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How much of potassium nitrate (in grams) would be needed to lower the melting point of...

How much of potassium nitrate (in grams) would be needed to lower the melting point of 100 grams of water by 1 degree Celsius? Please show your work! Thank you.

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Answer #1

∆T = 1°C

KNO3 = ( K+ & NO3- means i=2)

∆T = i* Kf * molality

Kf = 1.86°C/molality

1 = 2 * 1.86 * molality

Molality = 0.26882

Moles / mass of water ( in Kg) = 0.26882

Moles / ( 100 * 10^-3) = 0.26882

Moles = 0.026882

Mass of KNO3 = moles * molar mass

= 0.026882 * 101.1

= 2.718 grams

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