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General Chemistry

Valance Bands & Energy to Produce and Electron Hole Pair

3. A material has an effectively full valence band and an empty conduction band. Explain why that if these two bands overlap the material behaves as a metal and if they are separated by a few electron volts in energy the material is an insulator. 4. Calculate the minimum energy a photon must have to produce an electron hole p

Clinical Uses of Radioactivity & Decay

How long would it take for a radioactive isotope with a half life of 2 weeks to lose at least 70% of its radioactivity? Describe two clinical uses of Radioactivity.

MO theory and dissociation energy

Use simple MO Theory (LCAO-MO) to explain why the dissociation energy of neutral N2 is greater than the N2+ ion, but that the dissociation energy of the O2+ ion is greater than the O2 neutral.

AP Chemistry: Test Review

(See attached file for full problem description) --- I need full explanation of each step. Please help. 1. The helium ion, He+, has energy levels similar to those of the hydrogen atom, since both species have only one electron. The energy levels of the He+ ion are given by the equation En = - 5248.16 kj/mole n =

Percentage yields

A chemist isolates 17.43 g of product from a reaction that has a calculated theoretical yield of 21.34 g. What is the percentage yield?

Volatility

Suppose you were given samples of two different liquids. Describe how you would determine which one is more voliatile.

Conversions

The volume of a certain bacterial cell is 1.60 µm3. (a) What is its volume in cubic millimeters (mm3)? (b) What is the volume of 105 cells in liters (L)? [show all the conversion factors that were used in calculating the answers]

Particle in a Box Proportionality

A particle is constrained to lie along a one-dimensional line segment between 0 and a. The probability of finding the particle along this line segment is seen in attached file. A. Find the proportionality constant, ie., normalize the function. B. Calculate the expectation values of X and X^2 for n=1 and n=2. C. Find t

Dilution Processes

I need help in solving this word problem: A corrupt barman attempts to prepare 100ml of some drink by mixing 30ml of ethanol with 70 ml of water. Does he succeed? If not, what volumes should have been mixed in order to arrive at a mixture of the same strength but of the required volume?

Precipitation calculations

Precipitation Calculations. Will a precipitate of calcium sulfate (Ksp = 2.4 x 10-5) form when 50.0 mL of 0.00150 M calcium chloride and 25.0 mL of 0.0100 M sodium sulfate are mixed? Why or why not?

General Chemistry - Orbitals and Configuration

Which one of the following configurations depicts an excited oxygen atom? a. 1s22s22p2 b. 1s22s22p23s2 c. 1s22s22p4 d. [He]2s22p4 e. 1s22s22p1 In a ground-state manganese atoms, the _____ subshell is partially filled. a. 4s b

Calculate minimum OH

The solubility product of Mg(OH)2 is 1.2E-11. What minimum OH- concentration must be attained (for example, by adding NaOH) to decrease the Mg2+ concentration in a solution of Mg(NO3)2 to less than 1.9E-10 M?

Calculating volume of water evaporated

A 230mL sample of a 0.276 M CaCl2 solution was left on a hot plate overnight; the following morning, the solution is 1.10 M. What volume of water evaporated from the 0.276 M CaCl2 solution?

Measuring Water Hardness

In an experiment for measuring water hardness in a water sample, using Atomic Absorption Spectrophotometry, I obtained a value of 173.74 ppm hardness for my water sample. Using EDTA determination, I obtained a value of 440 ppm hardness for my sample. In both these methods, I was measuring the hardness in relation specifically to

Hazardous Dyes

Question: Many dyes used in food products are classified a hazardous chemicals in their pure form. Why then can they be safely used in those food products?

General Chemistry

4.60 You have 505 ml of a 0.125M HCI solution , and you want to dilute it to exactly 0.100 M. How much water should you add?

8 precipitate of magnesium flouride

Will a precipitate of magnesium flouride form when 200.0 milliliter of 1.9x10^-3mol/Litre MgClsubnumber2 solution is added to 300.0 milliliter of 1.4x10^-2mol/Litre NaFsolution? (ksubletterssp(MgFsubnumber2)=6.9x10^-9) Briefly explain by showing your numerical calculations show work. thanks

Conversion factors

Convert the following to the required units: 550 uL (microliters) per hour to milliliters per day Please show steps

Barium hydroxide

Write a balanced chemical equation, for the reaction that occurs, when Solid barium hydroxide, dissolves in water. Thank you

Half life

1) Radioisotopes such as aluminum -26, which is believed to have been present in the solar system when earth was formed but can no longer be detected, are known as extinct radionuclides. The half-life for the decay of aluminum -26 is 7.20 x 10 ^5 years. How many years did it take for 99.99% of the aluminum -26 to decay? If

Electromagnetic Waves: Radio Message from Mars

At its closest approach, Mars is 56 million km from Earth. How long would it take to send a radio message from a space probe of Mars to earth when the planets are at this closest distance?

Molar solubility

Calculate molar solubility of CuI in 1.0 M NaI. Assume the highest complex formed is CuI2 - .

Precipitation

Solid Na2SO4 is added to a solution that contains 0.150 M Ba 2+ and 0.0800 M Ca2+. Which sulfate precipitates first, BaSO4 or CaSO4? What calculations would porve this? What should be the concentration of sulfate ion for the best separation?