1. Unit #12 Chemical Reactions Part 2 Predicting Products

2. Review A chemical reaction is the rearrangement of atoms to form new substance(s). Reactant(s) appear on the left, and product(s) appear on the right. reactants product Example: 2 H 2 + O 2  2 H 2 O When we look at any chemical reaction, in order for it to be accurate, it must show that the law of conservation of mass is obeyed.

3. Law of Conservation of Mass mass is neither created nor destroyed in a chemical reaction total mass stays the same atoms can only rearrange So, we need to make sure that there are the same number of each type of atom on each side of the chemical equation. To do this, we add coefficients in front of the compounds until these atoms are “balanced.”

4. Refresh your memory by balancing these equations: __MgCl 2 +__NaOH  __Mg(OH) 2 +__NaCl __Fe 2 (SO 4 ) 3 +__KOH  __K 2 SO 4 +__Fe(OH) 3 2 2 632

5. 2 H 2 + O 2 → 2 H 2 O 3 Mg + N 2 → Mg 3 N 2 Synthesis Reaction A reaction in which two or more elements form a compound.

6. Synthesis 2 or more elements/compounds combine to form 1 product. Only one product! Analogy: Mixing 2 or more ingredients together to get 1 cake.. A + B  AB

7. Al(s)+ Cl 2 (g)  AlCl 3 (s) 2 3 2 Synthesis Example: 2 Mg + O 2  2 MgO Must crisscross to get new compound!

8. Practice Problems: Na + F 2  B + N 2  Na + F 2  NaF +1 Na + F 2  NaF 22

9. Practice Problems: Na + F 2  B + N 2  BN +3-3 B + N 2  BN 22

10. Decomposition Reaction 2 H 2 O → 2 H 2 + O 2 2HgO → 2 Hg + O 2 A reaction in which a compound is broken down into two or more elements.

11. Decomposition 1 compound is broken down into 2 or more simpler elements/compounds. only one reactant Analogy: A couple breaks up. Or a body decompses. AB  A + B

13. KBr  K + Br 2 2 2 Decomposition Example

14. Practice Problems: Na 2 O  CF 4  Na 2 O  NaO Na 2 O  Na + O 2 24 + 2

15. Single Replacement Reaction 2 KCl + F 2 → 2 KF + Cl 2 Mg + 2 HCl → H 2 + MgCl 2 A reaction in which one element reacts with one compound to form another element and another compound.

16. Single Replacement one element replaces another in a compound –metal replaces metal (+) –nonmetal replaces nonmetal (-) A + BC  B + AC

17. Fe(s)+ CuSO 4 (aq)  Cu(s)+ FeSO 4 (aq) Products: Metal replacement: 2 Na + CuCl 2  2 NaCl + Cu Halogen replacement: F 2 + 2 KCl  2 KF + Cl 2 –free element must be more active (check activity series)more active Br 2 (l)+ NaCl(aq)  N.R.

18. Activity Series MetalsNonmetals lithiumfluorine potassiumchlorine calciumbromine sodiumiodine magnesiumoxygen aluminumnitrogen zinc chromium iron nickel tin lead hydrogen* copper mercury silver platinum gold

19. Practice Can Al replace Li? ____ Can Cu replace Au? ____ Can Br replace I? ____ Can Cl replace F? ____ NO Yes YES

20. Practice Problems: H 2 + PbCl 2  Cl 2 + KBr  Zn + CuS  H 2 + PbCl 2  No rxn +1+2

21. Practice Problems: H 2 + PbCl 2  Cl 2 + KBr  Zn + CuS  Cl 2 + KBr  +1 KCl +1 + Br 2 Cl 2 + KBr  KCl + Br 2 22

22. Practice Problems: H 2 + PbCl 2  Cl 2 + KBr  Zn + CuS  +2-2+2 ZnS +2 -2 + Cu Zn + CuS  ZnS + Cu

23. Double Replacement Reaction Pb(NO 3 ) 2 + K 2 CrO 4  PbCrO 4 + 2 KNO 3 NaCl + AgNO 3  AgCl + NaNO 3 A reaction in which the metals present in two compounds change places to form two new compounds.

24. AB + CD  AD + CB Double Replacement Ions from 2 ionic compounds switch places. --put the inside ions together and the outside ions together --positive ion always goes first in the compound! Analogy: 2 couples are dancing, and they switch partners

25. Pb(NO 3 ) 2 (aq)+ KI(aq)  PbI 2 (s)+ KNO 3 (aq) Double Replacement Example: FeCl 2 + Na 2 CO 3  2 NaCl + FeCO 3

26. Practice #1 Na 2 CO 3 + Ca(NO 3 ) 2  Na 2 CO 3 + Ca(NO 3 ) 2  NaNO 3 +CaCO 3 NaNO 3 + CaCO 3 +1 -2 +2 2

27. Practice #2 K 3 PO 4 + MgCl 2  K 3 PO 4 + MgCl 2  KCl + Mg 3 (PO 4 ) 2 KCl + Mg 3 (PO 4 ) 2 +1-3+2 236

28. Combustion When a carbon compound reacts with oxygen to make carbon dioxide and water. –Hint: It will always have O 2 on reactant side It will always have CO 2 and H 2 O on product side Example: CH 4 + O 2 → CO 2 + H 2 O

29. Combustion CH 4 (g) + 2O 2 (g)  CO 2 (g) + 2H 2 O(g) Also known as burning; always follows the same form: The compound always burns in oxygen gas and always releases carbon dioxide and water. During incomplete combustion (a limited amt. of O2), carbon monoxide (CO) is also produced. C & H (& sometimes O) + O 2  CO 2 + H 2 O

30. Example: 2 C 3 H 6 + 9 O 2  6 CO 2 + 6 H 2 O *always balance in order: C, H, O Practice Problems: CH 4 + O 2  C 6 H 14 + O 2  CO 2 + H 2 O 22 1214219