Explore BrainMass
Share

General Chemistry

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.

Degrees of freedom of a saturated solution

A saturated solution of Na2SO4 with excess of the solid is present in equilibrium with its vapor in a closed vessel. Calculate the number of degrees of freedom, f, of the system. Ignore the autoprotolysis of water and assume that the salt solvates without ionizing. F = c - p +2 or use f = c-p +2 -r -a c = chem species

Calculate the Number of Moles

A steel tank with a volume of 9.583 L contains N2 gas under a pressure of 4.972 atm at 31.8 °C. Calculate the number of moles of N2 in the tank.

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?

Wavelength and Frequency Example Problem

Question 1: M. tuberculosis, the organism that causes tuberculosis, can be completely destroyed by irradiation with UV light with a wavelength of 254 nm. What is the frequency? Question 2: Aradio station's signal broadcasts at a freq. 1240kHZ. What is the wavelength in meters?

Chemical Symbol Elements

Give the name and chemical symbol for: a) An element with 50 electrons b) An element with 28 protons c) An element with 2 electrons in the first shell, 8 electrons in the second shell, 8 electrons in the third shell, and 2 electrons in the fourth shell d) An element with atomic number of 78

Distinguish Ionic or Covalent Bonding

While you are working in the lab your instructor hands you a vial of red, crystalline material and asks you to tell if it has ionic or covalent bonding. Describe at least one experiment you would do to answer the instructor's question.

Compound or a mixture?

Tell whether the following is a property of a compound or a mixture: a) Can contain three elements in a specific ratio b) Varies in chemical composition depending on the sample size c) Can be classified as either homogeneous or heterogeneous

Heterogeneous and homogeneous mixture

Tell if the mixture is homogeneous or heterogeneous and explain why you classified it as homogeneous or heterogeneous. a) Iced tea b) Salad c) Chocolate chip cookie

Volatility

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

Working with molecules in first excited rotational state

Calculate the ratio of HCL molecules in the first excited rotational state to those in the ground state @ 25 C. Assume an equilibrium bond distance of 1.275 angstroms. the angstrom part of the problem throws me off, I usually start these out by solving Change in E = ( h ) ( c )(Wo), but this is a q (rot) prob, not a q (elec).

Isotopes of Hydrogen Elements

Name the three isotopes of the element whose atomic number is 1. (b) What collective name do we give to a mixture of these three isotopes when they are present in the same ratios as in the universe as a whole?

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