1. Chemical Equations

2. When chemicals are added together and a reaction occurs a chemical equation can be written The reactants go on the left of the equation and the products on the right An arrow indicates a reaction has occurred

3. Chemical Equation EXAMPLE: Burn a piece of Magnesium ribbon in air (oxygen). The product of which is Magnesium Oxide. REACTANTSPRODUCTS Magnesium + Oxygen Magnesium Oxide Mg + O 2 MgO

4. This equation is NOT balanced There are not equal numbers of each atom on both sides of the equation The correct way to write a chemical equation is to write it as a balanced equation BECAUSE: The Law of Conservation of Matter states that "matter can neither be created nor destroyed". This means that we have to balance chemical equations, so that each side of the equation has the same number of atoms of each element.

5. How to Balance an Equation 1.To balance equations we write coefficients (numbers) in front of formulas. 2.You CAN NOT change the subscripts (little numbers) of the formulas. 3.Use a pencil so you can go back and change. 4.Balance the atoms one at a time. 5.Check to make sure that the equation is balanced, with the smallest ratio of coefficients.

6. EXAMPLE: Burn a piece of Magnesium ribbon in air (oxygen). The product of which is Magnesium Oxide. REACTANTSPRODUCTS Magnesium + Oxygen Magnesium Oxide Mg + O 2 MgO 2Mg + O 2 2MgO This is now balanced! ReactantsProducts Magnesium atoms 2 x Mg Oxygen atoms 2 x O Magnesium atoms 2 x Mg Oxygen atoms 2 x O

7. Some to try…… Zn + HCl  ZnCl 2 + H 2 Mg + HCl  MgCl 2 + H 2 Fe + Al 2 O 3  Fe 2 O 3 + Al

8. ___ Mg + __HCl __MgCl 2 + __ H 2 ___ Zn + __HCl __ZnCl 2 + __ H 2 ___ Pb(NO 3 ) 2 + __KI __Pbl 2 + __ KNO 3 ___ Ba(NO 3 ) 2 + __Al __Ba + __ Al(NO 3 ) 3 ___Cu(NO 3 ) 2 + __ Na 2 SO 4 __CuSO 4 + __NaNO 3 ___Ba(NO 3 ) 2 + __ Al 2 (SO 4 ) 3 __BaSO 4 + __Al(NO 3 ) 3