I presume you have calculated this by calculating the heat to raise the water from 23 to 100 degress then added the latent heat of water ?

Since the mass of 2.5 decilitres of water is 250g, I make this

250 (4.2(100-23) + 2.26) Joules = 81,415 J = 81.4 kJ.

But your water also expands on evaporation and the energy for the expansion work against the atmosphere also comes from the absorbed heat.

So the total energy input is higher than this.

Some call this

**total** the enthalpy of vapourisation, some call it the heat of vapourisation.

This is 2.4465 kJ /g

so 250 * 2.4465 = 611.5 kJ

There is a vapourisation calculator, starting from any temp in degrees C here

Online calculator, figures and tables showing heat of vaporization of water, at temperatures from 0 - 370 °C (32 - 700 °F) - SI and Imperial units

www.engineeringtoolbox.com