Calcium reacts with water according to the chemical equation below:

Ca + 2H2O--> Ca(OH)2 + H2
All but which reaction is expected to occur on the basis of the reaction of calcium and water?

To determine which reaction is not expected to occur based on the reaction of calcium and water, let's analyze the products formed in the given chemical equation:

Ca + 2H2O → Ca(OH)2 + H2

According to this equation, calcium (Ca) reacts with water (H2O) to form calcium hydroxide (Ca(OH)2) and hydrogen gas (H2). The expected reactions are the formation of Ca(OH)2 and H2.

Now, let's consider the potential reactions that could occur when calcium reacts with water:

1. Formation of calcium hydroxide (Ca(OH)2) and hydrogen gas (H2) - This reaction is expected based on the equation provided.

2. Formation of calcium oxide (CaO) and hydrogen gas (H2):
Ca + 2H2O → CaO + H2
This reaction is expected because calcium oxide can form when calcium reacts with water vapor instead of liquid water.

3. Formation of calcium hydroxide (Ca(OH)2) and dihydrogen monoxide (H2O):
2Ca + 4H2O → 2Ca(OH)2 + 2H2O
This reaction is also expected since it involves the formation of Ca(OH)2 and H2O, which are both products in the given equation.

4. Formation of calcium chloride (CaCl2) and hydrogen gas (H2):
Ca + 2H2O → CaCl2 + H2
This reaction is not expected based on the given equation. Calcium chloride does not appear as a product in the equation, so this reaction is not anticipated to occur.

Hence, the reaction that is not expected to occur based on the reaction of calcium and water is the fourth reaction, the formation of calcium chloride (CaCl2) and hydrogen gas (H2).