What volume of methanol should be used to make 1.25 L of a 21.0% by volume solution

0.2625 litres is the volume of methanol should be used to make 1.25 L of a 21.0% by volume solution.

Explanation:

Given that:

Volume of solution = 1.25 litres

methanol to be present in the composition of 21% of the volume.

To make 21 % solution by volume of a substance it means that 21 L of the substance is present in 100 L of the solution which is made upto 100 L by adding the solvent.

So, 21 L in 100 L will make 21% solution

x litres of methanol in 1.25 L of solution

So, =

x = 0.2625 litres

hence, 0.2625 litres of the methanol will be added and the volume will be made to 1.25 litres so that 21% solution by volume gets form.

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally