A sidewalk 1 m by 3m is covered with 05 cm of ice at a tempe

A sidewalk 1 m by 3m is covered with 0.5 cm of ice at a temperature of -9 degreeC. What is the minimum mass of solid NaCl which must be evenly spread over the sidewalk in order to melt the ice?

Solution

We know for heat equation:

Heat loss by the NaCl = heat gain by the ice for melting

we take atmospheric temp. = 25 deg C

NaCl specific heat = 0.207

Now

mass of ice = density x volume = 1g/cm ³ * 0.5*100*300 = 15000 gram

mcdt = MCdt

15000*0.5*9 = M*0.207*25

M = 13043 gm or 13.043 kg......Ans.