ionic bond is formed between ca and cl forming molecule cacl2 ca has 2 velancy and cl has one velancy (ca has 2 electrons in its outer most shell while cl has 1 electron vecancy in its outermost shell). So ca would make bond with 2 cl atoms
Since the substance absorbs heat, it is expected that the temperature will rise. The formula for the internal energy of a substance is given by the equation:
ΔU = mCpΔT
where:
ΔU = internal energy
m = mass of substance
Cp = specific heat capacity of substance
ΔT = change in temperature
ΔU = 2722 Joules = 16.2 grams (9.22 J/g-°C) (Tf - 26°C)
This gives a final temperature of Tf = 44.22 °C
I think it is trace evidence since it is really small and hard to find.