Which statement about the combustion of propane (C3H8) is not correct?

all of them ...

The equation you have written for the combustion of propane is correct.

The equation you provided for the combustion of propane (C3H8 + 5O2 = 3CO2 + 4H2O) is correct. Therefore, there is no statement about the combustion of propane in the equation that is not correct.

The correct statement about the combustion of propane (C3H8) is that when it reacts with oxygen (O2), it produces carbon dioxide (CO2) and water (H2O) according to the balanced equation: C3H8 + 5O2 = 3CO2 + 4H2O. However, to determine which statement is not correct, we need to consider multiple possibilities. Here's how:

1. Propane reacts with oxygen: This statement is correct as it describes the combustion process of propane.

2. 5 moles of oxygen react: This statement is correct and is based on the stoichiometry of the balanced equation, which shows that 5 moles of oxygen are needed to completely react with 1 mole of propane.

3. 3 moles of carbon dioxide are produced: This statement is also correct and is based on the balanced equation, which states that 1 mole of propane produces 3 moles of carbon dioxide.

4. 6 moles of water are produced: This statement is not correct. According to the balanced equation, 1 mole of propane produces 4 moles of water (H2O), not 6 moles.

Therefore, the statement "6 moles of water are produced" is not correct.