Question

What is the molarity of a solution that has 29.25 grams of NaCl dissolved to make 1.5 L of a solution?
(a) 19.5 M
(b) 3.0M
(c) 1.75 M
(d) 0.33 M
(e) 1.0 M

Answer 1

Molarity is the number of moles of solute to the volume of solution and we can easily find the molarity by using the formula as; $Molarity=\dfrac{moles\text{ }of\text{ }solute}{volume\text{ }of\text{ }the\text{ }solution(in\text{ }liters)}$. Now solve the given statement.

Complete step-by-step answer: First of let’s discuss what is molarity. By the term molarity we simply mean the number of moles of the solute to the total volume of the solution in 1 liter or 1000 ml of the solution.
Mathematically, molarity is as;
$Molarity=\dfrac{moles\text{ }of\text{ }solute}{volume\text{ }of\text{ }the\text{ }solution(in\text{ }liters)}$
It is denoted by M. The molarity of the solution depends on the temperature of the solution. as the temperature changes, volume of the solution changes and vice-versa.
Now considering the statement as;
Using the molarity formula as;
$Molarity=\dfrac{moles\text{ }of\text{ }solute}{volume\text{ }of\text{ }the\text{ }solution(in\text{ }liters)}$
Number of moles of the solute=$\dfrac{Given\text{ }mass}{molar\text{ }mass}$
Given mass of NaCl=29.25 grams
Molar mass of NaCl=$23+35.5=55.5$ grams
Then;
Number of moles of the solute=$\dfrac{29.25}{55.5}=0.527$
Volume of the solution =1.5 L (given)
Thus, molarity of the NaCl solution is as;
$Molarity=\dfrac{0.527}{1.5}=0.33M$
So, the molarity of a solution that has 29.25 grams of NaCl dissolved to make 1.5 L of a solution is 0.33 M.

Hence, option (d) is correct.

Note: Don’t get confused in the molarity and molarity of the solution. By the term molarity, we mean the number of moles of the solute to the total volume of the solution in liters whereas on the other hand, by the term molality, we mean the number of moles of the solute to the total mass of the solvent in kilograms.