Question

Which of the following statements describes the correct method of preparation of 1.00 L of a 2.0 M urea solution?
urea = 60.06 g/mol
A) Dissolve 120 g of urea in 1.00 kg of distilled water.
B) Dissolve 120 g of urea in 880 g of distilled water.
C) Dissolve 120 g of urea in enough distilled water to produce 1.00 L of solution.
D) Dissolve 120 g of urea in 1.00 liter of distilled water.
E) The density of urea is needed in order to do this calculation

Answer 1

Answer:

To prepare 1.00 L of 2.0 M urea solution, we need to dissolve 120 g of urea in enough water to produce a total of 1.00 L solution

Explanation:

Molarity of a solute in a solution denotes number of moles of solute dissolved in 1 L of solution.

So, moles of urea in 1.00 L of a 2.0 M urea solution = 2 moles

We know, number of moles of a compound is the ratio of mass to molar mass of that compound.

So, mass of  2 moles of urea = $(2\times 60.06)g=120 g$

Therefore to prepare 1.00 L of 2.0 M urea solution, we need to dissolve 120 g of urea in enough water to produce a total of 1.00 L solution

So, option (C) is correct.

Answer 2

The correct statement that describes method of preparation of 1.00 L of a 2.0 M urea solution is:

C) Dissolve 120 g of urea in enough distilled water to produce 1.00 L of solution.

Molarity:

It is the concentration of a solution measured as the number of moles of solute per liter of solution.

So, moles of urea in 1.00 L of a 2.0 M urea solution = 2 moles

Number of moles is defined as the ratio of given mass over molar mass.

$\text{Number of moles}= \frac{\text{Given mass}}{\text{Molar mass}}$

Then, mass of 2 moles of urea = $2*60.06g/mol=120g$

In order to prepare 1.00 L of 2.0 M urea solution, we need to dissolve 120 g of urea in enough water to produce a total of 1.00 L solution

Thus, correct option is C.

Find more information about Molarity here:

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