# Chemistry 102 Dr. Don DeCoste 367J Noyes Lab 3-4 pm Tuesdays and Thursdays By appointment; open door policy

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Chemistry 102 Dr. Don DeCoste 367J Noyes Lab decoste@illinois.edu 3-4 pm Tuesdays and Thursdays By appointment; open door policy http://chem.illinois.edu 1

To Do Finish reading Chapter 3. Text homework for Chapter 3. Quiz #2 on Friday, February 13 Lon-Capa assignment #2. If new to course, email me about Lon-Capa assignment #1 2

Clicker Question Substance AB 2 is 42.86% A by mass. Determine the percent B by mass for substance A 2 B. a) 14.28% B b) 25.00% B c) 28.57% B d) 57.14% B e) I do not know/I can’t get any of the above answers. 3

Stoichiometry Determine the amount(s) of reactant(s) or product(s) given amount(s) of reactant(s) or product(s). We must have a balanced chemical equation. Reactions occur by numbers of atoms/molecules.

Balanced Chemical Equations Chemical reactions are rearrangements of atoms. Atoms are not changed in a chemical reaction. 5

Clicker Question When iron(III) oxide is heated with carbon, the products are iron metal and carbon monoxide. Balance the equation in standard form and determine the sum of the coefficients. a)4 b)5 c)6 d)8 e)9 6

N 2 (g) + H 2 (g)  NH 3 (g) 7

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Method 1: Have vs. Need Compare what you HAVE with what you NEED. The limiting reactant determines the amount of product. The amount of leftover reactant is the difference between what you HAVE and what you NEED.

Method 2: Maximum Product Determine the maximum amount of product from each reactant. The reactant which produces the least amount of product is the limiting reactant. The least amount of product is the amount of product formed.

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