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AP Chemistry Stoichiometry Review Pages Mass to Mass Stoichiometry Problem (Review)

Mass A ® Moles A ® Moles B ® Mass B Mass of given ® Amount of given ® Amount of unknown ® Mass of unknown in grams in Moles in moles in grams inverted molar mass Mole ratio molar mass (periodic table) (from the equation) (periodic table)

Mass given 1 mol given mol unknown mass unknown Mass in grams mol given 1 mol unknown = mass in grams of the unknown Given Conversion Factors Calculated Example: The combustion of Hydrogen occurs according to the following equation 2H2(g) + O2(g) ® 2H2O (g) If we react 64.0 g of Oxygen with excess Hydrogen, how many grams of water vapor will be produced? 64.0g O2 1mol O2 2mol H2O 18.02g H2O 32.00 g O2 1mol O2 1mol H2O

= 72.08 g H2O = 72.1 g H2O

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Limiting Reactants, Excess Reactants and Percent Yield

I. The Limiting Reactant is the reactant that limits the amount of the other reactant that can combine and the amount of product that can be formed in a chemical reaction

II. The Excess Reactant is the reactant that is not used up completely in a chemical reaction III. The Theoretical Yield is the maximum amount of product that can be produced from a given amount of reactant IV. The Actual Yield is the measured amount of product obtained from a chemical reaction V. The Percent Yield is the ratio of the actual yield to the theoretical yield multiplied by 100

Determining the Limiting Reactant Sample Problem

Silicon Dioxide reacts with Hydrofluoric acid according to the following equation. SiO2 (s) + 4HF(g) ® SiF4(g) + 2H2O(l)

If 6.0 moles of HF is reacted with 4.5 moles of SiO2, what is the limiting reactant and how many moles of SiF4 can be produced? To determine the limiting reactant, chose one of the reactants and perform a mole to mole stoichiometry problem to determine the amount of the other reactant needed

6.0 mol HF 1 mol SiO2 = 1.5 mol SiO2 4 mol HF The problem above shows that if 6.0 moles of HF is completely used up 1.5 moles of SiO2 will also be used. Are 1.5 moles of SiO2 available?

• Yes there are 4.5 moles of SiO2 available and only 1.5 moles would be used. • Therefore the limiting reactant is HF • The excess reactant is SiO2 •

Now use the limiting reactant to solve for the amount of SiF4 that can be produced

6.0 mol HF 1 mol SiF4 = 1.5 mol SiF4 4 mol HF

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Oxidation Numbers Review Pages • In order to indicate the general distribution of electrons among bonded atoms in

molecular compounds or polyatomic ions, oxidation numbers, also called oxidation states, are assigned to the atoms composing the compound or ion.

• Oxidation numbers are useful in naming compounds, writing chemical formulas and in the balancing of chemical equations

• We will use the following rules to assign oxidation numbers to atoms in compounds and polyatomic ions

Examples; Assign oxidation numbers to each atom in the following compounds or ions 1. UF6 U= ____+6____ F= ___-1_____ 2. SO4

-2 S= ____+6___ O= ___-2___ 3. Fe+3 Fe=_____+3___ 4. H2SO3 H= ___+1_ S= ___+4____ O= ___-2___

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Determining the Empirical Formula or Simplest Formula The empirical formula or simplest formula consists of the symbols for the elements combined, with the subscripts showing the smallest whole-number ratio of the atoms. • If the chemical compound is already expressed in whole numbers simply reduce them

to the smallest whole numbers Formula Empirical formula Examples C2H6 CH3 C6H10O4 C3H5O2

Determine the empirical formula of the following compounds I. 1. B2H6 _____________ 2. C12H22O2 ______________ 3. N2O4 _____________ 4. P4O10 _________________ When the compound contains the percent composition of the elements use the following method to determine the empirical formula Example Analysis shows a compound to contain 32.38% Na, 22.65% S and 44.99% O, Determine the empirical formula of the compound. Solution % composition → Composition in mass→ Composition in moles → Smallest whole number ratio of atoms Composition composition smallest whole number ratio By mass in moles 32.38g Na / 22.99g/mol = 1.408 mol Na 2 22.65 g S / 32.06 g/mol = 0.7065 mol S 1 44.99 g O / 16.00 g/mol = 2.812 mol O 4 Empirical formula _Na2SO4___

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Calculation of the Molecular Formula The empirical formula contains the smallest whole numbers that describe the atomic ratio. The molecular formula is the actual formula of the molecular compound. An empirical formula may or may not be the molecular formula. The molecule diborane has an empirical formula of BH3. The molecular formula may be any multiple of BH3, such as B2H6, B3H9, or even B4H12. The relationship between a compound’s empirical formula and its molecular formula is as follows.

x(empirical formula) = molecular formula The number represented by x is a whole number multiple indicating the factor by which the subscripts in the empirical formula must be multiplied to obtain the molecular formula. The formula masses (or the molar mass of the compound) have a similar relationship.

x(empirical formula mass) = molecular formula mass To determine the molecular formula, you must know the compound’s molar mass. For example experimentation shows the molar mass of the compound diborane to be 27.67 g/mol. The molar mass of the empirical formula BH3 is 13.84 g/mol. Dividing the experimentally determined molar mass by the empirical formula’s molar mass gives the following values.

x= 27.67g/mol = 2.000 13.84g/mol Therefore the empirical formula is multiplied by a factor of 2 (the value of x in this case) to achieve the molecular formula of diborane 2(BH3) = B2H6 This is the molecular formula of diborane.

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Polyatomic Ions needed for naming compounds

Negative ions 1. OH-1 Hydroxide ion 2. NO3

-1 Nitrate ion 3. NO2

-1 Nitrite ion 4. CO3

2- Carbonate ion 5. HCO3

- Hydrogen Carbonate ion (or Bicarbonate ion) 6. SO4

2- Sulfate ion (HSO4- is the hydrogen sulfate ion)

7. SO3

2- Sulfite ion (HSO3- is the hydrogen sulfite ion)

8. PO4

3- Phosphate ion (HPO42- is the monohydrogen phosphate ion)

(H2PO4- is the dihydrogen phosphate ion)

9. PO3

3- Phosphite ion (HPO32- is the monohydrogen phosphite ion)

(H2PO3- is the dihydrogen phosphite ion)

10. CrO42- Chromate ion

11. ClO3

- Chlorate ion 13. C2H3O2

- Acetate ion 14. MnO4

-1 Permanganate ion 15. CN-1 Cyanide ion 16. Cr2O7

-2 Dichromate ion 17. ClO4

-1 Perchlorate ion 18. S2O3

-2 Thiosulfate ion

Positive ion 1. NH4

+ Ammonium ion

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AP Chemistry Summer Review Assignment Please print out the following pages (from page 7 to the end) and complete by the first

day of classes in September Name _____________________________________________________________

Name the following compounds using the stock system of nomenclature

1. Ca(OH)2__________________________________

2. KNO2______________________________________

3. Fe2(SO3)3____________________________________

4. MgHSO4______________________________________

5. Co3N2__________________________________

6. MnSO3•4H2O ___________________________________________

7. KMnO4______________________________________

8. PbBr2____________________________________

9. SrCrO4___________________________________

10. Li2S____________________________________

Write the chemical formulas for the following compounds

1. Dinitrogen Tetroxide____________________________________ 2. Magnesium carbonate ______________________________

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3. Phosphorous pentabromide ____________________________________

4. Carbon tetrabromide________________________________

5. Copper(II) nitrite________________________________

6. Vanadium (V) sulfate ___________________________________

7. Sodium carbonate pentahydrate_____________________________________

8. Ammonium nitrate __________________________________

9. zinc nitride_____________________________________

10. Iron (II) sulfide _____________________________________

Assign oxidation numbers to each atom in the following compounds or ions

1. H2Se _________________________

2. SO3 __________________________

3. H2SO4 ___________________________

4. CO2 ___________________________

5. PBr3 ___________________________

6. I2 __________________________

7. CN- ___________________________

8. Fe+3 ___________________________

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Percent Composition Molar Mass and Empirical Formula Problems For one mole of the compound listed below

(show all work below) A. Determine the anion and the cation, the number of moles of each and indicate the

charge of each ion. B. Determine the number of moles of individual atoms C. Calculate the molar mass of the compound D. Determine the percent composition of each element. E. Name the compound using the stock system of nomenclature F.

The compound Mn3(PO4)2

(A.) Cation________Number of moles______,Anion________ Number of moles____

(B.) Moles of each atom (C.) Molar mass ______________

Mn______ (D.) Percent composition of each element (show all work below to 2 decimal places)

P_______ Mn___________%

O______ P_____________%

O_____________%

(E.) Name the compound using the stock system________________________________

Determine the mass in grams of the following

1. 8.65 x 105 Moles of Mn3(PO4)2

V. Determine the number of moles in the following

1. 3.87 x 10-5 g of Mn3(PO4)2

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Empirical and Molecular Formula Problems 1. Analysis shows a sample to contain 52.11% Carbon, 13.14% hydrogen, and

34.75% oxygen. Find the empirical formula for this compound.

a. Determine the molecular formula of a compound that has an empirical formula of CH2O and a molar mass of 120.12 g/mol

b. The empirical formula of a compound that contains only Carbon and Hydrogen is CH, what is the molecular formula of the compound if the molar mass of the molecular formula is 78.12 g/mol

c. What is the empirical formula for a compound that contains 1.20% H, 42.0%Cl, and 56.8% O?

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Stoichiometry problems 1. For the balanced reaction

SiO2(s) + 4HF ® SiF4 + 2H2O (a) Determine the mass in grams of SiF4 that can be produced if 10.0

moles of SiO2 is reacted with excess HF?

Answer_________________

(b) If 100.3 g of HF are reacted with 410.g of SiO2, what is the limiting

reactant? How many moles of SiF4can be produced? Determine the mass in grams of the excess reactant remaining upon completion of the reaction.

Limiting reactant_______________ Moles SiF4 ___________________

Mass of excess reactant___________

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The combustion of propane is carried out under the balanced equation C3H8(g) + 5O2(g) ® 3CO2(g) + 4H2O(g) (a) What mass in grams of propane (C3H8) is needed to produce 24.4g of CO2? Answer____________________ (b) How many moles of Propane can be reacted with 18.5 moles of O2?

Answer_____________________

(c) If 280.9 g of propane is reacted with 220.5g of oxygen, what mass of carbon dioxide can be theoretically produced?

Answer______________________

(d) If 153.9 g of Carbon Dioxide are actually produced from the reaction in (c), calculate the percent yield of the reaction

Answer_______________________

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4. Write the equation for the decomposition of potassium chlorate below and balance the equation. If 2.59 moles of potassium chlorate are decomposed, determine the number of moles of each product formed? Answer_______________________

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Solution Stoichiometry

Aqueous Lead(II) nitrate reacts with aqueous potassium iodide to form precipitated Lead(II) Iodide (a very nice yellow color) and aqueous potassium nitrate according to the balanced equation below Pb(NO3)2(aq) + 2KI(aq) → PbI2(s) + 2KNO3(aq) Write the net ionic equation for this reaction 250. mL of a 0.117 M Lead (II) Nitrate solution was mixed with 250.0 mL of a 0.200 M KI solution (a) What is the limiting reactant? (b) Determine the theoretical yield in grams of the precipitate from the above reaction (PbI2 461.00 g/mol) (c) What is the molarity of the excess reactant that remains when the reaction is complete (Assume the volumes are additive and no change in volume occurs when the precipitate is removed) Initial (mol)

Change (mol)

Equilibrium (mol)

Equilibrium (conc)

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Solution stoichiometry(cont) 1. Iron (III) Nitrate reacts with Sodium hydroxide according to the equation

listed below.

Fe(NO3)3(aq) + 3NaOH(aq) → Fe(OH)3 (s) + 3NaNO3 (aq) Write the net ionic equation If 200. mL of a 0.700 M iron nitrate solution is reacted with 100. mL of a 0.350 M sodium hydroxide solution, determine the following

a. The limiting reactant (Calculate the number of moles of each

reactant) b. The theoretical mass in grams of the precipitate that is

formed. [Fe(OH)3 = 106.88g/mol]

c. The molarity of the excess reactant that remain in solution (assume the volumes are additive)

Initial (mol)

Change (mol)

Equilibrium (mol)

Equilibrium (conc)

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Balance the following chemical equations 1. ______Al4C3 + _____H2O ® _____CH4 + _____Al(OH)3 2. ____Fe2O3 + ____CO ® ____ Fe + ____CO2 3. ____C8H18 + ____O2 ® ____CO2 + ____H2O 4. ____Fe (s) + ____H2O(g) ® ____ Fe3O4(s) + ____ H2(g) 5. ____Mg + ____Ag(NO3) ® ____Mg(NO3)2 + ____Ag 6. ____NH4Cl + ____ Ca(OH)2 ® ____NH3 + ___ H2O + ____ CaCl2

Complete each of the following synthesis reactions by writing both a word equation and a formula equation

1. Sodium reacts with Oxygen

2. Magnesium reacts with fluorine

3. Aluminum reacts with sulfur

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Complete and balance the following decomposition reactions

1. ____HgO (s) →

2. _____AlCl3(s) →

3. _____Al2(CO3)3(s) →

4. _____KClO3(s) →

Complete and balance the following single replacement reactions

1. ____Zn (s) + _____Pb(NO3)2(aq) → 2. _____Na (s) + _____H2O(l) → 3. _____Al (s) + ______NiSO4(aq) → 4. _____F2 (g) + ______ NaI (aq) →

Complete and balance the following double replacement reactions. You must use the correct symbols (in other words determine the precipitate).

For the word equations, write the correct chemical formulas for the reactants and then complete the reactions and balance

1. ____AgNO3 (aq) + ____ NaCl (aq) → 2. ____ Mg(NO3)2 (aq) + ____ KOH (aq) → 3. Aqueous sodium hydroxide reacts with Iron(III) Nitrate 4. Aqueous aluminum sulfate reacts with aqueous calcium nitrate

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Complete and balance the following combustion reactions

1. _____C2H5OH (l) + _____O2(g) → 2. _____ C10H22 (l) + _____ O2 (g) →

Determine the type of chemical reaction for the following

(Synthesis, decomposition, single-replacement, double-replacement or combustion)

1. 2KClO3(s) ® 2KCl(s) + 3O2(g)____________________________________

2. Zn(s) + CuSO4(aq) ® ZnSO4(aq) + Cu(s)___________________________

3. Pb(NO3)2(aq) + 2KI(aq) ® PbI2(s) + 2KNO3(aq)_________________________

4. H2O(l) + SO3(g) ® H2SO4(g)____________________________________

5. C3H8(g) + 5O2(g) ® 3CO2(g) +4H2O(g)________________________