Answer: 0.5 M
Step-by-step explanation:
Ammonium chloride has a gram formula mass of 53.49 g/mol, so 26.8 grams of ammonium chloride is 26.8/53.49 = 0.501 mol.
So since molarity = (moles of solute)/(liters of solution), the answer is 0.501 / 0.25 = 0.5 M