Strong Acids and Bases, sympy.physics.units

Using Jupyter as a Worksheet for Strong Acid / Strong Base Calculations¶

In [1]:

import sympy.physics.units as u
from math import log10

In [2]:

# atomic mass, taken from a Periodic Table of the Elements
H=1.0079
Cl=35.453
Na=22.990
O=15.999
K=39.098
Ca=40.078
Ba=137.33
S=32.065

$$ Ba(OH)_2 $$

In [3]:

# Barium Hydroxide molecular mass computed using the atomic mass variables, with units "mmu", molar mass units
# ... automatically converted to kg/mol
moleculeMass=(Ba+2*(O+H))*u.mmu
moleculeMass

Out[3]:

0.1713438*kg/mol

In [4]:

# 4 grams of Barium Hydroxide
# ... automatically converted to kg
labWeight=4.00*u.g
labWeight

Out[4]:

0.004*kg

In [5]:

# kg of substance divided by kg/mol gives number of moles, rounded to 3 significant digits
(labWeight/moleculeMass).n(3)

Out[5]:

0.0233*mol

$$ [OH^-] $$

In [6]:

# 4 grams of Barium Hydroxide dissolved in 0.500L water
# if concentration is calculated with Sympy Units, it will automatically convert from liters to m**3
# so best to abandon Sympy Units at this point, and simply divide moles by liters
OHconcentration=2*(0.0233/0.500)  # moles x2 because 2 moles hydroxide ions for each mole of barium hydroxide
OHconcentration

Out[6]:

0.0932

In [7]:

# Hydroxide Ion concentration is in mol/L, so it can be used to find pOH
pOH = -1*log10(OHconcentration)
pOH

Out[7]:

1.0305840876460186

In [8]:

# pH is 14 minus pOH
14-pOH

Out[8]:

12.96941591235398

$$ [H^+] $$

In [9]:

# Hydrogen Ion concentration can be computed with 10**(-14) equilibrium constant
Hconcentration=(10**(-14))/OHconcentration
Hconcentration

Out[9]:

1.0729613733905579e-13

In [10]:

# pH can also be computed from the Hydrogen Ion concentration, and compared to pH compute above
-1*log10(Hconcentration)

Out[10]:

12.96941591235398