Final water temperature

[Dalia Torres 3I]

Hi, I was wondering if anyone could explain how to figure out the final temperature of water in a mixture?? I am kind of confused and I don't really know where to start?? Thank you!!!

This is my achieve #9 question for reference.

If you combine 270.0 ml of water at 25.00 ∘C and 100.0 mL of water at 95.00 ∘C, what is the final temperature of the mixture? Use 1.00 g/mL as the density of water.

[Tricia Tran 1G]

Remember that heat given off by a reaction = - heat absorbed by the surroundings. Therefore, you have to set the heat transfer between both waters equal to each other and use the specific heat formula: q=mcdeltaT where delta T is the change in temperature (Tf - Ti).
You will get: (270.0mL)(1.00g/mL)(4.18J/gdegreeC)(Tf - 25.00degreeC) = - (100.0mL)(1.00g/mL)(4.18J/gdegreeC)(Tf - 95.00degree C) then solve for Tf.

[Rachel 1J]

Adding on to Tricia’s response, I wanted to clarify how you know which water portion is absorbing versus giving off heat. If I’m understanding correctly, I believe the water that is added with the higher temperature will give off heat and the water with lower temperature will absorb it. Although you will end up with the correct final temperature either way, I think the distinction may be helpful to keep in mind.

Another thing is that if c (specific heat constant) is not given, this problem is still solvable, as they cancel out on each side. Canceling out c also gives you easier calculations!