# Programme pour tableau avancement chimie terminale

**URL:** <https://discuss.python.org/t/programme-pour-tableau-avancement-chimie-terminale/11686>\
**Category:** Python Help\
**Tags:** help\
**Created:** [November 1, 2021, 8:07pm UTC](https://discuss.python.org/t/programme-pour-tableau-avancement-chimie-terminale/11686 "2021-11-01T20:07:35Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![chu123](https://avatars.discourse-cdn.com/v4/letter/c/e19adc/32.png) [@chu123](https://discuss.python.org/u/chu123)\
**Post date:** [November 1, 2021, 8:07pm UTC](https://discuss.python.org/t/programme-pour-tableau-avancement-chimie-terminale/11686/1 "2021-11-01T20:07:35Z")

</div>

Bonjour,  
Nous voyons en ce moment les avancements finaux en chimie et nous devons compléter un code python permettant de calculer l’avancement final selon différentes variables.  
Voilà mon code:

import numpy as np  
import matplotlib.pyplot as plt

# La reaction consideree est A + B → C + D

# Coefficients stoechiometriques

a, b, c, d = 1, 1, 1, 1

# Quantites de matiere initiales et volume initial

n\_iA, n\_iB, n\_iC, n\_iD = 0.1, 0.1, 0, 0  
V = 100.0e-3

# Constante d’equilibre

K = 1e-1

# Calcul de l’avancement final et generation des valeurs de x entre 0 mol et xmax

xmax = min(n\_iA/a, n\_iB/b)  
x = np.arange(0, xmax, xmax/10000.0)  
tau = x/xmax

# Calcul des quantites de matiere et du quotient de reaction a chaque avancement x

n\_A = n\_iA-a_x  
n\_B = n\_iB-b_x  
n\_C = n\_iC+c_x  
n\_D = n\_iD+d_x  
Q\_r = ((n\_C/V)\*_c_(n\_D/V)\*\*d)/((n\_A/V)\*_a_(n\_B/V)\*\*b)

# Determination de l’avancement final x\_f

for i in range(len(x)) :  
if Q\_r\<K:  
x\_f = x[i]  
i = i+1  
else :  
continue  
plt.subplot(2,1,1)  
plt.ylabel(‘Quantites de matiere \n de A, B, C et D (mol/L)’, fontsize=8)  
plt.title(‘Evolutions des concentrations’, fontsize=8)  
plt.grid()  
plt.axis(xmin=0, xmax=1)  
plt.axvline(x = x\_f/xmax, label = ‘\\tau\_f’)  
plt.plot(tau, n\_A, color = ‘red’, label=‘n\_A’)  
plt.plot(tau, n\_B, color = ‘blue’, label=‘n\_B’)  
plt.plot(tau, n\_C, color = ‘green’, label=‘n\_C’)  
plt.plot(tau, n\_D, color = ‘orange’, label=‘n\_D’)  
plt.legend()  
plt.show()  
plt.subplot(2,1,2)  
plt.xlabel(‘Taux d'avancement \\tau’, fontsize=8)  
plt.ylabel(‘Constante de reaction Q\_r \n et constante d'equilibre K’, fontsize=8)  
plt.title(‘Evolution du quotient de reaction \n en fonction de l'avancement’, fontsize=8)  
plt.axvline(x = x\_f/xmax, label = ‘\\tau\_f’)  
plt.axis(xmin=0, xmax=1)  
plt.plot(tau, K\*np.ones(len(x)), color = ‘blue’, label=‘K’)  
plt.plot(tau, Q\_r, color = ‘red’, label=‘Q\_r’)  
plt.yscale(‘log’)  
plt.legend()  
plt.show()  
print('L'avancement final correspond a x\_f = ’ + str(x\_f) + ’ mol, soit un taux d'avancement final tau\_f = ’ + str(x\_f/xmax) + ‘.’)

Mais en l’exécutant, je reçois le message d’erreur suivant:  
ValueError Traceback (most recent call last)  
 in ()  
21 # Determination de l’avancement final x\_f  
22 for i in range(len(x)) :  
—\> 23 if Q\_r\<K:  
24 x\_f = x[i]  
25 i = i+0,1

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Je suis bloquée ☹  
Merci d’avance pour votre aide!

---

<div class="post-metadata">

**Author:** ![cameron](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/cameron/32/2658_2.png) [@cameron](https://discuss.python.org/u/cameron)\
**Post date:** [November 1, 2021, 9:56pm UTC](https://discuss.python.org/t/programme-pour-tableau-avancement-chimie-terminale/11686/2 "2021-11-01T21:56:43Z")

</div>

My French is very poor, so I will not try to respond in French. Comments  
inline below.

> Nous voyons en ce moment les avancements finaux en chimie et nous  
> devons compléter un code python permettant de calculer l’avancement  
> final selon différentes variables.  
> Voilà mon code:

Your cut/paste has lost all the indenting, which is important in Python.  
Next time, enclose the code (and error messages) in triple backticks to  
preserve leading spaces, eg:

```auto
your code
goes here

```

In the leading up code you have:

```
import numpy as np
[...]
# La reaction consideree est A + B -> C + D
# Coefficients stoechiometriques
a, b, c, d = 1, 1, 1, 1
# Quantites de matiere initiales et volume initial
n_iA, n_iB, n_iC, n_iD = 0.1, 0.1, 0, 0
V = 100.0e-3
# Constante d'equilibre
K = 1e-1
# Calcul de l'avancement final et generation des valeurs de x entre 0 mol et xmax
xmax = min(n_iA/a, n_iB/b)
x = np.arange(0, xmax, xmax/10000.0)
tau = x/xmax
# Calcul des quantites de matiere et du quotient de reaction a chaque avancement x
n_A = n_iA-a*x
n_B = n_iB-b*x
n_C = n_iC+c*x
n_D = n_iD+d*x
Q_r = ((n_C/V)**c*(n_D/V)**d)/((n_A/V)**a*(n_B/V)**b)

```

Just offering my guess at the correct indenting here:

```
# Determination de l'avancement final x_f
for i in range(len(x)) :
    if Q_r<K:
        x_f = x[i]
        i = i+1
    else :
        continue

```

So, let us look at your error message:

```
ValueError Traceback (most recent call last)
<ipython-input-13-8b9e8f373c4f> in <module>()
21 # Determination de l'avancement final x_f
22 for i in range(len(x)) :
---> 23 if Q_r<K:
24 x_f = x[i]
25 i = i+0,1
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

```

Since K is 0.1, this implies that Q\_r is not a scalar but probably a  
numpy array. If I run your code interactively I get:

```
>>> Q_r = ((n_C/V)**c*(n_D/V)**d)/((n_A/V)**a*(n_B/V)**b)
>>> Q_r
array([0.00000000e+00, 1.00020003e-08, 4.00160048e-08, ...,
       1.11044454e+07, 2.49900010e+07, 9.99800010e+07])

```

So it is an array. That is not comparable to a float such as K (0.1).

I am guessing that what you are doing is looking for values in Q\_r which  
are less than K, and setting x\_f in accordance with that. If that is so,  
you want to compare each element of Q\_r, like this:

```
# Determination de l'avancement final x_f
for i in range(len(x)) :
    if Q_r[i]<K:
        x_f = x[i]
        i = i+1
    else :
        continue

```

I notice also that you have:

```
i = i+1

```

inside the loop. This will be ineffective, because the for-loop will  
advance i. Usually you do not want to fiddle with a loop variable (“i”)  
inside the loop. However, because the for-loop is advancing i you can  
omit this line.

Note that there is a better way to write this for-loop, using the  
builtin enumerate() function. Knowing that Q\_r and x are the same  
length, you can go:

```
# Determination de l'avancement final x_f
for i, Q_r_i in enumerate(Q_r):
    if Q_r_i<K:
        x_f = x[i]
    else :
        continue

```

The enumerate() function returns an (index,value) pair for the thing it  
is iterating, so you get (0,Q\_r[0]), (1,Q\_r[1]) and so on. This lets you  
use the value from Q\_r directly as Q\_r\_i in the test.

Another thing you can do, ifyou do not care about “i” at the end (you  
only seem to want x\_f), is use the zip() function:

```
# Determination de l'avancement final x_f
for Q_r_i, x_i in zip(Q_r, x):
    if Q_r_i<K:
        x_f = x_i
    else :
        continue

```

The zip() function pairs up elements from 2 (or more) arrays, yielding  
(Q\_r[0],x[0]), (Q\_r[1],x[1]) and so on. This gets you Q\_r\_i and x\_i as  
each pair of values from the 2 arrays, without bothering with “i” at  
all.

Finally, regarding the for-loop logic. Your if-statement goes like this:

```
    if Q_r_i<K:
        x_f = x_i
    else :
        continue

```

The “else:continue” is redundant - the loop will continue anyway. You  
can get rid of it:

```
    if Q_r_i<K:
        x_f = x_i

```

and if you only care about the first x\_f value you find, you can exit  
the loop early using “break”.

```
    if Q_r_i<K:
        x_f = x_i
        break

```

Finally, I recommend putting print() statements in your code to see  
values before failures if the code is unclear. Example from your  
original loop:

```
print("K =", K)
for i in range(len(x)) :
    print("i =", i)
    print("Q_r =", Q_r)
    if Q_r<K:
        x_f = x[i]
        i = i+1
    else :
        continue

```

This would at least make it clear that Q\_r was an array and not the  
value from the array, which may have helped understand the error  
message.

Salut,  
Cameron Simpson [cs@cskk.id.au](mailto:cs@cskk.id.au)