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# Chemistry - Chap 7

### Section 3 - Using Chemical Formulas

Hydrogen atoms have an average atomic mass of 1.007 94
Oxygen atoms have an average atomic mass of 159994 amu
The percentage by mass of each element in a compound Percentage composition
The sum of the average atomic masses of all atoms represented in the formula of any molecule, formula unit, or ion. Formula mass
A compounds molar mass and formula mass are numerically equal
What is the formula mass for KCIO3 122.55 amu
The molar mass of a compound is calculated by Summing the masses of teh elements present in a mole of the molecules or forumla units that make up the compound.
What is the molar mass of barium nitrate, Ba(NO3)2? 261.35 g/mol
The molar mass of a compund can be used as a conversion factor to relate An amount in moles to a mass in grams for a given substance.
To convert a known amount of a compound in moles to a mass in grams, you should multiply the amount in moles by the molar mass. amount in moles x molar mass (g/mol) = mass in grams.
What is the mass in grams of 2.50 mol of oxyge gas 75 g (2.50 mol x 30 g/mol)
How To convert a known mass of a compound in grams to an amount in moles, The mass must be divided by the molar mass OR invert the molar mass and multiply so that the units are easily canceled.
To find teh mass percentage of an element in a compound Divide the mass of the element in a sample of the compound by the total mass of teh sample, then multiply this by value by 100
The percentage by mass of each element in a compound Percentage composition
The mass percentage of an element in a compound is the same regardless of the sample's size.
How many moles of atoms of each element are there in one mole of the following compound: Al2S3 2 mol Al, 3 mol S
How many moles of atoms of each element are there in one mole of the following compound: NaNO3 1 mol Na, 1 mol N, 3 mol O
How many moles of atoms of each element are there in one mole of the following compound: Ba(OH)2 1 mol Ba, 2 mol O, 2 mol H
What is the molar mass of each of the compounds: Al2S3 150.17 g/mol
What is the molar mass of each of the compounds: NaNO3 85.00 g/mol
What is the molar mass of each of the compounds: Ba(OH)2 171.35 g/mol
What is the mass in grams of 2.50 mol of oxygen gas? 75g (2.50 mol x 30 g/mol)
Find the percentage composition of PbCl2 74.51% Pb, 25.49% Cl
Find the percentage composition of Ba(NO3)2 52.55% Ba, 10.72% N, 36.73% O
Find the mass percentage of water in ZnSO4 * 7H2O. 43.85% H2O
Created by: tbstinso