Question

What will be the molality of the solution containing 18.25gof HCl gas in 500g of water?​

Answer 1

$\huge\sf\bold\pink{\underline{ANSWER:-}}$

$\sf{mass \: of \: HCl \: (solute) = 18.25 \: g}$

$\sf{molar \: mass \: of \: HCl = 1 + 35.5 = 36.5 \: g/mol}$

$\sf{mass \: of \: H2O \: (Solvent) = 500 \: g = 0.5 \: Kg}$

$\sf{Number \: of \: moles \: (n) =\dfrac{Mass}{Molar \: mass}}$

$\sf{Number \: of \: moles \: of \: NaCl - }$

$\sf{=\dfrac{18.25}{36.5} =\dfrac{1}{2} = 0.5 \: mole}$

Now ,

$\sf{Molality \: (m) =\dfrac{No. \: of \: moles \: of \: Solute}{mass \: of \: solvent}}$

So ,

$\sf{m =\dfrac{moles \: of \: NaCl}{mass \: of \: H2O}}$

$\: \: \: \:$$\sf{m =\dfrac{0.5}{0.5}}$

$\: \: \: \:$$\sf{m = 1 \: mol/kg \: (molal)}$

Answer 2

Answer:

massofHCl(solute)=18.25g

\sf{molar \: mass \: of \: HCl = 1 + 35.5 = 36.5 \: g/mol}molarmassofHCl=1+35.5=36.5g/mol

\sf{mass \: of \: H2O \: (Solvent) = 500 \: g = 0.5 \: Kg}massofH2O(Solvent)=500g=0.5Kg

\sf{Number \: of \: moles \: (n) =\dfrac{Mass}{Molar \: mass}}Numberofmoles(n)=

Molarmass

Mass

\sf{Number \: of \: moles \: of \: NaCl - }NumberofmolesofNaCl−

\sf{=\dfrac{18.25}{36.5} =\dfrac{1}{2} = 0.5 \: mole}=

36.5

18.25

=

2

1

=0.5mole

Now ,

\sf{Molality \: (m) =\dfrac{No. \: of \: moles \: of \: Solute}{mass \: of \: solvent}}Molality(m)=

massofsolvent

No.ofmolesofSolute

So ,

\sf{m =\dfrac{moles \: of \: NaCl}{mass \: of \: H2O}}m=

massofH2O

molesofNaCl

\: \: \: \: \sf{m =\dfrac{0.5}{0.5}}m=

0.5

0.5

\: \: \: \: \sf{m = 1 \: mol/kg \: (molal)}m=1mol/kg(molal)