Question

Which one of the following pairs of solution can we expect to be isotonic at the same temperature?

• A. 0.1 M urea and 0.1 M NaCl
• B. 0.1 M urea and 0.2 M $MgCl_{2}$
• C. 0.1 M NaCl and 0.1 M $Na_{2}SO_{4}$
• D. $0.1 M Ca _{\left( NO _3\right)_2}$ and $0.1 M Na _2 SO _4$

Answer 1

Answer: (D)

Here $0.1 M Ca _{\left( NO _3\right)_2}$ and $0.1 M Na _2 SO _4$ are isotonic at same temperature as follows $\pi\left[ Ca \left( NO _3\right)_2\right]= iCRT$
$ =3 \times 0.1 RT =0.3 RT $
$ \pi\left[ Na _2 SO _4\right]= iCRT $
$ =3 \times 0.1 RT =0.3 RT $