Which observation(s) reflect(s) colligative properties? (i) a 0.80 m nabr aqueous solution has a lower vapor pressure than pure water. (ii) a salt and water solution will remain liquid even below 0°c (iii) pure water freezes at a higher temperature than pure methanol (ch3oh)

(I) A 0.80 m NaBr aqueous solution has a lower vapor pressure than pure water.

(II) A salt and water solution will remain liquid even below 0°C

Explanation:

The properties of a solution are quite different from the properties of the pure solvent. A pure solvent will have greater vapour pressure than its solution. Also, a solution will have a lesser freezing point than the pure solvent. All these observations are called colligative properties. They depend on the amount of solute present in the sample and not really the identity of the solute particles.

Hence the answer provided above.

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm

the answer is d. 74.02