The density of H₂O(s) is 0.920 g.cm^-3 at 0°C and is therefore lower than that of H₂O(l). So water expands when it freezes.

How much work does 50.0 g of water do when it freezes at 0°C and bursts a water pipe with an opposing pressure of 1000 atm?

Question

The density of H₂O(s) is 0.920 g.cm^-3 at 0°C and is therefore lower than that of H₂O(l). So water expands when it freezes.

How much work does 50.0 g of water do when it freezes at 0°C and bursts a water pipe with an opposing pressure of 1000 atm?

| General Chemistry 2

Accepted Answer

By definition, work W = -Pext ΔV

with Pext = constant external pressure (in Pa) and ΔV = Vf – V_i (in m³)

P_ext = 1000 atm = 1.013 x 10⁸ Pa

density d = $\frac{m}{V}$ ⇒ V = $\frac{m}{d}$
V_H2O(l) = V_i = $\frac{50.0}{1.00}$ = 50.0 cm³ = 50.0 x 10^-6 m³

V_H2O(g) = V_f = $\frac{50.0}{0.920}$ = 54.3 cm³ = 54.3 x 10^-6 m³

W = -Pext ΔV

⇒ W = -(1.013 x 10⁸) x (54.3-50.0) x 10^-6 = - 4.36 x 10² J

Midterm 2 - Question 3 | General Chemistry 2