Respuesta :
Raoult's law accounts for the fact that the vapor pressure of a solvent will decrease as the mole fraction of the solvent is decreased. In considering the mole fraction, it is important to consider the total moles of dissolved particles. Remember: a particle can be a dissolved molecule or ion. Which aqueous solutions would have the lowest vapor pressure.
0.1 M [tex]NH_4NO_3(aq)[/tex] , 0.1 M [tex]NaF(aq)[/tex], 0.1 M [tex]LiNO_3(aq)[/tex], 0.1 M [tex]Na_3PO_4(aq)[/tex] and 0.1 M [tex]HC_2H_3O_2(aq)[/tex]
Answer: 0.1 M [tex]Na_3PO_4[/tex]
Explanation:
As the relative lowering of vapor pressure is directly proportional to the amount of dissolved solute.
The formula for relative lowering of vapor pressure will be,
[tex]\frac{p^o-p_s}{p^o}=i\times x_2[/tex]
where,
[tex]\frac{p^o-p_s}{p^o}[/tex]= relative lowering in vapor pressure
i = Van'T Hoff factor
[tex]x_2[/tex] = mole fraction of solute
1. For 0.1 M [tex]NH_4NO_3[/tex]
[tex]NH_4NO_3\rightarrow NH_4^{+}+NO_3^{-}[/tex]
, i= 2 as it is a electrolyte and dissociate to give 2 ions. and concentration of ions will be [tex]1\times 0.1+1\times 0.1=0.2[/tex]
2. For 0.1 M [tex]NaF[/tex]
[tex]NaF\rightarrow Na^{+}+F^{-}[/tex]
, i= 2 as it is a electrolyte and dissociate to give 2 ions, concentration of ions will be [tex]1\times 0.1+1\times 0.1=0.2[/tex]
3. For 0.1 M [tex]LiNO_3[/tex]
[tex]LiNO_3\rightarrow Li^{+}+NO_3^{-}[/tex]
, i= 2 as it is a electrolyte and dissociate to give 2 ions. and concentration of ions will be [tex]1\times 0.1+1\times 0.1=0.2[/tex]
4. For 0.1 M [tex]Na_3PO_4[/tex]
[tex]Na_3PO_4\rightarrow 3Na^{+}+PO_4^{3-}[/tex]
, i= 4 as it is a electrolyte and dissociate to give 4 ions. and concentration of ions will be [tex]3\times 0.1+1\times 0.1=0.4[/tex]
5. For 0.1 M [tex]HC_2H_3O_2(aq)[/tex]
[tex]HC_2H_3O_2(aq)\rightarrow CH_3COO^{-}+H^{+}[/tex] [/tex]
, i= 2 as it is a electrolyte and dissociate to give two ions, concentration of ions will be [tex]2\times 0.1=0.2[/tex]
Thus as concentration of solute is highest for 0.1 M [tex]Na_3PO_4[/tex] , the vapor pressure will be lowest.
