Question

If the density of methanol is 0.8 kgL-1, what is the
volume needed for making 2.5 L of its 0.4 M
solution ?
(1) 0.4 L
(2) 4.0 L
(4) 40 L
(3) 0.04 L​

Answer 1

Molarity = 0.4 M

Volume of solution = 2.5 L

Molarity = (moles of Methanol)/Litres of solution)

0.4 = (moles of CH3OH)/2.5

moles of CH3OH = 1 mole.

Molar mass of CH3OH = 12 + 3 + 16 + 1 => 32 grams per mole.

So, 32 x 1 => 32 grams of Methanol is needed to make the solution.

=> 0.032 kg of Methanol is needed.

Density = 0.8 kgL-1

Density = mass/volume

0.8 kgL-1= 0.032 kg / x L

x = 0.032 / 0.8

x= 0.04 L

Hence, the correct answer is 4) 0.04 L

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