[dumb__x]

Question: Potassium reacts vigorously with water.
Predict and explain how the temperature of the mixture changes during the reaction.

I wrote: Globule of molten potassium will skate over the surface, producing heat. Temperature will suddenly go up to about 90℃. At first, potassium oxide will be produced, but it will furthur react and potassium hydroxide will be produced producing more heat.

and got 1/2 points. Why is it wrong?

[Borek]

Two reasons at least. No intermediate oxide, no idea where did you get 90 deg C from. For sure it gets hot, but why not 83 or 95?  The only thing you can be sure about is that for obvious reasons no more than 100.

[dumb__x]

oh i see thanks

[IITian]

The local temperature might well above 100°C.

2 Na(s) + 2 H2O  2 Na+(aq) + 2 HO-(aq) + H2(g)

The heat generated by this reaction is sufficient in most cases to ignite the hydrogen gas (H₂) that is evolved in the reaction.