Here's how to calculate the molarity of the hydrochloric acid solution:

1. Convert Units:

* Volume of HCl gas (L): 2.14 L (already in liters)

* Pressure of HCl gas (atm): 2.61 atm (already in atmospheres)

* Temperature of HCl gas (K): 28 °C + 273.15 = 301.15 K

* Volume of water (L): 668 mL / 1000 mL/L = 0.668 L

2. Use the Ideal Gas Law to find moles of HCl:

* Ideal Gas Law: PV = nRT

* P = Pressure (atm)

* V = Volume (L)

* n = Number of moles

* R = Ideal gas constant (0.0821 L⋅atm/mol⋅K)

* T = Temperature (K)

* Solve for n (moles of HCl):

* n = PV / RT

* n = (2.61 atm) * (2.14 L) / (0.0821 L⋅atm/mol⋅K) * (301.15 K)

* n ≈ 0.222 moles of HCl

3. Calculate Molarity:

* Molarity (M) = moles of solute / liters of solution

* M = 0.222 moles HCl / 0.668 L solution

* M ≈ 0.332 M

Therefore, the molarity of the hydrochloric acid solution is approximately 0.332 M.