Question

HELP The question is in the picture, I will give 5 stars!

Answer 1

The answer is 4.9 moles of salt will be needed to add to 1 kg of water to change the boiling point by 5 °C.

What is Boiling Point Elevation ?

Boiling point elevation is the phenomenon that occurs when the boiling point of a liquid (a solvent) is increased when another compound is added, such that the solution has a higher boiling point than the pure solvent.

Boiling point elevation occurs whenever a non-volatile solute is added to a pure solvent.

ΔT = i * Kb * m

where m, Kb and i are the molality of solution, ebullioscopic constant and Van't Hoff factor respectively

The data given in the question is ΔT = 5 °C

mass of solvent = 1 kg

Kb = 0.51 °C/(mol/kg)

Van't Hoff Factor for NaCl is 2

Substituting the values in the above equation

$\rm 5 = \rm\dfrac{2\times0.51\times moles \;of \;salt}{1}$

$\rm moles \;of \;salt = \rm\dfrac{5}{2\times0.51}$

moles of salt = 4.9

Therefore 4.9 moles of salt will be needed to add to 1 kg of water to change the boiling point by 5 °C.

To know more about Boiling point elevation

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