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Weak Acid Solutions

Weak Acid Solutions

Few compounds act as strong acids. A far greater number of compounds behave as weak acids and only partially react with water, leaving a large majority of dissolved molecules in their original form and generating a relatively small amount of hydronium ions. Weak acids are commonly encountered in nature, being the substances partly responsible for the tangy taste of citrus fruits, the stinging sensation of insect bites, and the unpleasant smells associated with body odor. A familiar example of a...

Polyprotic Acids

Polyprotic Acids

Acids are classified by the number of protons per molecule that they can give up in a reaction. Acids such as HCl, HNO3, and HCN that contain one ionizable hydrogen atom in each molecule are called monoprotic acids. Their reactions with water are:

Titration of a Weak Base with a Strong Acid

Titration of a Weak Base with a Strong Acid

The titration curve of a weak base like ammonia with a strong acid like hydrochloric acid is the mirror image of the titration curve of a weak acid with a strong base.
Using the ICE table and substituting the Kb value, we calculate the initial pH of 50 mL of 0.1 M ammonia to be 11.11. Addition of 25 mL of 0.1 M hydrochloric acid to this solution of ammonia results in a buffer with an equal concentration of ammonia and ammonium ions. The pH of this buffer can be calculated by substituting these...

Acid-Catalyzed Hydration of Alkenes

Acid-Catalyzed Hydration of Alkenes

Alkenes react with water in the presence of an acid to form an alcohol. In the absence of acid, hydration of alkenes does not occur at a significant rate, and the acid is not consumed in the reaction. Therefore, alkene hydration is an acid-catalyzed reaction.

Composition of Polyprotic Acid Solutions as a Function of pH

Composition of Polyprotic Acid Solutions as a Function of pH

Polyprotic acids of the type H2M constitute two ionizable protons. As a result, on titration with a base, they exhibit two equivalence points in the titration curve. During titration, the species H2M, HM−, and M2− will be present in the solution at different points. The fractions of H2M, HM−, and M2− present at the various instances of the titration are denoted by α0, α1, and α2, respectively.
A graph with the alpha values is plotted against the volume of base added during titration. Here, a...

Mixtures of Acids

Mixtures of Acids

The pH of a solution containing an acid can be determined using its acid dissociation constant and its initial concentration. If a solution contains two different acids, then its pH can be determined using one of several methods depending upon the relative strength of the acids and their dissociation constants.
A Mixture of a Strong Acid and a Weak Acid
In a mixture of a strong acid and a weak acid, the strong acid dissociates completely and becomes a source of almost all the hydronium ions...

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Related Experiment Video

Updated: Jun 23, 2026

Hydrogen Production and Utilization in a Membrane Reactor

Hydrogen Production and Utilization in a Membrane Reactor

Published on: March 10, 2023

Apparent hydrogen consumption in acid reactors: observations and implications.

C Dinamarca¹, R Bakke

¹Institute of Processes, Energy and Environmental Technology, Telemark University College, Kjølnes Ring 56, Porsgrunn 3918, Norway. carlos.dinamarca@hit.no

Water Science and Technology : a Journal of the International Association on Water Pollution Research

|April 22, 2009

Summary

Hydrogen consumption significantly reduces yields in dark fermentation, challenging its viability as a sole green fuel source. Controlling this consumption is key for optimizing other biofuel production processes.

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Hydrogen Production and Utilization in a Membrane Reactor

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Published on: March 10, 2023

A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions

A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions

Published on: August 17, 2016

Area of Science:

Biotechnology
Renewable Energy
Environmental Science

Background:

Dark fermentation is a focus for green fuel production, primarily studied for hydrogen yields and rates.
Previous research has largely overlooked the significant impact of hydrogen consumption within these systems.

Purpose of the Study:

To investigate the role and impact of hydrogen consumption in lab-scale dark fermentation reactors.
To evaluate the feasibility of sustainable hydrogen (H2) production solely through dark fermentation.

Main Methods:

Experiments utilized mixed cultures under varying hydraulic retention times (HRT: 6-40 hours) and temperatures (25-55°C).
Hydrogen yields and headspace composition were monitored throughout the fermentation process.

Main Results:

Initial hydrogen yields ranged from 0.8-1.5 mol H2/mol glucose with ~50% H2 in headspace.
Mature cultures showed drastically reduced yields (down to 0.02 mol H2/mol glucose) due to significant hydrogen consumption.
Consumption was most pronounced in reactors with high biomass concentration and/or high sludge age.

Conclusions:

Sustainable hydrogen production via dark fermentation alone is unlikely due to significant internal hydrogen consumption.
Controlling or minimizing hydrogen production in dark fermentation is feasible and beneficial for preparing feedstocks for other bioprocesses like methanogenesis and bio-electrochemical systems.