Section 8-1Describing Chemical Reactions
Chemical Reactions
• Watch closely• Record all
indications of a chemical reaction.
Write a word equation…
• Silver nitrate reacts with sodium chloride dissolved in water to form silver chloride and sodium nitrate
Silver nitrate + sodium chloride silver chloride + sodium nitrate
Now a formula equation…
• Silver nitrate reacts with sodium chloride dissolved in water to form silver chloride and sodium nitrate
Silver nitrate + sodium chloride silver chloride + sodium nitrate
AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
Chemical Reactions
• Watch closely• Record all
indications of a chemical reaction.
Try writing a word equation• potassium metal
reacts with water to produce aqueous potassium hydroxide and hydrogen gas.
Potassium + water potassium hydroxide + hydrogen
Now a formula equation…• potassium metal
reacts with water to produce aqueous potassium hydroxide and hydrogen gas.
Potassium + water potassium hydroxide + hydrogen
K (s) + H2O KOH (aq) + H2 (g)
Chemical Reactions
• Watch closely• Record all
indications of a chemical reaction.
(NH4)2Cr2O7(s) → N2(g) + Cr2O3(s) + 4H2O(g)Δ
Start with a word equation…• The reactant,
Ammonium dichromate is heated to yield the products nitrogen, chromium(III) oxide, and water
Ammonium dichromate nitrogen + chromium(III) oxide + water
Δ
Turn the word equation into a formula equation…
• The reactant, Ammonium dichromate is heated to yield the products nitrogen, chromium(III) oxide, and water
(NH4)2Cr2O7(s) → N2(g) + Cr2O3(s) + H2O(g)Δ
Turn the word equation into a formula equation…
• Our formula equation states the facts, and gives the correct chemical formulas for the reactants and products.
• What are we missing?
(NH4)2Cr2O7(s) → N2(g) + Cr2O3(s) + H2O(g)Δ
All Equations Can Be Translated Into A Sentence
2HgO(s) → 2Hg(l) + O2(g)
When heated, solid mercury (II) oxide yieldsliquid mercury and oxygen gas.
Example #1
• Solid sodium combines with chlorine gas to produce solid sodium chloride.
Example #2
• When solid copper reacts with aqueous silver nitrate, the products are aqueous copper (II) nitrate and solid silver.
Example #3
• In a blast furnace, the reaction between solid iron (III) oxide and carbon monoxide gas produces solid iron and carbon dioxide gas.
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