Calculation of Volume of Methanol for Making a 0.25 Molar Solution

To determine the volume of methanol required to make a 0.25 molar solution, the following calculations need to be performed:

Step 1: Calculate the molecular weight of methanol.

The molecular weight of methanol is calculated by adding the atomic weights of carbon, hydrogen, and oxygen present in the molecule. The molecular formula of methanol is CH3OH, which means it has one carbon atom, four hydrogen atoms, and one oxygen atom.

Therefore, the molecular weight of methanol can be calculated as follows:

Molecular weight of methanol = (1 x atomic weight of carbon) + (4 x atomic weight of hydrogen) + (1 x atomic weight of oxygen)

= (1 x 12.01) + (4 x 1.01) + (1 x 16.00)

= 32.04 g/mol

Step 2: Calculate the number of moles of the solute required.

The molarity of a solution is defined as the number of moles of solute present in one liter of the solution. Therefore, to calculate the number of moles of methanol required to make a 0.25 molar solution, we need to multiply the molarity with the volume of the solution.

Moles of Methanol = Molarity x Volume

Given that the volume of the solution is 2.5 L and the molarity is 0.25 M, we can calculate the number of moles of methanol required as follows:

Moles of Methanol = 0.25 x 2.5

= 0.625 moles

Step 3: Calculate the mass of methanol required.

The mass of methanol required can be calculated by multiplying the number of moles of methanol with its molecular weight.

Mass of Methanol = Moles of Methanol x Molecular Weight

= 0.625 x 32.04

= 20.025 g

Step 4: Calculate the volume of methanol required.

The density of methanol is given as 0.793 kg/L. Therefore, we can calculate the volume of methanol required as follows:

Volume of Methanol = Mass of Methanol / Density

= 20.025 / 0.793

= 25.25 mL

Therefore, the volume of methanol required to make a 0.25 molar solution with a volume of 2.5 L is 25.25 mL.