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.

answer: c.

explanation:

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6