Pure pools of benzo [a] pyren and p-xylene are found floating in the Groundwater. What concentrations do you expect to find dissolved in the water directly belo the pools (mg/L and mM)? What concentrations do you expect to find in the air above the pools? (mg/L and mM). Compare how two chemicals behave in the environment. Benzo a pyrene MW: 252.32 g/mol; Henry's law constnt= 2.4 x10^-6 atm m^3/mol; Vapor pressure= 5.6 x10^-9 mmHg; Solubility=0.0038 mg/L; Log Koc=5.60-6.29. For p-xylene MW=106.17 g/mol; Henrys constant=0.0063 atm m^3/mol;Vapor pressure=8.763mmHg ; Solubiity =200 mg/L ; Log Koc=2.31
In: Chemistry
1. a) Band theory is used to explain the conductivity of different solid crystals. Define the band width and calculate s band width assuming there is indefinite number of molecular orbitals in the s band.
b) Explain how metallic conductor, semiconductor and insulator are identified by band theory.
c)
3.0 mol CO2
behaving as a van
der Waals gas, when it is confined under the following conditions:
at 750 K in 150 cm3.
For CO2
Van der
Waals coefficients, a: 3.610 L2
atm
mol-2,
b: 4.29x10-2
Lmol-1.
Gas constant R is 8.206 x 10-2
L atm
K-1mol-1
i) Calculate the
gas pressure (in atm),
ii)
What is the molar volume of the gas (in L/mol),
iii) What is the
pressure when it is ideal gas and use it to state dominating force
in
the above gas?
2. a) Use one example to describe Born-Haber cycle
b)
Calculate
i) The resultant of two stationary dipole moments of magnitude 1.2D
and 1.8D that make an angle of 130o
to each
other in vacuum (expressed in D)
ii) The interaction between pairs of rotating molecules with μ = 1.5D and r =0.1 nm in one material at 325K in air (expressed in kJ/mol)
3. a) Account for two kinds of semiconductor and use schemes to explain charge flow between n-type and p-type semiconductors in the dark condition without a bias
b)A substance known to have a cubic unit cell gives reflections with Cu Karadiation (wavelength 154 pm) at the glancing angle of 32.6o.
The
reflection is known to be due to the (220) plane. Index the
reflection at the glancing angle of 39.4o
.
In: Chemistry
3. Assume that a particle is confined to a box of length L, and that the system wave function is
ψ(x)=sqrt(2/L)*sin[(π*x)/(L)]
(1) Is this state an eigenfunction of the momentum operator? Show
your work.
(2) Calculate the average value of the momentum <p> that
would be obtained for a large number of measurements. Explain your
result.
(3) Calculate the probability that the particle is found between
0.31 L and 0.35 L.
In: Chemistry
(a) Calculate the percent ionization of 0.00690 M hypochlorous acid (Ka = 3e-08). % ionization =
(b) Calculate the percent ionization of 0.00690 M hypochlorous acid in a solution containing 0.0300 M sodium hypochlorite. % ionization =
In: Chemistry
consider space group Fdd2
1) What is point symmetry of an atom located at (0,0,Z)
2) give d-glides coordinates of Fdd2
3) what is multiplicity at a general position on Fdd2
4) Give a possible maximal non-isomorphic subgroup of Fdd2 that would be considered a translationengleiche group. What is the crystal system of this subgroup?
In: Chemistry
Band Theory
(A) Give a brief description of the formation of electron bands in crystals including reference to the atomic structure of the constituent atoms.
(B) Explain the following
i.Sodium, which has 2 atoms in a bcc (conventional cubic) unit cell, is a metal
ii.Calcium, which has 4 atoms in a fcc (conventional cubic) unit cell, is a metal
iii.Diamond, which has 8 atoms in a fcc (conventional cubic unit cell with a basis, is an electrical insulator, whereas silicon and germanium, which have similar structures, are semiconductors.
(C) Why is diamond transparent?
In: Chemistry
consider space group Fdd2
1) What is point symmetry of an atom located at (0,0,Z)
2) give d-glides coordinates of Fdd2
3) what is multiplicity at a general position on Fdd2
4) Give a possible maximal non-isomorphic subgroup of Fdd2 that would be considered a translationengleiche group. What is the crystal system of this subgroup?
In: Chemistry
Temperature and Phase Changes In this exercise, you will make observations of the phase changes of water (H 2 O). You will measure temperature and create a heating curve to determine the melting point and boiling point of water. 1. Gather the 250-mL beaker, approximately 150 mL of crushed ice, a watch or timer, the thermometer, burner stand, burner fuel, and matches. Note: Large ice cubes may be crushed by placing them in a large plastic bag, placing the bag on a durable surface, and breaking the pieces apart with a hammer or other heavy object. 2. Fill the beaker to about the 150-mL line with crushed ice. 3. Place the thermometer in the center of the ice. Do not allow the thermometer to touch the sides or bottom of the beaker. 4. After holding the thermometer in the ice for about a minute, note the time and record temperature at 0 minutes in Data Table 2 of your Lab Report Assistant . Additionally, record your observations about the state of matter (solid, liquid, or gas) of the water in Data Table 2 . 5. Uncap the burner fuel, light the wick with a match or lighter, and place the fuel under the stand on a pie pan. Burner setup. Note that the flame is blue which is sometimes difficult to see. 6. Place the beaker on the burner stand. Keep holding the thermometer in the middle of the ice. 7. Start the timer and begin taking temperature and observation readings every minute, recording your findings in Data Table 2 . Note: It is important that you record both the temperature AND the state or states of matter present every minute throughout the experiment. 8. Gently stir the ice with the thermometer as it heats. www.HOLscience.com 13 ©Hands-On Labs, Inc. Experiment Liquids and Solids 9. Continue to stir the ice or water and record temperature and observations every minute until the water has boiled for 5 minutes . Do not allow the thermometer to rest on the glass of the beaker. 10. Extinguish the burner fuel by lightly placing its cap over the flame; do not tighten cap until the burner fuel container has fully cooled. 11. Thoroughly wash and rinse the equipment for future use. Questions: A. Using the temperature data recorded in Data Table 2 , create a heating curve. ● Plot time (minutes) on the x-axis (horizontal axis) and temperature (°C) on the y-axis (vertical axis). Connect the plotted points with a line. ● Label the heating curve to show each phase of matter (solid, solid + liquid, liquid, liquid + gas). ● Label the melting point and boiling point on the heating curve. Note: An example heating curve is given in Figure 6 of the Background B. Are there parts of the curve with positive slopes and parts that are flat (slope of zero)? What states of matter are present when the slope of the heating curve is positive and what states of matter are present when the slope is zero or close to zero? C. Describe the key characteristics for the three states of matter. D. Define the melting point. What was the observed melting point of water?
E. Define boiling point. What was the observed boiling point of water?
F. What happens to heat energy when it is not increasing the temperature of the substance in the beaker? Use your heating curve to explain your answer. G. Was temperature perfectly constant during your test while the water was melting and while it was boiling? Explain why or why not.
H. The published melting point of H 2 O is 0°C, and the published boiling point is 100°C. Why may you have found different values?
I. Use the following information to determine if the intermolecular forces of isopropyl alcohol are greater or weaker than the intermolecular forces of water. Explain your answer. The melting point of isopropyl alcohol (rubbing alcohol, C 3 H 8 O) is about -90 °C and the boiling point is about 82 °C
In: Chemistry
0.1 M NaOH is titrated with 25 mL acetic acid. The equivalence point was reached at 23.25 mL.
a) Based on your experimentally observed equivalence point of 23.25 mL, calculate the original concentration of the acetic acid that came from the stock bottle.
b) Based on your experimentally observed half equivalence point of 11.625 mL pH= 4.8, calculate the Ka of acetic acid.
c) Based on your answers to 1& 2 calculate the expected pH at the equivalence point
In: Chemistry
1. Draw the Lewis structure, determine the molecular geometry and electronic geometry, hybridization, and bond angles of the following molecules: ICl2-, SnCl3-
2. Draw the energy diagram for aluminum and indicate which ones are the valence shell orbitals. Then draw the hybridization orbitals if the atom was sp hybridized
In: Chemistry
Determine the pH of each solution.
a) 0.0200 M HClO4
b)0.120 M HClO2 (for HClO2, Ka=1.1×10−2)
c)0.050 M Sr(OH)2
d)0.0856 M KCN (for HCN, Ka=4.9×10−10)
e)0.165 M NH4Cl (for NH3, Kb=1.76×10−5)
In: Chemistry
1. Calculate the pH when 24.9 mL of 0.011 M HCl is added to 100.0 mL of the above buffer.
2. Calculate how many mL of 0.100 M NaOH are needed to neutralize completely 91.0 mL of 0.0600 M H2SO4 (forming Na2SO4 and water).
3.
Calculate the pH of 0.057 M phosphoric acid
(H3PO4, a triprotic acid). Ka1 =
7.5 x 10-3, Ka2 = 6.2 x 10-8, and
Ka3 = 4.8 x 10-13.
Hint, if you are doing much work, you are making the problem harder
than it needs to be.
In: Chemistry
define variables in sin(theta)= (n * lamda)/d for Chemical grating, Emission spectra
In: Chemistry
Please use sig figs and dimensional analysis and explain process!
1. Dissolve 69.0 g NaNO2 in 1.00 x 102 mL H2O.
(a) If the temperature of the solution is 100°C, what is the vapor pressure above the solution? The density of H2O at 100°C is 0.9591 g/mL.
(b) Calculate the change in the boiling point of the solution, and calculate the boiling point of the aqueous solution.
(c) Calculate the freezing point of the solution. The density of H2O at 0°C is 0.9998 g/mL.
(d) Which change is greater, the boiling point elevation or the freezing point depression?
(e) Estimate the osmotic pressure at 25 °C for the solution. Assume that dissolved sodium nitrite does not affect the volume of the solution.
In: Chemistry
What detector system would be best to use for I-131 in a mixture of all the I isotopes? Explain why.
In: Chemistry