Chem 1075 Chapter 9 The Mole Concept Learning Goals / Study Guide
Suggested Homework:
Key Terms on p. 246
Exercises on p. 247-249 #5, 7, 9, 11, 13, 15, 17, 19, 23, 24, 25, 27, 31, 33, 37, 39, 45, 53, 55, 57, 59, 63
Learning Goals:
1. Know Avogadro’s number (6.02 x 1023) and how to use it to count particles of a substance:
N
[Particles <—> Mole]
2. Be able to calculate Molar Mass of a compound if given its formula.
3. Use Molar Mass to relate mass of a substance to moles or particles of substance.
N MM
[Particles <—> Mole <—> Grams]
4. Know what STP represents and what the values are.
5. Know the molar volume of any gas at STP conditions (1 mole = 22.4 L @ STP)
6. Be able to calculate the density of a gas at STP using D = MM/MV
7. Be able to calculate the Molar Mass of a gas at STP using D = MM/MV
8. Relate Molar Volume of a gas to its mass and number of particles:
N MM
[Particles <—> Mole <—> Grams]
MV
Volume
At STP
9. Calculate % Composition from a Formula
10. Determine Empirical Formula from % Composition information
11. Determine the Molecular Formula from Empirical Formula and Molar Mass information
Extra Practice:
1. How many particles are in 5.55g of K2CO3?
2. What is the density of CO gas at STP?
3. What is the density of CO2 gas at STP?
4. What is the molar mass of a gas having a density of 0.0900 g/L? What gas would it be?
5. What mass in grams would 7.21L of SO3 be at STP? How many molecules of SO3 would be in that sample
of gas?
6. Determine the % Composition for Ca(HCO3)2.
7. Determine the empirical formula for the compound made of 84.09% C and 15.91% H. If the molar mass
of the compound is 114 g/mole, what is its molecular formula?
Answers: 1. 2.42 x 1022 formula units of K2CO3, 2. 1.25 g/L, 3. 1.96 g/L, 4. 2.02 g/mole or H 2, 5. 25.8g or 1.94 x 1023 molecules
SO3, 6. 24.72%Ca, 1.25%H, 14.82%C, 59.22%O, 7. Emp form C 4H9, Mol form C8H18
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