Question

The molarity of a glucose solution containing 36 g of glucose per 400 mL of the solution is:

• A. $1.0$
• B. $0.5$
• C. $2.0$
• D. $0.05$

Answer 1

Answer: (B)

$0.5$

Molarity is a measure of the concentration of a solute in a solution or of any chemical species, in terms of amount of a substance in a given volume. A commonly used unit for molar concentration used in chemistry is mol/L. A solution of concentration 1 mol/L is also denoted as 1 molar (1 M).

Molar concentration or molarity is most commonly expressed in units of moles of solute per litre of solution. For use in broader applications, it is defined as amount of solute per unit volume of solution, or per unit volume available for the species, represented by lowercase c:

$c=\frac{n}{V}$

where,

$n$= no. of moles of solute.

$V$= volume of solution in liters.

Calculation:

Number of moles of glucose is $n=\frac{36}{180}=0.2$ moles

The volume of solution in liters is $V=\frac{400}{1000}=0.4$ litres

Molarity of the given solution is given as $c=\frac{n}{V}$

$⟹c=\frac{0.2}{0.4}⟹c=0.5M$