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How many grams of rock salt, NaCl, do you need to add to a 3.78 kg of ice, to get the temperature
to drop to -19C?

Respuesta :

mickymike92

1129.9 grams of rock salt, NaCl needs to be added to a 3.78 kg of ice, to get the temperature to drop to -19C .

What is freezing point depression?

Freezing point depression refers to a property of solutions where addition of a solute lowers the normal freezing point of the solvent.

The Blagden's Law given as the equation above is used to determine the freezing point depression of ice:

  • [tex]ΔT = iK_fm[/tex]

where;

  • ΔT = Change in temperature in °C
  • i = van 't Hoff factor
  • Kf = molal freezing point depression constant
  • m = molality of the solute in mol solute/kg solvent.

For NaCl, i = 2

Kf for water/ice = 1.86 °C kg/mol

molalityof NaCl = (mass/molar mass

l)/kg of ice

  • mass of NaCl = molality × mass of ice × molar mass

molar mass of NaCl = 58.5

mass of ice = 3.78 kg

Let molality of NaCl = m

ΔT = 19 °C

Substituting the values:

19 = 2 x 1.86 °C kg/mol x m

m = 5.11 mol/kg

mass of NaCl = 5.11 × 3.78 × 58.5

mass of NaCl = 1129.9 g

Therefore, the mass in grams of rock salt, NaCl that needs to be added to a 3.78 kg of ice, to get the temperature to drop to -19C is 1129.9 g

Learn more about freezing point depression at: https://brainly.com/question/26525184

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