The correct option is C 0.62
Mass of alcohol =200 gm
When water is added to calorimeter,
Given water equivalent of calorimeter, W=10 gm
Fall of temperature =60−55=5∘C
Time taken by water to cool =130 sec.
Heat lost by water and calorimeter
=(250+10)(1)5=260×5=1300 cal
Rate of loss of heat =10calsec
When alcohol is added,
Heat lost by alcohol and calorimeter is =(200s+10)5 cal
Heat lost by alcohol and calorimeter is =(200s+10)567calsec
Rates of loss of heat in the two cases are equal
∴(200s+10)567=10
1000s+50=670
1000s=620
s=0.62calg∘C
Hence, the correct answer is option (c).