Question

A 45.3 g sample of potassium nitrate is dissolved in enough water to make

225 mL of solution. Determine the molar concentration of the potassium nitrate.

Answer 1

1.99 M

Step-by-step explanation:

It gives the mass of a compound, KNO3. First, find the gram formula mass of KNO3. You should get 101.102 g/mol, or something very close. Next, divide given mass by g/mol mass to get number of moles. In this case, 45.3/101.102 = .44806, roughly.

Now, since it says molar concentration, it is asking for moles per liter of solution. If it only gives you 225 mL, or .225 L, you have to adjust for that value. Divide the number of moles you have by number of liters.

.44806/.225 = 1.99 M. This isn't the exact answer, but always remember to round for significant figures. Since both numbers contain 3 significant figures, your answer should have 3. Therefore 1.99 is your answer.