Describing Chemical Reactions

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Describing Chemical Reactions
http//www.youtube.com/watch?vF54rqDh2mWA
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Writing Chemical Equations

• used to convey as much info. as possible about
  what happens in a chemical reaction

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• Word Equations
• write out what chemicals are reacting
• hydrogen peroxide ? water oxygen
• hydrogen oxygen ? water
• Chemical Equations
• show the chemical formulas of the chemicals
  reacting
• H2O2 (aq) ? H2O(l) O2(g)
• H2(g) O2(g) ? H2O (l)
• (s) solid, (l) liquid, (g) gas, (aq)
  aqueous solution see Table 11.1 in text
• the above are often referred to as skeletal
  equations because they are not mathematically
  balanced

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• a catalyst is a substance that speeds up the
  reaction but is not used up in the reaction
• H2(g) O2(g) H2O (l)

MnO4
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Balancing Chemical Equations

• each side of the equation must have the same
  number of atoms of each elements
• bicycle example
• frame wheel handlebar pedal ? bike
• frame 2 wheels handlebar 2 pedals ? bike
• tricycle example
• frame wheels handlebar bell ? tricycle
• frame 3 wheels handlebar bell ? tricycle

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• this is NOT balanced

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• A solution of sodium iodide is added to a
  solution of potassium nitrate to make a potassium
  iodide precipitate and a sodium nitrate solution.
• NaI (aq) KNO3 (aq) ? KI (s) NaNO3 (aq)
• 2. Magnesium metal burns in oxygen gas with a
  bright white light to make a white powder called
  magnesium oxide.
• Mg (s) O2 (g) ? MgO (s) heat
• 2Mg (s) O2 (g) ? 2MgO (s) heat
• 3. Gaseous hydrogen (dihydride) and gaseous
  oxygen (dioxide) react explosively to form water
  vapor.
• H2 (g) O2 (g) ? H2O (g) heat
• 2H2(g) O2(g) ? 2H2O (g) heat

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?
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How about these?

• Na2SiO3 HF ? H2SiF6 NaF H2O
• Na2SiO3 8HF ? H2SiF6 2NaF 3H2O
• NaCl (aq) AgNO3 (aq) ? AgCl (s) NaNO3 (aq)
• balanced
• Al(s) O2(g) ? Al2O3(s)
• 4Al(s) 3O2(g) ? 2Al2O3(s)

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