Chapter 10 CHEMICAL QUANTITIES The MOLE Avogadro s Hypothesis Equal volumes of gases (@ same T and p) have the same # molecules. The number of 12 C atoms in 12.00 grams of carbon is called Avogadro s Number = 6.02(10) 23 This quantity is called a MOLE (Just as a dozen = 12) 1 mole = 6.02(10) 23 particles [ atoms / molecules / formula units ] STP: Standard Temperature and Pressure 0 o C 1 atm At STP... 1 mole = 22.4 L for any gas. CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 1
gram atomic mass - MOLAR MASS of atoms gram molecular mass - MOLAR MASS of molecules gram formula mass - MOLAR MASS of ionic cmpd. MOLAR MASS: The mass of one mole of a substance. It is found by adding the molar masses of each individual element proportionally (using the Periodic Table as a reference). Ex: Atom or Molecule or Formula Unit Atomic or Molecular or Molar Formula Mass Mass He 1(4.0) = 4.0 amu 4.0 g O2 2(16.0) = 32.0 amu 32.0 g H2O 2(1.0) + (16.0) = 18.0 amu 18.0 g MgCl2 (24.3) + 2(35.5) = 95.3 amu 95.3 g Ca(NO3)2 (40.1)+2(14.0)+6(16.0)= 164.1 amu 164.1g 1 mole = [Periodic Table] g CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 2
1 mole = 6.02(10)23 particles 1 mole = [Periodic Table] grams 1 mole = 22.4 L of gas @ STP Practice: 1.5 mol CO2 L CO2 (@STP) 1.5 mol CO2 grams CO2 1.5 mol CO2 molecules CO2 11.2 L CO2 (@STP) g CO2 110. g CO2 molecules CO2 2.00(10)23 molecules CO2 L CO2 (@STP) CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 3
% Composition is by MASS (Grams) Ex. Finding % Composition from empirical formula methane CH4 carbon hydrogen mass C = 12.0 g x 100 = 75.0% C mass CH4 16.0 g mass H = 4.0 g x 100 = 25.0 % H mass CH4 16.0 g Empirical formula is by MOLES Ex. Find empirical formula of a compound that is 75.0% C and 25.0% H by mass. Assume 100.0 grams of the compound: 75.0 g C x 1 mol = 6.25 mol C 1 12.0 g 25.0 g H x 1 mol = 25.0 mol H 4 1.0 g CH4 CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 4
Molecular Formulas Simplest Empirical Formula Real Life Molecular Formula Hydrates: Composed of a salt and water CuSO4 5H2O mass of Salt + mass of H2O = mass of hydrate Find % H2O Find grams of water in a 8.88 g sample of CuSO4 5H2O Find Empirical Formula of hydrate from sample data CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 5
ws Molar Mass Formula 1 NaCl 2 CaBr2 3 K2SO4 4 Mg(NO3)2 5 KMnO4 6 CuSO4 5H2O 7 Na2CrO4 8 LiBrO3 9 Zn3(PO4)2 4H2O 10 Mg3(PO4)2 11 MgSO4 7H2O 12 (NH4)2SO4 13 Cu(OH)2 14 CaCO3 15 NaOH 16 NH4Cl 17 KCl 18 K3PO4 19 NH4OH 20 Ba(C2H3O2)2 Molar Mass Sol Insol Name CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 6
ws Moles and Particles (using Avogadro s Number) 1. How many molecules are in 3.5 moles H2O? 2. How many atoms are in 1.5 moles of Ne? 3. How many formula units are in 2.25 moles of NaCl? 4. How many molecules are in 0.50 moles of C6H12O6? 5. How many moles are in 3.01(10) 23 molecules of H2O? 6. How many moles are in 3.01(10) 23 atoms of Ne? 7. How many moles are in 9.03(10) 23 formula units of NaCl? 8. How many moles are in 2.01(10) 24 molecules of C6H12O6? CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 7
ws Moles and Mass (Using the Periodic Table) 1. How many grams are in 3.5 moles H2O? 2. How many grams are in 1.5 moles of Ne? 3. How many grams are in 2.25 moles of NaCl? 4. How many grams are in 0.50 moles of C6H12O6? 5. How many moles are in 75.0 grams of H2O? 6. How many moles are in 75.0 grams of Ne? 7. How many moles are in 50.0 grams of NaCl? 8. How many moles are in 50.0 grams of C6H12O6? CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 8
ws Moles and Volume (Using Molar Volume) 1. How many Liters are in 3.5 moles SO2(g) @ STP? 2. How many Liters are in 1.5 moles of Ne(g) @STP? 3. How many Liters are in 2.25 moles of CO2(g) @STP? 4. How many Liters are in 0.50 moles of SO2(g) @STP? 5. How many moles are in 75.0 L SO2(g) @ STP? 6. How many moles are in 75.0 L of Ne(g) @STP? 7. How many moles are in 135 L of CO2(g) @STP? 8. How many moles are in 49.0 L of SO2(g) @STP? CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 9
ws Mixed Mole Problems 1. How many Liters are in 32.0 g of SO2(g) @ STP? 2. How many grams are in 1.50(10) 24 atoms of Ne? 3. How many molecules are in 53.0 L of CO2(g) @STP? 4. How many Liters are in 8.75(10) 23 molecules of SO2(g) @STP? 5. How many grams are in 75.0 L SO2(g) @ STP? 6. How many atoms are in 75.0 g of Ne? 7. How many grams are in 135 L of CO2(g) @STP? 8. How many molecules are in 49.0 L of SO2(g) @STP? CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 10
ws Mole Conversions Directions: Perform the following conversions using the appropriate conversion factors. NOTE: (g) after a formula means gas. * designates more than one step may be required. 1. 4.50 mol O2 g O2 2. 4.50 mol O2(g) L O2(g) @STP 3. 91.0 g N2 mol N2 4. 2.75 mol CH4 # molecules 5. 2.75 mol CH4 g CH4 6. 2.75 mol CH4(g) L CH4(g) @STP *7. 110. g CO2(g) L CO2(g) @STP *8. 110. g CO2 # molecules *9. 3.01(10) 23 molecules H2O g H2O *10. 100.8 L SO2(g) @STP g SO2(g) CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 11
ws Percent Composition Directions: Find the % composition for each of the following compounds and refer to #1-5 to answer #6-8. 1. H2O 2. MgCl2 H= O = 3. Ca(NO3)2 Mg= Cl = 4. (NH4)3PO4 Ca= N= O= N= H= P= O= 5. Al2(CO3)3 Al= C= O= 6. How many grams of oxygen can be produced from the decomposition of 60.0 g of H2O? 7. What mass of magnesium is in 75.0 g of MgCl2? 8. What mass of carbon is necessary to make 38.0 g of Al2(CO3)3? CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 12
ws - Hydrates and % H2O Directions: Name each hydrate and find the % water (by mass) in each. 1. Na2SO4 10H2O % H2O Name 2. MgSO4 7H2O 3. CaCl2 2H2O 4. FeSO4 7H2O 5. CoCl2 2H2O CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 13
ws Composition of Hydrates 1. What is the percentage of water in Na2S 9H2O? 2. If you heated 7.7 g of Na2S 9H2O, how much water would be driven off? 3. What is the percentage of water in Na2CO3 H2O? 4. If you heated 5.00 g of Na2CO3 H2O, how much salt would remain? 5. An 8.00 g sample of BaCl2 was heated, and only 6.88 g of the anhydrous salt remained. What is the percentage of water in the hydrate? 6. A 12.0 g sample of Cu(NO3)2 nh2o was heated and 9.36 g of the anhydrous salt remained. What is the value of n? CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 14
ws - Hydrate Empirical Formulas Directions: Find the percentage of water, empirical formula, and name for each hydrate below using the experimental data given for problems #1-3. 1. A hydrate of CuSO4 was found to be composed of 12.76 g of copper sulfate and 7.200 g of water. % H2O = Empirical Formula = Name = 2. A hydrate of sulfuric acid (H2SO4) had a mass of 3.48 g before heating. After heating the salt had a mass of 2.94 g. % H2O = Empirical Formula = Name = 3. A hydrate of barium hydroxide (Ba(OH)2) had a total mass of 14.19 g before heating. After heating 6.48 grams of water were driven off. % H2O = Empirical Formula = Name = *4. A sample of sodium sulfate decahydrate was heated and the resulting salt remaining was 0.142 grams. How many grams of water must have been driven off? CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 15
ws Determining Empirical Formulas 1. 11.1% hydrogen, 88.9% oxygen 2. 39.3 % sodium, 60.7% chlorine 3. 32.4% sodium, 22.6% sulfur, 45.0% oxygen 4. 22.1% aluminum, 25.4% phosphorus, 52.5% oxygen 5. 56.6% potassium, 8.68% carbon, 34.7% oxygen 6. 25.3% copper, 12.9% sulfur, 25.7% oxygen, 36.1% water CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 16
ws Determining Molecular Formulas 1. A compound has an empirical formula of NH2. Its gram molecular mass is 32.0 g/mol. What is its molecular formula? 2. The empirical formula of a compound is CH2. Its molar mass is 42.0 g/mol. What is its molecular formula? 3. A compound is found to be 40.0% carbon, 6.67% hydrogen, and 53.3% oxygen. Its molar mass is 180.0 g/mol. What is its molecular formula? 4. A compound has 40.0% carbon, 6.67% hydrogen, and 53.3% oxygen. It has a molar mass of 120.0 g/mol. Find its molecular formula. 5. A compound has 29.1% sodium, 40.6% sulfur, and 30.3% oxygen. What is its molecular formula if has a molar mass of 158.2 g/mol? CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 17
Experiment: Finding % Sugar in Gum (Rough Copy) Name: Date: Period: Purpose: Materials: Procedure: Data: Brand of Gum Mass of Gum before chewing Mass of Gum after chewing Calculations: Show your work! Find the mass of sugar in the Gum Find the % sugar in the Gum Conclusion: Mention your result what assumption you made in this lab which Gum in the class was the highest % sugar which was the lowest % sugar CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 18
Experiment: Finding % Sugar in Gum (Final Copy) Name: Date: Period: Purpose: Materials: Procedure: Data: Brand of Gum Mass of Gum before chewing Mass of Gum after chewing Calculations: Show your work! Find the mass of sugar in the Gum Find the % sugar in the Gum Conclusion: CHEMISTRY Chapter 10 Scotch Plains-Fanwood High School Page 19