Explanation:
The given data is as follows.
Density of vinegar = 1.0 g/ml
Specific heat capacity = 4.25 
=
, and
= 
Relation between enthalpy and specific heat is as follows.

Hence, putting the values into the above formula as follows.

=
(as density =
)
= - 315 J
Thus, we can conclude that the enthalpy of reaction is -315 J.
As the value is negative so, it means that heat is releasing. Hence, the reaction is exothermic in nature.
Answer:
Well, that was just me........................
Its 2+! Dont mind this hdhdhdjhdndbdbdbdbsnnsjdndsnjd
It should just be one for it to be balanced.
Reaction of Cu(NO₃)₂ with each salt is as follow,
1) with KNO₃;
Cu(NO₃)₂ + KNO₃ → Cu(NO₃)₂ + KNO₃
Both salt products are water soluble.
2) With CuSO₄;
Cu(NO₃)₂ + CuSO₄ → CuSO₄ + Cu(NO₃)₂
Again both Salt products are water soluble.
3) With K₂SO₄;
Cu(NO₃)₂ + K₂SO₄ → CuSO₄ + 2 KNO₃
Again both salt products are water soluble.
4) With K₂S;
Cu(NO₃)₂ + K₂S → CuS + 2 KNO₃
In this case CuS is water insoluble, hence precipitates out.
Result:
Option-4 is the correct answer.