<p>The pressure of a gas depends on the number density of particles and the temperature. There is therefore no unique relationship between <span class="math-container">$P_g$</span> and <span class="math-container">$N_{I+1}/N_I$</span>.</p>

CC BY-SA 4.0
2022-03-25T19:13:32.883Z
Let's assume I also know the temperature. Is it possible then?
Pedro Nogueira
CC BY-SA 4.0
2022-03-25T13:07:57.077Z
2022-03-25T13:07:57.077Z
ProfRob
<p>Knowing the pressure, <span class="math-container">$P_g$</span>, how can I calculate <span class="math-container">$\frac{N_{I+1}}{N_I}$</span> using Saha's equation?</p>
<p>If I assume that <span class="math-container">$P_g=(n_e+n_{H^+}+n_H)K_B T$</span> and that <span class="math-container">$n_e=n_{H^+}$</span>, I can find the electronic pressure, <span class="math-container">$P_e$</span>, and plug it in Saha's equation, but then I'm left with <span class="math-container">$n_H K_B T$</span>, which is gonna screw my calculations.</p>

<star><mathematics><hydrogen><gas>
Using Saha's equation knowing the overall pressure
Pedro Nogueira
# Using Saha's equation knowing the overall pressure

(Asked by: username_0 on 2022-03-25)

Knowing the pressure, $P\_g$, how can I calculate $\frac{N\_{I+1}}{N\_I}$ using Saha's equation?

If I assume that $P\_g=(n\_e+n\_{H^+}+n\_H)K\_B T$ and that $n\_e=n\_{H^+}$, I can find the electronic pressure, $P\_e$, and plug it in Saha's equation, but then I'm left with $n\_H K\_B T$, which is gonna screw my calculations.

**Tags:** star, mathematics, hydrogen, gas

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## 1 answers

### Answer by username_1 on 2022-03-25. Score: 2

The pressure of a gas depends on the number density of particles and the temperature. There is therefore no unique relationship between $P\_g$ and $N\_{I+1}/N\_I$.

> **Comments:**
> **username_0**: Let's assume I also know the temperature. Is it possible then?  

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