Download Percent composition

Avogadro's hypothesis
*Equal volumes of gases at same T and P contain equal numbers of particles
*Particles not the same size but spaced far apart
STP
Molar Volume
Feb 21­8:56 PM
Calculating Molar Mass from Density
Molar mass = density at STP x Molar volume at STP
23. What is the density of krypton gas at STP?
22. A gaseous compound composed of
sulfur and oxygen, which is linked to the formation of acid rain, has a density of 3.58 g/L at STP. What is the molar mass of this gas?
Feb 16­9:45 AM
Percent Composition of a Compound
Relative amounts of the elements in a cmpd.
Percent comp. from mass data
What is the percent composition of the compound formed when 2.70 g of aluminum combine with oxygen to form 5.10 g of aluminum oxide?
Percent Comp. from Formula
34. Calculate the % comp. of a. ethane, C2H6
b. sodium hydrogen sulfate, NaHSO4
% Composition as a conversion factor
64d. Calculate the number of grams of phosphorus in 804 g of Na3PO4
1. Calculate the percent nitrogen in the fertilizer, ammonium nitrate.
Feb 22­4:55 PM
2. When a 14.2 gram sample of mercury(II) oxide
is decomposed into its elements by heating, 13.2 grams
of Hg is obtained. What is the percent composition of the compound?
Empirical Formula
Empirical
information gained by observation, experience, experiment
‐Lowest whole no. ratio of atoms in the compound
‐May or may not be same as molecular formula
Hydrogen peroxide
CO2
Feb 22­4:58 PM
Molecular Formula
tells actual # of each kind of atom in a molecule of the cmpd.
either the same as its experimentally determined
empirical formula, or a simple whole‐number multiple of empirical formula
Determining Empirical Formula
1) find ratio of moles
A cmpd. is 36.1% Ca and 63.9% Cl. What is the empirical formula?
2) reduce to lowest whole‐number ratio
A cmpd. contains 67.6% Hg, 10.8% S, and 21.6% O. What is the empirical formula of the compound?
If you know the empirical formula, you can determine the molecular formula
1. calculate empirical formula mass (efm)
2. divide molar mass by efm
3. use the multiplier in #2 to convert empirical form. to molecular form.
Calculate the molecular formula of a cmpd. with a molar mass of 60.0 g/mol and empirical formula of CH4N.