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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: ILoveISO on February 07, 2010, 02:34:53 AM

Title: Intermolecular Force
Post by: ILoveISO on February 07, 2010, 02:34:53 AM

Calculate the total heat needed to convert 1.00 g of ice at -5.00 oC to water vapor at 105 oC.
Specific heat of liquid water = 4.184 J/(g oC), specific heat of solid water = 2.06 J/(g oC),
specific heat of water vapor = 1.84 J/(g oC), ΔHfusion = 6.02 kJ/mol, ΔHvap = 40.7 kJ/mol.

How come q5 = Cvapor ⋅ m ⋅ ΔT = 1.84 J/(g oC) × 1.00 g × 5.00 oC = 9.20 J

Why is it multiplied by 5 degree C? and
q3 = Cwater ⋅ m ⋅ ΔT = 4.184 J/(g oC) × 1.00 g × 100. oC = 418 J

Why is that 100 degree C?

Title: Re: Intermolecular Force
Post by: Borek on February 07, 2010, 04:50:36 AM

What is boiling point of water?

Title: Re: Intermolecular Force
Post by: ILoveISO on February 07, 2010, 05:32:34 PM

Why is the vapor one multiplied by 5 degrees

Title: Re: Intermolecular Force
Post by: Borek on February 07, 2010, 06:18:03 PM

Think what changes must ice come through before it becomes steam at 105 deg C.

Title: Re: Intermolecular Force
Post by: ILoveISO on February 07, 2010, 07:35:22 PM

Wouldn't it have to go thru 100 degree C before it boils? Don't get why is it multipled by only 5 degrees wouldn't it need another 100?

Title: Re: Intermolecular Force
Post by: Borek on February 08, 2010, 03:39:26 AM

Steam already has temperature of 100 deg C, so it has to be heated by 5 deg C only. Water was already heated to 100 deg C earlier.