John Smith is a chemistry student who lives in Florida and the mosquitoes are ho

Question

John Smith is a chemistry student who lives in Florida and the mosquitoes are horrible this year. He is sweating…thinking…why don’t I live in Colorado, I would be much cooler. He is thinking about phase changes, intermolecular forces and the many natural phenomena that occur around him every day.

a) He has a glass of cold lemonade with ice in it and he notices that his glass is also sweating. What phase change was occurring when sweat was forming on the outside of his glass and why(how) was it happening?

What about the ice in his drink. It was definitely melting. How much energy does it take to convert ice to steam anyway, which is essentially what he was doing by drinking, then sweating

Calculate the energy required to convert John’s 10g ice cube, which began at -3oC, to water vapor at 100oC. Show all your work.

Note:ice began at -3 degrees celcius shown above

Explanation / Answer

a)  A tiny amount of vapor present in the air settles and cools on the glass of cool water
  and it gets condensed. So basically condensation is taking place hence the phase changes
from gas (water vapor) to liquid (water).
The energy required to convert John’s 10g ice cube :
from -3oC to 0oC
q1 = 10gm * Cp,ice * (0-(-3)) = __ in J (convert into kJ by dividing with 1000)
q2 = (10gm / 18gm/mol ) *  Hfus (kJ/mol) = __ kJ
from 0oC to 25oC
q3 = 10gm * Cp,liq * (25 - 0) =____ in J (convert into kJ by dividing with 1000)
from 25oC to 100oC
q4 = 10gm * Cp,liq * (100-25) = ___ in J (convert into kJ by dividing with 1000)
q5 = (10gm / 18gm/mol ) *  Hvap (kJ/mol) = __ kJ
  The energy required to convert John’s 10g ice cube = q1+q2+q3+q4+q5
Note : Cp,liq , Cp,ice , Hfus ,  Hvap are not known , substitute these values and sum them up
accoedingly to get the answer.

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