Question

Q. If the density of methanol is 0.793 kg L–1, what is its volume needed for making 2.5 L of its 0.25 M
solution?

Answer 1

Explanation:

Molarity" = "Moles of solute"/"Volume of solution (in litres)"#

For given solution

#"0.25 M" = "n"/"2.5 L"#

#"n = 0.625 moles"#

#"0.625 moles"# of methanol is needed.

Molar mass of methanol #("CH"_3"OH") = "32 g/mol"#

• Mass of methanol needed #= 0.625 cancel"mol" × "32 g"/cancel"mol" = "20 g"#

Density of methanol #= "0.793 kg/L" = "793 g/L"#

#"Volume" = "Mass"/"Density"#

• Volume of methanol needed #= "20 g"/"793 g/L" = "0.0252 L" = "25.2 mL"#