Identify the following as combination, decomposition, replacement, or ion exchange reactions: Al (s) + 3 Cl2 (g) → 2 AlCl3 (s) Ca (OH) 2 (aq) + H2SO4 (aq) → CaSO4 (aq) + 2 H2O (l

2 Al (s) + 3Cl₂ (g) → 2AlCl₃ (s)

This is a combination reaction.

Ca (OH) ₂ (aq) + H₂SO₄ (aq) → CaSO₄ (aq) + 2H₂O (l)

This is a replacement reaction.

Explanation:

A combination reaction is a reaction in which two reagents are combined into one product. The reaction has the following general form:

A + B → AB

where A and B represent any two chemical substances.

2 Al (s) + 3Cl₂ (g) → 2AlCl₃ (s)

This is a combination reaction because a single compound forms from two or more reacting species.

Double Substitution, Double Displacement or Metastasis Reactions are those in which two elements found in different compounds exchange their positions forming two new compounds. These chemical reactions do not present changes in the number of oxidation or relative load of the elements. So they are not considered redox reactions.

The solvent of the double displacement reactions usually is water and the reagents and products are usually ionic compounds (cations or anions are exchanged), although they can also be acids or bases.

In general, this type of reaction can be expressed as:

AB + CD ⇒ AD + CD

In the reaction:

Ca (OH) ₂ (aq) + H₂SO₄ (aq) → CaSO₄ (aq) + 2H₂O (l)

This is a replacement reaction because it is a double replacement reaction in which the ions are exchanged to form new compounds.