Midterm 1 Review
Define a precipitation reaction.
A reaction that results in the formation of solid when an insoluble ion species in combined in solvent.
What makes a compound organic?
Contains carbon and usually hydrogen (example: CH4)
How do we determine the total number of orbitals for a given ‘n’ energy level?
n2
What is Zeff and its trend?
- Actual amount of (+) charge experienced by electron
- Increases from left to right across a period, so atomic radius increases right to left because electrons are more tightly held
You have 1.00 L of 6.00 M HCl solution. You take 250mL of sol’n and dilute with water to final volume of 1.00 L. What’s the new molarity?
Use M1V1 = M2V2
M1 = 6 M
V1 = 0.250 L
M2 = unknown
V2 = 1.00 L
Provide all possible quantum numbers for an electron in the 3d orbital.
n=3
l=2 (d orbital)
ml=−2,−1,0,+1,+2,
ms=±1/2
What are two different ways we can calculate formal charge?
1) FC = VE - (LP + 1/2 BE)
2) FC = VE - (Total # of electrons surrounding atom)
#2 is faster!
What are 3 exceptions to the octet rule?
Some atoms are favored to have less than 8 electrons
Atoms in period 3 and beyond can have expanded octets
There are cases where we have odd number of electrons so we don’t have perfect pairs
What is the mass % of carbon in C11H17N3O8?
41.37% → (11(12.01))/319.31
What is the electron configuration for Fe2+?
The two electrons are removed from s orbital first.
1s22s22p63s23p63d6(4s0)
What is the purpose of a formal charge?
It helps us predict which Lewis structures have the lowest energy based on the atom arrangement, as we want the formal charge to be as low as possible
Draw two structures of SO3, one with an octet and the other with an expanded octet. Which structure would be favored?
Expanded octet with 3 double bonds because the formal charge is zero
94% yield of iron in reaction. How many grams of iron produced in experiment if theoretical yield was 134.5 grams?
126.43 grams → (135.4)(0.94)
Calculate the wavelength of light emitted when an electron transitions from n=4 to n=2 in the hydrogen atom.
Using the Rydberg formula, wavelength is 486 nm
What is the difference between electron affinity and ionization energy?
Electron affinity: energy released when electron added to neutral atom (think atom’s tendency to gain electron)
Ionization energy: energy required to remove an electron from neutral atom (think atom’s tendency to lose an electron)
What are values are “allowed” for each of the four quantum numbers? (Numerical Values)
n: Non-zero integers (1,2,3,..)
l: 0 to n-1
ml: -l to l
ms: 1/2 or -1/2
Bonus 200pts: What properties are associated with the first three quantum numbers?
Suppose a solution containing 25.0 g NaI reacts with 5.00 g of Cl2. What is the mass of iodine produced from the reaction? Reaction: Cl2(aq) + NaI(aq) → NaCl(aq) + I2(aq)
17.9 grams I2
Consider the following reaction, 4Al + 3O2 → 2Al2O3. If Julia combines 15 grams of aluminum with excess oxygen and produces 25 grams of aluminum oxide, what is her percent yield of Al2O3?
87.53%
What’s Hund’s Rule?
If more than 1 subshell is available, add electrons with parallel spins to different orbitals of subshell vs. two in 1 orbital (electrons need to be more spread out!)
What is the molecular geometry of SbCl4-?
See-Saw