Percent Composition: Determine the percent composition of a compound when given its molecular formula.

Calculate the percent composition of HNO3 by mass.

Determination of Empirical Formulas: Determine the empirical formula of a compound when given its percent composition.

Calculate the empirical formula of a compound made up of 50.1% sulfur and 49.9% oxygen.

Wavelength Calculations: Determine the wavelength of light when its frequency is known.

The frequency of red light is 4.57 x 10^14 sec-1. Calculate its wavelength in nanometers.

pKa and equilibrium constant values

I have the following problem: the pKa values for H2SeO3 at 25 degrees C are 2.64 and 8.27. Write the base hydrolysis equilibrium equations for SeO3^2-(aq) and HSeO3 ^- (aq) ions, and calculate the equlibrium constant values for each equlibrium. I think that I am completely stuck on how to approach this equation. Please help ...continues

AP Problem

Methylamine, CH3NH2, is a weak base that reacts according to the equation CH2NH2 + H2O <--> CH3NH3^1+ + OH^1-. The value of the ionization constant, Kb, is 5,25 x 10^-4. Methylamine forms salts such as methylammonium nitrate, (CH3NH3^1+)(NO3^1-). (b) Calculate the pH of a solution maded by adding 0.0100 mole of a solid methyl ...continues

AP Problem

Methylamine, CH3NH2, is a weak base that reacts according to the equation CH2NH2 + H2O <--> CH3NH3^1+ + OH^1-. The value of the ionization constant, Kb, is 5,25 x 10^-4. Methylamine forms salts such as methylammonium nitrate, (CH3NH3^1+)(NO3^1-). (b) Calculate the pH of a solution maded by adding 0.0100 mole of a solid methylamm ...continues

Heat capacity and calorimetry

When steam condenses to liquid water, 2.26 kj of heat is released per gram. The heat from 168g of steam is used to heat a room containing 6.44 x 10 to the 4th grams of air (20ft x 12 ft x 8 ft). The specific heat of air at normal pressure is 1.015 j/(g.C). What is the change in air temperature, assuming the heat from the stea ...continues

Molecular speeds; effusion

If 4.83 ml of an unknown gas effuses through a hole in a plate in the same time it takes 9.23 ml of Argon to effuse through the same whole under the same conditions, what is the molecular weight of the unknown gas?

Hess's law

Calculate the enthalpy change for this reaction, using the following combustion data: C2H4(g) + 3 O2(g) yields 2CO2(g)+ 2H2O(l) deltaH= -1401 kj C2H6(g) + 7/2 O2(g) yields 2CO2(g) + 3H2O(l) deltaH= -1550kj H2(g) + 1/2 O2(g) yields H2O(l) deltaH= -286kj

moles and grams conversion

1. How many moles are in 325g of PCl3 ? 2. How many grams of CO2 contain 5.32 moles?