# Homework Help: H = u + pv

1. Oct 5, 2008

### p3t3r1

So the equation

$$\Delta H = \Delta U + \Delta (PV)$$

I know you can transform this equation into the form

$$\Delta H = \Delta U + \Delta (nRT)$$

I commonly see the previous equation transfered in to the following

$$\Delta H = \Delta U + \Delta n(RT)$$

What I want to know is.. can you transform it into

$$\Delta H = \Delta U + nR \Delta T$$

2. Oct 6, 2008

### DeShark

I'd say so. But only if n is constant. What are you trying to do?

3. Oct 6, 2008

### p3t3r1

It was really in relation to this problem

Calculate the values of delta U, delta S, and delta H for the following process

1 mole of liquid water at 25 c and 1 atm to 1 mole of steam at 100 c and 1 atm

I figured out the delta H for the entire process.

then I tried to figure out delta U from delta H using the relationship

delta H = delta U + delta (nRT)

See the thing is... delta H I figured out is for the entire process (temperature rise and state change) and I forget about that.. so I was tryign to get the equation into the form

delta H = delta U + n x delta T x R

but that isn't right since delta H already included the delta T variable. and n is really delta n = 1 since I generated 1 mole of gas.

so yeah all I had to do was times it by T to the right answer