## Search found 65 matches

Fri Jan 22, 2021 4:43 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bromine standard state
Replies: 4
Views: 14

### Re: Bromine standard state

When he said I2 he was talking about Iodine.
Fri Jan 22, 2021 4:38 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy units
Replies: 7
Views: 24

### Re: Enthalpy units

All enthalpy values will usually be given in kJ/mol unless it is for the overall reaction.
Fri Jan 22, 2021 4:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Preferred way to calculate enthalpy
Replies: 6
Views: 24

### Re: Preferred way to calculate enthalpy

I think it will all come down to how the problem is structured and what is given to you. I don't think you will be able to just choose one of the methods but you will have to calculate using equations or enthalpies given.
Fri Jan 22, 2021 4:18 pm
Forum: Phase Changes & Related Calculations
Topic: Endothermic v. Exothermic
Replies: 61
Views: 159

### Re: Endothermic v. Exothermic

Endothermic reactions will always have a +$\Delta$H and exothermic reactions will have a -$\Delta$H. if heat is showed in the reaction on the reactants side it is endothermic and if it is present on the products side it is an exothermic reaction.
Fri Jan 22, 2021 4:16 pm
Forum: Phase Changes & Related Calculations
Topic: Vapor vs gas
Replies: 31
Views: 75

### Re: Vapor vs gas

Vapor and gas are interchangeable. So when they say enthalpy of vaporization, they mean the phase change from a liquid to the gas state.
Fri Jan 15, 2021 5:17 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: What is autoprotolysis? lavelle's lecture 1/15 [ENDORSED]
Replies: 7
Views: 54

### Re: What is autoprotolysis? lavelle's lecture 1/15[ENDORSED]

Autoprotolysis : A proton (hydron) transfer reaction between two identical molecules (usually a solvent), one acting as a Brønsted acid and the other as a Brønsted base
Fri Jan 15, 2021 5:15 pm
Forum: Ideal Gases
Topic: Does temperature matter?
Replies: 19
Views: 69

### Re: Does temperature matter?

In this case it does not really matter for your calculations, but it will in other questions .
Fri Jan 15, 2021 5:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure Rule
Replies: 29
Views: 191

### Re: Pressure Rule

Liquids and Solids from the reaction are not included, you only need to account for the moles of gas
Fri Jan 15, 2021 5:09 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: q and K
Replies: 11
Views: 29

### Re: q and K

K is the equilibrium constant and can only be calculated at equilibrium.
Q is the reaction quotient and can be calculated the same way as K, but at any point in the reaction.
If T is not given, it is implied the reaction is at 25 degrees C.
Fri Jan 15, 2021 4:59 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: the different Ks
Replies: 7
Views: 31

### Re: the different Ks

All K are equilibrium constants and are calculated the same way, but the letters are used to specify which it needed for a certain situation. The a means it is for an acid, b is for a base, c is for concentration, p is for pressure, and w is for water.
Wed Jan 06, 2021 9:59 pm
Forum: Ideal Gases
Topic: Gas constant R
Replies: 26
Views: 105

### Re: Gas constant R

R is the universal gas constant and it = 8.3144598 J/mol·K
Wed Jan 06, 2021 9:57 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: H2O
Replies: 44
Views: 289

### Re: H2O

There is no need to have the H2O because you don't include any solids or liquids.
Wed Jan 06, 2021 9:56 pm
Forum: Ideal Gases
Topic: PV=nRT
Replies: 74
Views: 451

### Re: PV=nRT

P=pressure
V=volume
n=moles
R=universal gas constant
T=temperature
Wed Jan 06, 2021 9:53 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q and K
Replies: 17
Views: 99

### Re: Q and K

K will always be the same value because it is the equilibrium constant and will only be relevant at equilibrium. At any point the reaction is not at equilibrium you want to solve for Q, the reaction quotient.
Wed Jan 06, 2021 9:49 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: names for reaction quotient Q
Replies: 19
Views: 68

### Re: names for reaction quotient Q

Qp and Qc are just more specific ways to account for Q, the reaction quotient. This is the same for K, Kp and Kc.
Wed Dec 16, 2020 6:53 pm
Forum: Naming
Topic: Cobalt vs Cobaltate
Replies: 12
Views: 77

### Re: Cobalt vs Cobaltate

If the complex contains a negative charge, you add the suffix -ate to it.
Wed Dec 16, 2020 6:52 pm
Forum: Hybridization
Topic: Hybridization and Shape
Replies: 6
Views: 54

### Re: Hybridization and Shape

They are connected because the regions of electron density correspond directly to the hybridization. Two regions = sp. Three regions = sp2. Four regions = sp3. And so forth. Double/triple bonds still only count as one region of electron density.
Wed Dec 16, 2020 6:47 pm
Forum: Einstein Equation
Topic: units for E=hv
Replies: 11
Views: 131

### Re: units for E=hv

Depending on the question, the units can either be J/photon or J/atom.
Wed Dec 16, 2020 6:45 pm
Forum: Conjugate Acids & Bases
Topic: Sapling #3
Replies: 12
Views: 88

### Re: Sapling #3

When the question asks for a conjugate acid of a certain molecule, you just add a proton (H+) to it. The conjugate acid of HSO4- should have been H2SO4
Wed Dec 16, 2020 6:39 pm
Forum: Conjugate Acids & Bases
Topic: Conjugate Acids and Bases
Replies: 5
Views: 39

### Re: Conjugate Acids and Bases

For the conjugate acid you want to add a proton to the molecule. For the base, you want to take one away.
Wed Dec 16, 2020 6:37 pm
Forum: Conjugate Acids & Bases
Topic: Alkaline
Replies: 15
Views: 89

### Re: Alkaline

Yes, if a solution is basic it can be referred to as alkaline. The definition for alkaline : having the properties of an alkali, or containing alkali; having a pH greater than 7.
Wed Dec 16, 2020 6:34 pm
Forum: Amphoteric Compounds
Topic: Amphoteric vs Amphiprotic
Replies: 7
Views: 46

### Re: Amphoteric vs Amphiprotic

Amphoteric means the molecule can act as an acid or a base.
Amphiprotic means it can either donate or accept an H+
Wed Dec 16, 2020 6:30 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Why isn't HF a strong acid?
Replies: 23
Views: 141

### Re: Why isn't HF a strong acid?

Fluorine's atomic radius is not very large meaning the molecule's bond is stronger compared to HCl, HBr, or HI. The bigger the atom, the weaker the bond and the stronger the acid.
Sun Dec 06, 2020 9:59 pm
Forum: Ionic & Covalent Bonds
Topic: Polar Bonds
Replies: 19
Views: 111

### Re: Polar Bonds

If the molecule has different atoms bonded to each other, it will be polar. However, the geometry of a molecule can cancel out these polar bonds and make it nonpolar due to its symmetry.
Sun Dec 06, 2020 9:34 pm
Forum: Dipole Moments
Topic: Dipole canceling
Replies: 13
Views: 81

### Re: Dipole canceling

Yes, a molecule may have polar bonds within it, but based on the geometry these dipoles may cancel out and result in a nonpolar molecule.
Sun Dec 06, 2020 7:16 pm
Forum: Lewis Acids & Bases
Topic: Application to the Period Table
Replies: 6
Views: 49

### Re: Application to the Period Table

Not exactly, but Lavelle mentioned a few trends. The first two columns, the alkali metals and alkaline earth metals, produce bases while most of the elements on the right hand side of the table produce acids. There is also a diagonal band of amphoteric oxides that matches the diagonal band of metall...
Sun Dec 06, 2020 7:04 pm
Forum: Conjugate Acids & Bases
Topic: Conjugate acids vs conjugate base
Replies: 12
Views: 74

### Re: Conjugate acids vs conjugate base

For your conjugate acid you take the original formula and add a hydrogen. You take a hydrogen out of it to find your conjugate base.
Sun Dec 06, 2020 7:02 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Sapling #6
Replies: 3
Views: 21

### Sapling #6

In this sapling question, it asks to give the oxidation state of the metal species in the complex [Co(NH3)5Cl]Cl
The answer turns out to be +2 but I am not too sure why. Any help?
Sun Nov 29, 2020 7:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Axial vs Equatorial Bonds
Replies: 11
Views: 104

### Re: Axial vs Equatorial Bonds

Equatorial bonds are those that stick out of the sides of the central atom and lie in the same plane, creating shapes like trigonal planar or square planar. The axial bonds are the ones that stick up or down from the central atom, creating 180 degree bond angles with each other and 90 degree bond an...
Sun Nov 29, 2020 7:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: #13 Sapling Week 8
Replies: 18
Views: 100

### Re: #13 Sapling Week 8

when you take a look at each individual carbon atom, it contains 4 bonding regions, making the shape tetrahedral.
Sun Nov 29, 2020 7:36 pm
Forum: Hybridization
Topic: Sapling #12
Replies: 27
Views: 191

### Re: Sapling #12

Remember that double and triple bonds don't matter in hybridization, only regions (so any type of bond counts as 1) and lone pairs are counted. Oxygen has two bonds and two lone pairs which gives it an sp3 hybridization.
Sun Nov 29, 2020 7:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape
Replies: 12
Views: 71

### Re: Molecular Shape

Yes, lone pairs are significant because they count as bonding regions. Lone pairs cause more repulsion between atoms in a molecule which alter the shape and bond angles. However, lone pairs in regions usually occupied by atoms will produce a different shape.
Sun Nov 29, 2020 7:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Molecular Shape
Replies: 9
Views: 50

### Re: Determining Molecular Shape

No, the type of bond doesn't matter, only bonding regions are counted when determining shape.
Sun Nov 22, 2020 9:11 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polarity from lewis structure
Replies: 7
Views: 30

### Re: polarity from lewis structure

CO2 assumes a linear geometry and since the atoms are the same on each side, the electronegativity cancels and the molecule is nonpolar.
Sun Nov 22, 2020 9:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pair E-
Replies: 47
Views: 268

### Re: Lone Pair E-

Yes, bonds and lone pairs count as regions of electron density and contribute to the overall shape of the molecule.
Sun Nov 22, 2020 6:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: shape
Replies: 6
Views: 48

### Re: shape

I recommend always drawing your lewis structure first, then determining how many bonding regions there are. From there, you can use the VSEPR model to find out what the specific shape is.
Sun Nov 22, 2020 5:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angle of Molecule
Replies: 7
Views: 42

### Re: Bond Angle of Molecule

When lone pairs are present in the VSEPR model, it often uses for the approximation of less than 109.5 degrees. Since you got the angle correct, you were correct, but we technically don't need to know the exact angle, just that it is less than 109.5 degrees.
Sun Nov 22, 2020 5:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Memorizing Shape Names
Replies: 12
Views: 75

### Re: Memorizing Shape Names

I feel like specifically understanding why certain shapes are named the way they are helps you memorize them more easily. Shapes like linear, bent, trigonal planar, and trigonal pyramidal all describe the shape given, so try not to get worked up by all the new terms just try to figure out why they h...
Mon Nov 16, 2020 1:51 am
Forum: Lewis Structures
Topic: Sapling Week 5-6 HW Question 13
Replies: 4
Views: 19

### Re: Sapling Week 5-6 HW Question 13

It has a maximum of 8 water molecules because it is accounting for each hydrogen as well as available lone pairs in the molecule that could potentially exert these attractions.
Mon Nov 16, 2020 1:45 am
Forum: Coordinate Covalent Bonds
Topic: Just to clear it up
Replies: 13
Views: 239

### Re: Just to clear it up

Yes, they are Lewis Bases because they are electron donors. Electron acceptors aka proton donors are the Lewis Acids
Mon Nov 16, 2020 1:44 am
Forum: Lewis Structures
Topic: Central Atom of Lewis Structure
Replies: 3
Views: 15

### Re: Central Atom of Lewis Structure

The central atom should be the one with the lowest electronegativity.
Mon Nov 16, 2020 1:43 am
Forum: Lewis Structures
Topic: Hydrogen Bonding
Replies: 12
Views: 62

### Re: Hydrogen Bonding

Hydrogen bonding only occurs in atoms containing Nitrogen, Oxygen, and Flourine.
Mon Nov 16, 2020 1:37 am
Forum: Lewis Structures
Topic: Brackets
Replies: 9
Views: 52

### Re: Brackets

The brackets are used when the molecule has an overall charge. This charge results from adding up all of the formal charges of each atom in the molecule.
Mon Nov 16, 2020 1:29 am
Forum: Resonance Structures
Topic: Sapling 9
Replies: 5
Views: 52

### Re: Sapling 9

The closer the formal charge is to 0 the more stable it is.
Sun Nov 08, 2020 7:03 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge Equation
Replies: 16
Views: 72

### Re: Formal Charge Equation

L represents the number of lone pairs around an atom. Lone pairs on lewis dot structures just look like two dots which aren't bonded to anything. When calculating formal charge of an atom, you just count how many pairs are located around that atom.
Sun Nov 08, 2020 4:03 pm
Forum: Electronegativity
Topic: Electronegativity trend
Replies: 18
Views: 92

### Re: Electronegativity trend

The trend in electronegativity is closely related with ionization energy and electron affinity. If the both of these are high, then the atom will have high electronegativity and will pull shared electrons towards it, and vice versa. Elements in the top right experience the highest electronegativity.
Sun Nov 08, 2020 4:00 pm
Forum: Coordinate Covalent Bonds
Topic: Definition
Replies: 17
Views: 238

### Re: Definition

A coordinate covalent bond is when one element provides both of the electrons necessary in creating the bond.
Sun Nov 08, 2020 3:59 pm
Forum: Lewis Structures
Topic: Lone Pairs Question
Replies: 22
Views: 119

### Re: Lone Pairs Question

A lone pair is a set of two valence electrons that belong to one atom that are not bonded or shared with another.
Sun Nov 08, 2020 3:53 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent Character
Replies: 7
Views: 49

### Re: Covalent Character

All ionic bonds have some covalent character because when bonding, the cation exerts an electrostatic attraction on the electrons surrounding an anion and the anion's electrons are being pulled into the bonding region, they are not just taken or given away, they end up in the middle, similar to the ...
Sun Nov 01, 2020 10:29 pm
Forum: DeBroglie Equation
Topic: p
Replies: 19
Views: 170

### Re: p

p stands for momentum
p=mv
where m=mass and v=velocity

in Heisenberg uncertainty problems you will sometimes have $\Delta$p
$\Delta$p=m$\Delta$v
Sun Nov 01, 2020 10:24 pm
Forum: Trends in The Periodic Table
Topic: Tips for remembering
Replies: 14
Views: 106

### Re: Tips for remembering

Atomic radius gets larger as you move toward the bottom left of the periodic table.

Electronegativity is highest as you move toward the top left of the periodic table.

Electron affinity and ionization energy both increase as you move from left to right on the table.
Sun Nov 01, 2020 10:20 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Replies: 6
Views: 56

For the most part you just want to remember that atoms get bigger as you move toward the bottom left and smaller towards the top right and as you move right along a period due to higher nuclear charges and more protons pulling the electrons closer to the center.
Sun Nov 01, 2020 9:45 pm
Forum: DeBroglie Equation
Replies: 21
Views: 129

You want to use Avogadro's number hen you are given moles but the question asks for an answer in terms of one atom, molecule, formula unit, etc.
Sun Nov 01, 2020 9:31 pm
Forum: DeBroglie Equation
Topic: Sapling Week 2-4 HW Question 24
Replies: 11
Views: 127

### Re: Sapling Week 2-4 HW Question 24

The last two are not compatible because the waves ends do not perfectly match up if you were to model them on an orbit around the atom. If there is a break in the wave, it won't be compatible.
Sun Oct 18, 2020 6:23 pm
Forum: Properties of Electrons
Topic: Work function/Threshold Energy
Replies: 19
Views: 91

### Re: Work function/Threshold Energy

In the photoelectric experiment, the threshold energy is the minimum amount of energy needed to remove an electron from the metal surface. Not overcoming this threshold results in an electron reaching its excited state, but not to the point where it can be removed.
Sun Oct 18, 2020 6:23 pm
Forum: Properties of Electrons
Topic: Work function/Threshold Energy
Replies: 19
Views: 91

### Re: Work function/Threshold Energy

In the photoelectric experiment, the threshold energy is the minimum amount of energy needed to remove an electron from the metal surface. Not overcoming this threshold results in an electron reaching its excited state, but not to the point where it can be removed.
Sun Oct 18, 2020 6:17 pm
Forum: Limiting Reactant Calculations
Topic: Limiting Reactants (Practice Problem)
Replies: 5
Views: 52

### Re: Limiting Reactants (Practice Problem)

Once you have the moles of each reactant, you want to use the coefficients you found in the balanced chemical equation and using stoichiometry determine which makes less product. The one which creates less is the limiting reactant because it is hindering the potential amount of the substance created.
Sun Oct 18, 2020 6:15 pm
Forum: SI Units, Unit Conversions
Topic: (M1)(V1)=(M2)(V2) with L vs mL
Replies: 5
Views: 39

### Re: (M1)(V1)=(M2)(V2) with L vs mL

You do not necessarily need to convert your mL to L if both units correspond, however I recommend converting to liters for the most part because when calculating molarity in other cases you will need to convert. This will just make you accustomed to making liters the norm
Sun Oct 18, 2020 6:12 pm
Forum: Significant Figures
Topic: Sapling HW #4
Replies: 31
Views: 327

### Re: Sapling HW #4

950000 only has two significant figures because trailing zeroes do not count. The only time trailing zeroes become significant is when a decimal point is present (950000.)
Sun Oct 18, 2020 6:06 pm
Forum: Properties of Light
Topic: Frequency vs Wavelength
Replies: 22
Views: 141

### Re: Frequency vs Wavelength

The frequency is the number of waves that pass a point in space during any time interval, usually per one second. The wavelength is the distance between two crests. A higher frequency results in a shorter wavelength and vice versa.
Sun Oct 11, 2020 9:56 pm
Forum: SI Units, Unit Conversions
Topic: Showing Unit Conversions in work
Replies: 7
Views: 79

### Re: Showing Unit Conversions in work

Showing all of your conversions helps you cancel out the unnecessary units along the way leading you to the desired units in your final value. I also think Prof. Lavelle mentioned partial credit, so showing all of your work would definitely help especially if you do end up with the wrong answer but ...
Sun Oct 11, 2020 9:51 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Test Accuracy
Replies: 13
Views: 155

### Re: Test Accuracy

You usually want to end up with the same amount of sig figs as you started. Once you find how many are in the initial value you use to start your calculations you want to preserve that amount.
Sat Oct 10, 2020 8:53 pm
Forum: Limiting Reactant Calculations
Topic: Determining the Limiting Reactant
Replies: 4
Views: 43

### Re: Determining the Limiting Reactant

You have to use the grams which are given and solve for the moles for each reactant. Depending on the coefficients in the balanced equation, the limiting reactant is what is constricting the amount of product. If you had the same amount of moles of each substance but you need one mole of one yet two...
Sat Oct 10, 2020 8:26 pm
Forum: Limiting Reactant Calculations
Topic: Theoretical yield: confused
Replies: 8
Views: 111

### Re: Theoretical yield: confused

The theoretical yield is basically what you would end up with if you did a reaction in a perfect world. This means all of your numbers would be 100% spot on with no human error. Because there is no way around human error in a real experiment, we have the theoretical yield which we calculate based on...
Sat Oct 10, 2020 8:22 pm
Forum: Limiting Reactant Calculations
Topic: Question 10 homework
Replies: 9
Views: 128

### Re: Question 10 homework

I am quite confused on this question as well. The rest were all straight forward however this one I found myself having to look up additional information just to get the answers wrong still. I am using the same numbers as Rachel mentioned but ended up at incorrect answers nonetheless. Not really sur...