Question

${CaCl}_2.6H_{2}O\left(s\right)\rightleftharpoons {CaCl}_2\left(s\right)+6H_{2}O\left(g\right)K_0=6.4\times {10}^{-17}{atm}^6$. Excess solid ${CaCl}_2.6H_{2}O$ & ${CaCl}_2$ are taken in a container containing some water vapours at a pressure of 1.14 torr at a particular temp. Then:

• A. ${CaCl}_2\left(s\right)$ acts as drying agent under given condition
• B. ${CaCl}_2\left(s\right)$ acts as hydroscopic substance given condition
• C. ${CaCl}_2.6H_{2}O\left(s\right)$ acts as efflorescent substance.
• D. mass of ${CaCl}_2.6H_{2}O\left(s\right)$ increases due to some reaction.

Answer 1

The correct option is A ${CaCl}_2\left(s\right)$ acts as drying agent under given condition

$P_{water}=1.44torr$

$=\frac{1.14}{760}\times 100=\frac{{10}^{-2}}{5}atm$

$\therefore Q_p=P_{H_{2}O}^6$

$=(\frac{{10}^{-2}}{5}{)}^6=\frac{{10}^{-12}}{5^6}={10}^{-18}\times 2^6$

$=64\times {10}^{-18}$

$Q_p>K_p$

reaction mean in backward direction it act as drying agent.