Question

How many joules are required to completely convert 5.0 g of ice at 0.0 degrees Celsius into water vapor at 100 degrees Celsius?

Answer 1

In this question, we have to use 3 equations. 
E = mcΔT,  E = mlf and E = mlv
E is the energy required (in joules), m is the mass, c is the specific heat capacity of water, ΔT is the change in temperature, lf is the specific latent heat of fusion, and lv is the specific latent heat of vaporization.

Since this question requires the change in temperature during the water state, so the first equation is used, and last 2 equations are for finding the energy required to change state (from ice to water and from water to vapor) (in their mp and bp).

For the specific latent heat and heat capacity, generally they should be given for the question, but we can also look it up online since each substance has their own value. 

So the first step is to find the amount of energy needed to convert ice at 0°C to water at 0°C. We can use the second equation. The specific latent heat of fusion of ice is around 334 J kg^-1

E = mlf
E = 5 x 334
E = 1670 J

Next, we have to find the energy required to heat water at 0°C to 100°C. The specific heat capacity of water is around 4.2 J g^-1 °C^-1.

E = mcΔT
E = 5 x 4.2 x (100-0)
E =  2100 J

Then we have to find the amount of heat required to change water at 100°C to water vapor at 100°C. The specific latent heat of vaporization of water is around 2230 J g^-1.

E = mlv
E = 5 x 2230
E = 11150 J

Therefore, to find the final answer, just add up the 3 values for the total energy required.

1670 + 2100 + 11150
= 14920 J

Your final answer should be 14920 joules.