Classwork #1 – Molar Mass Problems

Directions: Calculate the molar mass of each compound. All answers must have the correct significant figures and a unit for full credit.

  1. Cl29. H3PO4
  1. KOH10. (NH4)2SO4
  1. BeCl211. Pb(NO3)2
  1. FeCl312. Ge2(SO3)3
  1. CClF213. Cu3(PO4)2
  1. BF314. Mn(ClO2)3
  1. Mg(OH)215. NaHCO3
  1. UF6

CW #2 – Mass – Mole Calculations

Directions: Use the relationship between mass and moles to calculate the answers to the following problems. All answers must have the correct significant figures and a unit for full credit.

  1. How many grams are in 30.0g of H3PO4?
  1. How many moles are in 4.00mol of Cu(CN)2?
  1. How many grams are in 25.0g of HF?
  1. How many moles are in 5.60mol of C6H6?
  1. What is the mass, in grams, of 21.30mol of BaCO3?
  1. How many moles are in 1.10g of Ra(OH)2?
  1. What is the mass, in grams, of 1.2mol of (NH4)3PO3?
  1. How many moles are in 967g of CO2?
  1. What is the mass, in grams, of 9.30 × 10-3mol of K2SO4?
  1. How many moles are in 12.30g of ZnO?

CW #3 – Moles and Molecules Problems

Directions: Use the relationship between atoms/molecules/formula units and moles to solve these problems. All answers must have the correct significant figures and a unit for full credit.

  1. How many atoms are in 2.0 moles of He gas?
  1. How many moles are in 3.01 × 1024 atoms of gold, Au?
  1. How many molecules are in 0.75 moles of H2O?
  1. How many moles are in 4.21 × 1022 formula units of iron (II) nitrate, Fe(NO3)2?
  1. How many formula units are in 120.60 moles of magnesium chloride, MgCl2?
  1. How many moles are in 8.40 × 1023 molecules of sulfur trioxide?
  1. How many molecules are in 50.0 moles of nitric acid?
  1. How many moles are in 6.95 × 1020 formula units of potassium sulfide?

CW #4 – The Mole and Volume of a Gas at STP

Directions: Use the relationship between the moles and the volume of a gas at standard temperature and pressure to calculate the following problems. All answers must have the correct significant figures and a unit for full credit.

  1. How many moles are in 13.0 L of SO3 gas at STP?
  1. What is the volume of 40.0 mol of O2 gas at STP?
  1. How many moles are in 0.99 L N2O gas at STP?
  1. What is the volume of 1.75 mol of CO2 gas at STP?
  1. How many moles are in 14.5 L of NH3 gas at STP?
  1. What is the volume of 111.0 mol of ozone, O3 at STP?

Challenge Problems

  1. What is the volume of 6.64 × 1024 molecules of He gas at STP?
  1. What is the mass, in grams, of 25.0 L of argon gas at STP?

CW #5 – Combined Mole Problems

Directions: Use your knowledge of mole relationships to solve these problems. All answers must have the correct significant figures and a unit for full credit.

  1. What is the mass, in grams, of 4.44 × 1021 formula units of Li2O?
  1. How many molecules are in 100.0g of Mg(OH)2?
  1. What is the mass of 65.10 L of ammonia (NH3) gas at STP?
  1. What is the volume, in liters, of 33.3 g of F2 gas at STP??
  1. How many molecules are in 75.0L of Ne gas at STP?
  1. What is the volume of 5.15 × 1024 molecules of ozone (O3) at STP?

CW $6 - % Composition

Directions: Determine the % by mass of each element in the compound.

  1. CuBr2
  1. H2O
  1. Ba(NO3)2
  1. (NH4)2SO4
  1. H2CO3

Challenge Problems

  1. Lithium phosphate
  1. Aluminum oxalate
  1. Gold (III) cyanide
  1. Lead (II) oxide
  1. Hydrochloric acid

CW #7 – Empirical and Molecular Formulas

Directions: Determine the empirical and/or molecular formula using the following data.

  1. Determine the empirical formula for the following molecular formulas:
  2. H2O2
  3. C2H6
  4. H2S
  5. K2C2O4
  6. C4H10
  1. Determine the empirical formula for a substance that is 75% carbon and 25% hydrogen.
  1. Determine the empirical formula for a substance that is 52.7% potassium and 47.3% chlorine.
  1. Determine the empirical formula for a substance that is 22.1% aluminum and 25.4% phosphorous, and 52.5% oxygen.
  1. Calculate the empirical formula for a substance that is 32.4% sodium, 22.5% sulfur, and 45.1% oxygen.
  1. The empirical formula of a compound is NO2, its molecular mass is 92g/mol. What is its molecular formula?
  1. The empirical formula of a compound is CH2, its molecular mass us 70g/mol. What is its molecular formula?
  1. A compound is found to be 40.0% carbon, 6.7% hydrogen, and 53.5% oxygen. Its molecular mass is 60. g/mol. What is its molecular formula?
  1. A compound is found to be 64.9% carbon, 13.5% hydrogen, and 21.6% oxygen. Its molecular mass is 74 g/mol. What is its molecular formula?
  1. A compound is 54.5% carbon, 9.1% hydrogen, and 36.4% oxygen. Its molecular mass is 88 g/mol. What is its molecular formula?

HW – The Mole

***FOR ALL CALCULATIONS, SHOW YOUR WORK AND INCLUDE UNITS & SIG FIGS***

Part A – Molar Mass

  1. Calculate the molar mass for each of the following compounds. Include units!

calcium nitrate / Formula: / lead(II) iodide / Formula:
Molar mass: / Molar mass:

Part B – Molar Conversions (Show your work and include units!)

  1. How many moles of ammonia are in 1.20  1025 molecules of ammonia?

Formula: / Molar mass:
Answer:
  1. You need 2.5 moles of aluminum for an experiment. How many atoms of aluminum is this?

Formula: / Molar mass:
Answer:
  1. 380 g of sucrose (C12H22O11) are required to make 2 quarts of Kool-Aid. How many molecules of sucrose are used in this recipe?

Formula: / Molar mass:
Answer:
  1. There are 3.20  1022 atoms of copper in the outer shell of pennies. How many grams of copper is this?

Formula: / Molar mass:
Answer:
  1. If you pump 40.88 kg of octane (C8H18) into your gas tank, how many molecules of octane are you pumping?

Formula: / Molar mass:
Answer:

Percent Composition and Molecular Formula Worksheet

1)What’s the empirical formula of a molecule containing 65.5% carbon, 5.5% hydrogen, and 29.0% oxygen?

2)If the molar mass of the compound in problem 1 is 110 grams/mole, what’s the molecular formula?

3)What’s the empirical formula of a molecule containing 18.7% lithium, 16.3% carbon, and 65.0% oxygen?

4)If the molar mass of the compound in problem 3 is 73.8 grams/mole, what’s the molecular formula?

5)A well-known reagent in analytical chemistry, dimethylglyoxime, has the empirical formula C2H4NO. If its molar mass is 116.1 g/mol, what is the molecular formula?

6)A sample of indium chloride weighing 0.5000 g is found to contain 0.2404 g of chlorine. What is the empirical formula of the indium compound?

7)An unknown compound was found to have a percent composition as follows:
47.0 % potassium, 14.5 % carbon, and 38.5 % oxygen. What is its empirical formula? If the true molar mass of the compound is 166.22 g/mol, what is its molecular formula?