Cumulative Review (past exam Qs)
In the following chemical equation, what is the limiting reagent?
2H2 + O2 --> 2H2O
H2 is the limiting reagent because it will be used up first.
Same color - same frequency, wavelength
One is brighter - different amplitudes
Fill in the blank: no two electrons can have the same____
Quantum number.
What is the least electronegative element on the periodic table? How do you know - both based off of the bohr model and the periodic trend?
Electronegativity increases up and to the right, so the most electronegative element is Francium, which is in the bottom left. This makes sense, because francium has so many electrons that it is not really looking to gain more when you view its bohr model. In addition, it is a group 1 element which prefers to lost electrons rather than gain.
Draw the lewis structure for O2 2- and explain the bond polarity/electron sharing. What kind of bond is this?
Solution in slides
23892U goes through alpha decay, once. Craft a nuclear equation to show this.
23892U --> 23490Th + 42He
If the wavelength of light decreases, how are energy and frequency affected? Please explain your reasoning using the relationship (equation) between these concepts.
Energy = planck's constant x frequency
Energy = (planck's constant x speed of light) / wavelength
If energy increases, wavelength decreases, and frequency increases. This is because energy and frequency are directly related, and energy and wavelength are inversely related (view equations above.)
I have two electrons occupying the same energy level, orbital, and orbital orientation. What is the difference between them? What is each?
On the periodic table, what is the trend of atomic radius as it increases? How do you know, based off of the locations of the most and least electronegative elements?
Down and across (to the left). We know this because fluorine is the most electronegative element, so it wants to hold on tight to all of its electrons, making its radius smaller. Francium is the least electronegative, so it has a lot of electrons and doesn't care to hold on to them much, it would rather give them away, making its radius larger.
Draw the lewis structure for CO2. Explain what bond type this compound has and the overall polarity of the ENTIRE MOLECULE (not JUST the bonds, but everything together). Explain why you believe this to be true.
Answer in slides.
In the following chemical equation, what is oxidized and what is reduced?
Zn + CuSO4 --> ZnSO4 + Cu
Zn - oxidized
Cu - reduced
SO4 - stays the same
(detailed solution in slides)
On a whiteboard, draw an image of a light wave. Then, label and define the following:
1) Crest
2) Trough
3) Amplitude
4) Wavelength
5) Frequency
1) Crest - the highest point on the wave
2) Trough - the lowest point on the wave
3) Amplitude - the measurement from the middle of the wave, up to the crest. It is the overall 'energy' of the wave.
4) Wavelength - The length between two crests or between two troughs.
5) Frequency - The amount of wavelengths that can pass through one point in 1 second. High frequency = wavelengths are more "pushed" together. Low frequency = farther apart.
What is the electron configuration for chromium? (Ground state AND shortened)
Full: 1s22s22p63s23p64s13d5
Shortened: [Ar]4s13d5
Use the ACS periodic table (I will pull it up) to label the following trends: electron affinity, electronegativity, ionization energy, atomic radius
Answer in marathon slideshow
Create and draw: The lewis structure for a compound with moderately polar bonds, as well as the lewis structure for extremely polar bonds. Draw the electron clouds based on how you think electrons are shared in these molecules. Explain what bond type these compounds have, which bonds are stronger, and how you know.
Answer in slides. (multiple answers accepted)
Chlorine has two naturally occurring isotopes:
35Cl with a mass of 34.969 amu
37Cl with a mass of 36.966 amu
If the average atomic mass of chlorine is 35.45 amu, calculate the percent abundance of each isotope.
35Cl - 75.9%
37Cl - 24.1%
Worked solution in slides.
What is the energy of a photon with a wavelength of 319 nm?
6.231e-19 J (check slides for worked solution)
Remember the equation: E = hc / λ
E - energy
h - planck's constant (6.626 e - 34)
λ - wavelength
What is the electron configuration for Cu+ ? (Ground state AND shortened)
Full: 1s22s22p63s23p63d10
Shortened: [Ar]3d10
Label the following INDIVIDUAL BONDS as: polar covalent, nonpolar covalent, ionic:
1) HF
2) CaCl2
3) O2 2-
4) KF
5) I2
6) H2O
1) polar covalent
2) ionic
3) nonpolar covalent
4) ionic
5) nonpolar covalent
6) polar covalent
Draw O3 and its two resonance forms. Include formal charges on each atom. You do not need to include electron clouds.
Answer in slides.
4.50 g of aluminum (Al) reacts with 8.00 g of oxygen (O₂), aluminum oxide (Al₂O₃), according to the reaction:
4Al + 3O2 --> 2Al2O3
Determine the limiting reagent AND provide the amount of product produced.
Al is limiting, 8.50 g product produced. Worked solution in slides).
What is the frequency of a wavelength with an energy of 5e-22 J?
v = 7.546e11 hz
Remember the equation:
E = hv
E - energy of a photon
h - planck's constant
v - frequency
Name and define all four quantum numbers, in their correct order. Provide: symbol, range (of numbers), and a definition.
1) Principal Quantum Number. The main energy level or shell of the electron.
Symbol: n
Range: Positive integer (1, 2, 3, …)
2) Angular Momentum Quantum Number. The shape of the orbital.
Symbol: l
Range: Integer from 0 to n-1.
3) Magnetic Quantum Number. The orientation of the orbital in space.
Symbol: ml
Range: Integer from -l to + l
4) Spin Quantum Number. The spin direction of the electron.
Symbol: ms
Range: +½ or –½
Provide an example of three molecules and describe what kind of bonds they have. Draw what the electron cloud looks like for each molecule:
1) one molecule with an extremely polar bond
2) one molecule with a moderately polar bond
3) one molecule with a nonpolar bond
You should have (view drawings in slideshow as well):
1) one ionic bond
2) one polar covalent bond
3) one covalent bond
Draw NO3- and its three resonance forms. Include formal charges on each atom. You do not need to include electron clouds.
After you are finished, draw how NO3- ACTUALLY EXHISTS in real life. You do not need to include electron pairs and formal charges.
Answer in slides.