Question

If the concentration of glucose (${{C}_{6}}{{H}_{12}}{{O}_{6}}$) in blood is $0.9g\text{ }{{L}^{-1}}$ , what will be the molarity:
(a)- 5 M
(b)- 50 M
(c)- 0.005 M
(d)- 0.5 M

Answer 1

Hint: The molarity of the solution can be calculated by dividing the number of moles with the volume of the solution. The number of moles can be calculated by dividing the given mass to the molar mass of the compound.

Complete step by step answer:
Molarity: The molarity of the solution is defined as the number of moles of the solute present per liter. It is represented by the symbol, M.
Its formula is:
\[Molarity=\dfrac{\text{Moles of the solute}}{\text{Volume of the solution}}\]
Moles of the component is defined as the ratio of a given mass to the molar mass.
Its formula is:
\[Moles=\dfrac{given\text{ }mass}{\text{molar mass }}\]
So, the question says that the concentration of glucose in the blood is $0.9g\text{ }{{L}^{-1}}$
Therefore, the volume of the solution is $1L$
And the mass of glucose dissolved is $0.9g$.
So, the given mass of glucose is $0.9g$.

The formula of glucose is ${{C}_{6}}{{H}_{12}}{{O}_{6}}$.
We can find the molar mass of glucose:
The molar mass of C = 12
The molar mass of H = 1
The molar mass of O = 16.
So, the molar mass of ${{C}_{6}}{{H}_{12}}{{O}_{6}}$= $6\text{ x }(12)+12\text{ x }(1)+6\text{ x }(16)=180$
So, the molar mass of glucose is 180 g.
So, we can find the number of moles of ${{C}_{6}}{{H}_{12}}{{O}_{6}}$=
\[Moles=\dfrac{given\text{ }mass}{\text{molar mass }}\]$=\dfrac{0.9}{180}=5\text{ x 1}{{\text{0}}^{-3}} mol$
So, the moles of glucose present in the solution is $5\text{ x 1}{{\text{0}}^{-3}}mol$
Now, the volume of the solution is $1L$

The molarity of the solution can be calculated:
\[Molarity=\dfrac{\text{Moles of the solute}}{\text{Volume of the solution}}=\dfrac{5\text{ x 1}{{\text{0}}^{-3}}}{1}=0.005M\]
So, the molarity of the glucose in the blood is 0.005 M

So, the correct answer is “Option C”.

Note: The volume of the solution must be taken in liters only. If the concentration is given in kg or any other unit, it has to be converted into grams. Also, note that molarity is expressed in moles per litre of solution whereas molality is expressed in moles per kg of solvent.