chapter 20 chemical reactions. 20.3 conservation of mass antoine laurent __________ (1743-94),...
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CHAPTER 20CHAPTER 20
CHEMICAL REACTIONS
20.3 Conservation of Mass20.3 Conservation of Mass
Antoine Laurent __________ (1743-94), established an important principal based on his experiments with chemical reactions.
The total mass of the ________ of a reaction is equal to the total mass of the __________.
This is known as the law of ___________ of mass.
CONSERVATIONCONSERVATION OF MASS OF MASS
Total MASS of PRODUCTS EQUALS Total MASS of REACTANTS–Must MEASURE in a _________ SYSTEMAntoine Lavoisier
CONSERVATION OF CONSERVATION OF MASSMASS
Mass of WOOD and AIR before burning a fire
EQUALSMass of ASH and GASES after burning a fire
COOKING WITH COOKING WITH CHEMISTRYCHEMISTRY
CHEMICAL EQUATIONS ARE LIKE RECIPES
They tell you QUANTITIES of INGREDIENTS and Quantities of PRODUCTS
CHEMICAL EQUATIONSCHEMICAL EQUATIONS
NUMBER of REACTANT MOLECULES needed to MAKE a CERTAIN NUMBER of PRODUCT MOLECULES
2Na + Cl2 ----> 2NaCl
BALANCED BALANCED EQUATIONSEQUATIONS
Correct RATIOS of Molecules are shown as COEFFICIENTS in BALANCED EQUATIONS
2H2 + O2 ----> 2H2O
UNBALANCED UNBALANCED REACTIONSREACTIONS
REACTANTS ARE NOT ALWAYS PRESENT IN THE EXACT RATIOS NEEDED.
SO WHAT HAPPENS ?
_______ REACTANT The reactant molecule which is used up _____
_______ the AMOUNT of PRODUCT formed
UNBALANCED UNBALANCED REACTIONSREACTIONS
__________ REACTANT The reactant molecule which is _____ completely used up.
Some will be _____ _____ after reaction is complete.
UNBALANCED UNBALANCED REACTIONSREACTIONS
YIELDSYIELDS
REACTIONS DON’T ALWAYS TURN OUT AS PLANNED
HOW MUCH PRODUCT IS REALLY FORMED ?
_________ YIELD – The amount of Product ________ from the balanced equation
_________ YIELD – The amount of Product _________ formed
PERCENT YIELDPERCENT YIELD RATIO of Actual Yield to RATIO of Actual Yield to Predicted YieldPredicted Yield
%YIELD = %YIELD = Actual Yield Actual Yield x 100% x 100% Predicted YieldPredicted Yield
PERCENT YIELDPERCENT YIELD
IF we expect 100g. of product from chemical equation, BUT we only get 85g. of product, THEN
% YIELD = (85g./100g.)x100%
= 85%
20.4 Using Equations as 20.4 Using Equations as RecipesRecipes
Recipe #1: Chocolate Cake Recipe1 cup flour
1/2 cup cocoapowder
1/2 cup butter1 tsp vanilla1 cup sugar
1 teaspoon baking powder1/2 cup milk
1 egg
In a bowl, combine flour, sugar, cocoa powder, and baking power. Add butter, milk, vanilla, and egg. Mix until smooth. Bake in a 350°F oven for 35 minutes. Makes 8 servings
20.4 Using Equations as 20.4 Using Equations as RecipesRecipes
Recipe #2: Water
2 molecules of hydrogen gas1 molecule of oxygen gas
Combine the molecules in a closed container. Add a spark of electricity. Makes two molecules of water.
20.4 Using Equations as 20.4 Using Equations as RecipesRecipes
Balanced equations show how mass and atoms are conserved.
20.4 Using Equations as 20.4 Using Equations as RecipesRecipes
20.4 Using Equations20.4 Using Equations
Key Question:
How can you predict the amount of product in a reaction?
*Read text section 20.4 BEFORE Investigation 20.4