The number of moles of hydrogen ions available for reaction can be calculated using the formula:

Moles of hydrogen ions = Concentration of HCl (in moles per liter) * Volume of HCl (in liters)

Given:

Concentration of HCl = 1.0 M

Volume of HCl = 18 mL = 0.018 L

Substituting the values in the formula:

Moles of hydrogen ions = 1.0 M * 0.018 L = 0.018 moles

Therefore, 0.018 moles of hydrogen ions are available for reaction.