Understanding the Concepts

* Molarity (M): Molarity is a measure of concentration, defined as moles of solute per liter of solution.

* Moles (mol): A mole is a unit of measurement that represents a specific number of particles (6.022 x 10^23).

Calculation

1. Use the formula: moles = Molarity x Volume (in liters)

2. Plug in the values:

* Molarity = 0.5 M

* Volume = 2.5 L

3. Calculate:

* moles = 0.5 M * 2.5 L = 1.25 mol

Answer: There are 1.25 moles of HCl in 2.5 L of a 0.5 M solution.