Law of Conservation of Mass Lavoisier (1743-1794) Coal is completely burned 100 g 100 g START END What do you observe?

Law of Conservation of Mass Lavoisier (1743-1794) Coal is completely burned 100 g 100 g Weight of jar & its contents remains the same. Mass is conserved In a chemical reaction, matter is neither created nor destroyed, it is transformed into something else.

balanced mass Since matter can not be created or destroyed, chemical reactions must be __________ in terms of _________. balanced mass The amount of mass you start with must equal to the mass of the products: Reactants  Products 100g total = 100g total

The mass on both sides of the arrow must be equal. According to the law of conservation of mass, how much zinc was present in the zinc carbonate? + = + 256g 256g REMEMBER !!! The mass on both sides of the arrow must be equal. A 40 g B 88 g C 104 g D 256 g ANSWER: 256- 152 = 104g of Zn

CuCO3(s)  CuO(s) + CO2(g) 123.6 g 79.6 g ? g 44.0 g According to the law of conservation of mass, how much carbon dioxide was present in the copper (II) carbonate? CuCO3(s)  CuO(s) + CO2(g) 123.6 g 79.6 g ? g + 44.0 g 123.6g 123.6g What are the reactants? CuCO3 123.6 g What is the mass of reactants? Mass? CuO & CO2 What are the products? What is the mass of products? 79.6 g + CO2 Answer: 123.6 – 79.6 = 44.0g of CO2

For the Last Two Examples You can set every Chemical Equation up like an Algebraic Equation and solve it for the variable. For instance this equation, can be written algebraically using the masses given on the previous slide like below. Now you only have to solve for x! 123.6 [g] = 79.6 [g] + x CuCO3(s)  CuO(s) + CO2(g)