Explore BrainMass

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?


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


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?


How can i find the pressure of oxygen if it's in a mixture of .40 moles of oxygen and .20 moles of nitrogen at 1.2 atm pressure

Partial pressure

I cant remember how to find the partial pressure of o2 when the container has .76 mol of N2, .18 mol of O2, .031 MOl of He, and .026 mol of H2 at 744mmHg.

Combustion of c3h5n3o9

I cant remember how to find the volume of the gas produced when 1kg of nitroglycerine explodes at a temp of 1985*C at 1 atm.

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?

Solving a Wavefunction

Question: What is the complete wavefunction for n=2, L=0, and m(sub L)= 0? What radius of the orbital specified is required to contain 95% probability of finding an electron?

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?

Kf & vapor pressure

A soluation of HO-CH2-CH2-OH is prepared by dissolving 651g of ethylene gylcol in 1.50kg of water. Determine the freezing point of the soluaiton and the vapor pressure of water above the solution 25.0 degrees C. The normal freezing point of water is water is 0.00 degrees C with a freezing oint depression constant of 1.86 degr

General Chemistry

5.17 A gas occupying a volume of 725 ML at a pressure of 0.970 atm is allowed to expand at constant temperature until its final volume?

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?

General Chemistry

A quantity of 5.25 g of NaOH is dissolved in a sufficient amount of water to make up exactly 1L of solution. What is the molarity of the solution?

Jacobians and Polar Coordinates

Please view the attachment for proper formatting of the question. Question: The range of the polar coordinates are 0 <= r <= ~, 0 <= theta <= pi, and 0 <= phi <= 2pi and the range of the Cartesian coordinates are - ~ < x,y,z, < ~. In the integrals we must relate the two. This is done by the Jacobian, and the result is, d