Search found 56 matches

by J Medina 2I
Sun Jan 12, 2020 11:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homogenous Equilibrium
Replies: 13
Views: 28

Re: Homogenous Equilibrium

Is there a different way we should approach a problem where we have to calculate the equilibrium constant if the given chemical reaction is heterogeneous and not homogeneous.
by J Medina 2I
Sun Jan 12, 2020 11:31 pm
Forum: Ideal Gases
Topic: K and Units
Replies: 7
Views: 20

Re: K and Units

The units cancel out (concentration/concentration), making K unitless.
by J Medina 2I
Sun Jan 12, 2020 11:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Types of Equilibrium Constants
Replies: 7
Views: 23

Re: Types of Equilibrium Constants

005384106 wrote:In what instances would the state of a molecule be important? (gaseous, aqueous, solid, or liquid)


Solids and liquids are excluded from calculating K. But, a gaseous reaction indicated using Kp and an aqueous reaction indicates using Kc.
by J Medina 2I
Sun Jan 12, 2020 10:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Comparing K
Replies: 9
Views: 33

Re: Comparing K

I don't think K can equal 0. If K were to equal 0, then that means there would be no product, meaning a reaction isn't taking place.
by J Medina 2I
Sun Jan 12, 2020 10:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q
Replies: 10
Views: 22

Re: Q

You could calculate Q and if it matches K, then the reaction is at equilibrium.
by J Medina 2I
Sun Dec 08, 2019 1:07 am
Forum: Identifying Acidic & Basic Salts
Topic: homework question 6D.11
Replies: 2
Views: 39

Re: homework question 6D.11

Why is part d neutral?

d) KBR

And is asking whether an aqueous solution of this will have a pH < 7 , pH > 7, or be neutral
by J Medina 2I
Sat Dec 07, 2019 10:45 pm
Forum: DeBroglie Equation
Topic: Identifying the need to use DeBroglie Equation
Replies: 3
Views: 31

Identifying the need to use DeBroglie Equation

What kind of things in a problem suggest that we use DeBroglie's equation?
by J Medina 2I
Sat Dec 07, 2019 9:11 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH sig figs
Replies: 11
Views: 67

Re: pH sig figs

Does this work the other way around too? If we were given a H3O+ concentration of 1.56 x 10^-4 where there are 3 sig figs, would we have to write the pH as 3.807 or as 3.81 ?
by J Medina 2I
Sat Dec 07, 2019 7:41 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Negative pH
Replies: 5
Views: 34

Negative pH

What does it mean for pH to be negative?
by J Medina 2I
Sat Dec 07, 2019 12:19 pm
Forum: Naming
Topic: Abbreviations (oxalato)
Replies: 2
Views: 25

Abbreviations (oxalato)

When writing the formula for a coordination compound containing a ligand that can be abbreviated, such as sodium bisoxalato(diaqaua)ferrate(III) containing oxalato, are we able to also write the abbreviation in the formula. For example can this coordination compound be written as: Na[Fe(OH2)2(ox)2] ...
by J Medina 2I
Sun Dec 01, 2019 5:25 pm
Forum: Lewis Acids & Bases
Topic: acid v. base?
Replies: 16
Views: 71

Re: acid v. base?

Lewis bases are positively charged. Lewis acids are negatively charged and usually have a lone pair.
by J Medina 2I
Sun Dec 01, 2019 5:20 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH scale
Replies: 12
Views: 59

Re: pH scale

Most solutions are in this range. Remember that pH is logarithmic so a pH of 15 would have a concentration of ions 10x greater than a solution with a pH of 14, which is not common.
by J Medina 2I
Sun Dec 01, 2019 5:13 pm
Forum: Naming
Topic: Naming for the final
Replies: 6
Views: 54

Re: Naming for the final

Neutral ligands have the same name except for a few. Water turns to "aqua," ammonia turns to "ammine," and CO turns to "carbonyl." Ligands that are anions end with o.
by J Medina 2I
Sun Dec 01, 2019 4:58 pm
Forum: Trends in The Periodic Table
Topic: Exceptions to Electroaffinity
Replies: 3
Views: 46

Re: Exceptions to Electroaffinity

I don't think we have been told of any exceptions in lecture so I think it's safe to assume that we wouldn't be asked any questions where knowledge of an exception would be needed to answer the question.
by J Medina 2I
Sun Dec 01, 2019 4:18 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 6
Views: 33

Re: Coordination Number

However many ligands are attached to the central atom is what determines the coordination number. You can determine this by looking inside the brackets.
by J Medina 2I
Sun Dec 01, 2019 4:09 pm
Forum: Sigma & Pi Bonds
Topic: Drawing Sigma and Pi bonds
Replies: 7
Views: 45

Re: Drawing Sigma and Pi bonds

I think it's safest to label each bond individually with a "σ" on top of one line and a "π" on top of the other line.
by J Medina 2I
Sun Nov 24, 2019 5:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw
Replies: 23
Views: 124

Re: Seesaw

If a lone pair is present in a molecule, then it will affect the bond angles of the surrounding atoms since the repulsion force lone pairs is greater than bonded atoms.
by J Medina 2I
Sun Nov 24, 2019 4:46 pm
Forum: Resonance Structures
Topic: Resonance structures
Replies: 15
Views: 90

Re: Resonance structures

Patricia Cardenas wrote:Does anyone have advice on how to start drawing lewis structures/resonance structures?


The first step would be to identify the least electronegative atom because this one will typically be the central atom.
by J Medina 2I
Sun Nov 24, 2019 4:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent Shape
Replies: 29
Views: 181

Re: Bent Shape

Yea if the formula is AX2E then the angles are similar to a trigonal planar molecule (<120) but if the formula is AX2E2 then the bond angles are similar to a tetrahedral molecule (<109.5)
by J Medina 2I
Sun Nov 24, 2019 4:39 pm
Forum: Biological Examples
Topic: cisplatin
Replies: 6
Views: 46

Re: cisplatin

I think Lavelle mentioned in lecture that cisplatin not only stops cell division of cancer cells but stops division for all cells
by J Medina 2I
Sun Nov 24, 2019 4:31 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: square planar vs tetrahedral
Replies: 5
Views: 32

Re: square planar vs tetrahedral

Square planar has 6 electron dense regions but two of those are lone pairs, making the formula AX4E2 whereas tetrahedral only has 4 electron dense regions, all of which are bonds to another atom, making the formula AX4. The two lone pairs in a square planar molecule repulse the 4 bonds to form a squ...
by J Medina 2I
Sun Nov 17, 2019 11:04 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone vs. Bonding Pair
Replies: 6
Views: 32

Re: Lone vs. Bonding Pair

Lone pairs take up more space making the rest of the bonds move away in order to lower repulsion.
by J Medina 2I
Sun Nov 17, 2019 10:49 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Vsepr Rules
Replies: 2
Views: 40

Re: Vsepr Rules

If you're talking about the rules stated in the textbook, Rule 2 is telling us that multiple bonds (double bonds, triple bonds) count as only a single region of high electron density. The same way a single bond is counted as one. And the same way a lone pair counts as one. Adding up all the electron...
by J Medina 2I
Sun Nov 17, 2019 10:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: SF4
Replies: 3
Views: 20

Re: SF4

Lone pairs and bonds need to be placed where they will cause the least amount of repulsion. Considering lone-pairs have a stronger amount of repulsion than bonds do, their placement is prioritized in terms of where it will cause the least amount of repulsion. In the see-saw example shown in class th...
by J Medina 2I
Sun Nov 17, 2019 10:23 pm
Forum: Lewis Structures
Topic: Why can Xenon break the octet rule?
Replies: 8
Views: 39

Re: Why can Xenon break the octet rule?

Xenon has d-orbitals, allowing it to store more electrons in its valence shell than atoms without any d-orbitals, like those that are at or come before 4s^2 .
by J Medina 2I
Sun Nov 17, 2019 10:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angles
Replies: 8
Views: 35

Re: bond angles

Lone pairs have the strongest repulsion strength because lone pairs are less restrained than a bonding pair would be so it takes up more space making the rest of the atoms move away to lower the repulsion acting upon them.
by J Medina 2I
Sun Nov 10, 2019 11:35 pm
Forum: Bond Lengths & Energies
Topic: Rankings
Replies: 2
Views: 22

Re: Rankings

Hydrogen bonds are the strongest intermolecular force
by J Medina 2I
Sun Nov 10, 2019 11:34 pm
Forum: Trends in The Periodic Table
Topic: Atomic Radius
Replies: 9
Views: 55

Re: Atomic Radius

Atomic radius increases going left across and down groups of the periodic table. Having higher atomic numbers means having more protons that pull the electrons closer to the nucleus, decreasing the atomic radius as you move right across the periodic table.
by J Medina 2I
Sun Nov 10, 2019 11:07 pm
Forum: Coordinate Covalent Bonds
Topic: Coordinate Covalent Bond
Replies: 3
Views: 36

Re: Coordinate Covalent Bond

A coordinate covalent bond is when one atom is responsible for giving off a lone pair that contributes to making the bond with another atom without the second atom having to sacrifice one of their own electrons to create the bond.
by J Medina 2I
Sun Nov 10, 2019 10:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Writing e- Configurations
Replies: 15
Views: 85

Re: Writing e- Configurations

I think the question would specify if you had to use a specific notation.
by J Medina 2I
Sun Nov 10, 2019 10:45 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: Interaction Strength
Replies: 4
Views: 16

Re: Interaction Strength

This is why rod-shaped molecules will generally have higher melting points. A lot more dipole interactions have to be broken.
by J Medina 2I
Sun Nov 03, 2019 10:52 pm
Forum: Resonance Structures
Topic: Octet
Replies: 13
Views: 81

Re: Octet

Hydrogen and Helium fill up a duplet (2 valence electrons). Other exceptions include atoms in the d-block since they have 5 orbitals allowing them to hold more than 8 outer electrons.
by J Medina 2I
Sun Nov 03, 2019 10:34 pm
Forum: Lewis Structures
Topic: Lone Pairs
Replies: 12
Views: 51

Re: Lone Pairs

It's easy to think of it as any valence electrons that aren't touching (being shared by) any other atoms in the lewis structure
by J Medina 2I
Sun Nov 03, 2019 10:28 pm
Forum: Electronegativity
Topic: electronegativity trend
Replies: 9
Views: 35

Re: electronegativity trend

Electronegativity decreases down a column because the atom gets larger and the electron gets farther away from the pull of the positively charged nucleus. Ionization is related to this since this weaker pull allows less energy to be needed to remove an electron from an atom.
by J Medina 2I
Sun Nov 03, 2019 10:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Writing e- Configurations
Replies: 15
Views: 85

Re: Writing e- Configurations

I think you can assume you're able to write the shorthand notation unless told directly by the question to write the entire configuration out.
by J Medina 2I
Sun Nov 03, 2019 9:59 pm
Forum: Bond Lengths & Energies
Topic: Does bond length have any effects?
Replies: 5
Views: 25

Re: Does bond length have any effects?

Bond length does have effects. Shorter bonds (such as triple bonds) will require more energy to break apart because the shared electrons are closer to the positively charged nuclei and thus have a stronger pull on these electrons.
by J Medina 2I
Sun Oct 27, 2019 8:11 pm
Forum: Lewis Structures
Topic: Lone Pairs
Replies: 12
Views: 51

Re: Lone Pairs

In a Lewis structure they're the two dots on the sides.
by J Medina 2I
Sun Oct 27, 2019 8:09 pm
Forum: Trends in The Periodic Table
Topic: Central Atom
Replies: 13
Views: 57

Re: Central Atom

Atom ionization energy levels generally follow a trend of decreasing as you move left across and down the periodic table.
by J Medina 2I
Sun Oct 27, 2019 7:58 pm
Forum: Resonance Structures
Topic: Octet
Replies: 13
Views: 81

Re: Octet

I think in lecture Lavelle mentioned that H, He, Li, and Be are exceptions to the octet rule.
by J Medina 2I
Sun Oct 27, 2019 7:56 pm
Forum: Bond Lengths & Energies
Topic: Single bond vs double bond
Replies: 14
Views: 122

Re: Single bond vs double bond

These numbers are the length of each bond. The double bonds are shorter because there is a stronger pull there which makes it tighter.
by J Medina 2I
Tue Oct 22, 2019 9:02 am
Forum: Trends in The Periodic Table
Topic: Periodic Table trends
Replies: 11
Views: 112

Re: Periodic Table trends

The biggest difference is their shape and their ability to hold e-. The s-orbital can only hold 2 e-. The p-orbital can only only 6 e-. The d-orbital can only hold 10 e-. The f-block can hold 14 e-. In the ground state of an atom, the electrons must fill up all spots in lower energy levels before m...
by J Medina 2I
Sun Oct 20, 2019 11:36 pm
Forum: *Black Body Radiation
Topic: Black Body Radiation
Replies: 12
Views: 109

Re: Black Body Radiation

A black body is a material that absorbs all radiation. No object is a true black body, it is more of an idea in the same way frictionless surfaces are used in physics problems.
by J Medina 2I
Sun Oct 20, 2019 11:25 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodal Planes
Replies: 3
Views: 37

Re: Nodal Planes

Orbitals are probability density functions and nodal planes are where there is a 0 percent likelihood of finding an electron.
by J Medina 2I
Sun Oct 20, 2019 8:29 pm
Forum: Properties of Light
Topic: Unit for Wavelength
Replies: 34
Views: 160

Re: Unit for Wavelength

Wavelengths are measured in meters since it is a distance. It is common to see them measured in nanometers which is 1x10^-9 of a meter.
by J Medina 2I
Sun Oct 20, 2019 8:07 pm
Forum: Properties of Light
Topic: What are the units of hertz
Replies: 41
Views: 234

Re: What are the units of hertz

s^-1

refers to cycles per second
by J Medina 2I
Sun Oct 20, 2019 8:02 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Advice for studying
Replies: 58
Views: 499

Re: Advice for studying

I found it helpful to read the chapters covered in lecture and going through all the example problems given. I also write question marks in my notes during lecture to remind myself what seemed confusing at the time so I can study it later.
by J Medina 2I
Sun Oct 13, 2019 11:19 pm
Forum: Properties of Light
Topic: Energy Equation
Replies: 3
Views: 19

Re: Energy Equation

It's Planck's Constant. If you multiply it with frequency (v) you get the energy of the photon.
by J Medina 2I
Sun Oct 13, 2019 10:39 pm
Forum: Significant Figures
Topic: sig figs and periodic tables
Replies: 11
Views: 140

Re: sig figs and periodic tables

If we use the rounded version of the atomic mass (let's say to the hundredths) and correctly use significant figures, would our answer be wrong if the answer we get is right according to the rounded calculations we made?
by J Medina 2I
Sun Oct 13, 2019 10:31 pm
Forum: Photoelectric Effect
Topic: Intensity vs. Length of Waves
Replies: 4
Views: 32

Re: Intensity vs. Length of Waves

Shorter wavelengths imply higher frequency (v), means more crowded bumps and higher energy for removing electrons
by J Medina 2I
Sun Oct 13, 2019 9:59 pm
Forum: Properties of Light
Topic: Wavelength
Replies: 4
Views: 38

Re: Wavelength

I think you can use the Mass of electron given in the constants sheet and plug that into the 1/2mv^2 equation which will give you the kinetic energy of the electron. Then you use c=(lambda)v to get the wavelength.
by J Medina 2I
Sun Oct 13, 2019 9:32 pm
Forum: SI Units, Unit Conversions
Topic: Angstrom
Replies: 16
Views: 194

Re: Angstrom

It's also important to remember that the Angstrom is not an SI unit
by J Medina 2I
Fri Oct 04, 2019 1:29 am
Forum: SI Units, Unit Conversions
Topic: scientific notation
Replies: 7
Views: 51

Re: scientific notation

I think it'd be a good idea to leave an answer in scientific notation if the answer in normal form would be an ambiguous number of significant figures. For example if you want to show 1000 with 3 significant figures just write 1.00 x 10^3
by J Medina 2I
Fri Oct 04, 2019 1:21 am
Forum: SI Units, Unit Conversions
Topic: Sig Fig Rules
Replies: 2
Views: 35

Re: Sig Fig Rules

No the rules are different. For adding and subtracting when dealing with decimals you can only include the decimal value that was closest to the decimal. For example if we had to add 522.7 + 49.44 = 572.14, we would have to round down so that the answer is 572.1 But for multiply or dividing you can ...
by J Medina 2I
Fri Oct 04, 2019 1:00 am
Forum: Empirical & Molecular Formulas
Topic: Homework Question F.9
Replies: 6
Views: 59

Re: Homework Question F.9

Yes, you would assume that your sample is 100 g, but to convert to moles, you actually have to divide by the molar mass of each element as found on the periodic table (so 12.01 g/mol for C). You don't need to divide 63.15 by 100 because if you assume the sample is 100 g, then 63.15% of 100 would ju...
by J Medina 2I
Fri Oct 04, 2019 12:51 am
Forum: Significant Figures
Topic: How many sig figs when in decimals?
Replies: 6
Views: 68

Re: Significant Figures if last digit is 5

I was reading through the link "EVERYTHING YOU WANTED TO KNOW ABOUT SF" posted on the class website to review significant figures and was confused when I read that if a number ends in the number '5' and you are rounding, that you must round the number up or down to the nearest even number....
by J Medina 2I
Fri Oct 04, 2019 12:40 am
Forum: Student Social/Study Group
Topic: Study Tips
Replies: 58
Views: 712

Re: Study Tips

I too have not taken a chemistry class in years but I found the Video Modules and Post-Assessments helpful in keeping me on the right track without being overwhelmed by the amount of content I believed I had forgotten completely.

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