Question

Explain how you would make up a one molar (1m) solution of ethyl alcohol.

Answer 1

The formula of molarity is:

`molarity = (number of moles of solute)/(volume of solution in Liter)`

Number of moles is given as:

`number of moles of solute= (mass of solute)/(Molar mass of solute)`

So, the formula of molarity can be written as:

`molarity = ((mass of solute)/(Molar mass of solute))/(volume of solution in Liter)` -(1)

Molar mass of ethyl alcohol,
`C_2H_5OH` =
`2* 12+6* 1+16 = 46 g/mol`

Molarity of ethyl alcohol,
`C_2H_5OH` = 1 molar (given)

Let the volume of solvent that is water be 1 L.

Substituting the values in formula (1):

`1 M = ((mass of solute)/(46 g/mol))/(1 L)`

`mass of solute = 46 g/mol* 1 mol/L* 1 L`

`mass of solute = 46 g`

Since, ethyl alcohol is liquid in room temperature:

Density of ethyl alcohol is
`0.7892 g/mL`

Density =
`(mass)/(volume)`

So, volume of ethyl alcohol =
`(mass of ethyl alcohol)/(density of ethyl alcohol)`

Volume of ethyl alcohol =
`(46 g)/(0.7892 g/mL)`

Volume of ethyl alcohol =
`58.29 mL`

Hence, by dissolving 58.29 mL of ethyl alcohol in 1 L of water, 1 M solution of ethyl alcohol can be prepared.