Question

If $6$ g urea is dissolved in $1L$ of water , what is the resultant concentration?

Answer 1

Here in the question, the most important thing to keep in mind is that what they are asking, it’s a simple question, they have just played with the words, so, they are asking for the concentration of the urea and its mass and volume is given to us, so basically they are asking to find the molarity of the urea.

Complete Step By Step Answer:
So, as we can see in the question that they are asking us to find the molarity of the urea for the $6$ g urea is dissolved in $1L$ of water.
So before that let’s have a quick look at the definition of the molarity for a better understanding.
So, molarity can be defined as the number of moles of the solute divided by the volume of the solution.
Also we can write it in the form of formula, thus we will get:
$M = \dfrac{{Number{\text{ of moles of solute(n)}}}}{{Volume(L)}}$
Now we will look for the entities given in the question:
Mass of urea is $6$ g
Volume of the solution is $1L$
And the molar mass of urea is $(N{H_2}CON{H_2})$ $= 60.06$
and also we know that:
Number of moles $= \dfrac{{mass}}{{molar{\text{ }}mass}}$
$n = \dfrac{6}{{60.06}}$
Now we will put this value in the formula of molarity and we will get:
$M = \dfrac{{Number{\text{ of moles of solute(n)}}}}{{Volume(L)}}$
$M = \dfrac{6}{{60.06 \times 1L}}$
$M = 0.010{\text{ Mol }}{{\text{L}}^{ - 1}}$
Thus the resultant concentration is $0.010{\text{ Mol }}{{\text{L}}^{ - 1}}$ .

Note:
Always keep in mind to notice the tricky words given in the question and first try to find out in which formula they fit the best according to their given chemical species like in the above given question, by concentration, they mean the molarity.