Question

- Equal mass of 18% (w/w) glucose solution is
mixed with 36% (w/w) glucose solution. If the
density of resultant solution is 1.25 g ml-1 then
molarity of the resulting glucose solution will be
approximately
(1) 2.5 M
(2) 3.2 M
(3) 1.9 M
(4) 5.4 M.​

Answer 1

Answer: (3) 1.9 M

Explanation:

Molarity of a solution is defined as the number of moles of solute dissolved per Liter of the solution.

$Molarity=\frac{n\times 1000}{V_s}$

where,

n= moles of solute

$V_s$ = volume of solution in ml

Given : 18 g of glucose contained in 100 g of solution is mixed with 36 g glucose contained in 100 g of solution. Both the solutions are mixed.

moles of solute=$\frac{\text {given mass}}{\text {molar mass}}=\frac{(18+36)g}{180g/mol}=0.3moles$

mass of solution = 200 g

Density of solution = 1.25g/ml

Volume of solution =$\frac{mass}{density}=\frac{200g}{1.25g/ml}=160ml$

Now put all the given values in the formula of molarity, we get

$Molarity=\frac{0.3\times 1000}{160ml}=1.9M$

Thus molarity of the resulting glucose solution will be 1.9 M