Chemical Reactions Apply the Laws of Conservation of Mass/Energy to balance chemical equations. Construct chemical formulas for common compounds.

Equations Used to demonstrate reactions and predict products Reactants on the left Products on the right NaOH + HCl → NaCl + H2O

Law of the Conservation of Mass Mass is neither created nor destroyed You end up with the same mass and same amount of atoms C + O2 → CO2

Balancing Equations Must have the same amount of atoms on the left as on the right H2 + O2 → H2O Not balanced! 2H2 + O2 → 2H2O Balanced! __Cu + __O2 → __CuO __Na + __H2O → __NaOH + __H2 __NaOH + __H2SO4 → Na2SO4 + __H2O

Molar Mass Mole--6.022 X 1023 atoms of a substance Molar mass—mass of one mole of a substance Unit—g/mol Find the molar mass on the periodic table Add the masses of elements to determine mass of compound 22.99g/mol + 35.45g/mol = 58.44 g/mol

Conversion How many grams in 3 moles of NaCl How many moles in 90.1g of H2O How many grams in 1.5 moles of BaSO4 How many moles in 103.6g of Pb

Molar Ratio Use the numbers in equations to tell the molar ratio CH4 + 2O2 → CO2 + 2H2O 1 unit of methane for every 2 units of water 2 units of oxygen for every unit of carbon dioxide 16.05g of CH4 gives 36.04 g of H2O and 44.01g of CO2 How much water would 2 moles of methane give?

Types of Reactions Synthesis Decomposition Single-Displacement A + B → AB Decomposition AB → A + B Single-Displacement AB + C → A + BC Double-Displacement AB + CD → AC + BD

Synthesis & Decomposition Two or more substances react to form one new substance A + B → AB 2H2 + O2 → 2H2O http://boyles.sdsmt.edu/znsulf /zincsul.htm One substance breaks down to form two or more substances AB → A + B 2H2O2 → 2H2O + O2 http://www.chem.uic.edu/mar ek/cgi-bin/vid7b.cgi

Single-displacement & Double-displacement One element takes the place of another AB + C → A + BC Zn + 2HCl → ZnCl2 + H2 Both elements switch places AB + CD → AC + BD AgNO3 + NaCl → AgCl + NaNO3

Energy Changes Energy is stored in bonds between atoms Conservation of energy Can’t be created or destroyed Reactions break bonds or create new ones Breaking bonds produces energy Creating bonds requires energy Exothermic—energy is released Combustion—energy given off as heat and light Endothermic—energy is absorbed (put in) 2HgO + energy → 2Hg + O2