# Calculate the change in enthalpy

1. Nov 5, 2005

### asdf1

how do you solve the following problem?

calculate the change in enthalpy and the change in entropy when 1 mole of SiC is heated from 25 degrees C to 1000 degrees C.
Cp=50.79+1.97*(10^-3)T-4.92*(10^6)(T^-2)+8.2*(10^8)(T^-3) J/(mole*K)

2. Nov 5, 2005

### siddharth

The variation of Entropy with temperature for a system is given by
$$S(T_f) = S(T_i) + \int \frac{dq_{rev}}{T}$$
When the system is under constant pressure and there is no non-expansion work,
$$dq_{rev} = C_p dT$$

3. Nov 6, 2005

### asdf1

how do you know that the question is under constant pressure?

4. Nov 6, 2005

because they give u Cp, which is the specific heat at constant pressure

5. Nov 6, 2005

### asdf1

@@
how do you know that there's no non-expansion?

6. Nov 6, 2005

### siddharth

Non expansion work is work done by the system other than in expansion.
For example, electrical work. So unless it is specifically stated, there is usually no non-expansion work.

7. Nov 6, 2005

### asdf1

thank you very much!!!