Molar Mass
Particles to Moles or Molecules
Grams to Moles/Moles to grams
Percent Composition
Empirical & Molecular
100
What is a mole? What is molar mass?
The mole is the "counting unit" used by chemists to indicate the number of atoms, ions, molecules, or formula units present in a particular chemical sample.
The mole is similar to other counting units that you've used before....pair (2), dozen (12), and gross (144).
The molar mass of a compound tells you the mass of 1 mole of that substance. In other words, it tells you the number of grams per mole of a compound. So the units for molar mass are grams/mole.
100
How many moles are there in 24.0 grams of FeF3?
.213 moles
100
How can you convert grams to moles?
To convert grams to moles, start by multiplying the number of atoms by the atomic weight for each element in the compound. Then, add all of your answers together to find the molar mass of the compound. Finally, divide the number of grams of the compound by the molar mass of the compound to find the number of moles.
100
Calculate the percent composition of NaHSO4
% Na = 22.99/120.06 x 100% = 19.15%
% H = 1/120.06 x 100% = 0.83%
% S = 26.71%
% O = 64/ 120.06 x 100% = 53.31%
100
What is an empirical formula?
A formula that gives the simplest whole-number ratio of atoms in a compound.Once the empirical formula is found, the molecular formula for a compound can be determined if the molar mass of the compound is known. Simply calculate the mass of the empirical formula and divide the molar mass of the compound by the mass of the empirical formula to find the ratio between the molecular formula and the empirical formula. Multiply all the atoms (subscripts) by this ratio to find the molecular formula.
200
What is the molar mass of this compound: NaBr
102.9 g/mol
200
How many moles are there in 458 grams of Na2SO4?
3.22 moles
200
How many moles of KCl are in 27.5 g of KCl?
0.369 moles
200
Calculate the percent composition of the compound that forms when 222.6 g N combines completely with 77.4 g O.
74.2% N and 25.8% O
200
Determine the empirical formula of the following:
13.5 g Ca, 10.8 g O, and 0.675 g H
300
(NH4)2CO3
96.0 g/mol
300
How many molecules are there in 122 grams of NO2?
1.60 x 1024 molecules
300
Determine the number of grams from 1.70 moles KMnO4.
0.369 moles
300
Define percent composition
Percent composition is the percentage by mass of each element in a compound.
Example: The percent composition of water is 20% hydrogen and 80% oxygen
300
Determine the empirical formula of the following:
40.0 g C, 6.7 g H, and 53.3 g O
CH2O
400
H3PO4
97.994 g/mol
400
How many molecules are there in 9.34 grams of water?
3.12 x 1023 molecules
400
True or False:
Miss Michele is my favorite person.
True
400
When I'm completing classwork & homework (study guide included), and I don't know the answer to a chemistry question- I can use these 3 resources:
My notes
The textbook
Rosenquists' Tutoring Sessions
400
What is a molecular formula?
aka true formula
tells us the actual number of the different elements in one molecule of a compound.
each element is written as their symbols in the periodic table, and the number of atoms for each element is shown by the subscript
(the small number to the lower right of the element).
500
Ca(OH)2
74.1 g/mol
500
How many particles are in a mole?
6.022×10^23 particles *per mole.
500
What is the percent composition of the compound formed when 2.70g of aluminum combine with oxygen to form 5.10g of aluminum oxide?
Al – 52.9%
O – 47.1%
= A Hunnid
500
Calculate the molar mass of a gas at STP:
A gas has a density of 0.902 g/L. What is the molar mass of this gas?
20.2 g/mol
500
Determine molecular formula:
CH2O - empirical formula
Molar Mass: 90 g/mol
C3H6O3