Synthesis Reaction
A synthesis reaction or direct combination reaction is a type of chemical reaction in which two or more simple substances combine to form a more complex product. The reactants may be elements or compounds. The product is always a compound.
General Form of a Synthesis Reaction
The general form of a synthesis reaction is:
A + B → AB
Examples of synthesis reactions:
|
Example |
|
2 Mg (s) + O2 (g) → 2 MgO (s) | ||
2 MgCl (s) + O2 (g) → 2 MgClO3 (s) | ||
C (s) + O2 (g) → CO2 (g) | ||
MgO (s) + H2O (l) → Mg(OH)2 (s) | ||
MgO (s) + CO 2 (g) → MgCO3 (s) | ||
CO2 (g) + H2O (l) → H2CO3 (aq) | ||
2 Na(s) + Cl2 (g) → 2 NaCl (s) | ||
2 P (s) + 3 Cl2 (g) → 2 PCl3 (g) |
Remember to use the Criss-crossing Method, taking into account the valence of each element, to determine the correct formula of your products.
Examples:
Reactants |
Analysis |
BCE |
Mg (s) + O2 (s) → |
reaction of metal with oxygen will produce a metal oxide Mg has a valence of 2+ and O has a velence of 2-, criss cross and get MgO |
2 Mg (s) + O2 (g) → 2 MgO (s) |
CaO (s) + CO2 (g)→ | reaction of metal oxide with carbon dioxide will produce a metal carbonate Ca has a velence of 2+ and CO3 has a valence of 2-, criss cross and get CaCO3 |
CaO (s) + CO2 (s) → CaCO3 (s) |
CaO (s) + H2O (l)→ | reaction of metal oxide with water will produce metal hydroxide calcium has a valence of +2 and hydroxide has a valence of -2, criss cross and get Ca(OH)2 |
CaO (s) + H2O (l)→ Ca(OH)2 (s) |
P2O5 (s) + H2O (l) → | reaction of non-metal oxide with water will produce acid acid produced will most likely be phosphoric acid |
P2O5 (s) + 3 H2O (l) →2 H3PO4 (aq) |
Fe (s) + O2 (g) → | reaction of multivalent metal with oxygen will produce one product for each valences of the metal; iron as a cation is either +2 or +3 therefore the two possible products are iron (II) oxide or iron (III) oxide |
2 Fe (s) +3 O2 (g) →2 Fe2O3 (s)
|