If 4 liter of water at 0C is mixed with 1 liter of anti-water at 100C, what is the temprerature of te mixture?

Answer 1

HIGH

2 liters of water annihilate at E=mc^2

remaining 3 liters are heated up by that energy

E = 1.8e17J = 4.3e16 cal

vapor's specific hear is 2.01

so, ignoring the energy wasted to boil water, vapor will be at
~4.3e16 / 2.01 / 3 = 7.1e15 degrees C

Answer 2

Here's the thing: there are a few classes of antimatter, and the answer depends on the situation in which the two universes interact.

When a nuclear device detonnates, it creates a certain type of micro universe, so the antimatter involved in that universe is one type. In the instances where water molecules of this type of antimatter contact our universe, then the reaction is of one level of energy. BUT, the chances of water molecules surviving within this interface are smal - let alone liters of them, so I think at the level of nuclear devices made by man, the function approaches zero opportunity to be.
Ditto for our thermonuclear devices. This event is at a different level of activity and results in a separate type of antimatter than do the nukes. However, accumulating a liter of antimatter water here would not be probable.
Step up to our Sun. Hydrogen drives it and the chaos involved with this much matter actively working within the proximity of a huge core of antimatter, gives more chance of finding momentarily fabricated water and antiwater. The antimatter here is again, a step above thermo-nukes. In this maelstrom of activity, the chances of finding a liter of antiwater to throw at your universe's water would take a bit of doing.
There is a geometric factor to this question of yours when we get to the Sun and other stars. The conditions within which antimatter and matter interface includes some very specific angles. To simplify it, the two forms do not just collide, and must function within a certain range of phase angle or they just don't contact each other. When they are in sychronization, then they can connect.
With Black Holes, this becomes very efficient and by the time matter hits the event horizon it has been oriented, spun and vibrated to completely mesh with the antimatter: otherwise, Black Holes would either eat themselves or explode.
The best place to find your combination is within the gravity well of a heavy matter sun - one which primarily burns something other than hydrogen - with a fusion product material heavier than water. You could find anti-water there in more abundance because, as the atomic weight of the fusioning material increases, the fundamental frequencies of the reactions drops. This gives any chemical bonds a contrived, but longer duration of existence
Since temperature near such a sun is subjective and related to the materials and environment, I cannot state a range of temperature which is real.
So, define your environment in which the antiwater is fabricated, state how you expect it to survive in a place where universal water is also present, then there is a chance to properly answer.

Answer 3

(2 kg)(299,792,458 m/s)^2 = 1.797510e+17 J.
(1.797510e+17J)(1 cal/4.184 J) = 4.296153e+16 cal.
It takes 3,000 calories to raise 3 kg water from 0 to 100C, and another 1,620,000 calories to vaporize it, leaving 4.296153e+16 calories
(4.296153e+16 cal)(1 gC/0.5 cal)(1/3,000 g) = 2.864102e+13°C if you ignore the argument that relativistic effects limit the temperature.

Answer 4

There is no such thing as anti-water.

Antiparticles have never been shown to form stable atoms.