UNIT 4CHEMICAL REACTIONS: THE MOLE, STOICHIOMETRY AND THERMODYNAMICS
Part A: The Mole
Big Picture Ideas:
  1. The mole is a unit of count.
  2. Using conversion factors, one can convert between mass, moles, particles and volume for a given substance.
  3. Empirical data including percent composition can be used to determine chemical formulas.
Big Picture Questions:
  1. How do chemists count particles?
  2. How do chemists convert between mass, moles, particles and volume for a given substance?
  3. How do chemists determine chemical formulas?

Suggested Resources
Homework Assignments
Classwork Assignments
Laboratory Activities
Formative Assessments
Textbook pages: Chapter 10
Websites:

Key Terms

  1. mole
  2. Avogadro’s number
  3. atomic mass
  4. formula mass
  5. molecular mass
  6. molar mass
  7. molar volume
  8. percentage composition
  9. empirical formula
  10. molecular formula
  11. STP conditions

CALCULATING MOLAR MASS OF COMPOUNDS

  1. sodium hydroxide
  1. calcium cyanide
  1. magnesium phosphate
  1. iron(III) dichromate

PERCENT COMPOSITION

  1. Find the percent composition of calcium cyanide

Formula: ______

% Ca = ______

% C = ______

% N = ______

How many grams of calcium are in 40.0g of calcium cyanide?

  1. Find the percent composition of magnesium phosphate

Formula: ______

% Mg = ______

% P = ______

% O = ______

How many grams of magnesium are in 350g of magnesium phosphate?______

**What mass of magnesium phosphate contains 15g of magnesium?______

TRY

  1. Find the molar mass of each compound below
  1. lithium carbonate______
  1. calcium nitrate______
  1. tin (IV) sulfate______
  1. Find the percent composition of tin (IV) sulfate

% Sn = ______

% S = ______

% O = ______

How many grams of tin are in 250g of tin (IV) sulfate?

MOLECONVERSIONS

  1. Find the molar mass of each compound below
  1. diphosphorus pentoxide______
  1. copper (II) sulfate______
  1. calcium cyanide______
  1. aluminum nitrate______

MOLE CONVERSIONS

6.02 x 1023 molecules = 1 mole

6.02 x 1023 formula units = 1 mole

molar mass in grams = 1 mole

  1. Find the mass of 4.50moles of diphosphorus pentoxide______
  1. How many moles is 250.0g of copper (II) sulfate?______
  1. Find the mass of 0.545moles of calcium cyanide______
  1. How many molecules are in 110g of diphosphorus pentoxide?______

Make the following mole conversions.

STEP 1: Write the correct formula

STEP 2: Determine the molar mass

STEP 3: Use dimensional analysis to convert

  1. 575g of sodium sulfate to moles______
  1. 0.025moles of phosphorus pentachloride to grams______
  1. 15.0g of iron(III) nitrate to moles______
  1. 8.02 x 1023 molecules of carbon disulfide to grams______

MOLES AND VOLUME

Avogadro’s hypothesis:

STP:

Make the following mole conversions.

  1. 14.0L of nitrogen gas at STP to moles
  1. 2.5g of chlorine gas at STP to molecules
  1. 2.24 x 1025 atoms of neon at STP to liters
  1. 13.3L of fluorine gas at STP to grams

EMPIRICAL AND MOLECULAR FORMULAS

a.Find the percent composition of C2H4

%C = ______

%H = ______

  1. Find the percent composition of C5H10

%C = ______

%H = ______

empirical formula: ______

molecular formula: ______

Determine the empirical formula of each compound below

a. P4O10b. C6H12O6c. C3H6O

  1. The empirical formula of a compound is CH2O. Its molar mass is 360g/mol. Find its molecular formula.
  1. The empirical formula of a compound is P2O5. Its molar mass is 284g/mol. Find its molecular formula.

HOMEWORK - MOLAR MASS AND% COMPOSITION PRACTICE PROBLEMS

  1. Label each compound below as ionic or covalent. Write the formula and determine the molar mass of each compound.

compound / ionic/
covalent? / formula / molar mass
barium sulfate
tricarbon octahydride
iron (III) carbonate
tetraphosphorus decoxide
strontium phosphate
  1. Find the percent composition of iron (III) carbonate.

% Fe =

% C =

% O =

  1. How many grams of iron are in 125 g of iron (III) carbonate?
  1. What mass of iron(III) carbonate contains 10.0 g of iron?

HOMEWORK - PERCENT COMPOSITION

Determine the percent composition of each of the compounds below:

  1. KMnO4

% K = ______

% Mn = ______

% O = ______

  1. HCl

% H = ______

% Cl = ______

  1. Mg(NO3)2

% Mg = ______

% N = ______

% O = ______

  1. (NH4)3PO4

% N = ______

% H = ______

% P = ______

% O = ______

  1. Al2(SO4)3

% Al = ______

% S = ______

% O = ______

Solve the following problems

  1. How many grams of oxygen can be produced from the decomposition of 100g of KClO3?
  1. How much iron can be recovered from 25.0g of Fe2O3?
  1. How much silver can be produced from 125g of Ag2S?

HOMEWORK -PRACTICE CONVERSIONS

  1. Write the formula for each compound below. Then determine its molar mass.

formula / molar mass
calcium sulfate
aluminum cyanide
phosphorus triiodide
  1. Use the molar masses you found in # 1 to make the following conversions:
  1. Find the mass of 1.25moles of calcium sulfate.
  1. How many moles is 2.50 g of aluminum cyanide?
  1. Find the mass of 0.750 moles of phosphorus triiodide.
  1. How many molecules is 12.50 g of phosphorus triiodide?
  1. Find the number of formula units in 10.0g of calcium sulfate.

HOMEWORK - MIXED MOLE CONVERSIONS

  1. Convert the quantities below to moles
  1. 14.0g of lead______
  1. 20.5g of lithium hydroxide______
  1. 14.0L of oxygen gas at STP______
  1. Find the mass of
  1. 10.0L of hydrogen gas at STP______
  1. 3.21 x 1022 molecules of carbon tetrachloride______
  1. Find the empirical formula of each compound below
  1. C4H8b. C12H24O12c. Si3N4d. C4Cl10
  1. Find the molecular formula if the empirical formula is C3H8 and the molar mass is 132 g/mol.
  1. Find the molecular formula if the empirical formula is N2O5 and the molar mass is 216 g/mol.
    LAB: PERCENT SUGAR IN BUBBLE GUMNAME:

BACKGROUND: In this lab you are going to design and carry out an experiment to determine the percentage of sugar in bubble gum. To do so, you will assume that all of the flavoring removed from bubble gum during chewing is sugar. The chemical formula for sucrose, the sugar in bubble gum, is C12H22O11. After determining the percentage of sugar in bubble gum, you will then determine the mass of carbon and the number of carbon atoms in the sugar in a piece of bubble gum.

PROCEDURE: Write out the procedure you will follow in the space below. Include all details.

DATA: Set up a data table in the space below to record all necessary data.

CALCULATIONS: Show and explain all work. Calculations must be neat and easy to follow.

  1. mass of sugar in your piece of gum(show calculation!)
  1. mass of gum alone (without wrapper) (show calculation)
  1. average % sugar in bubble gum(show calculation based on your data!)
  1. % carbon in sugar (C12H22O11)(show calculation – use your class notes on % composition)
  1. mass of carbon in the sugar in your piece of bubble gum(show calculation, use class notes)

(HINT: How many grams of sugar were in your gum? What per cent of sugar is carbon?)

  1. atoms of carbon from the grams you calculated in “d”(show calculation, g carbon to atoms)

CONCLUSIONS:

  1. What did you learn from this experiment?
  1. List two sources of error and describe the effect each had on your results. (Would the error make the per cent sugar reported too high or too low and why).

a.

b.

1