Reminder If you are opting out of lab, please email Mr. Chris Scott ASAP! christopher.scott@acadiau.ca 11/23/2018

3.70) When baking soda (NaHCO3) is heated, it releases carbon dioxide gas, which is responsible for the rising of cookies, donuts, and bread. (a) Write a balanced equation for the decomposition of the compound (one of the products is Na2CO3). (b) Calculate the mass of NaHCO3 required to produce 20.5 g of CO2. 2NaHCO3 CO2 + Na2CO3 + H2O Δ CO2 is ~44 g/mol and NaHCO3 is about 84 g/mol. 78.3 g NaHCO3 11/23/2018

Do You Understand Limiting Reagents? In one process, 124 g of Al are reacted with 601 g of Fe2O3. Which reactant is the limiting reagent? 2Al + Fe2O3 Al2O3 + 2Fe g Al mol Al mol Fe2O3 needed g Fe2O3 needed OR g Fe2O3 mol Fe2O3 mol Al needed g Al needed 1 mol Al 27 g Al x 1 mol Fe2O3 2 mol Al x 160 g Fe2O3 1 mol Fe2O3 x = 124 g Al 367 g Fe2O3 Start with 124 g Al need 367 g Fe2O3 Have more Fe2O3 (601 g) so Al is limiting reagent 11/23/2018

Calculate the mass of Al2O3 that should be possible to obtain with the amounts of reactants used. . g Al mol Al mol Al2O3 g Al2O3 2Al + Fe2O3 Al2O3 + 2Fe 1 mol Al 27 g Al x 1 mol Al2O3 2 mol Al x 102 g Al2O3 1 mol Al2O3 x = 124 g Al 234 g Al2O3 Limiting reagent determines the amount of product possible! This amount is called the theoretical yield. 11/23/2018

Theoretical Yield is the amount of product that would result if all the limiting reagent reacted. Actual Yield is the amount of product actually obtained from a reaction. % Yield = Actual Yield Theoretical Yield x 100 11/23/2018

A sample problem Calculate the % yield for the formation of Al2O3 assuming that you obtained 100 g. % Yield = Actual Yield Theoretical Yield x 100 % Yield = 100 g 234 g x 100 = 42.7 % 11/23/2018

Remember Actual yield is the amount of product obtained when the reaction is carried out in the lab (2) Theoretical yield is the amount of product calculated from the balanced equation based on a given amount of limiting reagent (3) A measure of how well your reaction worked % Yield = Actual Yield Theoretical Yield x 100 11/23/2018

8.86) Consider the reaction MnO2 + 4HCl MnCl2 + Cl2 + 2H2O If 0.86 mole of MnO2 and 48.2 g of HCl react, which reagent will be used up first? How many grams of Cl2 will be produced? Calculate the % yield for an experiment that produced 10.0 g of Cl2. 125 g HCl needed, only have 48.2 g HCl… so HCl must be the limiting reagent considering 48.2 g HCl, 23.4 g Cl2 should be produced 10.0g/23.4g x 100% = 42.7% yield 11/23/2018

Sample problem 3.73) Each copper (II) sulfate unit is associated with 5 water molecules in crystalline copper (II) sulfate pentahydrate (CuSO4.5H2O). When this compound is heated in air above 100oC, it loses the water molecules and also its blue color. If 9.60 g of CuSO4 are left after heating 15.01 g of the blue compound, calculate the number of moles of water originally present in the compound. 0.300 mol 11/23/2018

Reactions in Aqueous Solution Chapter 4

A solution is a homogenous mixture of 2 or more substances The solute is the substance present in the smaller amount The solvent is the substance present in the larger amount Solution Solvent Solute Solder- usually a Pb-Sn alloy used to fuse metals. Soft drink (l) H2O Sugar, CO2 Air (g) N2 O2, Ar, CH4 Soft Solder (s) Pb Sn 11/23/2018

An electrolyte is a substance that, when dissolved in water, results in a solution that can conduct electricity. A nonelectrolyte is a substance that, when dissolved, results in a solution that does not conduct electricity. nonelectrolyte weak electrolyte strong electrolyte 11/23/2018

Conduct electricity in solution? Cations (+) and Anions (-) Strong Electrolyte – 100% dissociation NaCl (s) Na+ (aq) + Cl- (aq) H2O Weak Electrolyte – not completely dissociated CH3COOH CH3COO- (aq) + H+ (aq) 11/23/2018

Hydration is the process in which an ion is surrounded by water molecules arranged in a specific manner. -helps to stabilize ions in solution and prevents cation from combining with anions δ+ δ- H2O 11/23/2018

Ionization of acetic acid CH3COOH CH3COO- (aq) + H+ (aq) A reversible reaction. The reaction can occur in both directions. Acetic acid is a weak electrolyte because its ionization in water is incomplete. 11/23/2018

Nonelectrolyte does not conduct electricity? No cations (+) and anions (-) in solution C6H12O6 (s) C6H12O6 (aq) H2O 11/23/2018

Can we electrocute a pickle? 11/23/2018

Pickles are full of electrolytes… 11/23/2018

3 types of reactions in aqueous medium Precipitation Acid-base Oxidation-reduction 11/23/2018