Respuesta :
Answer:
Mole fraction of solute = 1.83×10⁻³
1.66 % by mass
Explanation:
Solute: 6.77 g of KI
Moles of solute: 6.77 g . 1mol / 166 g = 0.0408 moles
Solvent: water
In order to determine the mass, we use density.
Water density = Water mass / water volume
First we convert the volume of L to mL → 0.4 L . 1000 mL / 1L = 400 mL
1 g/mL = Water mass / 400 mL → Water mass = 400 g
Solvent moles : 400 g . 1 mol / 18g = 22.2 moles
Mole fraction of solute = Moles of solute / Total moles
Total moles = Moles of solute + Moles of solvent
Total moles = 0.0408 mol + 22.2 moles = 22.2408 moles
Mole fraction of solute = 0.0408 mol / 22.2408 moles = 1.83×10⁻³
In order to determine the % mass we need to know the mass of solution
Mass of solvent + mass of solute = Mass of solution
400 g + 6.77 g = 406.77g
Let's make a rule of three:
In 406.77 g of solution we have 6.77 g of solute
In 100 g of solution we may have (100 . 6.77) / 406.77 = 1.66 g of solute
Given:
Mass of solute: 6.77 g of KI
Molar mass of KI=166g/mol
To find:
Moles of solute: [tex]\frac{6.77g}{166g/mol} = 0.0408 moles[/tex]
The solvent is water.
In order to determine the mass, we use density.
Density:
[tex]\text{Density}=\frac{\text{Mass}}{\text{Volume}}[/tex]
Unit conversions:
1L=1000mL
1kg=1000g
Moles of solvent: [tex]\frac{400g}{18g/mol} = 22.2 moles[/tex]
Mole fraction of solute = [tex]\frac{\text{Moles of solute} }{\text{Total moles}}[/tex]
Total moles = Moles of solute + Moles of solvent
Total moles = 0.0408 moles + 22.2 moles = 22.2408 moles
a) [tex]\text{Mole fraction of solute} = \frac{0.0408 mol}{22.2408 moles} =1.83*10^{-3}[/tex]
b) Now, calculating mass percent of a solution.
Mass of solvent + mass of solute = Mass of solution
400 g + 6.77 g = 406.77g
In 406.77 g of solution we have 6.77 g of solute
Mass percentage= [tex]\frac{(100*6.77) }{ 406.77} = 1.66 \%[/tex]
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