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Finding the heat of a reaction?

Make the following assumptions:

1) The density of liquid water at 100C is 1.00

g/mL;

2) the vapor is adequately described by the

ideal gas equation;

3) the external pressure is constant at 1.00

atm; and

4) the heat of vaporization of water is 2.26

kJ/g.

What is q for the vaporization of 1.00 g of

liquid water at 1.00 atm and 100C, to the

formation of 1.00 g of steam at 1.00 atm and

100C?

I tried using q=mcT but since there is no change in temperature, I always get 0. It's in the list of possible answers, but I'm seriously doubting myself. Phuk it.

1 Answer

Relevance
  • 8 years ago
    Favorite Answer

    look at the heat of vaporization value. there is no temperature unit. therefore, you don't use temperature in the equation. this the heat required to vaporize 1 g water at the vaporization temperature. since this is 100ºC and all water must be converted to steam at 100ºC, there is no ∆T. if we were to heat the steam to greater than 100ºC. THEN you would use the ∆T

    ∆H = mass x heat of vaporization

    ∆H = 1g x 2.26kJ/g = 2.26kJ

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