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Molar Mass
Grams, Atoms, and Moles (oh my!)
Empirical and Molecular Formulas
% Composition
Grab Bag
100

What is the molar mass of an element? How do we calculate it?

Molar mass is the mass of one mole of a substance in grams. We calculate it by referencing the periodic table and if there are more than one element in a compound, we add them together. The units are g/mol

100

What is the mass of 5 moles of Fe2O3?

798.25 g Fe2O3

100

Find the empirical formula for a compound which contains 32.8% chromium and 67.2% chlorine.

Cr2Cl

100
What is the percent composition of K2CO3?
K = 56.58% C = 8.69% O = 34.73%
100
What is Avogadro's Number?
6.022 x 10^23
200

What is the molar mass of BF3

67.8 g/mol

200

Find the number of moles of argon in 452 g of argon.

11.3 mols Ar

200

What is the empirical formula for a compound which contains 67.1% zinc and the rest is oxygen?

ZnO2

200
Calculate the percent composition of carbon, nitrogen and oxygen in acetamide, C2H5NO.
C = 40.66%, N = 23.77% 0 = 27.08%
200
What unit is used for molar mass?
g/mol
300

What is the molar mass of Mg(OH)2?

58.3 g/mol

300

BONUS

BONUS

300
What is the molecular formula for a compound with an empirical formula of C2H8N and a molar mass of 46 grams per mole.
C2H8N (n=1)
300
Which compound has a higher percentage of oxygen, H20 or H2O2?
H2O2 H2O = 11.20%H and 88.80%O H2O2= 5.93%H and 94.06O
300
What is a mole?
A unit of measure (the bridge between particles and mass)
400

What is the molar mass of H3PO4

98 g/mol

400

Find the mass in grams of 2.00 x 10^23 molecules of F.

12.6 g F2


400
If a compound's empirical formula is CH2O, what is the molecular formula? (Experimental molar mass = 60.0 g/mol)
C2H4O2
400
What is the percent composition of NaOH?
Na = 57.46% O = 40.01% H = 2.53%
400
Why do we use scientific notation for Avogadro's number?
Because the number is too big (23 numbers the right of the decimal)!
500

What is the molar mass of Ga2(SO)3?

213.9 g/mol

500

what is the mass 0f 2. 55mol of Na2SO4 ?

362.23 g Na2SO4

500
What’s the empirical formula of a molecule containing 65.5% carbon, 5.5% hydrogen, and 29.0% oxygen? What is the molecular formula if the molar mass is 110 g/mol?
Empirical = C3H3O Molecular = C6H6O2
500
What is the percent composition of Ca3(PO4)2
Ca = 38.76% P = 19.97% O = 41.27%
500
What is the units for molar mass?
g/mol