Synthesis:
· two or more elements or compounds may combine to form a more complex compound.
· Basic form: A + X → AX
Examples of synthesis reactions:
1. Metal + oxygen → metal oxide
2Mg + O2 à 2MgO
2. Nonmetal + oxygen → nonmetallic oxide
EX. C(s) + O2(g) → CO2(g)
3. Metal oxide + water → metallic hydroxide (base)
EX. MgO(s) + H2O(l) → Mg(OH)2(s)
4. Nonmetallic oxide + water → acid
EX. CO2(g) + H2O(l) → ; H2CO3(aq)
5. Metal + nonmetal → salt
EX. 2 Na(s) + Cl2(g) → 2NaCl(s)
6. A few nonmetals combine with each other.
EX. 2P(s) + 3Cl2(g) → 2PCl3(g)
7. Metal oxide + carbon dioxide à metal carbonate
Ex. MgO + CO2 à MgCO3
8. Metal chloride + oxygen à Metal chlorate
Ex. 2NaCl + 3O2 à 2NaClO3
These two reactions must be remembered:
1. N2(g) + 3H2(g) → 2NH3(g)
2. NH3(g) + H2O(l) → NH4OH(aq)
Complete the following word equations, and write and balance the formula equation.
1. calcium + oxygen à
2. copper + sulfur à
3. calcium oxide + water à
4. hydrogen + nitrogen à
5. hydrogen + chlorine à
6. silver + sulfur à
7. chromium + oxygen à
8. aluminum + bromine à
9. sodium + iodine à
10. hydrogen + oxygen à
11. aluminum + oxygen à
Synthesis Reaction Practice
1) MgCl2 + O2 --->
2) Ag + O2 --->
3) P2O3+ H2O --->
4) K2O + H2O --->
6) BeO + CO2 --->
7) Al2O3 + H2O --->
8) SO3 + H2O --->
9) NaCl + O2 --->
5) BaO + CO2 --->
6) BeO + CO2 --->
7) Al2O3 + H2O --->
8) SO3 + H2O --->
9) NaCl + O2 --->
Decomposition:
· A single compound breaks down into its component parts or simpler compounds.
· Basic form: AX → A + X
Examples of decomposition reactions:
1. Metallic carbonates, when heated, form metallic oxides and CO2(g).
EX. CaCO3(s) → CaO(s) + CO2(g)
2. Most metallic hydroxides, when heated, decompose into metallic oxides and water.
EX. Ca(OH)2(s) → CaO(s) + H2O(g)
3. Metallic chlorates, when heated, decompose into metallic chlorides and oxygen.
EX. 2KClO3(s) → 2KCl(s) + 3O2(g)
4. Some acids, when heated, decompose into nonmetallic oxides and water.
EX. H2SO4 → H2O(l) + SO3(g)
5. Some oxides, when heated, decompose.
EX. 2HgO(s) → 2Hg(l) + O2(g)
6. Some decomposition reactions are produced by electricity.
EX. 2H2O(l) → 2H2(g) + O2(g)
EX. 2NaCl(l) → 2Na(s) + Cl2(g)
Predict the following decomposition reactions
1) Potassium chlorate →
2) Calcium carbonate →
3) Mercury (II) oxide →
4) Aluminum hydroxide →
5) Copper (I) bromide →
6) barium carbonate à
7) magnesium carbonateà
8) potassium carbonateà
9) zinc hydroxide à
10) Iron(II) hydroxide à
11) nickel(II) chlorate à
12) sodium chlorate à
13) potassium chlorate à
14)ulfuric acid à
15) carbonic acid à
16) aluminum oxide à
17) silver oxide à