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Convert between: atoms ↔ amu ↔ grams
Convert between: atoms/molecules/formula units ↔ moles ↔ grams
Calculate molar masses of compounds.
Calculate percent by mass of elements in compounds.
One mole = 6.022 x 10
23 items
1 amu = 1.66 x 10 -24 grams
The average atomic mass in amu = mass of one atom; the average atomic mass in grams = the mass of one mole of the element.
Ex: 1 average carbon atom has a mass of 12.01 amu; the mass of one mole of carbon = 12.01 grams.
Problems:
1. What is the mass in amu of 1.00 x 10
6
atoms of argon?
2. What is the mass in grams of 2.34 x 10 25 atoms of cobalt?
3. What is the mass in grams of 1.50 x 10
-3 moles of tin?
4. You have an estimated 135,000,000 atoms of zinc. What is the mass in amu? In grams?
5. A sample of strontium has a mass of 4.381 x 10 7 amu. How many atoms are there in the sample?
6. A chemist requires 3.65 moles of copper(I) sulfide as a reactant in a chemical reaction. How many grams of the chemical should she weigh out?
7. A chemical reaction produces 5.42 grams of chlorine gas. a. How many moles of gas were produced? b. How many atoms of chlorine are present in the chlorine gas product?
8. How many atoms of uranium are present in a 2.05 x 10
-5
gram sample of uranium?
9. How many atoms are in 5.51 millimoles of arsenic? What is the mass in grams?
10. a. How many sodium atoms are in 200.0 grams of sodium sulfide? b. What is the percent by mass of sulfur in sodium sulfide?
11. a. How many moles are in a 151-kg sample of iron? b. How many atoms of iron are in the sample?
12. How many formula units are in a 235-gram crystal of pure KH
2
PO
4
?
13. a. What is the molar mass of caffeine, C
8
H
10
N
4
O
2
? b. How many molecules are in 1.50 micrograms of caffeine?
14. a. How many moles each of silicon and fluorine are in 100.0 grams of silicon difluoride? b. How many total atoms are in 100.0 grams of silicon difluoride?