov 16, 2019 2:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: All VSEPR structures or just ones from class?
Replies: 11
Views: 207

### Re: All VSEPR structures or just ones from class?

It is probably best to memorize all of the shapes just to be safe. However, the shapes can be figured with the basic geometric structures (no lone pairs) and then adding lone pairs in the locations of least repulsion. A drawn model may also help to visualize the shape of the molecule.
Sat Nov 16, 2019 2:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSPER Formula for Compounds with No Lone Pairs
Replies: 4
Views: 97

### Re: VSPER Formula for Compounds with No Lone Pairs

The "E" is only included to show that lone pairs are present. For tetrahedral shape, the VSEPR notation is AX4.
Sat Nov 16, 2019 2:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 9
Views: 127

### Re: Bond Angles

if you can remember the bond angles of the basic molecular geometries containing no lone pairs (i.e. linear=180, trigonal planar=120, tetrahedral=109.5, trigonal bipyramidal=120, 90, & 180, and octahedral= 90) then you can predict that the bond angles with be slightly less than these numbers whe...
Sun Nov 10, 2019 4:06 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Magnetic Quantum numbers
Replies: 13
Views: 347

### Re: Magnetic Quantum numbers

if the angular momentum quantum number (l) is known, then the possible magnetic quantum numbers (ml) can be determined by listing all of the integer numbers from -l to +l.
Sun Nov 10, 2019 4:01 pm
Forum: Dipole Moments
Topic: hydrogen bonding
Replies: 2
Views: 30

### Re: hydrogen bonding

Dimers are important in organic chemistry. basically they are made up of two similar or identical units connected by either a covalent bond or intermolecular forces.
Sun Nov 10, 2019 3:50 pm
Forum: Bond Lengths & Energies
Topic: Strongest Bond
Replies: 15
Views: 224

### Re: Strongest Bond

the C to O triple bond is specifically one of the strongest bonds between atoms. it is one of the shortest bonds at 113pm and has the highest bond energy at 1072 KJ/mol.
Sun Nov 10, 2019 3:46 pm
Forum: Lewis Structures
Topic: Xenon
Replies: 4
Views: 129

### Re: Xenon

Xenon only has 8 valence electrons as a lone atom. However because it has an empty 4d-orbital, it can expand its octet when forming molecules and hold more electrons. Atoms in the 3p orbital and above have this ability to expand as long as there is space in the d-orbital to hold more electrons.
Sun Nov 10, 2019 3:32 pm
Forum: Dipole Moments
Topic: Dipole moments
Replies: 6
Views: 87

### Re: Dipole moments

dipole moments occur when a polar molecule comes within close proximity to a non-polar molecule. A partial positive of the polar molecule will attract the electrons of the non-polar molecule and cause them to migrate to one side of the molecule resulting in a momentary partial negative until the mol...
Fri Nov 01, 2019 1:36 pm
Forum: Trends in The Periodic Table
Topic: Noble Gases
Replies: 10
Views: 170

### Re: Noble Gases

Noble gases are exceptions to these trends because their are virtually unreactive. they have full valence shells already and typically do not gain or lose electrons.
Fri Nov 01, 2019 1:31 pm
Forum: Lewis Structures
Topic: Expanded Valence Shells
Replies: 4
Views: 57

### Re: Expanded Valence Shells

Atoms with empty spaces in the d-orbitals can expand their valence shells.
Fri Nov 01, 2019 1:30 pm
Forum: Ionic & Covalent Bonds
Topic: Anions and Cations
Replies: 9
Views: 184

### Re: Anions and Cations

cations, especially in groups 1 and 2, will become significantly smaller because they often achieve +1 and +2 charges respectively. When this occurs, these atoms completely lose their outer shells. Their positively charge nucleus will pull the remaining electrons extra tightly. ultimately, this resu...
Fri Nov 01, 2019 1:26 pm
Forum: Bond Lengths & Energies
Topic: bond lengths
Replies: 10
Views: 269

### Re: bond lengths

single bonds are the longest. then double bonds are shorter. triple bonds are shortest. additionally, the shorter the bond the stronger it is.
Fri Nov 01, 2019 1:23 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: What's the right equation?
Replies: 7
Views: 113

### Re: What's the right equation?

it should be the first equation for simplicity purposes. the second equation is the same thing as long as the "h" there is supposed to be an "h bar".
Wed Oct 23, 2019 4:09 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy
Replies: 8
Views: 118

### Re: Ionization Energy

As you get to removing electrons of the inner shells, they are experiencing a greater positive attraction to the nucleus at a closer distance and are therefore more difficult to remove.
Wed Oct 23, 2019 4:04 pm
Forum: Lewis Structures
Topic: Electronegativity
Replies: 5
Views: 65

### Re: Electronegativity

Elements that typically form negative ions are more electronegative. These are typically on the right side of the periodic table because these elements are trying to accept more electrons and complete their outer shells.
Wed Oct 23, 2019 4:02 pm
Forum: Octet Exceptions
Topic: Octet Rule
Replies: 6
Views: 64

### Re: Octet Rule

Two exceptions to the octet rule are B and Al which may form 3 bonds and Si which may form 6 bonds.
Wed Oct 23, 2019 3:57 pm
Forum: Trends in The Periodic Table
Topic: Trend in periodic table
Replies: 6
Views: 47

### Re: Trend in periodic table

Going down the columns of the periodic table, elements exhibit similar characteristics due to identical valence electron structure. For example, H, Li, Na, and K all have one valence electron in the outer shell s-orbital. These are all highly reactive elements that are quick to give up this outer el...
Wed Oct 23, 2019 3:50 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: E- removal
Replies: 3
Views: 39

### Re: E- removal

One reason for this is that once you remove the first electron from at atom, it is now a positively charged ion. Because of this greater positive charge in the nucleus, the electrons will be more attracted to the nucleus and therefore more difficult to remove. Additionally, subsequent electrons may ...
Fri Oct 18, 2019 2:38 pm
Forum: Quantum Numbers and The H-Atom
Topic: Electron Configuration
Replies: 2
Views: 63

### Re: Electron Configuration

Yes, when following Pauli's and Hund's rules for determining electron configurations, the ground state will be achieved. The quantum numbers of each individual electron will be unique to that individual atom. However, altogether the configuration of the electrons which can be represented through the...
Fri Oct 18, 2019 2:35 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Best Way To Study?
Replies: 56
Views: 1311

### Re: Best Way To Study?

I recommend completing the practice problems listed on the syllabus. Even though we are only require to complete 5 per week, I find that doing as many as possible ensures a well rounded understanding and preparation for potential exam questions.
Fri Oct 18, 2019 2:32 pm
Forum: Quantum Numbers and The H-Atom
Topic: Nodal Plane
Replies: 4
Views: 60

### Re: Nodal Plane

Nodal planes are only in the p, d, and f orbitals. They are caused by non-symmetric probability distribution of locating electrons. This probability is determined mathematically. s orbitals do not have nodal planes because they have symmetric probability distribution of electrons about the nucleus (...
Fri Oct 18, 2019 2:21 pm
Forum: Quantum Numbers and The H-Atom
Topic: Ground State [ENDORSED]
Replies: 5
Views: 130

### Re: Ground State[ENDORSED]

When in the ground state, an atoms electrons are configured to achieve the lowest possible energy. In this state, atoms are most stable.
Fri Oct 18, 2019 2:13 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Spin State
Replies: 6
Views: 97

### Re: Spin State

The spin state is determined by the fourth quantum number (Ms). This was originally demonstrated through shooting a Ag atom beam though a magnetic field. The Ag beam was then split into two separate electron beams, revealing that electrons within the Ag beam were not homogeneous. The differing beams...
Tue Oct 08, 2019 11:43 am
Forum: Properties of Light
Topic: Photons
Replies: 7
Views: 95

### Re: Photons

Increasing the intensity WILL increase the QUANTITY of e- ejected. This is because increasing the intensity, or amplitude, basically means you are increasing the number of photons that will strike the metal at a certain frequency. While only increasing the frequency will increase the energy on an in...
Tue Oct 08, 2019 11:38 am
Forum: Properties of Light
Topic: Photoelectric Effect
Replies: 4
Views: 62

### Re: Photoelectric Effect

In the simplest terms, only high frequencies of light will eject electrons. However, because each type of metal has a unique electron configuration, the specific high frequency required to eject electrons is relative to the metal that is being struck by the light. It is best to consider the high fre...
Tue Oct 08, 2019 11:24 am
Forum: Properties of Light
Topic: Light intensity
Replies: 10
Views: 134

### Re: Light intensity

Light intensity refers to the brightness of the light. In terms of the wave model, this references the amplitude of the light. Greater amplitudes would correlate to greater intensities. Still, as far as the photoelectric effect goes, greater amplitudes do not determine whether electrons will be ejec...
Tue Oct 08, 2019 11:08 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty
Replies: 3
Views: 318

### Re: Uncertainty

It is import to consider "uncertainty" in chemistry during experiments. Because atoms take part in reactions on such a small scale, it is nearly impossible to measure experiments with exact certainty. In fact, measurement errors often occur on a significant scale due to several potential h...
Tue Oct 08, 2019 11:02 am
Topic: Black Body
Replies: 5
Views: 111

### Re: Black Body

Although light and heat energy are not the same, they often go hand in hand. Does this mean that if a black body object absorbs all light, will it also become very hot? Or are these two forms of energy unrelated in this example?
Wed Oct 02, 2019 12:53 pm
Forum: SI Units, Unit Conversions
Replies: 22
Views: 408

### Re: Question about Showing Work

Showing work is usually a safe bet for receiving some points/partial credit. Generally, showing work may also help visualize the steps towards the correct answer and can prevent careless errors such as dividing by a conversion factor instead of multiplying by it. Showing work, if even just a little ...
Wed Oct 02, 2019 12:50 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical and Molecular Formula Masses
Replies: 5
Views: 130

### Re: Empirical and Molecular Formula Masses

The mass of the molecular formula can ONLY be greater than or equal to the mass of the empirical formula, never less than it. This is because the empirical formula is the smallest possible ratio of the molecule in question. The molecular formula is any whole number multiple of this empirical ratio i...
Wed Oct 02, 2019 12:18 pm
Forum: SI Units, Unit Conversions
Topic: Next Week's Test
Replies: 8
Views: 227

### Re: Next Week's Test

I believe the test is on the fundamental high school review topics covered in the 4 module videos that we completed before class. I think we are just going to be touching on these 4 fundamental modules in lectures before the test and I don't think we are going to get to any quantum stuff yet... I wa...
Wed Oct 02, 2019 12:12 pm
Forum: Balancing Chemical Reactions
Topic: Stoichiometric Coefficients [ENDORSED]
Replies: 8
Views: 198

### Re: Stoichiometric Coefficients[ENDORSED]

Though, the stoichiometric coefficients in chemical equations are meant to represent values in moles, these reactions are happening between individual atoms in equal proportions as the coefficients represent. Because the coefficients are simply representative of the ratios between atoms in chemical ...
Wed Oct 02, 2019 12:04 pm
Forum: Significant Figures
Topic: How Many significant figures to use ?
Replies: 9
Views: 229

### Re: How Many significant figures to use ?

Another important piece of info to remember in regards to significant figures is the place of ZEROS in a number. If a number has non-zero figures and zeros all before the decimal point, those are not included in significant figures. For example 12,000,000 only has two significant figures and would b...