If the density of methanol is 0.793 kgL-1 , what is the volume needed

1.	If the density of methanol is 0.793 kgL-1 , what is the volume needed for making 2.5 L of its 0.25 M solution?
Answer» Let us calculate moles of methanol present in 2.5 L of 0.25 M solution. Molarity = Moles of CH₃OH /Volume in L 0.25 = Moles of CH₃OH/2.5 Moles of CH₃OH = 0.25 x 2.5 = 0.625 moles Mass of CH₃OH = 0.625 x 32 = 20 g (Molecular mass of CH₃OH = 32) Now 0.793 x 10³ g of CH₃OH is present in 1000 mL 20 g of CH₃OH will be present in = 1000/ 0.793 x 103 x 20 = 25.2 mL

If the density of methanol is 0.793 kgL-1 , what is the volume needed for making 2.5 L of its 0.25 M solution?

Answer»

Let us calculate moles of methanol present in 2.5 L of 0.25 M solution.

Molarity = Moles of CH₃OH /Volume in L

0.25 = Moles of CH₃OH/2.5

Moles of CH₃OH = 0.25 x 2.5 = 0.625 moles

Mass of CH₃OH = 0.625 x 32 = 20 g

(Molecular mass of CH₃OH = 32)

Now 0.793 x 10³ g of CH₃OH is present in 1000 mL

20 g of CH₃OH will be present in = 1000/ 0.793 x 103 x 20 = 25.2 mL