Chemistry 101 Chapter 3 : Stoichiochemistry
Terms in this set (21)
What is the standard for atomic mass?
12(written like an exponent)C
Average Atomic Mass
Sum of (fractional abundance) x (isotope mass)
Example: 12C = 98.89%
(98.89/100 x 12amu) + (1.11/100 x 13 amu) +(0.01/100 x 14 amu) =12.01 amu
1 mole=6.022 x10^23
the mass in grams of one mole of the substance (g/mol)
Percent composition by mass/ mass percent
mass % = ((mass of the element in the compound)/mass of compound) x 100%
Molecular formula definition
lists the exact number and types of atoms of which the molecule is composed.
Empirical formula definition
lists the relative type and number of atoms in the compound. It is the simplest ratio of atoms in a compound.
What does n equal?
(molar mass of the molecular formula)/(molar mass of the empirical formula)
DicDetermining empirical formula
1. Use molar mass to convert to moles for each element present.
2. Divide each mole answer found by the smallest to get ratio.
3. multiply to get smallest whole number ratio
An example of the molecular formula
A compound has the empirical formula CH and a molar mass of 78.11 g/mol.
CH->molar mass 12.01 g/mol + 1.0079 g/mol=13.0179
n=(78.11g/mol)/13.079 g/mol= 6
molecular formula 6xCh
Balancing Chemical Equations
1. Begin with the element which appears in the fewest number of formulas.
2.Never change subscripts, only coefficients.
3. Changing a coefficient changes everything in hthat formula
4.Balance free elements last
1. Write a balanced chemical equation/.
2. Calculate moles of each reactant
3. Divide moles by the stoichiometric coefficient (from balanced equation)
4. Smallest number of moles is the L.R.
5. Use L.R. to calculate amount of product formed (theoretical yield)
Theoretical yield definition
The amount of product predicted by stoichiometry
Actual yield definition
The quantity of desired product actually formed
Percent yield formula
% yield= ((Actual yield)/Theoretical yield) x 100%
How many carbon atoms are there in 200 molecules of C3H8O
A sample of vitamin A, C20H30O, contains 4.0x10^22 atoms of carbon. How many atoms of hydrogen and how many molecules of vitamin A does it contain?
6.0x10^22 atoms of H, 2.0x10^21 molecules of vitamin A
How many iron ions (Fe3+) are present in 43.6g of FeCl3?
Which of these samples contains the most atoms?
a gram of germanium
a gram of europium
a gram of francium
a gram of americium
a gram of gallium
a gram of gallium
In making H2O from hydrogen and oxygen, if we start with 4.6 moles of hydrogen and 3.1 moles of oxygen, how many moles of water can be produced and what remains unreacted?
4.6 mol of water would be produced, with 0.8 mol of O2 remaining