Moles = 0.252
Molarity = 1.07
This question is badly worded. You're asking for moles and I suspect you really want molarity. The number of moles of ammonium chloride you have in the solution will remain constant regardless of the volume of the solution. However, the molarity of the solution will differ depending upon how concentrated it is. So I'll give you both the number of moles of ammonium chloride you have, and the molarity of the resulting solution. Please talk to your teacher if you're confused by the difference between moles and molarity.
The formula for ammonium chloride is NH4Cl. So let's calculate it's molar mass. Start by looking up the associated atomic weights.
Atomic weight nitrogen = 14.0067
Atomic weight hydrogen = 1.00794
Atomic weight chlorine = 35.453
Molar mass NH4Cl = 14.0067 + 4 * 1.00794 + 35.453 = 53.49146 g/mol
Moles NH4Cl = 13.5 g / 53.49146 g/mol = 0.252376735 mol
Molarity is defined as moles per liter, so let's divide the number of moles we have by the volume in liters. So:
0.252376735 mol / 0.235 l = 1.073943551 M
Rounding to 3 significant figures gives: 0.252 moles, 1.07 molarity.
