Final answer:
A 25 gram piece of graphite cooled from 35°C to 18°C loses 301.825 Joules of energy. This calculation is done using the specific heat capacity formula, considering the mass of the graphite, its specific heat, and the change in temperature.
Step-by-step explanation:
To calculate the energy lost by a 25 gram piece of graphite when it is cooled from 35°C to 18°C, we use the specific heat capacity formula which is:
q = m × c × ΔT
Where:
- q is the heat energy lost or gained, in Joules (J)
- m is the mass of the substance, in grams (g)
- c is the specific heat capacity of the substance, in J/(g°C)
- ΔT is the change in temperature, in degrees Celsius (°C)
Given that the specific heat (c) of graphite is 0.709 J/(g°C), the mass (m) is 25 g, and the temperature change (ΔT) is 18°C - 35°C (which is a decrease, so it will be a negative value), we can compute the heat energy lost as follows:
q = 25 g × 0.709 J/(g°C) × (18°C - 35°C)
q = 25 g × 0.709 J/(g°C) × (-17°C)
q = -301.825 J
Since the energy is lost, the value for q is negative, indicating an exothermic process. Therefore, the graphite has lost 301.825 Joules of energy.