REACTIONS

Reaction Types  Single-replacement  One element replaces a second element in a compound  Cl NaBr  2 NaCl + Br 2  Zn + H 2 SO 4  ZnSO 4 + H 2  Refer to Table 11.2 on page 333

Reaction Types (cont)  Decomposition  Single compound breaks down into 2 or more simpler compounds  2 H 2 O  2 H 2 + O 2  CaCO 3  CaO + CO 2

Reaction Types (cont)  Combination  2 or more reactants form a single new substance  Fe + S  FeS  2CaO + 2 H 2 O  2 Ca(OH) 2

Practice  Complete the worksheet in groups.  Have the first 5 equations completed by the end of class.

Reaction Types (cont)  Double-replacement  Positive ions are exchanged between two compounds  Generally occur in aqueous solution and produce a precipitate  AgNO 3 + NaCl  AgCl + NaNO 3  2 NaOH + H 2 SO 4  Na 2 SO H 2 O

Reaction Types (cont)  Combustion  Element, or compound, reacts with oxygen, producing heat  Oxygen always involved as reactant  CH O 2  CO H 2 O  C 2 H 5 OH + 3 O 2  2 CO H 2 O

BALANCING CHEMICAL EQUATIONS

Example  Bike Manufacturing  Frame + wheel + handlebar + pedal = bicycle  Identify the components, how many are needed?  1 frame, 2 wheels, 1 handlebar and 2 pedals  Skeleton equation:  F + W + H + P = FW 2 HP 2  Balanced?  F + 2 W + H + 2 P = FW 2 HP 2 

Example  Equation IS balanced:

Process  Write the skeleton equation first  Use coefficients to balance the equation  Law of Conservation of Mass  Mass is conserved  Atoms in products are the same as the reactants, but rearranged

Practice  Zn + HCl  ZnCl 2 + H 2  Zn + 2 HCl  ZnCl 2 + H 2  C 2 H 6 + O 2  CO 2 + H 2 O  2 C 2 H O 2  4 CO H 2 O

BCE Practice  ___ Al 2 O 3  ___ Al + ___ O 2  ___ BaCl + ___ H 2 SO 4  ___ BaSO + ___ HCl  ___ CuCl 2 + H 2 S  ___ CuS + ___ HCl

Questions?

Summary  What is a coefficient?  What are the on the left of the chemical equation? On the right?  Worksheet due tomorrow!!