Question

Explain why the molar mass of nacl as observed by using colligative property measurements is half of the calculated value ​

Answer 1

TOPIC :- COLLIGATIVE PROPERTY

Concept :- NaCl molecule dissociates in aqueous solution.

in such case ( Van't hoff's factor)

i = $\frac{no \:. \: of \: molecule \: after \: dissociation}{no. \: of \: molecule \: before \: }$

So, in case of NaCl i = 1/2 ( as it dissociates into Na+ and Cl-)

Now,

i also equals = $\frac{normal \: molar \: mass}{calculated \: molar \: mass}$

Since, i = 1/2

$\frac{normal \: molar \: mass}{calculated \: molar \: mass} = \frac{1}{2}$

Thus, normal molar mass × 2 = calculated molar mass.

Hence, molar mass of NaCl is half the calculated molar mass.