Question

A) how many kilocalories and joules are required to boil 28g of water?

B)draw a cooling diagram of water from 125c-15c. be specific and label each axis, each phase, and each phase change?

both question i need help on

Answer 1

A)

Latent Heat of vaporizaiton of water = 2264.76 kJ/kg approx

we have

m = 28 g = 28*10^-3 kg

Q total = mass of water * Latent Heat = (28*10^-3) * 2264.76

Q total = 63.413 kJ = 63413 J

change to kcl --> 63.413 kJ --> 63.413 /4.184 = 15.1560 kcal

B)

phase change is gven at 100°C. Vapor to liquid water

if this is -15°C; then it must be a chang ephase in 0°C from liquid water to solid ice.

As you can see, at T = 100°C; the enthalpy / heat decreases drastically, since this is the energy required to break interactions.