(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

What is the final temperature of water if 175 g steam at 150 C loses 423 KJ of energy?

2. Relevant equations

Q = M *C_p * Δ T

Q = m * heat of (phase_change)

3. The attempt at a solution

This is how I would go about solving this problem.

Going from steam to water requires energy of two types:

- Going from steam to water --> Q = m * heat of vap
- Cooling from 150C to 100C --> Q = m * Specific heat of steam * Δ T

Furthermore, we are told that steam is finally in the form of water, which has an unknown final temperature, so we have

Q = m * specific heat of water * ΔT

Add them together, and equates with the heat loss (which is given)

- 423KJ = Q (from steam to water) + Q (cooling from 150 to 100) + Q (cooling from 100 to unknown final temperature)

Is this correct?

If it is, my question would be: is it also correct to make Q (from steam to water) negative? I don't remember seeing heat of condensation. Can I make heat of evaporation negative in this case?

Anything else needs to be negative also?

Thank you.

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# Homework Help: Find the final temperature of water

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