## Search found 102 matches

Sat Mar 14, 2020 2:00 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Instantaneous rate of change
Replies: 3
Views: 81

### Re: Instantaneous rate of change

The instantaneous rate law has a negative because the amount of reactant decreases as the reaction takes place.
Sat Mar 14, 2020 1:50 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 5
Views: 31

### Re: Catalysts

It basically means the catalyst is not broken down into new molecules during the reaction.
Sat Mar 14, 2020 1:46 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Order reaction
Replies: 4
Views: 86

### Re: Order reaction

You can also look at the units of the k constant if it is given to determine the order.
Sat Mar 14, 2020 1:44 am
Forum: First Order Reactions
Topic: size
Replies: 6
Views: 109

### Re: size

Smaller particles have more surface area, which allow for the possibility of more collisions and increase the rate.
Sat Mar 14, 2020 1:38 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Temperature and Kinetics
Replies: 3
Views: 23

### Re: Temperature and Kinetics

If we increase temperature, molecules start to move faster, as we've learned when talking about phase changes, so higher temperatures garner faster moving molecules and more collisions per second.
Sat Mar 14, 2020 1:36 am
Forum: Balancing Redox Reactions
Topic: QD3 Midterm
Replies: 5
Views: 119

### Re: QD3 Midterm

Why would it be -1 exactly?
Sat Mar 14, 2020 1:35 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Collision theory
Replies: 2
Views: 17

### Re: Collision theory

There aren't any equations we learned that cover it, so if it is, I'm guessing it'll be a short concept question. Just know that molecules must collide with the right orientation to form a reaction.
Sat Mar 14, 2020 1:33 am
Forum: General Rate Laws
Topic: Natural Log Rate Order
Replies: 4
Views: 47

### Re: Natural Log Rate Order

In a first order reaction, the plot of the natural log over time must be a straight line with a slope of -k.
Sat Mar 14, 2020 1:32 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Endgame 1a
Replies: 5
Views: 100

### Re: Endgame 1a

Since cells flow from anode to cathode, it makes sense that the side with the lower concentration of cations will oxidize and the higher concentration will be reduced until both sides are balanced.
Sat Mar 14, 2020 1:27 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Calculations using Nernst Eq.
Replies: 2
Views: 39

### Re: Calculations using Nernst Eq.

When you make both sides exponents of e, the ln in front of the concentrations cancel and you can solve the other side of the equation to get your answer.
Sat Mar 14, 2020 1:15 am
Forum: Balancing Redox Reactions
Topic: OH vs H
Replies: 12
Views: 140

### Re: OH vs H

If it's a basic solution, there's a trick that usually works. First balance the H+ by placing H2O on the opposite side, then balance the original side by adding twice the molecules of H2O, and finally add the doubles coefficient of OH to the other side to balance the additional atoms you added. The ...
Sat Mar 14, 2020 1:04 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 2
Views: 26

### Re: Catalysts

If you compare the graphs of a reaction with and without the catalyst, it will show that the reaction with a catalyst didn't have to input as much energy to continue.
Wed Feb 26, 2020 2:28 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Which one is Product? Cathode or Anode?
Replies: 5
Views: 53

### Re: Which one is Product? Cathode or Anode?

In the cathode, we are adding electrons, which means that the aqueous cations are becoming solid molecules, which makes sense if the cathode is where products build.
Wed Feb 26, 2020 2:24 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.5 part A
Replies: 1
Views: 32

### Re: 6N.5 part A

When a question has to do with ph and/or concentration of H+ ions, we can use log instead of ln. The 2.303 is 1/log(e) which we have to use when switching from ln to log.
Wed Feb 26, 2020 2:20 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: nernst 2
Replies: 3
Views: 55

### Re: nernst 2

The units can be written as V or J/C. It might read confusing, but just know they're the same.
Wed Feb 26, 2020 2:18 pm
Forum: Balancing Redox Reactions
Topic: Help on 6L.7 part a
Replies: 2
Views: 60

### Re: Help on 6L.7 part a

It is based on the equations they give us in the SRP table. You want Ag to cancel since it's not in the original equation, so if you flip the first half reaction, the Ag cancels on each side and you get the original products.
Wed Feb 26, 2020 2:11 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Strength of a reducing agent
Replies: 3
Views: 46

### Re: Strength of a reducing agent

The closer an element is to the bottom left of the periodic table, the more electronegative it is, therefore the stronger reducing agent it is.
Sun Feb 23, 2020 1:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cathode gaining mass
Replies: 2
Views: 30

### Re: cathode gaining mass

Yes, the aqueous ions turn solid in reduction.
Sun Feb 23, 2020 1:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.5 D.
Replies: 7
Views: 92

### Re: 6L.5 D.

Just take each of the products, and see where you can place electrons and how many (on reactants side or products) in order to change Au+ into each product. Write each change as a separate equation.
Sun Feb 23, 2020 1:11 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Le Chatelier’s Principle
Replies: 11
Views: 124

### Re: Le Chatelier’s Principle

We are still dealing with concentrations like Al and Al3+ or Zn and Zn2+. Therefore, the same principles we learned in the equilibrium unit apply here. If there's too much concentration of one of these ions, the equilibrium will shift to satisfy LeChatelier's.
Wed Feb 19, 2020 2:38 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Question 1 on Midterm
Replies: 7
Views: 183

### Re: Question 1 on Midterm

If there's less reactant (NO) then there's less matter available to make product (NO2), this is why when the reaction shifts to the left due to Le Chatelier's Principle, the equation must balance at a lower partial pressure on both sides.
Wed Feb 19, 2020 2:34 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sign of delta G
Replies: 9
Views: 127

### Re: Sign of delta G

I agree, it depends on if they give you concentrations (use K vs Q) or information to find enthalpy and temperature (use G).
Fri Feb 14, 2020 2:38 pm
Forum: Phase Changes & Related Calculations
Topic: Equation Choice
Replies: 5
Views: 187

### Re: Equation Choice

Remember that if the phase change involves the atoms becoming more free and moving faster (i.e. solid to liquid, liquid to gas) the process is endothermic because the system is gaining heat and energy, meaning the q value is positive. The opposite is true for exothermic processes.
Fri Feb 14, 2020 2:35 pm
Forum: Ideal Gases
Topic: ideal gas
Replies: 5
Views: 122

### Re: ideal gas

Ideal gases are highly unlikely to occur in the natural world, but are useful for calculations in class and theory.
Fri Feb 14, 2020 2:33 pm
Forum: Ideal Gases
Topic: pv=nrt
Replies: 19
Views: 244

### Re: pv=nrt

Yes, just use 273.15K for temperature and 1atm for pressure.
Fri Feb 14, 2020 2:32 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure and Moles
Replies: 7
Views: 82

### Re: Pressure and Moles

Add up the coefficients of the products, add up the coefficients of the reactants, then subtract to find the total change in moles for your equation.
Fri Feb 14, 2020 2:30 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy equation
Replies: 3
Views: 54

### Re: Entropy equation

This equation is usually used to calculate isothermal reversible processes.
Sat Feb 08, 2020 1:37 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4D 3)
Replies: 1
Views: 21

### Re: 4D 3)

You divide by the moles of CO because the question is asking for the internal energy change per 1.00 mole of CO.
Sat Feb 08, 2020 1:35 am
Forum: Phase Changes & Related Calculations
Topic: Homework Problem 4C.13
Replies: 3
Views: 43

### Re: Homework Problem 4C.13

To go from 0 degrees ice to 45 degrees liquid water, we must first go from 0 degrees ice to 0 degrees liquid water, which required an enthalpy of formation calculation. We can then use mCdeltaT to find the heat necessary to go from liquid water at 0 to the final temperature.
Sat Feb 08, 2020 1:31 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hf and Hc
Replies: 3
Views: 44

### Re: Hf and Hc

Hc just means it is the enthalpy of combustion, so there must be oxygen in the reactants.
Sat Feb 08, 2020 1:29 am
Forum: Phase Changes & Related Calculations
Topic: 4C.13 phase change
Replies: 2
Views: 50

### Re: 4C.13 phase change

The n delta h represents the Heat of fusion of the ice cube as it melts to a liquid and the mCdeltaT is the heat needed to go from 0 degree liquid to the final temperature. Think of it as the graph we went over in class with the steps of alternating horizontal and diagonal lines.
Sat Feb 08, 2020 1:19 am
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Microstates and Entropy
Replies: 1
Views: 15

### Re: Microstates and Entropy

You can use the micro states to find degeneracy by using the W=#^n equation, and then you can use degeneracy to calculate change in entropy with the delta S=kB*lnW equation.
Fri Jan 31, 2020 2:48 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Unit
Replies: 6
Views: 40

### Re: Enthalpy Unit

Usually, we add or subtract other values to find delta H, so unless the problem specifically says to use kJ/mol, you can keep it in the units given for the other values of for example, q. Just make sure you are consistent throughout the equation.
Fri Jan 31, 2020 2:43 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Boltzmann Equation
Replies: 2
Views: 52

### Re: Boltzmann Equation

You can derive from the ideal gas law a variation equation where PV=NkBT, where the Boltzmann constant is kB and ratio of R over kB should be equal to Avogadro's constant.
Fri Jan 31, 2020 2:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test 1 # 4
Replies: 10
Views: 111

### Re: Test 1 # 4

You add 273 to the 27 to get temperature in 300 degrees Kelvin, and make sure the correct Rydberg constant is used so the units Kelvin, Liters, and atm cancel.
Fri Jan 31, 2020 2:30 pm
Forum: Administrative Questions and Class Announcements
Topic: Math Resources
Replies: 8
Views: 84

### Re: Math Resources

Yes, these are on his website under math assistance. Just click on Integration rules with application to chemistry.
Fri Jan 31, 2020 2:28 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Degeneracy
Replies: 9
Views: 112

### Re: Degeneracy

Degeneracy can be used to describe systems when the systems are of different states, such as solid, liquid, or gas, but equal in energy levels.
Sun Jan 26, 2020 11:22 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Using Bond Enthalpies
Replies: 2
Views: 11

### Re: Using Bond Enthalpies

It's the same as the ice table when we either subtracted x or added x, depending on whether it was a product or a reactant. The same applies here, we just look if that molecule is being broken down, or created, and put the corresponding positive or negative sign.
Sun Jan 26, 2020 11:19 am
Forum: Phase Changes & Related Calculations
Topic: thermochemistry vs thermodynamics
Replies: 2
Views: 25

### Re: thermochemistry vs thermodynamics

Thermochemistry is just a branch of thermodynamics that involves the heat given off or absorbed during chemical reactions.
Sun Jan 26, 2020 11:16 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: state functions
Replies: 4
Views: 29

### Re: state functions

State functions are important in thermochemistry because enthalpy, entropy, Gibbs free energy, etc. are all state functions, which is what allows us to add and subtract heat in the equations.
Sun Jan 26, 2020 11:12 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Negative Square Root solving an ICE box
Replies: 13
Views: 92

### Re: Negative Square Root solving an ICE box

When this happens to me, it's because I usually forget to square the b inside the square root, which leads to a negative inside. You should not get a negative value inside the square root.
Sun Jan 26, 2020 11:11 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Irreversible Expansion
Replies: 4
Views: 58

### Re: Irreversible Expansion

The difference between irreversible and reversible expansion is that in irreversible, the reaction does not remain in thermodynamic equilibrium.
Fri Jan 17, 2020 4:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Strong or weak acid?
Replies: 5
Views: 52

### Re: Strong or weak acid?

Usually H with any of the halogens is a strong acid such as HCl, HI, HBr, and H2SO4. Also for strong bases, they'll usually have OH at the end like LiOH, NaOH, or Ba(OH)2.
Fri Jan 17, 2020 4:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Value of Kw
Replies: 6
Views: 51

### Re: Value of Kw

Since we haven't gone over any problems where we need to know Kw at a temperature other than 25 degrees Celsius, I don't think there will be any on the test. However, if both Kb and Ka are given you can find it.
Fri Jan 17, 2020 4:10 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Temperature Change
Replies: 9
Views: 181

### Re: Temperature Change

Think of heat as a reactant in endothermic reactions. When heat is added, its like the reactant side becomes overwhelmed, so the system needs to tip to the other side (products) to balance at equilibrium.
Fri Jan 17, 2020 4:08 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: ICE table
Replies: 11
Views: 64

### Re: ICE table

You should use an ice table in both cases, the only difference is for weak acid and bases, the K is less than 10^-3 which means that the [number-x ] concentration can just be calculated as [number] to save time.
Fri Jan 17, 2020 4:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc & Kp
Replies: 12
Views: 108

### Re: Kc & Kp

Kc is when the numbers given are concentrations while Kp is when the values are partial pressures.
Thu Jan 09, 2020 4:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Why is K unitless?
Replies: 10
Views: 90

### Re: Why is K unitless?

When we set up the equation for K, it is K= [M]/[M], as in a concentration over another concentration. So just think of it as canceling out the units M in the fraction, leaving you with a unitless number.
Thu Jan 09, 2020 4:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reactants and Products Affecting Equilibrium
Replies: 2
Views: 13

### Re: Reactants and Products Affecting Equilibrium

^The above comment is true because if you add more of a substance on the reactants side, this increases the likelihood of the correct reactants colliding with the correct geometry to create a chemical reaction, which means the forward reaction would be favored.
Thu Jan 09, 2020 4:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q vs K
Replies: 7
Views: 50

### Re: Q vs K

If Q is less than K at some time during the reaction, then compared to the equilibrium concentrations [R] > [P] and the forward reaction is favored, and vice versa.
Thu Jan 09, 2020 4:20 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Replies: 5
Views: 43

### Re: confused about ice table

ICE stands for the Initial concentrations, the Change in each, and the Equilibrium concentrations. So lets say a gas that is a reactant in the equation has a concentration of 1M, and in the balanced equation has a coefficient of 2, you'd have 1-2x in the final equilibrium row. Once you have calculat...
Thu Jan 09, 2020 3:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solid/liquid
Replies: 7
Views: 48

### Re: solid/liquid

Yes, solids and gases have no significant effect on the equilibrium reaction, so only include the gases and aqueous solutions.
Thu Dec 05, 2019 12:20 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate
Replies: 2
Views: 65

### Re: Polydentate

Elaborating on what the previous comment said, CN can’t take on 2 ligands because of the electron repulsion between the ligands if the bonds are too close to each other.
Thu Dec 05, 2019 12:14 pm
Forum: Naming
Topic: amine or ammine
Replies: 2
Views: 42

### Re: amine or ammine

Ammine has to do with ligands and coordination compounds while amine has to do with derivatives of ammonia like NH3 or NH4
Thu Dec 05, 2019 12:10 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: London disperson
Replies: 6
Views: 49

### Re: London disperson

London dispersion is the same as Van der waals but not the same as dipole dipole. Dr.Lavelle said he prefers induced dipole induced dipole when describing London forces but it doesn’t matter all are correct.
Thu Dec 05, 2019 12:05 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxolate Chelate
Replies: 6
Views: 106

### Re: Oxolate Chelate

Chelates are polydentates so 2 or more bonding sites.
Thu Dec 05, 2019 12:03 pm
Forum: Bronsted Acids & Bases
Topic: Names of acids
Replies: 1
Views: 40

### Re: Names of acids

Just memorize the most common ones like HCl H2SO4 H3PO4 that we’ve learned and know how to find of its a strong acid or a weak acid.
Tue Dec 03, 2019 5:03 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Resonance and Formal Charge
Replies: 4
Views: 144

### Re: Resonance and Formal Charge

The formal charges differ because in some structures, the atoms have double bonds, single bonds, or Lone pairs. The major contributor is the one closest to a 0 total formal charge, and if that isn't possible usually the central atom should have 0 charge unless it violates the octet rule.
Tue Dec 03, 2019 4:54 pm
Forum: Bronsted Acids & Bases
Topic: Self-test J.1A/B
Replies: 3
Views: 53

### Re: Self-test J.1A/B

For a, KCl has neither H+ ions nor OH- ions, so it is neither. HClO and HF both donate H+ ions, so they're acids and Ca(OH)2 donates an OH- ion, so it's a base.
Tue Dec 03, 2019 4:49 pm
Forum: Lewis Acids & Bases
Topic: charges of transitional metals
Replies: 3
Views: 39

### Re: charges of transitional metals

For example, for iron in Fe2O3, since there is a neutral charge of 0, we know there is a 3 x -2 = -6 charge for oxygen, therefore the irons must total a +6 charge and when you divide by 2 atoms, you get +3 as the formal charge for each iron atom. We write this as iron(III)oxide.
Tue Dec 03, 2019 4:34 pm
Forum: Sigma & Pi Bonds
Topic: Unhybridized orbitals.
Replies: 3
Views: 110

### Re: Unhybridized orbitals.

Pi bonds don't allow rotation and sigma bonds do. Also, one single bond has a sigma bond while a double bond has one sigma and a pi bond.
Tue Dec 03, 2019 2:58 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Latin names
Replies: 2
Views: 28

### Re: Latin names

There is a link on Professor Lavelle's website that says "naming coordination compounds." I recommend looking at that page and just getting familiar with a few concepts.
Fri Nov 29, 2019 7:03 pm
Forum: Lewis Acids & Bases
Topic: 6A.13
Replies: 7
Views: 65

### Re: 6A.13

The positive charge means it is missing electrons in the full shell, making it an electron acceptor.
Fri Nov 29, 2019 6:42 pm
Forum: Bronsted Acids & Bases
Topic: Trichloroacetic acid vs acetic acid
Replies: 2
Views: 54

### Re: Trichloroacetic acid vs acetic acid

Trichloroacetic acid is just acetic acid with 3 Cl atoms instead of 3 H. Therefore, the Cl atoms have a stronger pull on the bonds of the carboxyl group, loosening the OH bond and making H+ions more likely to dissociate.
Fri Nov 29, 2019 6:36 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted base
Replies: 3
Views: 40

### Re: Bronsted base

It can be kind of confusing because NH3 has H atoms which makes us think of H+ ions and acids; however, in water, it gains H+ ions and becomes NH4, making it a bronzed base.
Fri Nov 29, 2019 6:34 pm
Forum: Bronsted Acids & Bases
Topic: Acids and Bases
Replies: 3
Views: 37

### Re: Acids and Bases

Usually acids have H+ ions that will dissociate, but in order to be 100% sure about any polar or non polar characteristics, draw the structure.
Fri Nov 29, 2019 6:32 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg
Replies: 4
Views: 153

### Re: Rydberg

Just think of it in relation to the nucleus. If an electron is emitted aka going away, it's a negative energy value. If it is being absorbed and coming closer, it is positive.
Wed Nov 20, 2019 5:57 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles in Square Pyramidal and T-Shaped
Replies: 4
Views: 74

### Re: Bond Angles in Square Pyramidal and T-Shaped

T shaped has a less than 90 degree angle for all of the angles between the bonds that form the actual T, but the 2 lone pairs at the top that repel each other are what forms the 120 degree angle with the bottom atom of the T.
Wed Nov 20, 2019 5:44 pm
Forum: General Science Questions
Topic: Test 2: IMF
Replies: 4
Views: 106

### Re: Test 2: IMF

Just to give a general ballpark for the values, here's the list he gave us in lecture,
Ion-Ion = -250kJ/mol
Ion-dipole = -15kJ/mol
Dipole-dipole = -2kJ/mol
Dipole-induced dipole = -kJ/mol
Wed Nov 20, 2019 5:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: T-Shaped ??
Replies: 9
Views: 150

### Re: T-Shaped ??

AX2E is bent v shaped and its bond angles are 120 each, separated symmetrically.
Wed Nov 20, 2019 5:38 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate
Replies: 2
Views: 53

### Re: Polydentate

I'd say yes draw it out to be sure the formal charges are correct and the number of lone pairs on the central atom are correct. I doubt there will be a test question where part a doesn't involve drawing the shape anyway.
Wed Nov 20, 2019 5:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: XA2E2
Replies: 9
Views: 86

### Re: XA2E2

The molecule is called bent (v shaped) and looks very similar to a tetrahedral except for one of the electron lone pairs takes the place of where the third bonded molecule would have gone, which is why the angles are slightly less than 109.5.
Sat Nov 16, 2019 10:03 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Subscript on E
Replies: 5
Views: 63

### Re: Subscript on E

It shouldn't matter, just like how when writing the charge of a molecule in a lewis structure, you can write "-" on the top right of the brackets or "1-"
Sat Nov 16, 2019 9:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 8
Views: 88

### Re: Bond Angles

You don't need to memorize every possible exception, just know that in some cases like ammonia and water, the bond angles are slightly less than 109.5 because of the strength of the repulsion of the lone pairs.
Sat Nov 16, 2019 9:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E 11 b)
Replies: 4
Views: 35

### Re: 2E 11 b)

Also, if we added double bonds, the Iodine atom would have a +2 charge since it would have 5 bonds around it, and we try to make the central atom have as close to a formal charge of 0 as possible.
Sat Nov 16, 2019 9:53 pm
Forum: Bond Lengths & Energies
Topic: Lone pairs
Replies: 7
Views: 222

### Re: Lone pairs

You determine whether a lone pair is axial or equatorial by looking at the bond angles and making sure the lone pair has enough room to evenly repel the other bonded electrons.
Sat Nov 16, 2019 9:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Model
Replies: 2
Views: 49

### Re: VSEPR Model

To solve this,, just count the amount of electrons - 34 if you add the negative charge - then continue doing a lewis structure like normal, then go down the charge and find which example fits the model with the same number regions of electron densities.
Sun Nov 10, 2019 11:20 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: Boiling and Melting Points
Replies: 7
Views: 61

### Re: Boiling and Melting Points

The boiling point of H2S is -60 degrees C while the boiling point of H2O is 100 degrees C. These molecules are very similar in structure, but H2O is harder to break down because the bonds are stronger.
Sun Nov 10, 2019 11:12 pm
Forum: Dipole Moments
Topic: Dipole moment units
Replies: 4
Views: 41

### Re: Dipole moment units

Usually they are written in Debye which are 1 x 10^-18 C*m. It is just more applicable for working with small numbers.
Sun Nov 10, 2019 11:10 pm
Forum: Octet Exceptions
Topic: Octet exception
Replies: 13
Views: 451

### Re: Octet exception

Some typical exceptions are S, P, and Cl.
Sun Nov 10, 2019 11:08 pm
Forum: Resonance Structures
Topic: octet v. expanded octet
Replies: 5
Views: 61

### Re: octet v. expanded octet

You don't physically draw the Lewis structure of an expanded octet bigger it just looks the same as a regular structure except for there are more bonds around the central atom.
Sun Nov 10, 2019 11:05 pm
Forum: Coordinate Covalent Bonds
Topic: Coordinate Covalent Bond
Replies: 3
Views: 70

### Re: Coordinate Covalent Bond

A coordinate covalent bond is a covalent bond where both of the electrons being shared come from one atom.
Mon Nov 04, 2019 7:55 pm
Forum: Molarity, Solutions, Dilutions
Topic: initial and final variables
Replies: 4
Views: 195

### Re: initial and final variables

Honestly, I always just label each number with an M1 or M2 or V1 or V2 in between the print just so I don't get confused, but you can write it out and find the missing value.
Mon Nov 04, 2019 5:52 pm
Forum: Lewis Structures
Topic: Electron Configuration & Formal Charge for Cu
Replies: 4
Views: 61

### Re: Electron Configuration & Formal Charge for Cu

my TA said to just always write the electron configuration as if it had no charge, and depending on if the charge is positive or negative, add or subtract electrons from the end. So in this case, 3d10 is to the left of 4s1. We take off one electron in the 4s because it is the rightmost one and then ...
Mon Nov 04, 2019 5:48 pm
Forum: Lewis Structures
Topic: How do I know when to use a double bond?
Replies: 7
Views: 102

### Re: How do I know when to use a double bond?

Regarding double bonds in molecules with resonance, he said to compute the formal charges for each atom to find the lowest state possible in each of the possible resonance structures. So just use the equation, FC=V-(L+S/2).
Mon Nov 04, 2019 5:45 pm
Forum: *Shrodinger Equation
Topic: Shrodinger equation
Replies: 7
Views: 264

### Re: Shrodinger equation

It wasn't on the equation sheet for the first test on fundamentals even though other quantum equations were on it, so I doubt it'll be on the midterm unless he changed the equation sheet. However, just in case, spend like 5 minutes on it to get a general understanding.
Mon Nov 04, 2019 5:41 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Atomic Orbitals in Terms of Probability
Replies: 6
Views: 191

### Re: Atomic Orbitals in Terms of Probability

This just means that there is a probability that the electron will be following the path of the orbital described in its l value. However, we cannot be 100% accurate in predicting the exact location of an electron as they don't follow rigid paths, which is why we use probability.
Wed Oct 30, 2019 5:26 pm
Forum: Octet Exceptions
Replies: 9
Views: 155

An example of a radical would be CH3 which we did in class. C has 4 valence electrons and each of the 3 hydrogens have 1, giving the molecule a total of 7 valence electrons. This makes the molecule highly radioactive and it only exists for a short time because it will try to bond with another CH3 mo...
Wed Oct 30, 2019 5:22 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity
Replies: 8
Views: 67

### Re: Electron Affinity

Electron affinity is also known as the likelihood of an atom gaining an electron. Therefore, it increases as you move to the right because the valence she’ll becomes closer to being full as the atom becomes more desperate to gain that last electron that will fill its shell. It increases as you move ...
Wed Oct 30, 2019 5:17 pm
Forum: Ionic & Covalent Bonds
Topic: ionic vs covalent bonds
Replies: 6
Views: 82

### Re: ionic vs covalent bonds

Yes, and also you can look at how far the elements are from each other on the periodic table. If there is a cation in the far left that is bonded with an anion in the far left, this means there is a great electronegativity difference and it is an ionic bond.
Wed Oct 30, 2019 5:14 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic Bonds
Replies: 6
Views: 62

### Re: Ionic Bonds

Usually ionic bonds are between cations, which are to the left of the periodic table, and anions, which are toward the right. This creates a difference in electronegativity which is greater than 2, therefore their stronger bond due to the attraction between opposite charges.
Wed Oct 30, 2019 5:10 pm
Forum: Lewis Structures
Topic: Valence Electrons from Periodic Table
Replies: 10
Views: 162

### Re: Valence Electrons from Periodic Table

It does correspond to the group but make sure you skip over the transition metals in the middle when looking at elements toward the right. For example, Boron has 3 valence electrons, not 13.
Mon Oct 21, 2019 8:44 pm
Forum: Trends in The Periodic Table
Topic: 2nd Ionization Energy
Replies: 7
Views: 59

### Re: 2nd Ionization Energy

The first ionization energy is how much energy is needed to remove an electron from a neutral atom. The second ionization energy is how much energy is needed to remove an electron from a positively charged atom, meaning it has already lost an electron. It would take more energy to remove a second on...
Mon Oct 21, 2019 8:41 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Cr and Cu Exceptions
Replies: 2
Views: 43

### Re: Cr and Cu Exceptions

The elements Cr and Cu are exceptions because their configuration, if you write it out, has 4 and 9 electrons in the 3d orbital. However, since these are one electron away from forming half shells (5 electrons in the 3d orbital) and full shells (10 electrons in the 3d orbital), an electron is pulled...
Mon Oct 21, 2019 8:34 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity Trends
Replies: 5
Views: 64

### Re: Electron Affinity Trends

The electron affinity increases as you move left to right because the rightmost elements have an almost full valence electron shell, making them more desperate to gain another electron to fill the outer shell. Electron affinity decreases moving down because the electrons are in farther shells to the...
Mon Oct 21, 2019 8:25 pm
Forum: Trends in The Periodic Table
Replies: 3
Views: 37

The atomic radius is half the diameter of a neutral atom while the ionic radius pertains to the radius of the cation and anion in an ionic bond. They tend to be larger for anions and smaller for cations.
Mon Oct 21, 2019 8:18 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: S-, P-, S-, and F- Orbitals
Replies: 3
Views: 61

### Re: S-, P-, S-, and F- Orbitals

Think of orbitals as surrounding shells that the electrons move really fast through. For example, for the s orbital, the electrons MOST LIKELY can be found traveling around the nucleus following a spherical path. The same goes for p d and f orbitals. However, we can't know 100% where an electron wil...
Thu Oct 03, 2019 11:44 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Determining Molar Mass
Replies: 19
Views: 166

### Re: Determining Molar Mass

If there is a possibility to be more accurate, honestly just take the extra time to do it because sometimes rounding can lead to drastic differences in the answer because of the small amount of substances in some problems.
Thu Oct 03, 2019 11:39 pm
Forum: Balancing Chemical Reactions
Topic: H.25 Question
Replies: 3
Views: 102

### Re: H.25 Question

There are a couple of other diatomic molecules that would be useful later. Hydrogen, Nitrogen, Oxygen, Fluorine, Iodine, Chlorine, and Bromine all have a subscript of 2 when alone.
Thu Oct 03, 2019 11:33 pm
Forum: Molarity, Solutions, Dilutions
Topic: Fundamentals G5
Replies: 3
Views: 83

### Re: Fundamentals G5

You kind of have to work backwards for this problem. You know you need 0.00215 mol Na at the end, which you need 0.001075 mol Na2CO3 since there is a ratio of 1:2. Since you are looking for volume and already have the final moles, you know you are looking for the molarity because of n=MV. The molari...