Question....problem in Kaplan book

[Greco28]

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I know this is an probably an easy problem to solve....but I have been struggling with it...

How much heat must be added to bring 20g of ice at 0 Celsius to water vapor at 100 Celsius? (The heat of fusion of ice is 80 cal/g. The heat of vaporization of water is 540 cal/g)

Kaplan's answer = 14,400 cal

How did they get this solution?

 

[GRAD]

okay theres three steps cause you hae to go from a solid to vapor-
the first step is to use heat of fusion - 80*m, which is 20g, so 80* 20 is 1600cal
Nect, you do mc delta T....this is actually changing the temp from 0-100,
so its 20*1*100= 2000
by the way, specific heat is always 1 for water

the last part is the heat of vapor... 540*80= something

add them up and you get the answer...just remember there are three parts for this kinda question, and the first and last just use mass and the heats they provide you

 

[Greco28]

540*20....🙂

Got it....Thanks!

 

[GRAD]

oops yea 20 i meant

 

[joonkimdds]

This is the question #50 from kaplan blue book.

which of the following could be the correct electron configuration for the ground state neutral atom of a nonmetallic element?

answer = choice D. 1s2 2s2 2p6 3s2 3p4


I want to know why this is ground state.
The definition I found says "Ground state means the lowest allowed energy state of an atom, molecule, or ion." but I am not very clear with this.

and could you also give me an example of electron configuration that is not ground state?

I would also wanna know how I know that this is neutral atom and not something that lost or gained electron. it has 16 electrons but who knows that it actually has 15 protons with 15 electrons in the beginning and gained 1 electron?