Search found 40 matches

by Claire Lo 3C
Thu Nov 14, 2019 8:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Drawing Molecular Structures
Replies: 8
Views: 23

Re: Drawing Molecular Structures

You determine the VSEPR structure of the molecule first. Then you can use lines to represent atoms on the same plane with the paper, solid triangles as atoms coming towards you, and dashed lines as atoms going away from you.
by Claire Lo 3C
Thu Nov 14, 2019 8:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Formula
Replies: 2
Views: 13

Re: VSEPR Formula

Essentially yes. The number of bonded electron pairs represents X, and the number of lone pairs represets E.

Notice that a single bond, double bond, and triple bond all count towards a single X.
by Claire Lo 3C
Thu Nov 14, 2019 8:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Trigonal Pyramid vs Trigonal Planar
Replies: 6
Views: 19

Re: Trigonal Pyramid vs Trigonal Planar

Also the bond angle is different. Trigonal planar has bond angles of 120 while trigonal pyramidal has bond angles of around 107, so these two are absolutely different.
by Claire Lo 3C
Thu Nov 14, 2019 8:15 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lewis Structures & VSEPR
Replies: 9
Views: 26

Re: Lewis Structures & VSEPR

Drawing lewis structures help you determine whether there are lone pairs or not, which influences the VSEPR structure. Thus to be safe, always draw out the VSEPR first.
by Claire Lo 3C
Thu Nov 14, 2019 8:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: varying VSEPRs
Replies: 7
Views: 25

Re: varying VSEPRs

Nope, because VSEPR relies on the lowest energy Lewis structure.
by Claire Lo 3C
Fri Nov 08, 2019 3:16 pm
Forum: Photoelectric Effect
Topic: Frequency and number of electrons ejected
Replies: 2
Views: 13

Frequency and number of electrons ejected

I know that to emit an electron, the photon has to reach a specific frequency. Is it true that the frequency of the photon has to double in order to emit the second electron?
by Claire Lo 3C
Fri Nov 08, 2019 3:08 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical formula
Replies: 3
Views: 16

Re: Empirical formula

Remember that the key is to find the molar ratio of the elements. You find the number of moles of CO2, for example, through dividing the given grams by molar mass. This number of moles of CO2 is also the number of moles of C, since there is only 1 C atom in one CO2 molecule. For H2O, you need to tim...
by Claire Lo 3C
Fri Nov 08, 2019 3:01 pm
Forum: Properties of Light
Topic: Work Function
Replies: 2
Views: 19

Re: Work Function

Another way to think about it is that work function is the threshold energy need to emit one single electron from the metal. Thus the single photon needs to possess an adequate amount of energy, or at least the threshold energy.
by Claire Lo 3C
Sat Nov 02, 2019 12:14 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Energy change and Energy of photon
Replies: 5
Views: 24

Energy change and Energy of photon

If a hydrogen atom goes from n=3 to n=1, why is the change in energy negative and why is the energy of the photon emitted positive?
by Claire Lo 3C
Sat Nov 02, 2019 12:12 pm
Forum: DeBroglie Equation
Topic: Question about Converting Units
Replies: 3
Views: 30

Re: Question about Converting Units

1keV = 1000 eV
1 eV = 1.60e-19 J

so 1keV = 1000 x 1.60e-19 J
by Claire Lo 3C
Sat Nov 02, 2019 12:08 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Indeterminacy Equation
Replies: 6
Views: 51

Heisenberg Indeterminacy Equation

Where does the 4 pi come from in the equation?
by Claire Lo 3C
Sat Nov 02, 2019 12:05 pm
Forum: Photoelectric Effect
Topic: Work Function
Replies: 6
Views: 29

Work Function

What exactly is the definition of work function? If it's the energy needed to remove a single electron from solid metal, why is the unit sometimes J per mole?
by Claire Lo 3C
Sat Nov 02, 2019 12:01 pm
Forum: Properties of Light
Topic: Waves
Replies: 4
Views: 44

Re: Waves

As long as it's greater than 10^-15 m, then it's considered to have measurable wavelike properties.
by Claire Lo 3C
Fri Oct 25, 2019 2:36 pm
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 8
Views: 51

Re: Drawing Lewis Structures

Hydrogen in some cases has lower ionization energy than other atoms. But it's almost never used as the central atom, except if the molecule is H2.
by Claire Lo 3C
Fri Oct 25, 2019 2:33 pm
Forum: Lewis Structures
Topic: Homework 2B.3 d
Replies: 2
Views: 28

Re: Homework 2B.3 d

First of all, BrF3 has a total of 28 valence electrons, instead of 24. Br has a lower ionization energy than F, so Br is the central atom. Each F-Br bond constitutes to 2 electrons, so that's a total of 6, and you still need to assign the rest of the 22 valence electrons. Put 4 electrons on Br so th...
by Claire Lo 3C
Fri Oct 25, 2019 2:29 pm
Forum: Lewis Structures
Topic: Charges on atoms with lower e- affinity
Replies: 4
Views: 13

Re: Charges on atoms with lower e- affinity

And by charge, he meant the calculated formal charge.
by Claire Lo 3C
Fri Oct 25, 2019 2:17 pm
Forum: Octet Exceptions
Topic: Octet exception examples
Replies: 9
Views: 75

Re: Octet exception examples

also P, S, Cl may exceed the octet rule
by Claire Lo 3C
Fri Oct 25, 2019 2:16 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Electron Affinity and Formal Charge
Replies: 3
Views: 20

Re: Electron Affinity and Formal Charge

Basically put the negative charge on the atom with the highest electron affinity
by Claire Lo 3C
Thu Oct 17, 2019 10:01 pm
Forum: Properties of Light
Topic: atomic spectra
Replies: 2
Views: 23

Re: atomic spectra

c = wavelength x frequency c= speed of light wavelength = 1850 nm (be sure to convert it to meters) You will get frequency. Plug the frequency value into E=hv, where h is planck's constant. You will get the energy of a single photon. Then use the total number of Energy, which is 11J, divide it by th...
by Claire Lo 3C
Thu Oct 17, 2019 9:56 pm
Forum: Properties of Light
Topic: 1A.9 Energy of Photon
Replies: 12
Views: 68

Re: 1A.9 Energy of Photon

E = hv

So after u calculate v from c=wavelength x frequency, u plug it into E=hv with h as Planck's constant
by Claire Lo 3C
Thu Oct 17, 2019 9:55 pm
Forum: *Shrodinger Equation
Topic: Nodal Planes
Replies: 6
Views: 22

Nodal Planes

How many nodal planes do f orbitals have?
by Claire Lo 3C
Thu Oct 17, 2019 9:54 pm
Forum: *Shrodinger Equation
Topic: Psi ^2
Replies: 2
Views: 17

Psi ^2

I know that psi represents the height of a wave at position x,y, z. But I don't understand why psi^2 represents the probability of finding an e-.
by Claire Lo 3C
Thu Oct 17, 2019 9:51 pm
Forum: *Shrodinger Equation
Topic: Quantum Number
Replies: 2
Views: 40

Quantum Number

If Schrodinger wave equation with 3 quantum numbers can only be used to solve for 1 e- atoms, then can you use 4 quantum numbers to solve for more electrons since the fourth number indicates the spin state?
by Claire Lo 3C
Wed Oct 09, 2019 4:11 pm
Forum: Significant Figures
Topic: %Mass Composition
Replies: 10
Views: 72

%Mass Composition

If we're asked to calculate the %mass composition of a compound, how many sig figs should we keep?
by Claire Lo 3C
Wed Oct 09, 2019 4:08 pm
Forum: Quantum Numbers and The H-Atom
Topic: Atomic Spectra
Replies: 5
Views: 37

Re: Atomic Spectra

Yea, as long as they are spectra of the same atom.
by Claire Lo 3C
Wed Oct 09, 2019 3:58 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Equation Question
Replies: 2
Views: 45

Re: Equation Question

Also this equation only applies to the H-atom
by Claire Lo 3C
Wed Oct 09, 2019 3:55 pm
Forum: Photoelectric Effect
Topic: Atomic Spectra [ENDORSED]
Replies: 3
Views: 38

Re: Atomic Spectra [ENDORSED]

It is grouped by the type of electromagnetic radiation or wavelength/frequency that is shone on the material. Thus it is grouped as UV, infrared, and visible and since they have different energies, the electrons will return to different shells.
by Claire Lo 3C
Wed Oct 09, 2019 3:48 pm
Forum: Photoelectric Effect
Topic: E=hv
Replies: 1
Views: 36

E=hv

If the question asks that a certain amount of energy is needed to remove 1 mole of electrons, you first divide the energy by Avogadro's number before proceeding to the rest of the calculation right?
by Claire Lo 3C
Sat Oct 05, 2019 6:13 pm
Forum: Molarity, Solutions, Dilutions
Topic: Which Volume to use for M1
Replies: 6
Views: 34

Re: Which Volume to use for M1

The first volume given usually allows you to calculate the molarity. Typically we use the second volume in the calculation.
by Claire Lo 3C
Sat Oct 05, 2019 6:10 pm
Forum: Limiting Reactant Calculations
Topic: Explaining why a reactant is limiting
Replies: 4
Views: 43

Re: Explaining why a reactant is limiting

I would write down my calculation first: 0.3moles / 2 = 0.15moles of B 0.2 moles /1 = 0.2 moles of A. Since 0.15 moles of B is less than 0.2 moles of A, B is the limiting reactant. I think your explanation is also acceptable, as long as you explain that since we only have .3 moles of B right now and...
by Claire Lo 3C
Sat Oct 05, 2019 6:03 pm
Forum: Empirical & Molecular Formulas
Topic: Combustion Analysis
Replies: 6
Views: 52

Re: Combustion Analysis

A combustion analysis allows you to deduce the formula of an organic compound, which is usually CxHy or CxHyOz. It can also be used to determine the percentage purity by mass of a given compound.
by Claire Lo 3C
Sat Oct 05, 2019 6:00 pm
Forum: Empirical & Molecular Formulas
Topic: Combustion Analysis
Replies: 1
Views: 83

Combustion Analysis

Hey guys Im confused about M.26. It states that a combustion analysis of the compound C14H20O2N gave the following data: 68.50%C, 8.18%H by mass. Because the data were considerably different from that expected for pure C14H20O2N, the sample was examined and found to contain a significant amount of C...
by Claire Lo 3C
Sat Sep 28, 2019 4:32 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Avogradro's Number [ENDORSED]
Replies: 5
Views: 107

Avogradro's Number [ENDORSED]

So I was doing E5 on the textbook and it asks how many moles of people inhabit Earth if the estimated population is 7.0 billion people. This made me question the definition of 1 mole and Avogadro's number.
by Claire Lo 3C
Sat Sep 28, 2019 4:27 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: MOLARITY
Replies: 17
Views: 631

Re: MOLARITY

Does anyone know the difference between molarity and molality?
by Claire Lo 3C
Sat Sep 28, 2019 4:23 pm
Forum: Molarity, Solutions, Dilutions
Topic: mass of solute
Replies: 3
Views: 36

Re: mass of solute

Becuz ur asked to prepare a solution. When copper (ii) sulfate pentahydrate is dissolved in water, the attached H2O joins with the surrounding water. Since copper (ii) sulfate pentahydrate contains 1 mole of CuSO4, the amount of copper (ii) sulfate pentahydrate you need is the same as the amount of ...
by Claire Lo 3C
Sat Sep 28, 2019 4:10 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Formula Unit
Replies: 7
Views: 71

Formula Unit

Could someone please explain the difference between a formula unit and a molecule? Thanks.
by Claire Lo 3C
Sat Sep 28, 2019 4:03 pm
Forum: Significant Figures
Topic: How does Significant Figures work? [ENDORSED]
Replies: 12
Views: 121

Re: How does Significant Figures work? [ENDORSED]

In inter-problem calculations, how many sig figs do u keep? Same as the question or one more?

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