Question

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

Answer:

25.2 mL

Explanation:

Molarity=Moles of soluteVolume of solution (in litres)

For given solution

0.25 M=n2.5 L

n = 0.625 moles

0.625 moles of methanol is needed.

Molar mass of methanol (CH3OH)=32 g/mol

• Mass of methanol needed =0.625mol×32 gmol=20 g

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

Volume=MassDensity

• Volume of methanol needed =20 g793 g/L=0.0252 L=25.2 mL

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Answer 2

"$Molarity\quad =\quad \frac { Moles\quad of\quad solute }{ Volume\quad of\quad solution\quad (in\quad Litres) }$

For given solution, $0.25\quad M\quad =\quad \frac { n }{ 0.25\quad L }$

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 $=\quad 0.625\quad mol\quad \times \quad 32\quad gmol\quad =\quad 20\quad g$

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

$Volume\quad =\quad \frac { Mass }{ Density }$

$Volume of methanol needed =\quad \frac { 20\quad g }{ 739\quad g/L } \quad =\quad 0.0252\quad L\quad =\quad 25.2\quad mL$"