Answer:
It will take 58 seconds
Step-by-step explanation:
If you have 1 kg of water in the jar, half of it will be 0.5 kg.
To vaporize half of the water (0.500 kg) the energy supply needed is
[tex]2297 kJ/kg*0.5kg=1148.5 kJ[/tex]
If the stove is supplying 20 kJ/s, the time its needed is
[tex]\frac{1148.5 kJ}{20\frac{KJ}{s} }=57.425 s[/tex]
It will last at least 58 seconds to vaporize half of the water.