Moles and Molecules Moles and Chemical Reactions Moles, Chemical Reactions, and Molarity All done as UNIT CONVERSIONS!!! …and practice, practice, practice Chemical Calculations CHM Sinex

Mass of substance in grams Moles of substance Number of particles of substance (atoms, molecules, or ions) Molar mass of substance - g/mole Avogrado’s number x particles/mole Mass-moles-particles conversions Conversion factors Molar mass – sum of atomic masses from periodic table 2

3 How many atoms of carbon? atoms C = 9 atoms/molecule * 3.3 x molecules = 3.0 x atoms Now find molecules: molecules = moles * 6.02x10 23 molecules/mole = 3.3 x molecules First find moles: moles = 1000 mg *1g/1000mg * 1mole/180g = moles How many molecules of aspirin (C 9 H 8 O 4 ) in a dose of 1000 mg? Find MM of aspirin: MM = 9*12+8*1+4*16 = 180 g/mole Conversion factors in boxes from the formula

4 For 12.6g NaHCO 3, how many moles do you have? Mass of substance AMoles of substance A MM How many CO 2 molecules in 0.17 moles CO 2 ? Moles of substance AMolecules of substance A 6.02 x 10 23

5 Another way to find moles… Molarity = moles of solute/volume of solution in liters (moles/L) A unit of concentration – amount solute per amount solution or solvent Rearranging the definition of molarity: moles = M x V L For a solution (homogeneous mixture), there are two components: solute (substance being dissolved) and solvent (dissolving medium, usually water) Another way to find moles! How many moles NaCl in 50 mL of 0.28 M NaCl? 50 mL x 1L/1000 mL x 0.28 mole/L = mole NaCl

6 What is the molarity if 35g KCl are dissolved to make 350 mL of solution? How many moles are in 300 mL of a 0.23 M NaOH solution? Moles of substance AVolume of substance A Molarity

7 2C 4 H O 2  8CO H 2 O X 13/2X 8/2X 10/ Mole ratios The ratio of moles in a reaction Click for answers

8 1 mole CaCO 3 x 2 mole HCl/1 mole CaCO 3 = 2 mole HCl Moles of substance AMoles of substance B Mole ratio This comes from the balanced chemical reaction! …and it relates substances in the reaction! Mole-to-mole conversions 2HCl + CaCO 3  CaCl 2 + H 2 O How many moles of HCl react with a mole of CaCO 3 ? mole ratio

9 Moles of substance AMoles of substance B Mole ratio Mass of substance A Molar mass of substance A Mass of substance B Molar mass of substance B Volume of substance AVolume of substance B Molarity of solution AMolarity of solution B Stoichiometry Molarity (M) = moles of solute/volume in liters of solution – moles/L Conversion factors

10 Moles of substance AMoles of substance B Mole ratio Mass of substance A Molar mass of substance A Mass of substance B Molar mass of substance B Volume of substance AVolume of substance B Molarity of solution AMolarity of solution B How many grams of O 2 are required to reaction with 10g C 3 H 8 ? 10g C 3 H 8 x 1 mole/44g = 0.23 moles C 3 H moles C 3 H 8 x 5 moles O 2 /1mole C 3 H 8 = 1.15 moles O moles O 2 x 32.0g/mole = 37 g O 2 C 3 H 8 + 5O 2  3CO 2 + 4H 2 O This is a classic stoichiometry problem! Conversion factors in boxes

11 Moles of substance AMoles of substance B Mole ratio Mass of substance A Molar mass of substance A Mass of substance B Molar mass of substance B Volume of substance AVolume of substance B Molarity of solution AMolarity of solution B How many grams of O 2 are required to reaction with 10g C 3 H 8 ? 10g C 3 H 8 x 1 mole/44g = 0.23 moles C 3 H moles C 3 H 8 x 5 moles O 2 /1mole C 3 H 8 = 1.15 moles O moles O 2 x 32.0g/mole = 37 g O 2 C 3 H 8 + 5O 2  3CO 2 + 4H 2 O Step 1 Step 3 Step 2 Another view of solving

12 Moles of substance AMoles of substance B Mole ratio Mass of substance A Molar mass of substance A Mass of substance B Molar mass of substance B Volume of substance AVolume of substance B Molarity of solution AMolarity of solution B C 3 H 8 + 5O 2  3CO 2 + 4H 2 O If 74g O 2 react, how many grams of CO 2 will be produced?

13 Moles of substance AMoles of substance B Mole ratio Mass of substance A Molar mass of substance A Mass of substance B Molar mass of substance B Volume of substance AVolume of substance B Molarity of solution AMolarity of solution B 2HCl + CaCO 3  CaCl 2 + H 2 O What volume of stomach acid, 0.16 M HCl, reacts with 1.0 g CaCO 3 ? mole CaCO 3 x 2 mole HCl/1 mole CaCO 3 = mole HCl 1.0 g CaCO 3 x 1 mole/100g = mole CaCO mole HCl x 1L/0.16 moles = 0.13 L = 130 mL stomach acid

14 Moles of substance AMoles of substance B Mole ratio Mass of substance A Molar mass of substance A Mass of substance B Molar mass of substance B Volume of substance AVolume of substance B Molarity of solution AMolarity of solution B This is a classic titration problem! CH 3 COOH + NaOH  CH 3 COONa + H 2 O What volume of 0.25 M CH 3 COOH will reaction with 25.0 mL of 0.37M NaOH? 25.0 mL x 1L/1000 mL x 0.37 mole/L = moles NaOH moles NaOH x 1 mole CH 3 COOH/1 mole NaOH = mole CH3COOH mole x 1L/0.25 moles = L = 37 mL CH 3 COOH

15 Could you find one of the conversion factors? Moles of substance AMoles of substance B Mole ratio Mass of substance A Molar mass of substance A Mass of substance B Molar mass of substance B Volume of substance AVolume of substance B Molarity of solution AMolarity of solution B 2HCl + CaCO 3  CaCl 2 + H 2 O Suppose 2.0g CaCO 3 reacted with 25.0 mL of HCl. What is the molarity of the HCl? 2.0 g CaCO 3 x 1 mole/100g = 0.020mole CaCO mole CaCO 3 x 2 mole HCl/1 mole CaCO 3 = mole HCl Molarity = moles/ V L = mole HCl / (25.0 mL x 1L/1000mL) = 1.6 M HCl Moles of substance B Volume of substance B

16 Moles of substance AMoles of substance B Mole ratio Mass of substance A Molar mass of substance A Mass of substance B Molar mass of substance B Volume of substance AVolume of substance B Molarity of solution AMolarity of solution B Al(OH) 3 + 3HCl  AlCl 3 + 3H2O How many grams of Al(OH) 3 will react with 100 mL of 0.15 M HCl?

17 2Al 2 O 3 (l) + 3C (s)  4Al (l) + 3CO 2 (g) For a 1.0 kg of Al 2 O 3, how much aluminum metal, in grams, can be produced? How many atoms of carbon are consumed for the problem above?

18 CH 3 COOH + NaOH  CH 3 COONa + H 2 O How many grams of CH 3 COOH are needed to react with 27.3 mL of 0.21 M NaOH? HX + NaOH  NaX + H 2 O If 0.121g HX react with 26.2 mL of M NaOH, what is the molar mass of HX? What is element X?

19 What if two reagents are added, how much product do you get? 2Na + Cl 2  2NaCl Suppose 10 g Na and 10 g Cl 2 are mixed together. How much NaCl can be produced? First find the moles of each reactant: 10 g Cl 2 x 1 mole/71.0 g = 0.14 mole Cl 2 10 g Na x 1 mole/23.0 g = 0.43 mole Na Find the moles of NaCl produced for each reactant: 0.14 mole Cl 2 x 2 mole NaCl/1 mole Cl 2 = 0.28 mole NaCl 0.43 mole Na x 2 mole NaCl/2 mole Na = 0.43 mole BrCl  This is what can be produced! Cl 2 is limiting reagent. 21 Have 0.43 Need 0.22 Need 0.28 Have Na + 1Cl 2

20 A chemical analysis problem A chemist decides to check the molarity of H 2 SO 4 in her car battery. A 10.0 mL sample is reacted with mL of 2.73M NaOH. What is the molarity of H 2 SO 4 ? H 2 SO 4 + 2NaOH  Na 2 SO 4 + 2H 2 O

21 Answers to problems by slide number: mole NaHCO 3 ; 1.0 x molecules CO M KCl; mole NaOH g CO g Al(OH) x 10 2 g Al; 8.9 x atoms C g CH 3 COOH; MM = 20.2 g/mole; X = F M H 2 SO 4