question_answer 19)

What is the concentration of sugar \[({{C}_{12}}{{H}_{22}}{{O}_{11}})\] in \[mol\,{{L}^{-1}}\] if its 20 g are dissolved in enough water to make a final volume upto \[2L?\]  

Answer:

We know, \[M=\frac{{{w}_{B}}\times 1000}{{{m}_{B}}\times V}\] Given : \[{{w}_{B}}\] = 20 g, \[{{m}_{B}}\] (molar mass of sugar) = 342 g \[mo{{l}^{-1}}\] \[V=2L=2000mL\] Putting these values in Eqn. (i), we get \[M=\frac{20\times 1000}{342\times 2000}=0.058\]