Answer:
18447 J
Step-by-step explanation:
To calculate the internal energy of steam at a given temperature, we need to know the specific heat capacity of steam and the enthalpy of vaporization. The specific heat capacity of steam at a constant pressure is approximately 2.08 J/g*K, and the enthalpy of vaporization (latent heat) at 100°C is 2257 kJ/kg.
We can use the following equation to calculate the internal energy of steam at a given temperature:
U = m * Cp * (T - T_b) + m * L
Where U is the internal energy, m is the mass of the steam, Cp is the specific heat capacity of steam, T is the temperature of the steam, Tb is the boiling temperature of the steam, and L is the enthalpy of vaporization.
Since we are given the amount of steam in moles (1.2 moles) and the temperature (177°C), we can convert the moles of steam to mass using the molar mass of water (18 g/mol). The boiling temperature of water at standard atmospheric pressure is 100°C, so we can use this value for Tb.
First, we need to convert the temperature from degrees Celsius to kelvins:
T = 177°C + 273 = 450 K
Then, we can calculate the mass of the steam:
m = 1.2 moles * 18 g/mol = 21.6 g
Substituting these values into the equation for internal energy, we get:
U = 21.6 g * 2.08 J/g*K * (450 K - 273 K) + 21.6 g * 2257 kJ/kg
Solving for the internal energy, we get:
U = 18,447 J
Therefore, the internal energy of 1.2 moles of steam at 177°C is approximately 18,447 J.