1. Balancing Chemical Equations

2. Chemical Equations A chemical reaction is a process in which at least one new substance is produced as a result of a chemical change. It is usually easy to see that a chemical reaction has occurred: color change, emission of heat/cold, gas evaporation, and solid formation.

3. Law of Conservation of Mass Mass is neither created nor destroyed in any chemical reaction The sum of the masses of the reactants is always the same as the sum of the products CH 4 + 2O 2 CO 2 + 2H 2 O COEFFICIENT

4. Balancing Chemical Equations NaOH + HCl NaCl + H 2 O When balancing a chemical equation the quantity and types of elements in the reactants has to be equal to the quantity and types of elements in the products.

5. NaOH + HCl NaCl + H 2 O Step 1. Break the reactants and products down into the type of elements. NaNa OO HH ClCl

6. Step 2. Place the quantity of each element in the reactants and products. Na:1Na:1 O:1O:1 H:2H:2 Cl:1Cl:1 NaOH + HCl NaCl + H 2 O

7. Step 3. If the quantity of each element in the reactants and products is not equal, multiply each side of the equation by a number that makes them equal. Place the number in front of the compound that contains that element that you want to balance. This will cause the other elements in the compound to increase also. Na:1Na:1 O:1O:1 H:2H:2 Cl:1Cl:1 NaOH + HCl NaCl + H 2 O

8. Fe + O 2 Fe 2 O 3 Step 1: FeFe OO

9. Fe + O 2 Fe 2 O 3 Step 2: Fe: 1Fe: 2 O: 2O: 3

10. Fe + 3O 2 2Fe 2 O 3 Step 3: (reactants)(products) Fe: 1Fe: 2 O: 2 x 3 = 6O: 3 x 2 = 6

11. Fe + 3O 2 2Fe 2 O 3 Step 3:The increase in O on the product side causes the Fe to increase too and now needs to be increased. (reactants)(products) Fe: 1Fe 2 x 2 = 4 O: 2 x 3 = 6O: 3 x 2 = 6

12. 4Fe + 3O 2 2Fe 2 O 3 Step 3: Now you need to balance the Fe on the reactant side. (reactants)(products) Fe 1 x 4 = 4Fe 2 x 2 = 4 O 2 x 3 = 6O 3 x 2 = 6

13. 4 Fe (s) + 3 O 2 2 Fe 2 O 3 What does this chemical reaction make?

14. 4 Fe + 3 O 2 2 Fe 2 O 3 What does this chemical reaction make? Answer: Rust!

15. Balancing a chemical equation with a Chemical Group Pb(NO 3 ) 2 + KI PbI 2 + KNO 3

16. Balancing a chemical equation with a Chemical Group Pb(NO 3 ) 2 + KI PbI 2 + KNO 3 NO 3 is a chemical group on both sides of the chemical equations.

17. Balancing a chemical equation with a Chemical Group Pb(NO 3 ) 2 + KI PbI 2 + KNO 3 Step 1: Pb: Pb: NO 3 : NO 3 : K: K : I: I:

18. Pb(NO 3 ) 2 + KI PbI 2 + KNO 3 Balancing a chemical equation with a Chemical Group Step 2: Pb: 1Pb :1 NO 3 : 2NO 3 :1 K: 1K :1 I: 1I: 2

19. Balancing a chemical equation with a Chemical Group Pb(NO 3 ) 2 + KI PbI 2 + 2KNO 3 Step 3: Balance the chemical group first. Pb:1Pb :1 NO 3 : 2NO 3 :1 x 2 =2 K: 1K :1 I: 1I: 2

20. Balancing a chemical equation with a Chemical Group Pb(NO 3 ) 2 + 2KI PbI 2 + 2KNO 3 Step 3: Pb: 1Pb :1 NO 3 : 2NO 3 :1 x 2 = 2 K: 1 x 2 = 2K :1 x 2= 2 I: 1I: 2

21. Balancing a chemical equation with a Chemical Group Pb(NO 3 ) 2 + 2KI PbI 2 + 2KNO 3 Step 3: Pb: 1Pb :1 NO 3 : 2NO 3 :1 x 2 = 2 K: 1 x 2 = 2K :1 x 2= 2 I: 1 X 2 = 2I: 2

22. Practice Problems Fe 2 O 3 + C Fe + CO 2 KClO 3 KCl + O 2 C 2 H 6 + O 2 CO 2 + H 2 O C 4 H 10 + O 2 CO 2 + H 2 O

23. Balanced Chemical Equations 2Fe 2 O 3 + 3C 4Fe + 3CO 2 2KClO 3 2KCl + 3O 2 2C 2 H 6 + 7O 2 4CO 2 + 6H 2 O 2C 4 H 10 + 13O 2 8CO 2 + 10H 2 O

24. Limiting Reagent Asubstance which determines how much product will be produced from a chemical reaction. This is the reactant that is used up first during a chemical reaction.

25. Balancing Chemical Equations – Links Start with: CHEMBALANCER. http://funbasedlearning.com/chemistry/chembalancer/default.htmhttp://funbasedlearning.com/chemistry/chembalancer/default.htm I have provided you with a handout that you can use as you follow along in this site. After you have completed the 12 problems challenge yourself to others found at the following sites. More challenges: Interactive Tutorial on Balancing Equations: This site will walk you through the process of balancing a single chemical equation. If you get stuck on a step, you can easily click on the answer and move on. http://www.wfu.edu/~ylwong/balanceeq/balanceq.html Balancing Chemical Equations: This site will start with an explanation of what it is to have a balanced equation. Read through it. It’s very helpful information. It will then walk you through the process of balancing equations using several examples. At the end of this site there are several equations you can work on. The site provides answers to these problems. http://members.aol.com/profchm/balance.html Balancing Chemical Equations: This site is animated and really helps you step by step through the process of balancing equations. Once again, they offer equations for you to solve. http://richardbowles.tripod.com/chemistry/balance.htm Balancing Chemical Equations: This site offers 20 equations for you to balance. It has a “hint” button and it provides the answers. http://www.mpcfaculty.net/mark_bishop/balancing_equations_tutorial.htm