CONSERVATION OF MASS

REVIEW Chemical equations consist of reactants and products Matter can be neither created nor destroyed 2 H2 + O2 2 H2O Reactants Products

…the mass of the reactants is always equal to the mass Law of Conservation of Matter …the mass of the reactants is always equal to the mass of the products Example Reactants Products 2H2 + O2 2H2O 2g + 16g = 18g 18g = 18 g

Example # 1 REMEMBER... 29 g + O2 = 88 g + 48 29 g + O2 = 136 g In a chemical reaction below, how many grams of oxygen (O2) was used given the following information. 29g ? 88g 48g REMEMBER... mass of reactants = mass of products 29 g + O2 = 88 g + 48 29 g + O2 = 136 g O2 = 107 grams

2 H2O  2 H2 + O2 Example # 2 2 H2O  2 H2 + O2 9 g = ? + 8 g Water (H2O) can be broken down into hydrogen and oxygen. During a reaction you notice that 9 grams of water will produce 8 grams of oxygen (O2) and a certain amount of hydrogen (H2). How much hydrogen is produced? 2 H2O  2 H2 + O2 2 H2O  2 H2 + O2 9 g = ? + 8 g H2 = 1 grams

Example # 3 H2SO4+ Ca(OH)2  CaSO4 + 2H2O 37 g + Ca(OH)2 = 51 g + 14 g 37 grams sulphuric acid (H2SO4) is neutralized with calcium hydroxide (Ca(OH)2). During the reaction, calcium sulphate (CaSO4), a salt, and water are produced. If 14g of water & 51g of salt are produced, how much calcium hydroxide was initially used? H2SO4+ Ca(OH)2  CaSO4 + 2H2O 37 g + Ca(OH)2 = 51 g + 14 g 37 g + Ca(OH)2 = 65 g Ca(OH)2 = 28 grams

KEY POINTS Conservation of matter states the mass of the reactants will equal the mass of the products. MASS OF REACTANTS = MASS OF PRODUCTS

PRACTICE PROBLEMS Study guide, Module 3, page 36 Worksheet # 10