How much energy would be absorbed or released by the h2o in the process 30 grams h2o(
g. at 100◦c → 30 grams h2o(ℓ) at 20◦c ?

Explanation:

In this case we have two processes. First, we have to convert the gas water into liquid water at 100 ºC and then we have to go from 100 ºC to 20 ºC  in the liquid state.

For the first part, we have to use the enthalpy of vaporization (), so:

In this case we go from gas to liquid, so energy is released, therefore:

In the second part we have to calculate the energy in the change from 100 ºC to 20 ºC, so:

ΔT

So, in total we will have:

or

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j