How to Estimate the pH of a Solution – Part 2

pH is a logarithmic scale used to specify the acidity or basicity of aqueous solutions.


Acidic solutions (with higher concentrations of hydrogen (H+) cations) are measured to have lower pH values than basic or alkaline solutions. The neutral pH is 7. A 𝑝𝐻 meter may be used for a precise and accurate measurement of the 𝑝𝐻 of a solution.

Mnemonic: ICE: Initial Change Equilibrium (molar concentration or partial pressure)

Question:

Report the expected pH in a range of two units difference when a 0.0100 M solution of Methylamine (Kb = 4.4 x 10─4) is prepared.

Solution:



Click/tap to enlarge the image

Ξ± = Degree of dissociation, c = Molar concentration, B = Base

NOTE: A weak base like Methylamine (CH3NH2) is partly ionized; and therefore, the molar concentration is NOT equal to the [OH─]. The concentration of undissociated water is nearly constant.

Premonition about pH❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com❗

NOTE: Post updated since published

References:

(1)    Wikipedia Contributors. pH. Wikipedia. https://en.wikipedia.org/wiki/PH.

(2)  Brown, C.; Ford, M. Higher Level Chemistry, 2nd ed.; Pearson Education: Harlow, Essex, 2014.

(3)    Ncert. Chemistry : Textbook for Class XI - Part.I; National Council Of Educational Research And Training: New Delhi.

(4)    Graham, T. W.; Fryhle, C. B.; Snyder, S. A. Organic Chemistry.; Hoboken, Nj John Wiley Et Sons, Inc, 2016.

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