Predicting Reactions
Flow Sheet
Method:
1. Write the correct formulas of reactants.
2. Remember key words, eg. burns means reacts with O2 (oxygen).
3. Draw pictures to see statement clearly.
4. Predict products using the correct formulas.
5. Balance the equation.
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DOUBLE DISPLACEMENT REACTIONS |
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(example) |
AB + CD ® AD + CB (Remember to always write the cation 1st then the anion) |
(solution) |
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Type I - Precipitation Reactions (refer to the solubility tables)
(aq) + (aq)
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(s) + (aq)
(aq) + (aq)
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(s) + (aq) |
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lead(II) nitrate reacts with potassium iodide to form (you know) |
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Pb(NO3)2 (aq) + 2 KI (aq) ® PbI2 (s) + 2 KNO3 (aq) |
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Type II - Neutralization Reactions acid + base ® water + salt + heat |
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hydrochloric acid reacts with sodium hydroxide to yield ( you know) |
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HCl (aq) + NaOH (aq)® H2O (l) + NaCl (aq) |
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Type III - Gaseous Reactions |
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Formation of CO2 gas Carbonate (CO3 2- ) reacts with an acid |
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NaHCO3 + HCl ® CO2(g) + H2O(l) + NaCl(aq) (via an intermediate reaction) |
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Formation of SO2 gas Sulfite (SO3 2- ) reacts with an acid |
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Na2SO3 + 2HNO3 ® SO2(g)+ H2O(l) + 2 NaNO3(aq) (via an intermediate reaction) |
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Formation of H2S gas (the rotten egg smell) Sulfide (S 2- ) reacts with an acid |
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Na2S + H2SO4 ® H2S(g)+ Na2SO4(aq) (directly) |
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Formation of HCN gas Cyanide (CN-) reacts with an acid |
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LiCN + HCl ® HCN(g) + LiCl(aq) |
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SINGLE REPLACEMENT REACTIONS |
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(example) |
A + BC ® AC + B metal or nonmetal replaces another element (refer to the activity series) |
(solution) |
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a piece of sodium metal is placed into a test tube containing lead (II) nitrate |
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2 Na + Pb(NO3)2 ® 2 NaNO3(aq) + Pb(s) |
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COMBUSTION |
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(example) |
CH or CHO + O2 ® CO2 + H2O + Heat
hydrocarbon or hydrocarbon with oxygen forms carbon dioxide water and heat
(YOU ARE EXPECTED TO KNOW THE PRODUCTS) |
(solution) |
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Methane Burns |
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CH4(g) + 2O2(g) ® CO2(g) + 2 H2O(g) + Heat (unbalanced equation) |
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COMBINATION REACTION |
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(example) |
A + B ® AB two or more substance forms only ONE substance |
(solution) |
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nitrogen reacts with hydrogen to form ammonia |
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N2 + 2 H2 ® 2 NH3 |
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DECOMPOSITION REACTION |
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(example) |
AB ® A + B ONE substance breaks down to two or more substances |
(solution) |
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sodium nitrate when heated to form sodium nitrite and oxygen |
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2 NaNO3 ® 2 NaNO2 + O2 |