1. Chemical reactions Chapter 10

2. Add ionic/net ionic equations Add activity series (metals/nonmetals)

3. Chemical changes Chemical change results in formation of a new substance Chemical bonds are made and broken Energy changes: Breaking bonds absorbs energy Making bonds releases energy Overall energy change may be + or -

4. Signs of a chemical reaction Certain physical changes can indicate the occurrence of chemical changes: Color change Precipitate: sudden formation of a solid from a liquid solution Formation of a gas (fizzing) Change in temperature (evolution or absorption of heat) Flame or explosion

5. Chemical equations Reactants produce Products A + B  C + D Reactants Products Word equations sodium + chlorine  sodium chloride “Skeleton” equations (unbalanced) Na + Cl 2  NaCl

6. Chemical equations Balanced chemical equations: required by the law of conservation of matter Na + Cl 2  NaCl Formulas may not be changed Coefficients are used to equalize the number of atoms on both sides of the equation

7. Balancing chemical equations Count atoms Na + Cl 2  NaCl Left side: 1 Na, 2Cl Right side: 1 Na, 1 Cl Add coefficients to balance equation 2Na + Cl 2  2NaCl Recount atoms to double check

8. Balancing chemical equations KOH + Co(NO 3 ) 3  KNO 3 + Co(OH) 3 If polyatomic ions are unchanged, they can be counted as a unit Left side: 1 K, 1 OH, 1 Co, 3NO 3 Right side: 1 K, 3 OH, 1 Co, 1 NO 3 Fix hydroxides 3KOH + Co(NO 3 ) 3  KNO 3 + Co(OH) 3

9. Balancing chemical equations Fix nitrates 3KOH + Co(NO 3 ) 3  3KNO 3 + Co(OH) 3 Al 2 (CO 3 ) 3  Al 2 O 3 + CO 2 Count atoms: Left side: 2 Al, 3 C, 9 O Right side: 2 Al, 1 C, 5 O Fix carbons

10. Balancing chemical equations Al 2 (CO 3 ) 3  Al 2 O 3 + 3CO 2 This fixes the oxygens also CH 4 + O 2  CO 2 + H 2 O 1C 4H 2O 1C 2H 3O In combustion reactions always leave the oxygen until the last Fix hydrogens CH 4 + O 2  CO 2 + 2H 2 O

11. Balancing chemical equations Fix oxygens CH 4 + 2O 2  CO 2 + 2H 2 O Burning even numbered alkanes C 2 H 6 + O 2  CO 2 + H 2 O Fix carbons C 2 H 6 + O 2  2CO 2 + H 2 O Fix hydrogens

12. Balancing chemical equations C 2 H 6 + O 2  2CO 2 + 3H 2 O Use fraction for oxygens C 2 H 6 + 3.5O 2  2CO 2 + 3H 2 O Double all coefficients to remove fraction 2C 2 H 6 + 7O 2  4CO 2 + 6H 2 O

13. Symbols for physical state (s) = solid (l) = liquid (g) = gas (aq) = aqueous (dissolved in water) HC 2 H 3 O 2(aq) + NaHCO 3(s)  NaC 2 H 3 O 2(aq) + CO 2(g) +H 2 O (l)

14. Types of Chemical Reactions Synthesis reaction A + B  C C + O 2  CO 2 2Na + Cl 2  2NaClNa + Cl 2  NaCl

15. Types of Chemical Reactions Decomposition C  A + B H 2 O  H 2 + O 2 KClO 3  KCl + O 2 2KClO 3  2KCl + 3O 2 (NH 4 ) 2 Cr 2 O 7  N 2 +4H 2 O+Cr 2 O 3 22

16. Types of Chemical Reactions Single displacement A + BC  AC + B Metals displace metals, nonmetals displace nonmetals Fe + CuSO 4  Cu + FeSO 4 Cl 2 +2NaBr (aq)  Br 2 +2NaCl (aq) Cl 2 +NaBr (aq)  Br 2 +NaCl (aq)

17. Types of Chemical Reactions Double displacement AB + CD  AD + CB Metals and nonmetals switch partners NaCl+AgNO 3  NaNO 3 +AgCl (s) 2KI + Pb(NO 3 ) 2  PbI 2 + 2KNO 3 KI+Pb(NO 3 ) 2  PbI 2(s) +KNO 3

18. Types of Chemical Reactions Combustion Element or compound reacting with oxygen 2Mg + O 2  2MgO 2H 2 + O 2  2H 2 O

19. Combustion Reactions Carbon containing compounds give CO 2 and water CH 4 + O 2  CO 2 + H 2 OCH 4 + 2O 2  CO 2 + 2H 2 O C 2 H 5 OH+O 2  CO 2 +H 2 OC 2 H 5 OH+3O 2  2CO 2 +3H 2 O