1. Do Now  Please write HW in your agenda.  Please update your table of contents.  Fold and attach the notes to page 119.  Answer the entrance ticket and hand it in. You have 10 minutes. Page #TitleDate 119-120Balancing Equations notes02/11

2. Chemical Equations Reactants ProductsBalanced? H 2 + O 2 H = O =  H 2 O H = O = 2H 2 + O 2 H = O =  2H 2 O H = O = CH 4 + O 2 C = H = O =  CO 2 + H 2 O C = H = O = CH 4 + O 2 C = H = O =  CO 2 + 2H 2 O C = H = O = CH 4 + 2O 2 C = H = O =  CO 2 + 2H 2 O C = H = O =

3. Chemical Equations ReactantsProductsBalanced? C 3 H 8 + 5O 2 C = H = O =  4H 2 O + 3CO 2 C = H = O = C 3 H 8 + 5O 2 C = H = O =  3H 2 O + 3CO 2 C = H = O = NaOH + H 2 SO 4 Na = O = H = S =  Na 2 SO 4 + H 2 O Na = O = H = S = 2NaOH + H 2 SO 4 Na = O = H = S =  Na 2 SO 4 + 2H 2 O Na = O = H = S =

4. Chemical Equations A chemical equation is a description of a reaction using element symbols and chemical formulas. H 2 + Cl 2  2HCl

5. H 2 + Cl 2 The starting substances in a chemical reaction are called reactants. Two or more reactants are separated by a + sign.

6.  The arrow means “yields” or “produces.” This is the direction where the reaction is going. ⇄ means that the reaction occurs back and forth (called equilibrium)

7. 2HCl The substances produced in a chemical reaction are called products. Two or more products are separated by a + sign. A coefficient in front of a compound indicates how many compounds there are. How many compounds of hydrochloric acid are there?

8. Counting atoms  The subscript describes the number of atoms of an element in a chemical formula  The coefficient in front of a chemical formula indicates how many compounds/molecules there are. NaCl Na= Cl= C 6 H 12 O 6 C= H= O= 2H 2 O H= O= 3NaCl Na= Cl=

9. Balancing chemical equations In order for a chemical equation to be balanced, meaning that it follows the law of conservation of mass, the number of atoms of each element must be the same from the reactants to the products. C + O 2  CO 2 Balanced? C= O= H 2 + O 2  H 2 O H= O=

10. Balancing Equations H 2 + O 2  H 2 O 1. Determine the number of atoms for each element. 2. Pick an element that is not equal on both sides of the equation. 3. Add a coefficient in front of the formula with that element and adjust your counts. 4. Continue adding coefficients to get the same number of atoms of each element on each side. Rules: You cannot change or add subscripts! That changes what the substance is! You cannot add a coefficient that is not a whole number!