Question

0.5 molal solution of ethylene glycol in water is used as a coolant in car. If the freezing point depression constant of water is $1.86^{o}Ckg$ per mole, the mixture will freeze at

• A. $0.93^{o}C$
• B. $- 0.93^{o}C$
• C. $1.86^{o}C$
• D. $- 1.86^{o}C$

Answer 1

Answer: (B)

$\Delta T_{f}=k_{f}\times m$
$=1.86\times 0.5=0.93^{o}C$
$\therefore \Delta T_{f}= \, T_{f}^{o}-T_{f}$
$\therefore T_{f}=T_{f}^{o}-\Delta T_{f}$
$=0-0.93= \, -0.93^{o}C$