Q.
A 42.12%(w/v) solution of NaCl causes precipitation of a certain sol in 10 hours. The coagulating value of NaCl for the sol is
[Given : Molar mass : Na=23.0gmol−1;Cl=35.5gmol−1]
Here 42.12%(w/v) ⇒42.12 gram salt in 100ml water ⇒421.2 gram salt (NaCl) in 1000ml or 1 lit water ⇒58.5421.2=7.2 moles of salt 7.2 moles →10 hours x moles →2 hours ⇒x=107.2×2=1.44mol/L⇒x=1440mmol/L