Mole Review Practice Problems [PDF]

Name _________________________ Period ____

MOLE Practice Problems

1.Atomic Mass vs. Molar Mass: Calculate the molar mass/ atomic mass of the following atoms and compounds:

H 2O Fe2O3 NaCl CO2 Ba(OH)2

List atom types & #’s of each type of atom

atomic mass (with correct units)

Molar mass (with correct units)

H= 2 O=1 Fe = 2 O = 3 Na = 1 Cl = 1 C=1 O=2 Ba = 1 O = 2 H =2

18.02 amu 159.70 amu 58.44 amu 44.01 amu 171.35 amu

18.02 grams/ mole 159.70 g/ mol 58.44 g/mol 44.01 g/ mol 171.35 g/mol

Conceptual Understanding Questions 2. How is the mole similar to a dozen?

It’s a word that represents an amount or a number 3. Which contains more atoms, a mole of copper or a mole of gold? (write down # in each one)

They both contain 6.02 x 10 23 atoms

4. Which weighs more, a mole of copper or a mole of gold? (write down how much each one weighs)

Gold = 196.97 g/mol 5.

Copper = 63.55 g/mol

a. How are the terms “molar mass” and “atomic mass” different from each other?

Molar Mass = Mass of 1 mol (6.02 x 10 23) of a substance (g/mol) Atomic Mass = Mass of 1 atom (amu) b. How are the terms the same?

Both the same number on the periodic table, you just need to change the units (g/mol –vs- amu) 6. Write down the conversion factors that would be used to convert between the following units: Molar Mass (periodic table) Avogadro’s # GRAMS -------------------------- MOLES ---------------------------- ATOMS & MOLECULES 1 mole/ # grams 1 mole = 6.02 x 1023 atoms & molecules

Conversion Problems: For each problem you must use Dimensional Analysis & box your answer. 7. Given 12 g of aluminum, how many moles do you have?

12 g Al

1 mol Al 26.98 g Al

= 0.44 mol Al

16. Given 34 moles CF4 , how many grams would you have?

34 mol CF4 88 g CF4 1 mol CF4

= 2992 =3.0x103 g CF4

8. How many atoms are in 2.00 moles of Li?

2.00 mol Li 6.02 x 10 Li 1 mol Li

23

atoms

17. Given 25 g of NaCl, how many moles do you have?

= 1.20 x 1024 atoms Li

9. How many atoms are in 55 grams of iron?

55 g Fe

1 mol Fe

55.85 g Fe

6.02 x 1023 atoms Fe 1 mol Fe

= 5.9 x 1023 atoms Fe

1 mol C 6.02 x 1023 atoms C

= 1. 00mol C

11. How much do 3.01 x 1023 atoms of He weigh? 23

3.01 x 10 atoms He

1 mol He

4.00 g He

6.02 x 1023 atoms He

1 mol He

0.345 mol H2O

18.02 g H2O 1 mol H2O

44.01 g CO2 1 mol CO2

= 6.22 g H 2O

= 48.9 g CO2

14. If you have 0.00812 mol of H2CO3, how many molecules do you have?

0.00812 mol H2CO3

6.02 x 1023 molecules H2CO3 1 mol H2CO3

1 mol Zn

65.41 g

23

= 4.89 x 1021 molecules H2CO3

1 mol Zn

= 1.7 x 106 grams

19. How many moles are in 4.9 x 1023 molecules of ZnCl2?

4.92 x 1023 molecules ZnCl2

1 mol C 6.02 x 1023 molecules ZnCl2

= 0.817 mol ZnCl2

20. How many molecules are in 0.83 moles of HCl?

= 2.00 g He

13. Given 1.11 mol of CO2 , how many grams would you have?

1.11 mol CO2

1.6 x 1028 atoms Zn

0.83 mol HCl

12. Given 0.345 mol of water, how many grams would you have?

= 0.43 mol NaCl

18. If you have 1.6 x 1028 atoms of Zn, how much would it weigh?

6.02 x 10 atoms Zn

10. How many moles are in 6.02 x 1023 atoms of carbon?

6.02 x 1023 atoms C

25 g NaCl 1 mol NaCl 58.44 g NaCl

6.02 x 1023 molecules HCl 1 mol HCl

= 5.0 x 1023 molecules HCl

21. How many molecules are in 74 grams of KI?

74 g KI

1 mol Fe

166.01 g KI

6.02 x 1023 atoms Fe 1 mol Fe

= 2.6 x 1023 atoms Fe

22. Given 125 g ofH2SO4, how many moles do you have?

125 g H2SO4

1 mol H2SO4 98.08 g H2SO4

= 1.27 mol H2SO4

23. If you have 7.46 x 1023 molecules of KNO3, how many moles do you have?

7.46 x 1023 molecules KNO3

1 mol KNO3 6.02 x 1023 molecules KNO3

= 1.24 mol KNO3

15. What is the mass of 3.13 x 1021 atoms of KBr?

3.13 x 1021 atoms Br

1 mol Br

6.02 x 1023 atoms Br

119 g

1 mol Br

= .619 grams

24. If you have a 100 g sample of KMnO4, how many molecules of KMnO4are in the sample?

100 g KMnO4

1 mol KMnO4 158.04 g KMnO4

6.02 x 1023 molecules KMnO4 1 mol KMnO4

= 4 x 1023 molecules KMnO4