Answer to Question #93371 in Physical Chemistry for Soumya Ranjan

Question

The co efficient of thermal expansion of water is 2×10 to the power - 4 per °C. 200 gm of water at 25 °C is heated to 50 °C under 2 atm. External pressure.given density of water at 25° C is 0.9970 gm /c.c and Cp =75.30JK-1 mole - 1. Calculate W, del H, Q

Answer 1

Solution.

$W = P \times \Delta V$

E - coefficient of thermal expansion of water

$E = \frac{\Delta V}{V0 \times \Delta t}$

$\Delta V = E \times V0 \times \Delta t$

$m = \rho \times V0$

$V0 = \frac{m}{\rho}$

$V0 = 200.60 cm^3$

$\Delta V = 2 \times 10^{-4} \times 200.60 \times (50-25) = 1.003 cm^3 = 0,000001003 m^3$

$W = 202650 \times 0,000001003 = 0,203 J$

$\Delta H = Cp \times \Delta T$

$\Delta H = 75.30 \times (323-298) = 1882.50 \frac{J}{mole}$

$Q = c(H2O) \times m \times \Delta t$

$Q = 4200 \times 0.2 \times 25 = 21000 J$

Answer:

$W = 0.203 J$

$\Delta H = 1882.50 \frac{J}{mole}$

$Q = 21000J$