# Mole Concept Extra Practice Problems

NOTE:  All scientific notation is written in the following manner:  (Coefficient)E(Exponent).  For example, 6.00 x 101 is written as 6.00E1, and 2.01 x 10-5 is written as 2.01E-5.    Problems marked with an asterisk are closer to the level that you may expect for the exams, and provide excellent practice with dimensional analysis and multiple concepts.  .

Please be aware that small differences between your answers and mine are most likely due to using differently rounded values for molar masses, etc.  (But, please let me know if I’ve made errors with typos, calculations, sig figs, etc.)

1. How many molecules or atoms of each substance are present in the following samples?  Be sure to include the correct labels with your answers.

a)  0.0012 moles of aluminum          b)  1.7 moles of ammonia                  c)  8.8 moles of octane, C8H18

2.  How many moles of each substance are contained in the following samples?  Be sure to include the correct labels as part of your answer.

a)  5.0E20 atoms of carbon, C    b)  1.709E13 molecules of oxygen, O2      c)  1E35 molecules of methane, CH4

3.  Determine the molar mass of each of the following substances, rounded to a whole number:

a) gold, Au        b)  C2F2Cl4   c) chlorine atoms  d)  chlorine molecules

4.  What is the mass, in grams (g), of the given amounts of the following substances?

a) 0.116 moles of gold    b)  1.5 millimoles of sulfur           c) 1.41 moles of octane, C8H18   d)  4.8 moles of sodium hydroxide

5.  Calculate the number of C atoms in each sample: a) 25.0 g of C  b)  0.688 mol of CO2  c)  0.275 kg C3H8  d)  7.5E24 molecules C2H4

6. How many moles of each substance are present in each of the following?

a)  5.6 kg of  NaOH     b) 30. mg of gold       c)  0.00500 g of sodium chloride    d) 2.5 kg of lead

7.  a)  How many oxygen atoms are present in 2.50 moles of oxygen atoms?   b)  How many oxygen atoms are present in 2.50 moles of oxygen molecules

8.  How many oxygen atoms are present in 40.0 grams of oxygen gas?

9.  How many millimoles (mmol) of each substance are contained in the following samples?  Be sure to include the correct labels as part of your answer.

a)  6.0E20 molecules of carbon dioxide    b)  7.409E13 molecules of water      c)  5E46 molecules of methane

10. Calculate the number of nanomoles of each substance in samples with the following masses:

a)  26.2 g of gold           b)  41.5 g of calcium  c)  49.2 mg of sulfur trioxide      d)  7.44E4 kg of lead(IV) oxide   e)  7.44E4 kg of plumbic iodide

11.  Calculate the number of grams of each substance contained in the following amounts:

a)  1.1 kmol of iron        b)  0.0563 Mmol of nickel   c)  2.50 cmol aluminum triiodide    d)  5E-3 µmol of benzene, C6H6

12. You have 1.50 grams of silver.  How many silver atoms do you have?

13. A typical balloon will hold about 2.69E22 molecules of hydrogen (H2).  What mass of hydrogen gas does the balloon hold?

14. Calculate the number of grams of each substance contained in the following amounts:

a)  2.00 mol of iron        b)  0.521 mol of nickel   c)  1.50 mol AlI3    d)  1.91E-3 mol of benzene, C6H6

15.  How many mol of a sample of xenon has the same number of particles as 7.5E10 molecules of C6H6?

16.  Many non-prescription pain relievers contain ibuprofen (C13H18O2), which in higher doses is a prescription drug (Motrin).  If all of the tablets in a bottle of pain reliever contain a total of 0.082 mol of ibuprofen, what is the total number of grams of ibuprofen present in the tablets?

17.  How many mol of ammonia has the same number of particles as 5.00 g of aluminum?

18.  How many grams of methane has the same number of particles as 12.30 g of iodine?

19. You have 10.0 g of aluminum and 73.0 g of gold.  Which sample contains more total atoms, the aluminum or gold?

20.  What is the density (in g/mL) of a sample of C9H20 if 9.4E23 molecules occupy a volume of 2.34E5 µL?

21.  A 45.0 g sample of (NH4)3AsO3 contains how many H atoms?

22.  How many atoms (regardless of type) are there in 0.196 kg of H2SO4?  How many grams do 3.01E24 molecules of sulfuric acid weigh?

23.  Which of the following samples weighs the most:  A sample containing 0.082 mol of water or a sample containing 3.01E21 molecules of sulfuric acid?

24.   The density of bromine is 3.10 g/mL.  How many liters of bromine must you take to have 2.11E22 molecules?

25.  What is the price for a million atoms of Pt, given that a cube of platinum 1.0 inch on an edge costs \$550?  The density of Pt is 22.0 g/mL.

26.  A compound is 63.97% carbon, 5.11% hydrogen, 20.26% bromine, and the rest is nitrogen. What is the EF and MF for this compound?

27.  If you rub a piece of gold, Au, vigorously, you can rub off 2.00 moles of gold atoms in a century.  How many minutes are needed to rub off 1.50 micrograms of gold?

28. Rating 2: Formic acid is responsible for the sting you feel when stung by fire ants.  By mass, formic acid is 26.10% C, 4.38% H, and 69.52% O.  The molar mass of formic acid is 46.02 g/mol.  Find the molecular formula of formic acid and draw its Lewis structure.   (Note: Lewis Structure is not covered until Chap J)

1.  a) 7.2E20 atoms of Al              b) 1.0E24 molecules of NH3             c) 5.3E24 molecules of octane

2.  a) 8.3E-4 moles of carbon atoms (C)  b) 2.838E-11 moles of oxygen molecules (O2)   c) 2E11 moles of methane molecules (CH4)

3.  a) 197 g/mol             b)  204 g/mol                 c) Cl = 36 g/mol                    d)  Cl2 = 71 g/mol

4.  a) 22.9 g of gold                   b)  0.048 g of sulfur       c) 161 g of octane         d)  1.9E2 g of NaOH

5.   a) 1.25E24 atoms C             b)  4.14E23 atoms C                   c) 1.13E25 atoms C                      d)  1.5E25 atoms C

6.  a)  140 moles of NaOH         b) 1.5E-4moles Au        c)  8.55E-5 moles of NaCl         d) 12 moles Pb

7. a)  1.51E24 atoms of O   b)   3.01E24 atoms of O

8.  1.51E24 atoms of O

9.  a) 1.0 mmol      b) 1.230E-7 mmol     c) 8E25 mmol

10. a)  1.33E8 nmol Au    b)  1.04E9 nmol Ca     c)  6.14E5 nmol SO3   d)  3.11E14 nmol PbO2   e)  1.04E14 nmol PbI4

11.  a) 6.1E4 g    b)  3.30E6 g     c)  10.2 g   d)  4E-7 g

12. 8.37E21 atoms

13.  0.0902 grams of hydrogen

14. a)  112 g Fe    b)  30.6 g Ni     c)  612 g    d)  0.149 g

15.  1.2E-13 mol

16.  17 grams of ibuprofen

17.  0.185 mol

18.  0.7778 g

19. Both contain the same number of atoms, 2.23E23 atoms

20.   0.86 g/mL

21.  1.84E24 atoms H

22.  8.42E24 atoms, 4.91E2 grams H2SO4

23.  The water sample  (1.5 g H2O vs. 0.490 g H2SO4)

24.  1.81E-3 L bromine

25.  4.9E-16 dollars (corresponds to just 3.2E-16 g Pt!)

26.  C21H20BrN3

27.  0.200 min