I need to figure this out before my exam

Question

A 5.10-g chunk of potassium is dropped into 1.10 kg water at 24.5°C. What is the final temperature of the water after the preceding reaction occurs? Assume that all the heat is used to raise the temperature of the water. (Never run this reaction. It is very dangerous; it bursts into flame!)

Answer 1

The reaction is as follows:

2K(s) + 2H2O(l) ==> 2KOH(aq) + H2(g)

For heat transfer to water, etc. we can use the following equation:

q = mC∆T

q = heat = ?

m = mass of water = 1.10 kg

C = specific heat of water = 4.184 kJ/kgº

∆T = change in temperature = ?

So, we have 2 unknowns (q and ∆T and cannot answer the question as written). You can either look up the ∆Hrxn or you can look up ∆Hformation of reactants and products and find ∆Hrxn. But without this value, we cannot solve the problem.