Question

How much heat is required to raise the temperature of $654g$ of water from $34.5^\circ C$ to $89.7^\circ C$?

Answer 1

Hint: The energy provided to the substance is not utilised to the full potential and a part of the energy is converted to heat and is used for raising the temperature of the substance. The energy provided to the substance is determined by the amount of the substance and the specific heat of the substance in the examination.

Complete step by step answer:
Amount of energy needed for the raising of the temperature of the substance is given by the formula as
$E = mc\Delta T$
Where E is the energy needed with m mass of the substance and c be the specific heat of the substance and T is the temperature of operations. The specific capacity of water is known to be 4181. The mass of water is given in the question as $654g$.
Converting the mass is $kg$ we have $0.654kg$
The change in the temperature is also given in the question as $89.7 - 34.5 = 55.2^\circ C$
Putting all these values in the relation above we have
$E = 0.654 \times 4181 \times 55.2 = 150937J$

The heat required to raise the temperature is $150937J$

Note: All naturally occurring processes tend to proceed in a single direction spontaneously. Here spontaneity means the potential to proceed without the assistance of external agents.
S is called the entropy of the reaction and is the measure of the disorder. The entropy is usually defined for an isolated system where there is always a tendency for the system to become more disordered. The greater the disorder in an isolated system the higher the entropy. Neither decrease in enthalpy nor the increase in entropy can determine the spontaneity of the system alone.
For a spontaneous process, the change in entropy should be greater than $0$ in other words $\Delta S > 0$
In the process of reduction, the change in enthalpy of the system is less than $0$ since it is generally an endothermic process.