Let`s go over the 1.5.2 Homework questions!

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1. Give the molar mass of the
substances listed. Include units!!
a.
b.
c.
d.
Nitrogen 14.01 g/mol
Oxygen gas, O2 2(16.0 g/mol) = 32 g/mol
Iron (III) chloride, FeCl3 55.85 + 3(35.45) =
162.2 g/mol
Aspirin, C9H8O4
9(12.01) + 8(1.01) + 4(16.0) =
180.21 g/mol
2. What is the mass of 5 moles of
calcium chloride, CaCl2?
Molar mass of CaCl2: 40.08 + 2(35.45) = 110.98 g/mol
5 moles x 110.98 g = 554.9 g
mol
3. If you have 40 grams of aluminum
foil, Al, how many moles of aluminum
atoms do you have?
Molar mass of aluminum: 26.98 g/mol
40 g x 1 mol = 1.48 mol
26.98 g
4. If you have 0.20 moles of gold, how
much would it weigh?
Molar mass: 196.97 g/mole
0.20 moles x 196.97 g = 39.4 g
mol
5. If you have 300 grams of glucose,
C6H12O6, how many moles of glucose
molecules do you have?
Molar mass: 6(12.01) + 12(1.01) + 6(16.0) =
180.24 g/mol
300 g x 1 mol = 1.66 moles
180.24 g
6. Calculate the molar masses for the
molecules methanol, CH4O, and
ethanol, C2H6O.
Molar mass of methanol: 12.01 + 4(1.01) + 16 =
32.06 g/mol
Molar mass of ethanol: 2(12.01) + 6(1.01) + 16 =
46.09 g/mol
b. If you had 1 gram of methanol and 1 gram of
ethanol, which would have more molecules?
Methanol – the molecules weigh less so
you need more of them to get the same mass
7. How many moles of H atoms are
there in 2.0 moles of C2H6O
molecules? Explain.
In 1 mole of C2H6O molecule there would be 6
moles of hydrogen atoms. So if you have 2
moles of C2H6O then you have:
2 mol C2H6O x 6 mol H
= 12 mol H
1 mol C2H6O
8. Which of these has the most moles of lead atoms?
Show your work and explain your answer.
a. 1.0 grams of PbCl2
1 g = 0.0036 mol
Molar mass: 207.2 + 2(35.45) 278.1 g
= 278.1 g/mol
mol
b. 1.0 grams of PbCl4
1
g
=
0.0029
mol
Molar mass: 207.2 +
g
349
4(35.45) = 349 g/mol
mol
c. 1.0 grams of PbCO3
1 g = 0.0037 mol
Molar mass: 207.2 + 12.01
267.2 g
+ 3(16) = 267.2 g/mol
mol
IT TAKES MORE MOLES OF A LIGHTER SUBSTANCE TO EQUAL THE SAME MASS
SO THE LIGHTEST MOLECULE WILL HAVE THE MOST MOLES
9. Which has more moles of oxygen
atoms, 153 g of BaO or 169 g of BaO2?
Show your work!
Molar mass BaO: 137.33 + 16 = 153.33 g/mol
1 mole
153 g = 1 mol BaO
Oxygen
153.33 g
atoms
mol
Molar mass BaO2: 137.33 + 2(16) = 169.33 g/mol
169 g = 1 mol BaO2
169.33 g
mol
2 moles
Oxygen
atoms

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