# Homework Help: General Chemistry-HELP

1. Aug 7, 2011

### BThomas1219

1. The problem statement, all variables and given/known data

Calculate the equilibrium constant if you are given gibbs energy for the following molecules
NH3=-26kJ/mol
H2O-237.13kJ/mol
NH4+=-79.31kJ/mol
OH-=157.3kJ/mol

How many moles of NH4Cl must be added to 1.0L of 0.10M NH3 to make a buffer whose pH is 9.0?

2. Relevant equations
Henderson hasselbach equation,
delta G=RTlnK

3. The attempt at a solution
1) How do you calculate equilibrium constant if you don’t have the temperature to use G=RTlnK
2) For the second half the question, I am thinking of using Henderson hasselbach equation to determine the concentration of NH4Cl. If not, how should I go about solving this question.

2. Aug 7, 2011

### BThomas1219

Just need some help starting out with the problem

3. Aug 9, 2011

### Doobwa

I believe unless otherwise stated, you assume T=298.15K (standard conditions).

I'm not familiar enough with buffer solutions to help with the rest, sorry!

4. Aug 16, 2011

### Staff: Mentor

Once you have K, Henderson-Hasselbalch is the way to go.