Question

A solution of 6% (wt/vol) of urea is isotonic with NaCl (aq) What js the weight % of NaCl solution ?​

Answer 1

Answer:

0.5m NaCl

Explanation:

Two solutions are isotonic if they have the same osmotic pressure.

Osmotic pressure π=iCRT

For NaCl, the van 't Hoff factor i=2 as one NaCl molecule dissociates into 2 ions.

For urea, the van 't Hoff factor i=1 as urea does not dissociate.

6% W/V aqueous solution of urea means 6 g urea in 100 mL solution or

$$ 60 g urea in 1000 mL (1 L) solution.

C=

60g/mol×1L

60 g

=1M

i

urea

×C

urea

=i

NaCl

×C

NaCl

1× 1 M= 2×C

NaCl

C

NaCl

=0.5 M