Question

How many moles of urea (60. g/mol) must be dissolved in 77.6g of water to give a 3.5 m solution? a) 2.1 x 10^2 molb) 3.5 molc) 0.0035 mold) 0.27 mole) 7.7 x 10^2 mol

Answer 1

Step 1 - Remembering the definition of concentration

The molar concentration of a solution is defined as the quotient between the number of moles of solute (n) and the total volume of solution (V):

`[X\rbrack=(n_x)/(V)`

This equation can be read as the concentration of solute X equals its number of moles divided by the total volume of the solution.

Step 2 - Calculating the molarity of the given solution

We must discover the required number of moles of solute. We have the total volume of the solution (77.6ml) and its final concentration.

Let's substitute these in the formula:

Answer: 0.27 mol would be needed