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What is the molality of a seminormal NaCl solution if the density of the solution is 1.16g cm-3?

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  • HPV
    Lv 7
    1 decade ago
    Favorite Answer

    For NaCl, seminormal = semimolar = 0.50 M

    Suppose that you have 1 L of solution. Then moles NaCl = M NaCl = 0.50 moles NaCl / L of solution

    The mass of the solution can be found using the density.

    1L x (1000 mL / 1 L) x (1 cm^3 / mL) x (1.16 g / cm^3) = 1160 grams of solution in 1 L

    That 1 L contains 0.50 moles NaCl.

    0.50 moles NaCl x (58.5 g NaCl / 1 mole NaCl) = 29.3 g NaCl.

    So the mass of H2O in the solution is 1160 g - 29.3 g = 1131 g H2O

    molality NaCl = moles NaCl / kg H2O = 0.50 / 1.131 = 0.44 molal NaCl

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