Miscellaneous
(Ch 3-5)
(Ch 3-5)
Solve for the oxidation state of Cr in CrSO4
Cr = +2
If 3.26 mol of an ideal gas has a pressure of 2.77 atm and a volume of 71.27 L, find the temperature in degrees Celsius
PV = nRT
738 K - 273.15 C = 465 degrees Celsius
Lithium has a work function of 4.65 x 10-19 J. If a violet photon with a wavelength of 405 nm impacts a lithium surface, will an electron be ejected?
E = h(c)/wavelength --> 4.91 x 10-19 J
Yes, because the energy is greater than the work function!
Using the octet rule, determine the number of bonds an atom of the elements will likely make in a molecule: N, Ne, F, and O
N = 5 valence electrons --> 3 bonds!
Ne = 8 valence electrons --> 0 bonds!
F = 7 valence electrons --> 1 bond!
O = 6 valence electrons --> 2 bonds!
Determine the molecular geometry of sulfur dioxide, SO2
molecular geometry = the shape occupied by the atoms and relates to the electron domain of the central atom
S = central atom: 2 double bonds = 2 electron domains
molecular geometry = bent!
Identify the oxidizing agent and reducing agent in Zn(s) + 2HCl (aq) --> ZnCl2(aq) + H2(g)
Zn = oxidized --> reducing agent
H = reduced --> oxidizing agent
Calculate the specific heat of ice if 128 J is required to raise the temperature of 4.00 g of ice by 15.3 degrees Celsius
q = "mcat"
c = 2.09 J/g x degrees Celsius
Write the full electron configuration of O+ and identify the neutral atom that is isoelectric with O+
1s22s22p3
isoelectric = same configuration = Nitrogen
Draw the Lewis Structure for the compound, CH2O, and identify the central atom!
Central atom = Carbon
Determine whether NH3 is polar or nonpolar using the Lewis structure
Polarity depends on electronegativity!
N-H has an electronegativity of 0.9 so it is polar!
Determine the percent yield of glucose (C6H12O6) from the reaction:
6CO2(g) + 6H2O(l) --> C6H12O6(aq) + 6O2(g)
and suppose that 12 grams of CO2 react with 8 grams of H2O to give 7.50 grams of glucose
7.50g/8.19g x 100% = 91.6%
If you combine 370.0 mL of water at 25 degrees Celsius ("cold water") and 100.0 mL of water at 95 degrees Celsius ("hot water"), what is the temperature of the mixture? (density of water = 1.00g/mL)
mcat of cold water = -mcat of hot water
Tfinal = 39.89 degrees Celsius (4 sig figs)
Give the electron configuration of Phosphorous, and determine the n, l, and ml for EACH subshell
[Ne]3s23p6
3s: n=3, l=0, ml=0
3p: n=3, l=1, ml=-1,0,+1
Draw all resonance structures for the ion, NO2-
There will be 2 resonance structures!
Determine the electron domain of Bromine Trifluoride
Br = central atom: 2 lone pairs and 3 bonded groups = 5 electron domains!
Fe2S3O9
A 1.000 gram sample of decane, C10H22, is ignited in a bomb calorimeter. The temperature rises from 20 degrees Celsius to 78.8. Given that the heat capacity of the calorimeter is 810.0 J/C, determine the change in internal energy of the reaction (delta Urxn) for the combustion of decane in kJ/mol.
qv=-Ccal(delta T)=(delta Urxn)
-47.634 kJ/0.007026 mol = -6.78 x 103 kJ/mol
Draw the energy level diagram for Aluminum and define Aufbau's Principle and Hund's Rule:
Al: 1s22s22p63s23p1
Aufbau's Principle: the process of filling the subshells from the lowest to the highest
Hund's Rule: an electron is placed in each subshell before pairing!
Calculate the percent ionic character for HCl if the measured dipole moment is 1.08 D and the bond length is 127 pm
% ionic character = 18%
Determine the polarity of SF6
the 6 S-F bonds cancel out because there is an even number, so the molecule is nonpolar!
A solution of 1.500 M sodium hydroxide is placed in a buret and is used to titrate 25.0 mL of a solution of sulfuric acid. if the initial buret reading is 1.28 mL and the reading at the equivalence point in 45.19 mL, calculate the concentration of sulfuric acid (hint: you will need a balanced equation to start!)
H2SO4(aq) + 2NaOH(aq) --> Na2SO4(aq) + 2H2O(l)
0.032933 mol / 0.025 mL = 1.317 M H2SO4
Using the enthalpy of reaction for 2 reactions with ozone, determine the enthalpy of reaction for the reaction of Cl(g) with ozone.
1. ClO(g) + O3(g) --> Cl(g) + 2O2(g)
(delta Hrxn = -122.8 kJ)
2. 2O3(g) --> 3O2(g)
(delta Hrxn = -285.3 kJ)
3. O3(g) + Cl(g) --> ClO(g) + O2(g)
(delta Hrxn = ?)
-1(-122.8 kJ) + (-285.3 kJ) = -162.5 kJ
An excited electron in a Phosphorous atom falls back to the ground state, and a photon with an energy of 3.06x10-19 J is emitted. Calculate the frequency and wavelength. Does the photon fall between 550-650 nm?
frequency = 4.62x1014 s-1
wavelength = 6.49x10-7 m
6.49x10-7m --> 649 nm --> yes, it does!
the resonance structure where the formal charge of -1 is placed on O is the structure that most likely resembles the real molecule
Draw the Lewis structure of CH2O and determine the central atom, electron geometry, and sigma and pi bonds