## Search found 57 matches

Sun Jan 17, 2021 11:55 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Increasing pressure
Replies: 11
Views: 23

### Increasing pressure

Can someone explain why the concentration of the reactants and products remain the same when inert gas is added?
Sun Jan 17, 2021 11:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Week 1 Sapling 10
Replies: 8
Views: 29

### Week 1 Sapling 10

When calculating the final concentration of NO2 for #10:
is the initial concentration for NO2=3.17 and N2O4=.422?
Sun Jan 17, 2021 11:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Week 1 Sapling 9
Replies: 4
Views: 30

### Week 1 Sapling 9

Hello. For Week 1's Sapling #9, can someone help with the steps to calculate the final concentration of NO?
Sun Jan 17, 2021 10:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: composition of the reaction mixture
Replies: 2
Views: 17

### composition of the reaction mixture

Is the composition of the reaction mixture the concentration of the compounds at equilibrium?
Sun Jan 17, 2021 10:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Total pressure calculation
Replies: 8
Views: 25

### Total pressure calculation

Hi. When given the Kp value and initial pressure of the product, how do you calculate total pressure?
Sun Jan 10, 2021 10:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling HW 1 #5
Replies: 8
Views: 51

### Re: Sapling HW 1 #5

You would use first and third reactions.
Cube Ka because you multiply the coefficients by 3 to get 3H2+3I2->6HI. Then take the inverse of Kc because you need the inverse reaction to get 2NH3->N2+3H2. Then you multiply those values to determine final K.
Hope this helped!
Sun Jan 10, 2021 10:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #3
Replies: 4
Views: 29

### Sapling #3

For week 1's sapling #3, how do I set up the equation for the equilibrium constant?
Sun Jan 10, 2021 10:24 pm
Forum: Ideal Gases
Topic: Pressure and partial pressure
Replies: 12
Views: 39

### Pressure and partial pressure

How is pressure and partial pressure different?
Sun Jan 10, 2021 10:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #2
Replies: 5
Views: 15

### Sapling #2

For Week 1's sapling #2, how do I calculate the moles of SO2?
Sun Jan 10, 2021 7:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K and pressure
Replies: 5
Views: 26

### K and pressure

Hi! If a reaction starts with higher pressure, why is Kc not affected?
Tue Dec 15, 2020 5:58 pm
Forum: Bond Lengths & Energies
Topic: Bond length
Replies: 7
Views: 49

### Bond length

How do you calculate the average bond length in a molecule when given the bond length of each atom?
Tue Dec 15, 2020 5:39 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pka and acidity
Replies: 6
Views: 20

### pka and acidity

Hi. I was kind of confused about pKa. What exactly is pKa, and if pKa is higher, does that mean the acid is strong?
Sun Dec 13, 2020 11:21 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Thymine Hydrogen bonding
Replies: 2
Views: 37

### Thymine Hydrogen bonding

In the Marshmallow Final Review, #41D, can someone explain why thymine only forms 6 hydrogen bonds?
Sun Dec 13, 2020 11:12 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Sapling #14
Replies: 1
Views: 30

### Sapling #14

Hi. I thought if the pH is greater than pKa, than the predominant species would be charged. Can someone explain why it would be neutral? Thank you!
Sun Dec 13, 2020 11:08 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Strength of acid
Replies: 12
Views: 71

### Strength of acid

On sapling #11, can someone explain why HClO is more acidic than HIO? Wouldn't HIO be more acidic because I has greater radius?
Sun Dec 06, 2020 11:41 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Finding Coordination Numbers
Replies: 7
Views: 57

### Re: Finding Coordination Numbers

Hi! I simply count the number of the ligands and that gives you the coordination number.
Sun Dec 06, 2020 11:37 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 4
Views: 34

### Re: Coordination Number

en contributes 2, and Cl contributes 2; therefore, the coordination number is 4.
Sun Dec 06, 2020 11:33 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Complex ion
Replies: 3
Views: 14

### Complex ion

Hi! Is a complex ion different from a coordination compound? If they are, can someone explain how they are different?
Sun Dec 06, 2020 11:31 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Geometry for coordination compound
Replies: 3
Views: 13

### Geometry for coordination compound

How is the rule different when determining the geometry of a coordination compound? For sapling #3, why does a complex with coordination # 4 have two different geometries?
Sun Dec 06, 2020 11:28 pm
Forum: Naming
Topic: Naming Coordination Compound
Replies: 4
Views: 32

### Naming Coordination Compound

When naming a coordination compound, how do I know which species come first? How do I determine the order?
Sun Nov 29, 2020 11:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling #18
Replies: 2
Views: 32

### Re: Sapling #18

According to the solution, the pi bonds in C=C are perpendicular to one another in H2CCCH2 molecules, while pi bonds in terminal C=C bonds are parallel to one another in even number of C molecules. Thus, H atoms are coplanar when there are even number of C atoms.
Sun Nov 29, 2020 11:48 pm
Forum: Sigma & Pi Bonds
Topic: Strength of bonds
Replies: 5
Views: 56

### Re: Strength of bonds

I think bonds are stronger when pi bonds are present rather than only sigma bond being present since the strength of bond order is triple bond>double bond>single bond.
Sun Nov 29, 2020 11:45 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Sapling #20
Replies: 1
Views: 18

### Sapling #20

Hi, on sapling 20, why is the AsO43- ion nonpolar? How are the dipoles canceled?
Sun Nov 29, 2020 11:20 pm
Forum: Hybridization
Topic: How to simply determine hybridization
Replies: 27
Views: 185

### How to simply determine hybridization

Hi, I am still confused on understanding the concept of hybridization. Does anyone know how to simply determine the hybridization of an atom?
Sun Nov 29, 2020 10:49 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling #6
Replies: 2
Views: 23

### Sapling #6

Hi, can someone explain how XeF2 molecule is linear? Thanks.
Sun Nov 22, 2020 10:56 pm
Forum: Coordinate Covalent Bonds
Topic: Non-charged molecules becoming Lewis acids/bases
Replies: 3
Views: 39

### Re: Non-charged molecules becoming Lewis acids/bases

Some molecules have net charge of 0 but do not have completed octets. A molecule that has a lone pair, whether negatively charged or not, can become a lewis base and donate its electron pair to the species that can accept the electron pair. For example, group 13 elements need 5 electrons to complete...
Sun Nov 22, 2020 10:36 pm
Forum: Ionic & Covalent Bonds
Topic: Ionization Energy
Replies: 19
Views: 148

### Re: Ionization Energy

First ionization energy is the energy needed to remove the outermost electron from an atom so it should be the outermost orbital! Second ionization energy is always greater than the first because the electron is more tightly held.
Sun Nov 22, 2020 10:21 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: Polarizablity
Replies: 10
Views: 78

### Re: Polarizablity

I think polarizability means the tendency of its electron density to be distorted. For example, when you compare Br2 to I2, I2 is has higher polarizability than Br2 because its electrons are not as tightly held, therefore its electron density is easily distorted.
Sun Nov 22, 2020 10:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining polar molecules
Replies: 7
Views: 50

### Determining polar molecules

Hi! If the molecule is symmetrical, can you assume that it's nonpolar? How do you determine if a molecule is polar or nonpolar?
Sun Nov 22, 2020 9:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling #1
Replies: 6
Views: 45

### Sapling #1

Hi! For #1 on sapling, why is the shape of the carbonate ion different from the sulfite ion? I can't really tell the difference.
Sun Nov 15, 2020 6:39 pm
Forum: Dipole Moments
Topic: Sapling #13
Replies: 9
Views: 52

### Sapling #13

Hi! I'm having difficulty with problem 13 in sapling assignment.
what is the maximum theoretical number of water molecules that one urea molecule can hydrogen bond with?
How can I solve this?
Sun Nov 08, 2020 11:47 pm
Forum: Lewis Structures
Topic: Lewis acids and bases
Replies: 10
Views: 71

### Re: Lewis acids and bases

Lewis acids are electron acceptor and lewis bases are electron donor. When you look at their chemical structure, the acid should be able to accept an electron pair while the base should be able to donate an electron pair.
Sun Nov 08, 2020 11:42 pm
Forum: Ionic & Covalent Bonds
Replies: 5
Views: 24

As more shells are added, they are more distant from the nucleus, therefore the radius of an atom increases when transitioning from a lower orbital to a higher orbital!
Sun Nov 08, 2020 11:35 pm
Forum: Dipole Moments
Topic: London dispersion
Replies: 4
Views: 40

### London dispersion

Is london dispersion force is always present in all molecules? If it does, why?
Sun Nov 08, 2020 11:30 pm
Forum: Lewis Structures
Topic: Resonance structure
Replies: 3
Views: 24

### Resonance structure

Hi! In our sapling hw, a question mentions resonance hybrid. Can someone explain what resonance structure is?
Sun Nov 08, 2020 11:17 pm
Forum: Bond Lengths & Energies
Topic: Bond length
Replies: 11
Views: 41

### Re: Bond length

More bonds, shorter length due to stronger attraction!
Sun Nov 01, 2020 11:42 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Sapling #4
Replies: 8
Views: 75

### Re: Sapling #4

For the second part of the question, you would divide the total energy by the value you got for the work function. Total Energy (J) / Work Function (J/photon) = Number of electrons (photons)
Sun Nov 01, 2020 11:35 pm
Forum: Properties of Light
Topic: Sapling #10
Replies: 8
Views: 159

### Re: Sapling #10

To find the mass of a single Fluorine molecule, you would multiply the molar mass of F by 2 and divide by the Avogadro's constant. And I did not have to use the temperature when solving this question, so I think it was just given.
Sun Nov 01, 2020 10:42 pm
Forum: DeBroglie Equation
Topic: Sapling #25
Replies: 4
Views: 54

### Sapling #25

Hi! I'm having difficulty figuring out how to solve #25 on sapling. #25) The E.coli bacterium is about 1.6 micrometers long. Suppose you want to study it using photons of that wavelength or electrons having that de Brogile wavelength. What is the energy Ephoton of the photon? Which equation should I...
Sun Nov 01, 2020 10:37 pm
Forum: Trends in The Periodic Table
Topic: Electron affinity and Ionization energy
Replies: 7
Views: 60

### Electron affinity and Ionization energy

Hi! Can someone explain the difference between electron affinity and ionization energy? Thank you!
Sun Nov 01, 2020 10:35 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum numbers
Replies: 2
Views: 34

### Quantum numbers

Hi!! While I was doing the sapling questions, I was just wondering if we have to memorize the quantum numbers for every subshell or there is a particular way to calculate/figure them out?
Thu Oct 29, 2020 4:53 am
Forum: Administrative Questions and Class Announcements
Topic: Sapling Access Code
Replies: 5
Views: 62

### Sapling Access Code

I ordered my textbook in early October and received an email that it was shipped on October 8th. I still haven't received my tracking code nor my textbooks. I emailed the UCLA store, but I did not get any reply. And I just found out that my sapling free trial has ended and there is no way for me to ...
Sun Oct 25, 2020 11:48 pm
Forum: Properties of Electrons
Topic: orbitals
Replies: 3
Views: 27

### Re: orbitals

Since we are learning the basics of atoms and their properties, I think orbitals are significant in the sense that we understand the wavelike behavior of electrons. Knowing more about orbitals allows us to specify properties of a specific element as well as the trend among periods and groups.
Sun Oct 25, 2020 11:43 pm
Forum: Properties of Electrons
Topic: Sapling #20
Replies: 1
Views: 16

### Sapling #20

Hi, the question on sapling asks why oxygen has lower first ionization energy than both nitrogen and fluorine.
Doesn't the first ionization energy increase as you move across a period? Can someone explain the reason of this?
Sun Oct 25, 2020 11:38 pm
Forum: Photoelectric Effect
Topic: Calculations
Replies: 18
Views: 97

### Re: Calculations

I always used the whole numbers from the calculator and rounded to correct sig figs at the end, but sometimes the question wants me to stick to the sig fig rules from the beginning. As far as I know, both of answers shouldn't be too different.
Sun Oct 25, 2020 11:33 pm
Forum: Photoelectric Effect
Topic: unit conversion hw Q 1.3
Replies: 7
Views: 233

### Re: unit conversion hw Q 1.3

I would suggest converting them to SI units so that you don't have to convert it every single time along the way. Whenever the wavelength is given in nm, I would convert it to m before using the equations like c=lambdav.
Sun Oct 25, 2020 11:27 pm
Forum: Photoelectric Effect
Topic: Textbook Problem 1B9
Replies: 3
Views: 40

### Re: Textbook Problem 1B9

Hi! 1)I would convert the wavelength from nm to m by multiplying 10^-9 so that you get 4.2x10^-7m. 2)Using the equation c=lambdav, you calculate the frequency, v=(3x10^8m/s/4.2x10^-7m)=7.1x10^14 s^-1. 3)Using the equation E=hv, E=(6.626x10^-34 Js)(7.1x10^14 s^-1)=4.7x10^-19 J/photon 4)(32 J/s)(2 s)=...
Sun Oct 18, 2020 11:55 pm
Forum: Properties of Light
Topic: Frequency vs Wavelength
Replies: 22
Views: 141

### Re: Frequency vs Wavelength

Frequency and wavelength are inversely proportional to each other. The greater the frequency, the shorter the wavelength and vice versa. Also, frequency is directly proportional to energy.
Sun Oct 18, 2020 11:48 pm
Forum: Einstein Equation
Topic: Sapling #5
Replies: 7
Views: 101

### Sapling #5

I am confused with number 5 on this week's sampling. The question asks: A liquid is exposed to infrared radiation with a wavelength of 5.68x10^-4cm. Assume that all the radiation is absorbed and converted to heat. How many photons are required for the liquid to absorb 17.97J of heat? How can I start...
Sun Oct 18, 2020 11:20 pm
Forum: Einstein Equation
Topic: What are the units for E
Replies: 16
Views: 124

### Re: What are the units for E

The SI unit for Energy is J(joule) and Joule = kgm^2s^-1. And yes the units are all the same in order for you to subtract from one another. If you are adding/subtracting something, the components must have the same unit!
Sun Oct 18, 2020 11:16 pm
Forum: Properties of Light
Topic: Sampling #8
Replies: 1
Views: 21

### Sampling #8

I am having difficulty with question 7 in the Sampling. The question is: how many photons with a wavelength of 889nm are needed to melt 451g of fusion. The enthalpy of fusion is given. What is enthalpy of fusion, and how can I approach this question?
Sun Oct 18, 2020 10:48 pm
Forum: Properties of Electrons
Topic: Energy levels
Replies: 8
Views: 56

### Energy levels

Hi. I am a little confused about the energy levels. Why do the gaps become smaller as the energy levels increase?
Sun Oct 11, 2020 7:59 pm
Forum: Empirical & Molecular Formulas
Topic: Sapling Wk 1 Question 10
Replies: 4
Views: 54

### Re: Sapling Wk 1 Question 10

Hi! The picture gives us skeletal structures. There is a carbon atom at each junction and at the end of each bond. Also, we assume that there are hydrogen atoms attached to the carbon atoms to make 4 bonds. Skeletal structures are difficult to understand at first, but once you understand, they allow...
Sun Oct 11, 2020 7:37 pm
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 228
Views: 117587

### Re: Advice from a Medical Student[ENDORSED]

I planned to be a premed student, but I never had the opportunity to talk to a real med student. This advice really helped me and I feel so relieved. Thank you!
Sun Oct 11, 2020 7:08 pm
Forum: Empirical & Molecular Formulas
Topic: Sapling Week 1 #8
Replies: 23
Views: 234

### Re: Sapling Week 1 #8

To find the molecular formula, simply count the number of each element in the picture. After finding the molecular formula, you multiply the number of subscripts to the molar mass of each element and the sum is the molecular mass.
Sun Oct 11, 2020 6:56 pm
Forum: Administrative Questions and Class Announcements
Topic: Students in different time zones [ENDORSED]
Replies: 27
Views: 1398

### Re: Students in different time zones[ENDORSED]

6. South Korea
Sun Oct 11, 2020 5:59 pm
Forum: Empirical & Molecular Formulas
Topic: Sampling #9
Replies: 7
Views: 66

### Sampling #9

Hello, everyone. This is my first time posting a question on chemistry community. I am having difficulties with the sampling question #9. The compound contains only C, H, and O and was experimentally found to have a molar mass of 110±10 g/mol . When a 1.000 g sample of caproic acid is burned in exce...