Bellwork 11-3-17

1. Bellwork 11-3-17 • Try balancing the following chemical equation: NaBr + Cl2→ NaCl + Br2

2. Bellwork 11-9-17 C3H8 + O2→ H2O + CO2 11/6-11/8 –Checking work from the following packets: Physical and Chemical Properties and Changes Acids and Bases Atomic Structure worksheet

3. Balancing Chemical Equations

4. Law of Conservation of Mass • In a chemical reaction, matter can neither be created nor destroyed. • So, however many atoms of each element you have on the left side with the reactants… • is same number of atoms of each element you will have on the right side with the products. • They will simply be rearranged.

5. Parts of Chemical Equations Element Symbols means “yields” 16Rb + S8 8Rb2S Coefficients Subscripts Reactants Products

6. + O O  H H H H O H2 + O2 H2O Draw your atoms of hydrogen and oxygen. Then draw your molecule of water. Now take an inventory: H ___ O ___ 2 H ___ O ___ 2 2 1 Balanced? Nope, now what?

7. O O H H H H O +  • The molecules themselves cannot be changed but there must be the same number of each type of atom on each side of the yields sign (the arrow) in order to be balanced. • When adding a coefficient to the equation, it will multiply the number of each type of atom in that formula.

8. O O H H H H O +  O H H H2 + O2 H2O 2 Now we have: H ___ O ___ 2 H ___ O ___ 2 4 Still not balanced! 2 1 2

9. O O +  H H H H O O H H H H 2 H2 + O2 H2O 2 Now we have: 4 H ___ O ___ 2 H ___ O ___ 2 4 TaDa!! 2 2 1

10. Cl Cl Cl + Na  + Mg Mg Na Na + MgCl2 NaCl + Mg Na ___ Mg ___ Cl ___ 1 Na ___ Mg ___ Cl ___ 1 1 1 2 1 Not balanced

11. Cl Cl Cl Cl Na Mg Mg Na Na 2 Na + MgCl2 NaCl + Mg + +  With 2 Cl’s on the reactant side, we want to make 2 Cl’s on the products side… 2 Na ___ Mg ___ Cl ___ 1 Na ___ Mg ___ Cl ___ 1 Not balanced yet… Now we have: 1 1 2 2 1

12. Cl Cl Cl Cl Na Na Mg Mg Na Na 2 Na + MgCl2 2 NaCl + Mg + +  Now we need to even up our sodiums (Na’s) 1 2 Na ___ Mg ___ Cl ___ 1 2 Na ___ Mg ___ Cl ___ Take inventory: Yippee!! 1 1 2 1 2

13. What is a chemical equation? • Chemical equation - Describes a chemical change. • Parts of an equation: • Reactant - The chemical(s) you start with before the reaction. • Written on left side of equation. • Product - The new chemical(s) formed by the reaction. • Right side of equation.

14. Subscript - shows how many atoms of an element are in a molecule. • EX: H2O • 2 atoms of hydrogen (H)‏ • 1 atom of oxygen (O)‏ • Coefficient - shows how many molecules there are of a particular chemical. • EX: 3 H2O • Means there are 3 water molecules.

15. Rules for balancing chemical equations • 1. Matter cannot be created or destroyed. • 2. Subscripts cannot be added, removed, or changed. • 3. You can only change coefficients. • 4. Coefficients can only go in front of chem. formulas...NEVER in the middle of a formula. • A few extra tips: • Try balancing big formulas first; save free elements for last. • If the same polyatomic ion appears on both sides of the equation, it’s usually okay to treat it as one unit. • There is no one particular way to balance equations. Some equations are harder to balance than others and might require some creativity to solve.

16. O O O  H H H C O H C H O H CH4 + O2 CO2 + H2O C ___ H ___ O ___ C ___ H ___ O ___ 1 1 Not balanced 4 2 2 3

17. O H H H H H C O O H C H O H CH4 + O2 CO2 + H2O 2 O  O C ___ H ___ O ___ 1 C ___ H ___ O ___ 1 4 4 Nope, not yet… 2 4 2 3

18. O H H H H H C O O H C H O O O H CH4 + O2 CO2 + H2O 2 2 O  O C ___ H ___ O ___ 1 C ___ H ___ O ___ 1 4 2 4 WooHoo!! 2 4 3 4

19. Now try this one on your own… Al2O3 + H2 H2O + Al 3 3 2 Box off your formulas so you don’t mess with them! Inventory: Wedidit!! Al ___ O ___ H ___ 2 Al ___ O ___ H ___ 1 2 3 1 3 6 2 6 2

20. Fe + O2 Fe2O3 4 3 2 I think we’ve got it!! 1 4 Fe ___ O ___ Fe ___ O ___ 2 4 2 6 3 6 This one’s tricky—start with oxygen and use the lowest common denominator.

21. The End!