Unit 9 Stoichiometry

formula mass Atomic Mass Unit (u): unit of mass for measuring atoms. (1 u = 1/12th the mass of a carbon – 12 atom)

formula mass

formula mass Example 2: Find the mass of one molecule of Acetic acid (HC2H3O2).

Formula mass Example 3: Find the formula mass of on molecule of magnesium phosphate.

Formula Mass Example 4: Find the mass of one molecule of copper (II) sulfate pentahydrate.

Percent Composition

Percent composition Example 2: What is the percent composition by mass of magnesium in Mg3(PO4)2?

Percent composition Example 3: What is the percent by mass of water present in 1.0 mol of MgCl2 • 6H2O

Percent Composition Example 4: A student obtained the following data to determine the percent by mass of water in a hydrate. Calculate the percent by mass of the water in the hydrated salt. Mass of empty crucible + cover ………………………………….15.5 g Mass of crucible + cover + hydrated salt ……………………….18.3 g Mass of crucible + cover + anhydrous salt ……………………..17.8 g

Empirical & Molecular Formulas

Empirical & molecular formulas Example 1: Circle the empirical formulas in the list below; put an “X” over the molecular formulas. C2H4 HCl CH4 NO2 C3H9 C5H9 PCl4 P2O4 C6H12O6 C12H22O11

Empirical & molecular formulas Example 1: Circle the empirical formulas in the list below; put an “X” over the molecular formulas. C2H4 HCl CH4 NO2 C3H9 C5H9 PCl4 P2O4 C6H12O6 C12H22O11

Empirical & molecular formulas Example 2: For the following, give the empirical formula. N2O4_________ C6H12O6 ________ C4H8O2 __________ C3H9 __________ C5H20 __________ C2H4 __________

Empirical & molecular formulas Example 2: For the following, give the empirical formula. N2O4_________ C6H12O6 ________ C4H8O2 __________ C3H9 __________ C5H20 __________ C2H4 __________

Empirical & Molecular Formulas Example 3: A compound has the empirical formula of NO . If the molecular mass of this compound is 138.0 g/mol, what is the molecular formula of the compound?

Empirical & Molecular Formulas Example 4: A compound has a molar mass of 120 g/mol and an empirical formula of CH2O. What is the molecular formula of this compound?

The mole Reflect: What do the terms dozen, gross, and ream have in common?

The Mole Mole: Amount of substance Stands for a number = 6.02 x 1023 (just as a dozen = 12, a gross = 144, etc) The mole allows us to compare numbers of particles (which may have different masses)

The Mole A mole of donuts = ____6.02 x 1023____donuts A mole of baseballs = ____6.02 x 1023___baseballs A mole of jelly beans = ___6.02 x 1023__ jelly beans

Ted Talk: How Big is a Mole? http://www.wimp.com/howbig/

The Mole

The Mole

The Mole

The Mole

Mole Conversions: 1 - Step Reflect: How many seconds are in 2 minutes? What did you need to solve that problem?

Mole Conversions: 1 – Step

Mole Conversions: 1 - Step The Mole 1 mole = Gram Formula Mass 1 mole = 6.02 x 10 23 1 mole = 22.4 Liters of a gas The mole establishes the relationship between the gram and atomic mass unit.

Mole Conversions: 1 - Step Directions: Complete each of the following mole conversions showing your work and labeling ALL numbers! Example 1: If you have 11.2 g of NaCl, how many moles do you have?  

Mole Conversions: 1 - Step Example 2: How many grams are in 2.50 moles of NaCl?

Mole Conversions:1 - Step Example 3: How many molecules in 2 moles of water? Example 4: How many moles are in 1.81 x 1024 formula units of zinc nitrate?

Mole Conversions: 1 - Step Example 5: How liters are in 4 moles of carbon dioxide gas? Example 6: How many moles are in 56 liters of ammonia gas?

Mole Conversions: 1 - step Avogadro’s Law: Equal volumes of a gas will contain the same number of particles. 1 mole of any gas = 22.4 Liters (molar volume)

Mole Conversions: 2 - Step Reflect: Look at the mole map in your notes. If I want to find out how many atoms are in a ten gram piece of copper wire, how many steps must I take?

Mole Conversions: 2 – Step Example 1: How many grams are in 7.2 x 1022atoms of Ca?

Mole Conversions: 2 – Step Example 2: How many sucrose molecules in 250 grams of sucrose? (Sucrose = C12H22O11)

Mole Conversions: 2 – Step Example 3: What is the volume of 4.00 x 1024 molecules of methane (CH4)?

Mole Conversions: 2 – Step Example 4: What is the mass of 64.5 liters of oxygen gas?

Mole Calculations: 2 – Step Example 5: How many grams are in 13 L of carbon dioxide?

Mole Calculations: 2 – Step Example 6: What is the volume, in liters, of 35.6 g of NH3 ?

Mole – Mole Reflect: If it takes 2 pieces of bread, 1 piece of cheese, 1 piece of ham, and 3 pieces of lettuce to make one sandwich… 2 Bread + 1 Cheese + 1 Ham + 3 Lettuce  1 Sandwich How many sandwiches could I make with 4 pieces of bread? How many pieces of cheese would I need to use up 6 slices of bread?

Mole – Mole

Mole to Mole Practice Problem 1: In the following equation, how many moles of HCl are needed to react with 2.3 moles of Zn? 2HCl + Zn --------> ZnCl2 + H2

Mole to Mole Practice Problem 2: In the following equation, how many moles of oxygen are needed to burn 0.52 moles of magnesium? 2 Mg + O2 -----------> 2 MgO

Mole to Mole Practice Problem 3: How many moles of Al(NO3)3 will be produced when 0.75 mole of AgNO3 reacts according to the following equation: AgNO3 + Al --------------> Al(NO3)3 + Ag

Mole - Mole Practice Problem 4: The Haber Process is shown below. How many moles of ammonia will be produced when 6 moles of hydrogen react according to the unbalanced equation below? (Hint: balance!) N2 + H2  NH3

Volume – Volume

Volume – Volume Practice Problem 5: If 0.38L of hydrogen gas reacts with chlorine gas, what volume of HCl gas will be produced?     H2 + Cl2  2HCl

Volume – Volume Practice Problem 6: If 2.51 L of water vapor decomposes, what volume of hydrogen gas will be produced?    2H2O  2H2 + O2

Volume – Volume Practice Problem 7: What volume of nitrogen gas will be consumed if 20.2 L of ammonia gas is produced? N2 + 3H2  2NH3

Mass to Mass MOLES Mass Particles Volume 6.02 x 1023 particles Molar mass 1 Mole Mole Ratio

Mass to Mass Practice Problem 1: Powdered Al reacts with iron (III) oxide to produce aluminum oxide and molten iron. What mass of aluminum oxide is produced when 2.3 grams of aluminum reacts with iron (III) oxide? 2Al + Fe2O3 -------------> 2Fe + Al2O3

Mass to Mass Practice Problem 2: What mass of NaOH is produced when 0.25 grams of Na reacts with water according to the following equation? 2Na + 2H2O ---------------> 2NaOH + H2

Mass to Mass Practice Problem 3: In the following chemical equation you are given 125 grams of sodium azide. What volume of nitrogen gas is produced at STP? 2NaN3 ---------------> 2Na + 3N2 (g)

Mass to Volume Practice Problem 4: Find the mass of Al required to produce 1.32 L of hydrogen gas at STP from the balanced chemical equation below: 2Al + 3H2SO4 ---------------> Al2(SO4)­3 + 3H2 (g)

Mass to Volume Practice Problem 5: If 0.38L of hydrogen gas reacts with chlorine gas, what mass of HCl gas will be produced? H2 (g) + Cl2 (g) ----------------> 2HCl (g)