how many moles of water are produced from the combustion of 3.5 mol of hydrogen and 5.2 mol of oxygen

This is a limiting reagent problem. You know that when BOTH of the reactants are listed. Print these instructions and remember them.

1. Write the equation and balance it.

2a. Using the coefficients in the balanced equation, convert 3.5 moles hydrogen to moles of H2O.
2b. Same procedure, convert 5.2 moles oxygen to moles H2O.
2c. It is likely that the answer from 2a and 2b will be different which means one of them is wrong. The correct answer, in limiting reagent problems. is ALWAYS the smaller value and the reactant producing that value is the limiting reagent.

To determine how many moles of water are produced from the combustion of hydrogen and oxygen, we'll first need to identify the balanced chemical equation for the reaction.

The balanced equation for the combustion of hydrogen can be represented as follows:

2 H₂ + O₂ → 2 H₂O

This equation tells us that 2 moles of hydrogen react with 1 mole of oxygen to produce 2 moles of water.

Now, let's use the stoichiometry of the balanced equation to find the moles of water produced.

1. Start with the given number of moles of hydrogen: 3.5 mol H₂
2. Convert the moles of hydrogen to moles of water using the mole ratio from the balanced equation:
3.5 mol H₂ × (2 mol H₂O / 2 mol H₂) = 3.5 mol H₂O
3. Now, repeat the steps for oxygen:
5.2 mol O₂ × (2 mol H₂O / 1 mol O₂) = 10.4 mol H₂O

Therefore, from the combustion of 3.5 mol of hydrogen and 5.2 mol of oxygen, we would produce 3.5 mol + 10.4 mol = 13.9 mol of water.