Ch 7 Chemical Reactions: An Introduction I.Evidence of a Chemical Reaction A.Color Change: B.Precipitate formed: Precipitate: A solid that is formed in a reaction. C.Energy Change: D.Gas Formed:

II.Chemical Equations A.Chemical Reaction: A rearranging of how atoms are grouped. B.Chemical Equation: A shorthand way of representing a reaction. Reactants on left  Products on right Example: Sodium reacts with chlorine to produce sodium chloride. Na + Cl 2  NaCl List all 7 diatomic elements

C.Law of Conservation of Matter: In a chemical reaction, atoms are neither created or destroyed. There must be the same number of each type of atom on the product side as on the reactant side of the arrow. Na + Cl 2  NaCl (what’s the problem here)

D.Balanced Chemical Equation: Shows the same number of each type of atom at the beginning of a reaction and at the end of a reaction. Use coefficients to balance a reaction. Never change the subscripts Coefficients always go before a compound never in the middle. If no coefficient is shown before a compound, it indicates one of that compound.

NaCl + AgNO 3  AgCl + NaNO 3 1.How many sodiums are in this reaction? 2.How many nitrates are in this reaction?

2HCl + Zn  ZnCl 2 + H 2 How many Hydrogens are in this reaction?

2MnSO 4 How many manganese's are in this formula How many Sulfurs are represented? How many oxygen's are represented? How many sulfates are represented?

Li + Cl 2  LiCl Balance the above equation

Mg + Na 2 O  MgO + Na Balance the above reaction

Al + Cl 2  AlCl 3 Balance the above reaction

Potassium reacts with chlorine to produce potassium chloride Write the balanced chemical equation for the above reaction

Silver oxide reacts with Chlorine to produce Silver chloride and oxygen. Write the balanced chemical equation for the above reaction.

E.Physical States in a balanced equation. Solid (s) Liquid (l) Gas (g) Aqueous (aq): dissolved in water Write the balanced chemical equation including the states of matter for the following reaction Solid Sodium react with liquid water to produce hydrogen gas and aqueous sodium oxide 2Na (s) + H 2 O (l)  H 2(g) + Na 2 O (aq) Hw 7a: pg 248: 5-8,35

Hw 7a answers 5a. N 2, H 2 b.NH 3 6.Atoms 7.Solid 8.Water 35a. 2H 2 O 2(aq)  2H 2 O (l) + O 2(g) b.2Ag (s) + H 2 S (g)  Ag 2 S (s) + H 2(g) c.2FeO (s) + C (s)  2Fe (l) + CO 2(g) d.Cl 2(g) + 2KI (aq)  2KCl (aq) + I 2(s)

Write the following formulas 1.Sulfur trioxide 2.Lithium Sulfate 3.Magnesium Nitride 4.Copper (I) oxide 5.Ammonium sulfide 6.Iron (II) phosphate 7.Lithium Iodide

Balance the following Equations 1.MgCl 2 + Li 2 CO 3  MgCO 3 + LiCl 2.NaNO 3 + K 3 N  Na 3 N + KNO 3 3.MgCl 2 + Al 2 (SO 4 ) 3  MgSO 4 + AlCl 3 4.Silver Oxide reacts with Chlorine to produce silver chloride and oxygen.