Unit 3 - Mole Concept Review Sheet

Note: The best way to review this unit is to do as many practice problems as possible. This sheet will get you started, but there are many more practice problems throughout Unit V of your textbook!

Part A - Mole Calculations

  1. How many atoms are there in 10 molecules of Co(ClO4)2·6H2O?
  2. How many molecules are there in 75.0 g of sugar (C12H22O11)?
  3. What is the volume occupied by 10.0 g of H2S(g) at STP?
  4. What is the mass of 1 atom of Au?
  5. How many moles are in 1.00 mL of O3(g) at STP?
  6. What is the molar mass of a substance if 0.179 mol of it has a mass of 74.0 g?
  7. How many moles are contained in 1.25 mL of CS2(l) if it has a density of 1.26 g/mL?
  8. What is the density of CuSO4·5H2O if 0.0275 mol of it has a volume of 3.01 mL?
  9. How many moles are in 25.0 mL of HCN(g) at STP?
  10. What is the mass of 25.0 mL of Kr(g) at STP?
  11. What is the molar mass of a subatomic particle with a mass of 9.11x10-28 g?
  12. What is the mass of 2.50 L of PF5(g) at STP?
  13. What is the density of C4H8(g) at STP?
  14. How many molecules are there in 5.00 g of OF2(g)?
  15. What is the volume of 0.0694 mol of molybdenite, MoS2, which has a density of 4.80 g/mL?
  16. What is the molar volume of mercury? (density = 13.55 g/mL)

Part B - Percentage Composition

  1. Calculate the percentage composition of NaOH.
  2. Calculate the percentage composition of (NH4)2Sn(OH)6.
  3. Calculate the percentage of water in Al2(SO4)3·18H2O.
  4. Calculate the percentage of water in Cr(NH3)6Cl3·H2O.

Part C - Empirical and Molecular Formulae

  1. Find the empirical formula for a compound containing 3.66% H, 37.8% P, and 58.4% O.
  2. A gas has the empirical formula CH2. If 0.500 L of the gas at STP has a mass of 0.938 g, what is the molecular formula of the compound?
  3. A gas sample is analyzed and found to contain 33.0% Si and 67.0% F. If the gas density is 7.60 g/L at STP, what is the molecular formula of the gas?

Part D - Molarity Calculations

  1. 184.6 mg of K2CrO4 is dissolved in enough water to make 500.0 mL of solution. What is the molarity of the solution?
  2. How much solid NaCl would you need to make 1.00 L of 0.100 M NaCl solution?
  3. What is the concentration of the solution produced when 125 mL of 3.55 M LiOH is mixed with 475 mL of 2.42 M LiOH?
  4. What is the molarity of the solution produced when 150.0 mL of 0.325 M LiBr and 225.0 mL of 0.500 M LiBr are mixed, and then the solution is boiled down to 275.0 mL?
  5. What mass of solid solute is dissolved in 350.0 mL of 0.250 M NaCl?
  6. What is the molarity of pure C8H18 if its density is 0.7025 g/mL?
  7. What is the density of pure C6H5CHO if its molarity is 9.825 M?
  8. A solution is made in such a way that when 100.0 mL of the solution is diluted to 5.00 L, the resulting mixture has a concentration of 0.100 M. What is the molarity of the original solution?
  9. What volume of 0.550 M HCl contains 50.0 g of HCl?
  10. What is the concentration of CaCl2 produced by mixing 145 mL of 0.550 M CaCl2 with 55 mL of 0.135 M CaCl2?

Answers

Part A: 1. 290, 2. 1.32x1023 molecules, 3. 6.57 L, 4. 3.27x10-22 g, 5. 4.46x10-5 mol, 6. 413 g/mol, 7. 0.0207 mol, 8. 2.28 g/mL, 9. 1.12x10-3 mol, 10. 0.0935 g, 11. 5.48x10-4 g/mol, 12. 14.1 g, 13. 0.00250 g/mL, 14. 5.57x1022 molecules, 15. 2.31 mL, 16. 0.01480 L/mol

Part B: 1. 57.5% Na, 40.0% O, 2.5% H, 2. 10.9% N, 5.4% H, 46.2% Sn, 37.4% O, 3. 48.6%, 4. 6.46%

Part C: 1. H3PO3, 2. C3H6, 3. Si2F6

Part D: 1. 1.901x10-3 M, 2. 5.85 g, 3. 2.66 M, 4. 0.586 M, 5. 5.12 g, 6. 6.162 M, 7. 1.041 g/mL, 8. 5.00 M, 9. 2.49 L, 10. 0.436 M