## Search found 95 matches

Mon Mar 16, 2020 1:37 pm
Forum: Calculating Work of Expansion
Topic: Choosing work equation
Replies: 10
Views: 331

### Re: Choosing work equation

Would the reversibility/irreversibility of a system be given explicitly in a problem, or would that be something that we have to figure out for ourselves? If so, how would we determine if a system was reversible or not? This information will most likely be given. It may be possible that two work va...
Mon Mar 16, 2020 1:35 pm
Forum: Calculating Work of Expansion
Topic: Choosing work equation
Replies: 10
Views: 331

### Re: Choosing work equation

Would the reversibility/irreversibility of a system be given explicitly in a problem, or would that be something that we have to figure out for ourselves? If so, how would we determine if a system was reversible or not? This information will most likely be given. It may be possible that two work va...
Tue Mar 10, 2020 3:18 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Calculating Gibbs Free Energy
Replies: 6
Views: 167

### Re: Calculating Gibbs Free Energy

When calculating deltaG using the products minus reactants method, you would have to take into account the stoichiometric coefficients.
Tue Mar 10, 2020 3:16 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Equations
Replies: 8
Views: 188

### Re: Equations

These equations are all on the formula sheet so there isn't really a need to memorize them.
Tue Mar 10, 2020 3:14 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs free energy and K
Replies: 3
Views: 57

### Re: Gibbs free energy and K

The two equation would be deltaG(standard)=-RTlnK and deltaG(reaction)=deltaG(standard)+RTlnQ, which as mentioned, can be found on the formula sheet.
Tue Mar 10, 2020 3:12 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: midterm 6 b
Replies: 6
Views: 109

### Re: midterm 6 b

For deltaH and deltaG to be very similar, the change in entropy has to be minimal, so you would look to see which reaction has the least change in entropy, which would be A since the phase remains a solid throughout the reaction.
Tue Mar 10, 2020 3:07 pm
Forum: Calculating Work of Expansion
Topic: Choosing work equation
Replies: 10
Views: 331

### Re: Choosing work equation

For an irreversible expansion, use w=-P(deltaX). For a reversible expansion (isothermal), use w=-nRT(ln deltaV2/deltaV1). Would the reversibility/irreversibility of a system be given explicitly in a problem, or would that be something that we have to figure out for ourselves? If so, how would we de...
Tue Mar 10, 2020 1:54 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: HW 4I. 5
Replies: 3
Views: 146

### Re: HW 4I. 5

I believe you would first find the final temperature of the system and then using that you would find the change in enthalpy of the hot and cold water. Then using the enthalpy, you would find the entropy of each and then combine the two entropies to find the total entropy.
Tue Mar 03, 2020 12:50 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Possible Solution Error on 6N.1 part b
Replies: 5
Views: 100

### Re: Possible Solution Error on 6N.1 part b

I also keep getting 107, so there probably is an error.
Sat Feb 29, 2020 12:31 pm
Forum: Balancing Redox Reactions
Topic: 6K5A
Replies: 3
Views: 110

### Re: 6K5A

You have to first balance the oxygens in the equation O3->O2 by adding one water to the right side. Then, the balance the hydrogens, you have to add 2 H+ to the left side. In order to balance the charge then, you have to add 2 e- to the left side. The question tells us that the reaction occurs in a...
Thu Feb 27, 2020 9:42 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 5G.15
Replies: 5
Views: 114

### Re: 5G.15

I believe the answer key in the book is incorrect.
Thu Feb 27, 2020 9:41 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: HW question 5G.15
Replies: 4
Views: 152

### Re: HW question 5G.15

You would first use deltaG(naught)=-RTlnk and then you would use deltaG(reaction)=deltaG(naught)+RTlnQ. Since the question is asking for the deltaG(reaction), you would have to use these 2 equations.
Thu Feb 27, 2020 9:31 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gas constant R
Replies: 5
Views: 99

### Re: Gas constant R

Since we want an answer with Joules and moles, we would use the R constant 8.314 J.K^-1.mol^-1.
Thu Feb 27, 2020 9:29 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 5J 15
Replies: 3
Views: 79

### Re: 5J 15

Those actually are actual molecules, you can find them at the bottom of page A10.
Thu Feb 27, 2020 9:18 pm
Forum: Balancing Redox Reactions
Topic: When to add H+ or H20
Replies: 19
Views: 445

### Re: When to add H+ or H20

Its also important to note that you add H+ when the solution is acidic and OH- when the solution is basic.
Thu Feb 27, 2020 9:14 pm
Forum: Balancing Redox Reactions
Topic: Acidic/Basic Solutions
Replies: 3
Views: 61

### Acidic/Basic Solutions

Will we typically be given the information of whether a solution is acidic or basic when trying to balance redox reactions or will we have to figure it out on our own?
Thu Feb 27, 2020 9:10 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.7
Replies: 2
Views: 27

### Re: 6M.7

Appendix 2B in the back of the book has a list of all the E naught values.
Thu Feb 27, 2020 9:02 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: When to apply Pt into cell diagrams
Replies: 9
Views: 171

### Re: When to apply Pt into cell diagrams

If I'm not mistaken, I believe you add Pt when there is no other metal. Since Hg is a metal, you would not need to add Pt.
Mon Feb 24, 2020 9:09 pm
Forum: Balancing Redox Reactions
Topic: redox reactions
Replies: 5
Views: 90

### Re: redox reactions

Oxidation is when electrons are lost, so electrons will be on the right hand side (products) of the reaction, while reduction will be on the left hand side (reactants), since reduction is when electrons are gained.
Mon Feb 24, 2020 9:04 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sign of delta G
Replies: 9
Views: 234

### Re: Sign of delta G

I believe you can, but just to be safe I would use the sign of G to determine the answer for that.
Mon Feb 17, 2020 9:24 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated versus closed
Replies: 7
Views: 231

### Re: Isolated versus closed

In an isolated system, no heat can be transferred and the volume remains constant, but in a closed system, heat can be transferred and the volume also remains constant.
Mon Feb 17, 2020 9:21 am
Forum: Calculating Work of Expansion
Topic: Irreversible and Reversible problem
Replies: 4
Views: 155

### Re: Irreversible and Reversible problem

Also, it is important to remember that under reversible expansions more work is always done than in irreversible expansions.
Mon Feb 17, 2020 9:13 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Spectator Ions
Replies: 3
Views: 45

### Re: Spectator Ions

No, spectator ions such as Cl, are not included.
Sun Feb 16, 2020 9:57 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Delta U = n*Cv,m*deltaT
Replies: 7
Views: 726

### Re: Delta U = n*Cv,m*deltaT

From information I gained from the book, discussion, and videos, I also believe that when talking about constant pressure, you use Cp, but when talking about constant volume, you use Cv.
Sun Feb 16, 2020 9:55 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Extensive and Intensive Properties
Replies: 12
Views: 344

### Re: Extensive and Intensive Properties

Extensive properties depend on the amount given to you, while intensive properties don't. Since the specific amount is not given to you for heat capacity, it is an extensive property however, since you are given the amount for specific heat capacity, it is an intensive property.
Sun Feb 16, 2020 9:51 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Units for Heat Capacity & Specific Heat Capacity
Replies: 2
Views: 102

### Re: Units for Heat Capacity & Specific Heat Capacity

I agree and believe its best to leave it in J/C unless told otherwise. Also, for heat capacity, the units are J/C, but for specific heat capacity, it should be J/g*C.
Sun Feb 09, 2020 5:19 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: U=3/2 nRT
Replies: 4
Views: 55

### Re: U=3/2 nRT

You would use this equation when you are asked to find deltaU at a constant volume.
Sun Feb 09, 2020 4:59 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Question regarding converting C to K in examples from textbook
Replies: 2
Views: 44

### Re: Question regarding converting C to K in examples from textbook

I think they initially converted the 100C and 20C to kelvin, which would result in 373K and 293K, and then they took the difference, which results in 80K.
Wed Feb 05, 2020 10:39 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: R constants
Replies: 40
Views: 907

### Re: R constants

A quick way of determining which R value to use is to look at the units given to you. The units you would need to cancel out should correspond with that of the R value you use.
Wed Feb 05, 2020 10:35 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 4f.13
Replies: 1
Views: 37

### 4f.13

For part b it asks to find the change in entropy for the vaporization of 50g of ethanol at 351.5K. So the way I went about solving this problem was to first calculate the change in entropy of the phase change since ethanol is still in the liquid phase and has not reached the boiling point. Then I ad...
Sun Feb 02, 2020 2:16 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: State Functions
Replies: 6
Views: 67

### Re: State Functions

The path taken to reach the end of state functions does not matter, however since the path taken does matter for heat and work, they are not considered state functions.
Sun Feb 02, 2020 2:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: hess's law
Replies: 13
Views: 93

### Re: hess's law

In order to cancel out, the molecules must be on opposite sides. This may require you to reverse a reaction and change the enthalpy of the reaction in order to make canceling them out possible.
Sun Feb 02, 2020 2:04 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D. 15
Replies: 2
Views: 22

### Re: 4D. 15

For this problem you would use Hess's Law. You would reverse C2H6 since you need to use the enthalpy for its production rather than its decomposition so the -1560 would turn into +1560. Then you would double the enthalpy for H2 since the coefficient in front of H2 is 2, giving you -572. Then you wou...
Sun Feb 02, 2020 1:58 pm
Forum: Phase Changes & Related Calculations
Topic: Cv and Cp
Replies: 9
Views: 100

### Re: Cv and Cp

If I'm not mistaken, Cv is used under constant volume while Cp is used under constant pressure.
Sun Feb 02, 2020 1:57 pm
Forum: Phase Changes & Related Calculations
Topic: internal energy
Replies: 11
Views: 188

### Re: internal energy

The equation you use for internal energy is deltaU=q+w.
Wed Jan 22, 2020 5:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Conjugate Seesaw
Replies: 3
Views: 43

### Re: Conjugate Seesaw

The conjugate seesaw simply states that the stronger the acid, the weaker its conjugate base and the stronger a base, the weaker its conjugate acid.
Wed Jan 22, 2020 5:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solids and Liquids
Replies: 6
Views: 54

### Re: Solids and Liquids

Solids and liquids are not included in the equation for the K constant, only gases and aqueous solutions.
Wed Jan 22, 2020 4:16 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure changes
Replies: 7
Views: 53

### Re: Pressure changes

If the pressure is increased, the system shifts to the side with less moles, and if the pressure is decreased, the system shifts to the side with more moles.
Wed Jan 22, 2020 4:11 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Prep for Test 1
Replies: 16
Views: 232

### Re: Prep for Test 1

No there are no specific values that you need to memorize. A helpful thing to know however, for the test is how to go from Ka to Kb and how to find the pH and pOH given the values of Ka or Kb.
Wed Jan 22, 2020 4:08 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J 5: increase in pressure
Replies: 4
Views: 65

### Re: 5J 5: increase in pressure

For part B, you do not take C into account since it is a solid so technically the left side would have 1 mol and the right side would have 2 mols, hence the reason why the system would shift to the left. For D, the amount of moles on both sides equals 2, so since the amount of moles are equal, there...
Sun Jan 19, 2020 9:17 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5% vs. K < 10^-3
Replies: 3
Views: 60

### Re: 5% vs. K < 10^-3

When K<10^-3, you are allowed to approximate and the 5% rule is just a means of confirming that your approximation is valid.
Sun Jan 19, 2020 9:03 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 4
Views: 34

### Re: Le Chatelier's Principle

Adding on to this, does the Le Chatelier's Principle only apply for the partial pressures or do I need to know how to apply it for concentrations? Le Chatelier's Principle is applied to both concentrations and partial pressures, however I believe that you would apply the principle to concentrations...
Sun Jan 19, 2020 8:59 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Relationship between pressure and volume
Replies: 10
Views: 111

### Re: Relationship between pressure and volume

According to the ideal gas law, PV=nRT, pressure and volume are inversely proportional.
Sun Jan 19, 2020 8:56 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.1
Replies: 4
Views: 79

### Re: 5J.1

The reason why CO2 would decrease when CO decreases is because, according to Le Chatelier's principle, the system will shift to the left of the reaction in order to provide a balance, meaning that CO2 will decrease in order to contribute to this balance.
Sun Jan 19, 2020 8:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 7
Views: 60

### Re: Le Chatelier's Principle

Le Chatelier's principle is significant because we can use it to predict what may happen to a substance when changes in things like temperature and concentration are inflicted. I think it applies to all reversible reaction.
Mon Jan 13, 2020 3:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kw calcuation
Replies: 5
Views: 56

### Re: Kw calcuation

Since water is a liquid, it is omitted from the equilibrium constant, giving the denominator in this specific equilibrium constant a value of 1.
Mon Jan 13, 2020 3:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.27
Replies: 8
Views: 100

### Re: 5I.27

Equilibrium composition means the stating the concentration for each products and reactant in the chemical equation.
Mon Jan 13, 2020 3:22 pm
Forum: Ideal Gases
Topic: Molar Concentration
Replies: 4
Views: 54

### Re: Molar Concentration

Depending if there is an initial amount of products or reactants, the one with no amount will increase and the other will decrease. To determine how many values of X increase or decrease, you must see if the reactant and products have a coefficient in the balanced equation.
Mon Jan 13, 2020 3:19 pm
Forum: Ideal Gases
Topic: converting Kc to Kp
Replies: 13
Views: 147

### Re: converting Kc to Kp

If you know the molar concentration, then you should technically be able to figure out the volume.
Mon Jan 13, 2020 3:16 pm
Forum: Ideal Gases
Topic: When to use this equation
Replies: 14
Views: 182

### Re: When to use this equation

An example of when to use this function is if you are given pressure and need to find concentration. You can also use it to find the pressure if you are given concentration.
Sun Dec 01, 2019 8:54 pm
Forum: Hybridization
Topic: 2F.3
Replies: 3
Views: 60

### Re: 2F.3

They used this version of the Lewis structure due to formal charge.
Sun Dec 01, 2019 8:52 pm
Forum: Hybridization
Topic: Hybridization
Replies: 7
Views: 137

### Re: Hybridization

Yes I think that should be it. An easy way to check if your hybridization is correct is that the exponents of the s, p, and d orbitals should add up to the amount of electron clouds. So sp^2 has an electron density of 3 since 2+1=3.
Sun Dec 01, 2019 8:50 pm
Forum: Hybridization
Topic: Hybridization (Lone Pairs)
Replies: 4
Views: 87

### Re: Hybridization (Lone Pairs)

Yes they do. You would count the lone pairs as an additional bonding site. So for example, a molecule with 2 shared pairs (2 sigma bonds) and one lone pair would have an electron density equal to 3. This would lead the molecule to have a hybridization of sp^2.
Sun Dec 01, 2019 8:45 pm
Forum: Hybridization
Topic: Order When Writing
Replies: 5
Views: 91

### Re: Order When Writing

Both are correct but I think the preferred way is to right it beginning with d.
Sun Dec 01, 2019 8:43 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation Number
Replies: 9
Views: 215

### Re: Oxidation Number

I think the oxidation number should always be included in Roman numerals after the transition metal because since the metal can have different oxidation numbers, it is important to specify the oxidation number.
Sun Nov 24, 2019 8:02 pm
Forum: Hybridization
Topic: Sigma and Pi bonds
Replies: 13
Views: 225

### Re: Sigma and Pi bonds

When drawing a molecule, you would go about drawing the bonds as you normally would and just label the sigma bonds and pi bonds.
1 bond= 1 sigma, 0 pi
2 bonds=1 sigma, 1 pi
3 bonds= 1 sigma, 2 pi
Sun Nov 24, 2019 7:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 5
Views: 82

### Re: Polarity

If a molecule has dipole moments that do not cancel, then it is polar. If the dipole moments do cancel, then it is non-polar. One general rule to know is that molecules with a tetrahedral shape generally are non-polar unless the the outer atoms are not identical. Also while linear shaped molecules a...
Sun Nov 24, 2019 7:55 pm
Forum: Hybridization
Topic: Hybridization
Replies: 3
Views: 49

### Re: Hybridization

To determine the hybridization you would look at the electron density of a molecule.
Sun Nov 24, 2019 7:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent vs linear
Replies: 56
Views: 1399

### Re: Bent vs linear

A linear shaped molecule has no lone pairs at the central atom, while a bent shaped molecule does have one or two lone pairs at the central atom.
Sat Nov 16, 2019 12:47 pm
Forum: Dipole Moments
Topic: London forces
Replies: 9
Views: 162

### Re: London forces

They are considered universal because every molecule, polar or non-polar, has London Dispersion Forces. However, it is important to know that London Dispersion Forces are the most prominent intermolecular force in non-polar molecules.
Sat Nov 16, 2019 12:42 pm
Forum: Dipole Moments
Topic: CH
Replies: 3
Views: 66

### Re: CH

Anytime a C atom bonds with an H atom (C2H2, CH6, C10H5, etc.), know that it is always non-polar and that there are no dipole moments.
Sat Nov 16, 2019 12:38 pm
Forum: Dipole Moments
Topic: Hydrogen bonds
Replies: 17
Views: 220

### Re: Hydrogen bonds

Hydrogen bonds can only be formed when H bonds with F, O, or N.
Sat Nov 16, 2019 12:37 pm
Forum: Dipole Moments
Topic: Polarity
Replies: 12
Views: 201

### Re: Polarity

Another tip is that if the atoms around the central atom are not the same (ex. CH3F), then the molecule is very likely to be polar.
Sat Nov 16, 2019 12:31 pm
Forum: Dipole Moments
Topic: Hydrogen Bond
Replies: 7
Views: 171

### Re: Hydrogen Bond

A hydrogen bond is a type of dipole-dipole interaction found amongst polar molecules. It is very strong, meaning that molecules that have hydrogen bonds have a high boiling point. Hydrogen bonds can only occur when an H atom bonds with either a F, O, or N atom.
Sat Nov 16, 2019 12:29 pm
Forum: Dipole Moments
Topic: Dipole-Dipole vs. Dipole-Induced Dipole
Replies: 3
Views: 52

### Dipole-Dipole vs. Dipole-Induced Dipole

What is the difference between a dipole-dipole force versus a dipole-induced dipole force?
Sun Nov 10, 2019 12:47 pm
Forum: Octet Exceptions
Topic: octet exceptions
Replies: 11
Views: 195

### Re: octet exceptions

C, N, O, F, and Ne are the main elements that must follow the octet rule. There are elements like hydrogen that only need two and those like boron that need 6. Also any element past phosphorus can hold more than 8 electrons.
Fri Nov 08, 2019 11:26 am
Forum: Lewis Structures
Topic: Exceptions to Octet Rule
Replies: 7
Views: 127

### Re: Exceptions to Octet Rule

Yes, elements Phosphorus and onward can hold more than 8 electrons in their shell and thus can exceed the octet rule.
Fri Nov 08, 2019 11:24 am
Forum: Formal Charge and Oxidation Numbers
Topic: central atom
Replies: 21
Views: 344

### Re: central atom

Yes, when drawing a lewis structure, the optimal structure will have a central atom with formal charge 0. It would be ideal for all of the atoms to have a formal charge of 0, but since this is not always possible your main concern should be to make the central atom have a formal charge of 0.
Fri Nov 08, 2019 11:21 am
Forum: Octet Exceptions
Topic: Why can't Aluminum have an expanded octet?
Replies: 5
Views: 531

### Re: Why can't Aluminum have an expanded octet?

Al can not have an expanded octet because only elements Phosphorus and onward can have more than 8 electrons. However, Al is one the exceptions to the octet rule in the case that it can have less than 8 electrons.
Fri Nov 08, 2019 11:18 am
Forum: Electronegativity
Topic: Determining Electronegativity
Replies: 4
Views: 96

### Re: Determining Electronegativity

The less electronegative a compound is, the more ionic it will be. When looking at the periodic table, you can confirm that Cl is more electronegative than Br, meaning that SiCl is more electronegative. With this information, you can determine that SiBr is more ionic than SiCl.
Sat Nov 02, 2019 10:25 am
Forum: Quantum Numbers and The H-Atom
Topic: determining the number of orbitals
Replies: 7
Views: 121

### Re: determining the number of orbitals

You would use m(l) to determine the number of orbitals. For example, if you were given n=2 and l=1, the m(l) would be -1,0,1 which tells you that there are 3 orbitals.
Sat Nov 02, 2019 10:15 am
Forum: Octet Exceptions
Topic: Octet Exception
Replies: 5
Views: 82

### Re: Octet Exception

Any element past Phosphorus (including P) are an exception to the octet rule and can hold more than 8 electrons.
Sat Nov 02, 2019 10:11 am
Forum: Lewis Structures
Topic: central atom
Replies: 16
Views: 1575

### Re: central atom

The least electronegative atom is the central atom when drawing Lewis structures.
Sat Nov 02, 2019 10:08 am
Forum: Formal Charge and Oxidation Numbers
Topic: Minimizing Formal Charges
Replies: 5
Views: 73

### Re: Minimizing Formal Charges

In the scenario you just described, it would be best to have 3 formal charges of 0 and one +1. When trying to draw the most stable lewis structure, you want the formal charge of the atoms to be as close to 0 as possible.
Tue Oct 29, 2019 12:30 pm
Forum: Lewis Structures
Topic: Homework problem 2C.3
Replies: 5
Views: 62

### Re: Homework problem 2C.3

For now, I don't think we're expected to know the formulas.
Tue Oct 29, 2019 12:19 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: HW Question 2A5
Replies: 3
Views: 74

### Re: HW Question 2A5

Cu is one of two exceptions when it comes to electron configurations (the other is Cr), so its electron configuration is [Ar]3d^10 4s^1. So when you subtract an electron due to the positive charge in part a, you would end up with the electron configuration [Ar]3d^10 since you subtracted the electron...
Tue Oct 29, 2019 12:04 pm
Forum: Resonance Structures
Topic: stability
Replies: 2
Views: 47

### Re: stability

Usually with different resonance structures, there are different formal charges. A formal charge of 0 means that the molecule is most stable so you want to draw the resonance structure that will give you a formal charge of 0, making it the most stable.
Sat Oct 26, 2019 11:49 am
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic Quantum Number
Replies: 5
Views: 70

### Re: Magnetic Quantum Number

You would have to write out all 5 values instead of just saying 5.
Sat Oct 26, 2019 11:47 am
Forum: Quantum Numbers and The H-Atom
Topic: 1D.19
Replies: 3
Views: 149

### Re: 1D.19

To determine the number of orbitals you would look at ml from l.
Sat Oct 26, 2019 11:11 am
Forum: Lewis Structures
Topic: HW question 2B.3
Replies: 2
Views: 49

### Re: HW question 2B.3

There needs to be a double bond between Si and the two oxygens because the double bonds allow for the octet rule to be satisfied for Si. If you were to use single bonds, Si would only have 4 electrons when 8 are needed.
Fri Oct 18, 2019 11:26 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: hw problem 1D.21
Replies: 2
Views: 56

### Re: hw problem 1D.21

The subshell notation is basically the n-value and and the subshell that corresponds to l. If l=0, s is the subshell, l=1 then p, l=2 then d, and l=3 f So for (a) the subshell notation would be 5d and for (b) it would be 1s For orbitals you would just look and see how many possible ml values the cer...
Fri Oct 18, 2019 11:13 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Homework 1D. 23
Replies: 2
Views: 38

### Re: Homework 1D. 23

(a) a is 3 orbitals because the possible outcomes for ml are -1, 0, 1 (b) b is only 1 orbital because the value of ml is already given to you. Since only 1 value of ml is given (ml=-2), there is only 1 orbital (c) for n=2, the possible l values are 0 and 1. The possible ml values for l=0 are ml=0 an...
Fri Oct 18, 2019 11:05 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Spin State
Replies: 6
Views: 98

### Spin State

Can someone please explain the concept of a spin state? I am having trouble understanding what a spin state is and what it means in regards to the orbital. Thank you.
Fri Oct 18, 2019 11:02 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: quantum number n, l, m
Replies: 13
Views: 169

### Re: quantum number n, l, m

n is the principal quantum number and it tells you what shell the electron is in l is the angular momentum quantum number and it describes shape. l=0,1,2,...n-1 Depending on what your l is you can determine whether your electron is in the s, p, d, or f orbital ml is the magnetic quantum number and i...
Fri Oct 18, 2019 10:29 am
Forum: Properties of Light
Topic: 1A.9 Energy of Photon
Replies: 12
Views: 165

### Re: 1A.9 Energy of Photon

You would use Energy=(Planck's constant)*(frequency) to find the energy of the photon. If you do not have the value of frequency, you would use speed of light=(wavelength)*(frequency) to find frequency and then plug it into the equation for energy.
Fri Oct 11, 2019 7:03 pm
Forum: Einstein Equation
Topic: Units
Replies: 17
Views: 979

### Re: Units

Kelvin Chung 1C wrote:Do we need to know the SI unit equivalents for each term, like the joule?

I am not sure if you need to know them, but for the quantum section it would extremely helpful to know that a J is equal to kg*m^2*s^-2
Fri Oct 11, 2019 6:45 pm
Forum: Empirical & Molecular Formulas
Topic: empirical = molecular?
Replies: 15
Views: 638

### Re: empirical = molecular?

If the molecular formula can no longer be simplified, then it is viewed as both the molecular and empirical formula.
Fri Oct 11, 2019 6:42 pm
Forum: Limiting Reactant Calculations
Topic: Fundamentals M.5
Replies: 3
Views: 202

### Re: Fundamentals M.5

You would use the amount of moles of the limiting reactant to find the amount of moles used of the excess reactant using the stoichiometric coefficients of the balanced chemical equation. Once you find out how many moles of the excess have been used, you can then subtract that amount from the amount...
Fri Oct 11, 2019 6:34 pm
Forum: Properties of Light
Topic: Homework Question 1A.7
Replies: 2
Views: 32

### Re: Homework Question 1A.7

It is a typo as the correct answer is 150 pm.
Fri Oct 11, 2019 6:23 pm
Forum: Einstein Equation
Topic: E=hv
Replies: 8
Views: 122

### Re: E=hv

h represents Planck's constant, which is 6.626*10^-34 J*s
Sat Oct 05, 2019 12:47 pm
Forum: Significant Figures
Topic: Sig Fig Addition and Subtraction
Replies: 5
Views: 172

### Re: Sig Fig Addition and Subtraction

Usually what I do when I'm adding/subtracting or multiplying/dividing, and the result is too long of a number to write down fully, is to just round the answer to 2 digits more than the amount of sig figs needed and then when I reach the final answer I will then round to the amount of sig figs needed.
Sat Oct 05, 2019 12:32 pm
Forum: Significant Figures
Topic: Sig Figs given in problem vs solution
Replies: 3
Views: 68

### Re: Sig Figs given in problem vs solution

Yes, you should and if you are presented with values that have a different amount of sig figs, remember to use the same amount of sig figs as the value that has the least amount of sig figs for your final answer.
Sat Oct 05, 2019 11:35 am
Forum: Significant Figures
Topic: Sig Figs
Replies: 3
Views: 50

### Re: Sig Figs

When you are trying to determine the amount of sig figs to use when carrying out tasks such as addition/subtraction or multiplication/division, the rule is to use the same amount of sig figs as the number with the least amount of sig figs presented in the problem.
Sat Oct 05, 2019 11:31 am
Forum: Significant Figures
Topic: Sig Figs in % Yield
Replies: 10
Views: 1814

### Re: Sig Figs in % Yield

Usually when you are given a decimal that is .5 or higher, you would round up to the next whole number.
Sat Oct 05, 2019 11:20 am
Forum: Significant Figures
Topic: Rules for Significant Figures
Replies: 4
Views: 115

### Re: Rules for Significant Figures

There are a few rules that one must take into consideration when dealing with significant figures. 1. Any number that is not zero is considered significant. 2. Zeros are only considered significant if they are between two significant figures (any non-zero number). 3. Also, zeros that are placed afte...