Unit 4: TOXINS Stoichiometry, Solution Chemistry, and Acids and Bases Living By Chemistry Unit 4: TOXINS Stoichiometry, Solution Chemistry, and Acids and Bases

In this unit you will learn: how toxins are defined how chemists determine toxicity the mechanisms by which toxic substances act in our bodies and what this has to do with chemical reactions

Section V: Toxic Cleanup Lesson 23 Solid Evidence Lesson 24 Mole to Mole Lesson 25 Mole Tunnel Lesson 26 Get the Lead Out Lesson 27 Call Poison Control

Lesson 23: Solid Evidence Precipitation Reactions

ChemCatalyst Kidney stones are solid blockages that sometimes occur in the kidney. Below is the chemical equation for a double exchange reaction between calcium chloride and sodium oxalate that results in the formation of one type of kidney stone. CaCl2(aq) + Na2C2O4(aq) 2NaCl(aq) + CaC2O4(s) What do you expect to see in the beaker if you complete this reaction? Which compound is the kidney stone? What is your reasoning?

Key Question Which substances precipitate from aqueous solutions?

You will be able to: explain what a precipitation reaction is write net ionic equations for precipitation reactions

Prepare for the Lab Work in pairs. Precipitate: A solid produced in a chemical reaction between two solutions.

Discussion Notes CaCl2(aq) + Na2C2O4(aq)  2NaCl(aq) + CaC2O4(s) The mixing of two ionic solutions sometimes results in the formation of a solid precipitate. Precipitation is not limited to solids. The degree to which a compound dissolves in water is called its solubility.

Discussion Notes (cont.) Solubility varies from compound to compound. Solubility Trends Anions NO3– CL– OH– SO42– CO32– C2O42– PO43– Most alkali metals, such as Li+, Na+, K+, NH4+ S Most alkaline earth metals, such as Mg2+, Ca2+, Sr2+ N Period 4 transition metals, such as Fe3+, Co3+, Ni2+, Cu2+, Zn2+ Other transition metals, such as Ag+, Pb2+, Hg2+

Discussion Notes (cont.) There are positive and negative aspects to the solubility of toxic substances. Once a substance is absorbed, it may be difficult for the body to get rid of it through its natural filtration systems, the kidneys and the liver.

Wrap Up Which substances precipitate from aqueous solutions? Precipitation depends on solubility; compounds that are not very soluble tend to form precipitates. Mixing two aqueous salt solutions often results in the formation of a precipitate. Soluble substances can interact with the human body in either positive or negative ways.

Check-in A solution of K2SO4 is mixed with a solution of Pb(NO3)2, and a precipitate forms. Write the chemical equation for this reaction. What is the precipitate that forms? How do you know?

Lesson 24: Mole to Mole Mole Ratios

ChemCatalyst One way to remove potentially toxic substances from a water source is to precipitate out the harmful ions. Consider the removal of copper ions by precipitation. 2NaOH(aq) + Cu(NO3)2(aq) 2NaNO3(aq) + Cu(OH)2(s) Suppose you add 100 mL of 0.10 M NaOH(aq) to 100 mL of 0.10 M Cu(NO3)2(aq). Have you added equal numbers of moles of the two substances? Explain your thinking. Have you added equal numbers of grams of the two substances? Explain your thinking. Have you added enough NaOH(aq) to remove all the copper from the solution? Explain your thinking.

Key Question How can you convert all the reactants to products?

You will be able to: define a mole ratio explain how to combine reactants in order to make the most product from a reaction identify a limiting reactant

Prepare for the Lab Work in groups of four. Wear safety goggles at all times. Sodium hydroxide, NaOH, is corrosive. Do not get any on skin or near eyes. In case of spills, rinse with large amounts of water.

Discussion Notes The coefficients in chemical equations indicate how many counting units (such as moles) of each reactant combine and how many counting units of each product formed in a single reaction. Coefficients in chemical equations always refer to the number of units (molecules, ions, moles) that are combining.

Discussion Notes (cont.) The mole ratios are the proportions in which two substances (reactants, products, or both) combine or form. Mole ratio: The ratio represented by the coefficients in a chemical equation showing how many units of each substance must combine to make the maximum amount of product. When reactants are not combined in their exact mole ratios, one of the reactants runs out and the other is left over.

Wrap Up How can you convert all the reactants to products? Coefficients in chemical equations represent the proportions in which reactants combine and products form. This proportion is also called the mole ratio. If reactants are not combined in their mole ratio, one will run out and the other will be excess. The one that runs out is called the limiting reactant.

Check-in The reaction to form silver phosphate, Ag3PO4(s), is given by this chemical equation: AgNO3(aq) + Na3PO4(aq) Ag3PO4(s) + NaNO3(aq) 1. Balance the equation. 2. Which combination of reactants results in the maximum amount of product? 1.0 g AgNO3 to 1.0 g Na3PO4 3.0 g AgNO3 to 1.0 g Na3PO4 1.0 mole AgNO3 to 1.0 mole Na3PO4 d. 3.0 moles AgNO3 to 1.0 mole Na3PO4

Lesson 25: Mole Tunnel Stoichiometry

ChemCatalyst This reaction produces the main substance found in human bones (calcium phosphate): How many moles of calcium phosphate can you make using 6 moles of calcium chloride, CaCl2? How many moles of calcium phosphate can you make using 111 g of CaCl2? 3CaCl2(aq) + 2Na3PO4(aq) Calcium Sodium chloride phosphate  Ca3(PO4)2(s) + 6NaCl(aq) Calcium Sodium phosphate chloride

Key Question How do you convert between grams and moles to determine the mass of product?

You will be able to: complete stoichiometric calculations for a variety of chemical reactions.

Prepare for the Classwork Work in pairs. Stoichiometry: the quantitative relationship between reactants and products in a chemical reaction.

Discussion Notes When working stoichiometric problems, grams must be converted to moles and then moles must be converted back to grams.

Wrap Up How do you convert between grams and moles to determine the mass of product? In order to calculate the mass of reactant needed to make a certain mass of product, it is necessary to convert mass to moles and then convert moles back to mass. Mole ratios assist in converting back and forth between moles of reactant and moles of product.

Check-in Consider this reaction: Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g) How many grams of magnesium, Mg, do you need to produce 190 g of magnesium chloride, MgCl2?

Lesson 26: Get the Lead Out Limiting Reactant and Percent Yield

ChemCatalyst Sodium bicarbonate, NaHCO3, and acetic acid, CH3COOH, react to generate CO2 gas: CH3COOH(aq) + NaHCO3(s)  CH3COOHNa(aq) + H2O(l) + CO2(g) You set up the reactions as shown. The gas generated by the reaction will inflate the balloon when the sodium bicarbonate is poured into the acetic acid. Predict the relative order of the balloon sizes. Justify your choice. a. 1 = 2 = 3 b. 1 < 2 < 3 c. 1 < 2 = 3 d. 1 = 2 < 3

Key Question Which reactant determines how much product is made?

You will be able to: complete stoichiometric calculations involving limiting reactant calculate percent yield when the actual yield is known

Prepare for the Activity Work in pairs.

Discussion Notes In the real world, substances are rarely mixed in the exact mole ratios specified by a chemical equation. In order to identify the limiting reactant, the number of moles of the reactants on hand must be compared with the mole ratio of the reactants.

Wrap Up Which reactant determines how much product is made? The limiting reactant is the substance that gets used up in a chemical reaction. To determine the limiting reactant, calculate how many moles of each reactant you have. Consult the mole ratio to see which reactant will get used up.

Check-in Consider this reaction: N2(g) + 3H2(g)  2NH3(g) If you mix 28.0 g of nitrogen gas, N2, and 12.0 g of hydrogen gas, H2, which reactant is the limiting reactant? Show your work. How much ammonia can be made from these amounts of reactants?

Lesson 27: Call Poison Control Unit Review

ChemCatalyst Imagine that your little brother has spilled a toxic substance on his skin. You decide to call Poison Control right away. a. What are some things you want to know about the substance? b. What kinds of questions do you think Poison Control will ask you? What might you be told to do? Explain your thinking.

Key Question What is the best way to deal with a toxic substance?

You will be able to: create a comprehensive list of topics to use as a study aid for a unit exam

Prepare for the Classwork Work individually or in pairs.

Check-in Balance this equation and fill in the phases for the products: Ba(NO3)2(aq) + Na2SO4(aq)  BaSO4 + NaNO3 What solid is formed? How many grams of barium nitrate must be in the solution to make 3 moles of barium sulfate?