The document discusses balancing chemical equations by ensuring that the number of each type of atom is equal on both sides of the reaction arrow. It provides examples of chemical equations and how to balance them by inspecting the numbers of each element in the reactants and products and adjusting coefficients as needed so the numbers are the same on both sides. The document also provides additional examples of chemical equations to balance.

1. BALANCING CHEMICAL REACTIONS

2. How molecules are symbolized Cl 2 2Cl 2Cl 2 Molecules may also have brackets to indicate numbers of atoms. E.g. Ca(OH) 2 Notice that the OH is a group The 2 refers to both H and O How many of each atom are in the following? a) NaOH b) Ca(OH) 2 c) 3Ca(OH) 2 Na = 1, O = 1, H = 1 Ca = 1, O = 2, H = 2 Ca = 3, O = 6, H = 6 O H O H Ca

3. Balancing equations: MgO The law of conservation of mass states that matter can neither be created or destroyed Atoms are neither created nor destroyed, only rearranged in a chemical reaction The number of a particular atom is the same on both sides of a chemical equation Example: Magnesium + Oxygen Mg + O 2  MgO However, this is not balanced Left: Mg = 1, O = 2 Right: Mg = 1, O = 1 O Mg O +  Mg O

4. Balance equations by “inspection” Hints: start with elements that occur in one compound on each side. Treat polyatomic ions that repeat as if they were a single entity. 5 2 3 3.5 2 7 4 6 2 2 2 2 6 3 C 2 H 6 + O 2  CO 2 + H 2 O a) P 4 + O 2  P 4 O 10 b) Li + H 2 O  H 2 + LiOH c) Bi(NO 3 ) 3 + K 2 S  Bi 2 S 3 + KNO 3 d) C 2 H 6 + O 2  CO 2 + H 2 O From Mg + O 2  MgO 2Mg + O 2  2MgO is correct Mg 2 + O 2  2MgO is incorrect Mg + O  MgO is incorrect

5. a) Mg + HCl  MgCl 2 + H 2 b) Ca + N 2  Ca 3 N 2 c) NH 4 NO 3  N 2 O + H 2 O d) BiCl 3 + H 2 S  Bi 2 S 3 + HCl e) C 4 H 10 + O 2  CO 2 + H 2 O f) O 2 + C 6 H 12 O 6  CO 2 + H 2 O g) NO 2 + H 2 O  HNO 3 + NO h) Cr 2 (SO 4 ) 3 + NaOH  Cr(OH) 3 + Na 2 SO 4 i) Al 4 C 3 + H 2 O  CH 4 + Al(OH) 3 Balance these equations:

6. We have looked at several types of reactions without worrying about balancing However, all equations should be balanced Predict the products and balance these: (recall, metals above replace metals below, reactions with water yield metal hydroxides) Cu + Fe 2 (SO 4 ) 3 NR (no reaction) Zn + Li 2 CO 3 Cu + AlCl 3 Returning to reaction types Fe + CuSO 4  LiOH + H 2 Al 2 O 3 2 Ni + NaCl  Al + CuCl 2  Li + ZnCO 3  Li + H 2 O  Al + O 2  3 3 3 2 2 3 2 ½ 2 2 2 3 2 4 Cu Hg Ag Ca Mg Al Zn Fe Ni Sn Pb H Au Li Na K

7. a) KNO 3  KNO 2 + O 2 b) Pb(NO 3 ) 2  PbO + NO 2 + O 2 c) P 4 + I 2  PI 3 d) MgO + H 3 PO 4  Mg 3 (PO 4 ) 2 + H 2 O e) Br 2 + KI  I 2 + KBr f) Ca(OH) 2 + HNO 3  Ca(NO 3 ) 2 + H 2 O g) Bi 2 O 3 + H 2  Bi + H 2 O h) Fe + O 2  Fe 3 O 4 i) CaO + C  CaC 2 + CO 2 Here are some more to balance:

8. Exercise: a) Li + H 2 O  H 2 + LiOH b) P 4 + O 2  P 4 O 10 c) C 2 H 6 + O 2  CO 2 + H 2 O d) CS 2 + O 2  CO 2 + SO 2 e) AsCl 3 + H 2 S  As 2 S 3 + HCl f) AgNO 3 + FeCl 3  AgCl + Fe(NO 3 ) 3 g) KClO 3  KCl + O 2 h) SO 2 + O 2  SO 3 For more lessons, visit www.chalkbored.com