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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?
800 g Fe2O3
100
Find the empirical formula for a compound which contains 32.8% chromium and 67.2% chlorine.
CrCl3
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
How many moles of magnesium is 3.01 x 10^22 atoms of magnesium?
0.05 mol Mg
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

300

Which compound has a higher percentage of oxygen, H20 or H2O2? Show calculations for a complete response.

H2O2 

H2O = 11.20%H and 88.80%O 

H2O2= 5.93%H and 94.06%O

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 F2.
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 (nx10#)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(SO3)3?
379.7 g/mol
500
How many molecules are in 10 g of aspartame (C14H18N2O5)?
2.05 x 10^22 molecules of aspartame
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 each element in Ca3(PO4)2

Ca = 38.76% P = 19.97% O = 41.27%

500

What poison was found to be in the Tylenol of the "Case of the Poisonous Pill?"

cyanide