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21 March, 23:02

What are the mole fraction and the mass percent of a solution made by dissolving 6.77 g of KI in 0.400 L of water (d = 1.00 g/mL) ?

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  1. 21 March, 23:37
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    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
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