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Which of the following pairs of solutions are expected to be isotonic?

$\begin{array}{1 1} 0.1\;M\;urea\;and\;0.1\;M\;NaCl \\0.1\;M\;urea\;and\;0.1\;M\;MgCl_2 \\ 0.1\;M\;Ca(NO_3)_2\;and\;0.1\;M\;Na_2SO_4 \\ 0.1\;M\;Nacl\;and\;0.1\;M\;glucose \end{array}$

Answer : $0.1\;M\;Ca(NO_3)_2\;and\;0.1\;M\;Na_2SO_4$
Isotonic solution have the same osmotic pressures.
The same osmotic pressures implies the same concentrations, $0.1\;M\;Ca(NO_3)_2$ produces $0.3 \;M$ species $(0.1\;M\;Ca^{2+}+0.2 M \;NO_3^{-})$ and also $0.1\;M\;Na_2SO_4$ produces $0.3\;M$ species $(0.2\;M\;Na^{+}$ and $0.1 \;M\;SO_4^{2-})$

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