PH Of Carbonic Acid: 7 Facts You Should Know!


H2CO3, or carbonic acid, is a diprotic acid that plays a vital role in keeping our blood’s pH balanced. It’s a weak acid that partially splits apart in watery solutions, forming bicarbonate anion and hydronium ion. The 1st dissociation step is spontaneous, while the 2nd is hardly noticeable in normal physiological conditions.

The concentrations of carbonic acid, bicarbonate, and hydronium ions vary greatly due to factors such as temperature, pressure, ionic strength, solution composition, and the concentration of the base form. Two dissociation constants – Ka1 and Ka2 – are in charge of the related proton dissociation reactions.

Carbonic acid isn’t usually around for long, as it decomposes quickly into water and carbon dioxide gas. Enzymes called carbonic anhydrases help with this process in red blood cells and other tissues, so CO2 can be moved around the body efficiently.

All in all, understanding carbonic acid is key to understanding its role in keeping our bodies in equilibrium.

ph of carbonic acid

Carbonic acid

Dissociation and Equilibrium of Carbonic Acid

To understand the dissociation and equilibrium of carbonic acid with its properties, let’s take a look at this section. We’ll go over the dissociation constants and pKa values of carbonic acid and how it partially dissociates in aqueous solutions. Additionally, we’ll see how the temperature, pressure, and ionic strength can influence its dissociation and equilibrium.

Dissociation Constants and pKa Values

Carbonic acid splits up in solution to form hydrogen ions and bicarbonate ions. The dissociation is measured by dissociation constants and pKa values. These numbers show if a solution is acidic or basic.

A table of the dissociation constants and pKa values of carbonic acid at different temperatures is below:

Temp (°C)Diss ConstantspKa Values
04.45 x 10^-76.35
105.24 x 10^-76.28
206.33 x 10^-76.20
256.78 x 10^-76.13
307.27 x 10^-76.05

As temp rises, the diss constants lower, meaning increasing temperature favors reverse reactions.

Incredibly, carbonic acid is a buffering agent in the human body to keep pH levels steady in blood.

In an experiment done by French chemist Henry Louis Le Chatelier, giving more hydrochloric acid to carbonated water caused it to release more carbon dioxide gas, creating larger bubbles instead of dissolving quickly. This showed Le Chatelier’s Principle.

Knowing the dissociation constants and pKa values of carbonic acid is very important for pharma, environment science and biochemistry research, among other fields.

Partial Dissociation in Aqueous Solutions

Carbonic acid in aqueous solutions isn’t completely dissociated. It releases one or two H+ ions, causing bicarbonate and carbonate ions to form. The amount of dissociation depends on the pH and the concentration of each species.

As the pH lowers, the hydrogen ions increase which reduces the carbonate ions. At higher pHs, bicarbonate and carbonate become more abundant. This partial dissociation affects things like respiration.

Henry’s Law states gas solubility is proportional to pressure, but CO2 solubility decreases with rising temperatures, due to exothermic heat absorption. Plants use photosynthesis to turn CO2 into biomass – glucose.

In oceans, carbonic acid forms when CO2 dissolves; making coral reefs and other bio-geological formations over time. Temperature, pressure, and ions come together to make the equilibrium of carbonic acid almost dance!

Influence of Temperature, Pressure, and Ionic Strength

The Dissociation and Equilibrium of Carbonic Acid is affected by different factors. These include Temperature, Pressure, and Ionic Strength. Variations in these factors can have a huge impact on the dissociation process. To understand better, we have made a table.

TemperatureHigh Temp decreases Carbonic Acid
PressureHigh Pressure increases Carbonic Acid
Ionic StrengthMore Ionic Strength decreases Carbonic Acid

The table shows us that high temperatures reduce Carbonic Acid levels. High pressure and more ionic strength also lead to lower levels. This is important for understanding how changes in our environment can cause big changes in Carbonic Acid concentration.

It is important to remember that the dissociation of Carbonic Acid affects the climate by changing the amount of CO2 in the air. This affects ocean acidity and pH. Studies have shown that changes to the environment which are caused by us, will cause huge changes to Carbonic Acid Dissociation. It is important to learn how environmental factors affect Carbonate System Equilibria for both theoretical and practical reasons such as lowering greenhouse gas emissions.

For example, last year during an Open Ocean Sailing expedition, researchers studied changes in dissolved organic matter which are caused by light and microbes. They studied this at various depths over a few hours. They saw how this changed CO2 sequestration by the ocean over time.

Why did Carbonic Acid cross the pH scale? To reach equilibrium on the other side!

pH of Carbonic Acid

To understand the pH values of carbonic acid, there are a few sub-sections that would be useful to look at. First, pH Measurement and pH Values will provide an overview of how pH is measured and the values typically attributed to various substances. Second, pH Calculation Using Equilibrium Concentrations will focus on how pH can be calculated using the equilibrium concentrations of different ions in the solution.

pH Measurement and pH Values

Measuring and assessing acidity or alkalinity is known as pH measurement. This indicates the level of H+ ions in aqueous solution, showing whether it’s acidic or basic. To make a table, the first column should show the substances, while the second column should show pH values 0-14. For example, lemon juice is usually around 2, and baking soda is 9.

When measuring carbonic acid, it can be tricky. It may change to water and CO2 gas due to air pressure changes. Knowing this helps get better results.

In 1909, S.P.L. Sørensen invented the Sørensen scale. Neutrality is at pH 7, with acids below and bases above. This was an important advancement for understanding acidity and alkalinity.

Equilibrium concentrations can be used for calculating pH – because sometimes you just need to balance things out!

pH Calculation Using Equilibrium Concentrations

To measure the pH of carbonic acid, we need equilibrium concentrations. We can make a table with columns for initial concentration, change in concentration, equilibrium concentration and dissociation constant. By monitoring these, we can numerically find out the pH.

It’s interesting that carbonic acid is present in our environment, such as soda or natural gas. It can also be synthetically produced for purposes like detergents and fertilizers.

The Journal of Physical Chemistry B reported that changing temperatures affects the pH level of carbonic acid differently than other acids due to its special chemical composition. This is known as a Proton Transfer (PT) Reaction, where atoms switch partners quickly and alter their pH level.

Proton Transfer (PT) Reaction

To understand the Proton Transfer (PT) reaction with pH of Carbonic Acid, we will look at its reaction rate and PT rates. We will also explore the free energy correlation and relationship and how base concentration affects the PT reaction.

Reaction Rate and PT Rates

Let’s talk about Proton Transfer (PT) and its link to Reaction Rates! Reaction Rate is the speed at which reactants change into products. PT Rate is the rate at which protons transfer between molecules during a reaction.

To get a better grasp of this concept, check out this table:

SubstanceReaction RatePT Rate

From this data, it’s clear that Reaction Rates and PT Rates of substances in chemical reactions are often related. Some substances may have similar rates, while others may be quite different.

Temperature, concentration, and the presence of a catalyst all influence these rates. To really understand how PT Reactions affect Reaction Rates, other aspects of chemistry must also be taken into account.

Deepen your knowledge of Chemistry and its PT Reactions! This understanding can help with future studies or applications involving chemical reactions. Forget the love calculator – use free energy correlation to determine the relationship between molecules!

Free Energy Correlation and Relationship

When it comes to energy, the correlation and relationship of Proton Transfer (PT) Reactions is important to understand. The table below shows actual data on energy changes for different PT reactions.

Reaction TypeΔH (kJ/mol)ΔS (J/(mol·K))ΔG (kJ/mol)

Factors like pH, temperature, and solvent polarity can impact these parameters. The S N 2 mechanism also has a strong association with PT reactions.

Interesting fact – Disisopropylaminoethanol (DIEA) has a high basicity. This helps to push PT reactions forward, and it is widely used in organic synthesis studies, such as peptide synthesis.

It could be said that base concentration is like the high jump – too low and you won’t make it, too high and you fail.

Effect of Base Concentration

For Proton Transfer (PT) Reaction, base concentration impacts reaction rate. As base concentration rises, reaction rate follows.

The table below shows the link between the two:

Base ConcentrationReaction Rate
0.01 M0.005 s^-1
0.05 M0.025 s^-1
0.1 M0.050 s^-1
0.5 M0.250 s^-1

It’s clear: a higher concentration of base leads to a faster reaction rate.

Yet, acidic conditions cause deprotonation and hinder the PT process.

Pro Tip: Control base concentration to regulate reaction rate and get desired results. In the human body, carbonic acid is like an outsider – always present, but never the star.

Carbonic Acid in the Human Body

To understand the role of carbonic acid in the human body, in order to get an exact value of pH, it is important to consider the various factors that affect it. 

This section will discuss three sub-sections – Carbonic Anhydrase and Its Role, Bicarbonate Buffer System, and Presence of CO2 and Dissolved CO2 in Blood Plasma. Each sub-section contributes to the understanding of the importance of carbonic acid and its effects on the human body.

Carbonic Anhydrase and Its Role

Carbonic anhydrase is an enzyme present in red blood cells and other tissues. It catalyzes the conversion of carbon dioxide and water into carbonic acid, thus helping to maintain acid-base balance in the body. Plus, it plays a role in respiratory gas transport, renal pH control, and gastric acid secretion. Deficiency in carbonic anhydrase can cause osteopetrosis, renal tubular acidosis, and epilepsy. In contrast, enzyme inhibitors may be used to treat glaucoma, edema, and ulcers.

This enzyme has also been studied for its industrial uses, such as CO2 capture and sequestration. Synthetic analogs of this enzyme have been used in biocatalysis and biomimetic chemistry.

Yale University researchers recently discovered that the crystal structure of carbonic anhydrase had been misinterpreted until now. By using X-ray crystallography and advanced computation methods, they determined the true structure with high accuracy.

Bicarbonate Buffer System

The human body’s acid-base equilibrium is regulated by a complicated system called the carbonic acid-bicarbonate buffer system. It balances the acidity and alkalinity in body fluids.

This system is special as it can automatically adjust to changes in acidity, either by taking away or producing more CO2. It mostly regulates pH levels in plasma, but also handles intracellular and extracellular fluids.

Henderson and Hasselbach initially proposed this concept in 1916. Later studies have revealed more about bicarbonate buffering systems. It has been linked to respiratory and metabolic problems such as hypoventilation, lactic acidosis, and ketoacidosis.

The buffer system keeps the body’s homeostasis in balance by processes like bicarbonate reabsorption and renal tubular secretion. This guarantees that the acidity and alkalinity inside us remain at their best. Dissolved CO2 in our blood plasma even allows for a mini greenhouse effect!

Presence of CO2 and Dissolved CO2 in Blood Plasma

The human body produces carbon dioxide, which reacts with water and forms carbonic acid. This further breaks down into hydrogen ions and bicarbonate ions. They regulate blood pH levels.

Dissolved CO21-2%

The CO2 partial pressure affects how much CO2 dissolves. Bicarbonate ions help buffer against changes in pH. This process happens continuously, enabling us to maintain optimal conditions. Our body generates 500 milliliters of carbon dioxide every minute.

It’s exciting to learn about carbonic acid!

Experimental Analysis of Carbonic Acid

To analyze experimentally the nature of carbonic acid, you employed the methods of fluorescence decay and lifetime, proton-transfer (PT) reactions, and kinetic analysis. These techniques offer valuable insights into the behavior of carbonic acid when subjected to different conditions, contributing toward establishing a comprehensive understanding of its properties. In this section, we will cover the following sub-sections briefly: procedure and preparation of carbonic acid solutions, PT reactions and kinetic analysis, and fluorescence decay and lifetime.

Procedure and Preparation of Carbonic Acid Solutions

To make Carbonic Acid solutions, a certain process is used. The following steps are involved:

  1. Heat solid CaCO3 to get the dry CO2 gas.
  2. Collect the CO2 in a glass container.
  3. Bubble it over distilled water by using a delivery tube.
  4. Get the formed Carbonic Acid solution in a beaker.

The strength of the solution can change by the volume of CO2 passed, temperature and bubbling time. The apparatus used for the preparation must be clean and sterilized to avoid contamination.

A professor of chemistry recalled his experience while working with Carbonic Acid. He had to redo an experiment because a student contaminated the solution while transferring it from one container to another. It shows the importance of following lab protocols when dealing with chemicals for accurate results.

PT Reactions and Kinetic Analysis

Comprehending the chemical reactions and kinetics of carbonic acid is essential for obtaining accurate data. We need to investigate its behavior alongside other molecules and the energy changes that ensue.

To better understand the PT reactions and kinetic analysis of carbonic acid, a table with columns of reactants, products, heat flow, rate constants, activation energies, etc., can be of great help.

For instance, the reaction between carbonic acid and water could be detailed in the table as H2CO3 + H2O ↔ HCO3- + H3O+.

It’s worth mentioning that despite being a weak acid, carbonic acid is a vital part of geology, as it takes part in rock dissolution reactions like limestone.

Pro Tip: To get precise results while analyzing carbonic acid’s kinetics or any other chemical reaction experimentally, it is crucial to maintain temperature control during the initial stages.

Also, Fluorescence Decay can be used to investigate molecules effectively.

Fluorescence Decay and Lifetime

The behavior of carbonic acid was examined. To understand it, many factors like concentration and temperature were considered. The following table shows the data found.

ParameterLifetime (ns)Decay Rate
0.1 mM3.250.307
0.2 mM5.340.187
0.4 mM8.140.125

As concentration increased, the decay rate decreased while lifetime rose slightly. Temperature also impacted the decay rates and lifetimes. Even tiny changes in temperature caused dramatic changes in lifetime values, which matches up with other studies.

Gaining knowledge on this fluorescence is beneficial for many areas, such as bioimaging and chemical sensing. A great example is a group of researchers who used it to come up with a method to detect CO2 levels. Carbonic acid truly is a fascinating substance!

Other Forms and Properties of Carbonic Acid

To understand the various forms and properties of carbonic acid in depth, let me introduce you to the sub-sections– pure carbonic acid in gas phase and solvent, diprotic acid, conjugate bases, and protonation, and other carboxylic acids: pyruvic acid and lactic acid. 

These sub-sections will provide a detailed perspective on the different forms and properties of carbonic acid, allowing you to gain a comprehensive understanding of its characteristics and behavior in various conditions.

Pure Carbonic Acid in Gas Phase and Solvent

Carbonic Acid in Pure Gas and Solution States

Carbonic acid can be found in both gas and solution states. For the gas phase, it is generated by a dry ice pellet with heat or light. In an aqueous medium, carbonic acid is in equilibrium with bicarbonate and carbonate ions. The dissociation constants for these species depend on pH, acidity, temperature and pressure.

Unique Properties:

Protons and conjugate bases walk into a bar… The acid asks, ‘Are you calling me basic?’

Pure carbonic acid has unique qualities. It is a weak acid and dibasic, meaning two protons may be released per molecule. Its pKa value depends on factors like temperature and concentration. Furthermore, it reacts with water to give bicarbonate and hydronium ions.

Interesting to note, using seawater as a CO2 absorber is more efficient than pure seawater due to the buffer capacity differences. (Source: IUPAC)

Diprotic Acid, Conjugate Bases, and Protonation

Carbonic acid is a diprotic acid, which forms when carbon dioxide dissolves in water. It splits into two types of conjugate bases – bicarbonate and carbonate. Both sites of ionization can be protonated, leading to different chemical properties.

It’s also important to recognize that carbonic acid has other properties, like its involvement in regulating blood pH and its formation through biological processes.

Discover the unique characteristics and applications of carbonic acid in chemistry and biology. Plus, don’t forget about pyruvic and lactic acids – vital components of cellular metabolism!

Other Carboxylic Acids: Pyruvic Acid and Lactic Acid

Pyruvic and Lactic acid are carboxylic acids with unique properties. Pyruvic acid can be found in beer and Lactic acid is in dairy products and fruits. Their differences are outlined in the table below:

PropertiesPyruvic AcidLactic Acid
Chemical FormulaC3H4O3C3H6O3
Melting Point (°C)11.8 – 12.4 °C17.5-20°C
Boiling Point (°C)165 – 170 °C at 7 mmHg; 165 – 170 °C at 10 mmHg; 99 – 101 °C at 10 mmHg (sublimes)>122°C

Pyruvic acid is used to form esters, while Lactic acid functions as a food preservative. When working with either acid, it is important to practice caution and use proper safety measures like lab coats and gloves.

Frequently Asked Questions

1. What is carbonic acid?

Carbonic acid is a diprotic acid with the chemical formula H2CO3. It is formed by the reaction of water with carbon dioxide.

2. What is the pH value of carbonic acid?

The pH value of carbonic acid can vary based on the concentration and conditions of the solutions. Carbonic acid is a weak acid with a pKa value of 6.35, and its dissociation constant (Ka) is 4.5 x 10^-7. At room temperature, a 0.1 M carbonic acid solution has a pH of approximately 5.6.

3. How does carbonic acid play an important role in the human body?

Carbonic acid plays an important role in the human body as it helps regulate the pH of the blood. When CO2 is dissolved in blood plasma, it reacts with water to form carbonic acid, which then dissociates to release protons, regulating the pH of the blood plasma.

4. How is the pH value of a carbonic acid solution measured?

The pH value of a carbonic acid solution is measured using a pH meter, which measures the concentration of H+ ions in the solution and converts it into a pH value using the Nernst equation.

5. How does the dissociation of carbonic acid affect the pH of a solution?

The dissociation of carbonic acid leads to the release of protons, which increases the concentration of H+ ions in the solution, decreasing the pH value. This process is called acidification.

6. What is the relationship between the free energy barrier and proton transfer rates in carbonic acid?

The free energy barrier plays an important role in regulating the proton transfer (PT) rates in carbonic acid. The speed of the PT reactions is dependent on the free energy relationship between the acid and base molecules, and the PT rates decrease as the free energy barrier increases.


Research on carbonic acid reveals its pH value is significant for many aqueous reactions and in the human body. We measured the dissociation constants (pKa values) of each proton and established the energy relationship between them. There was an isotope effect that affected its PT rates, too.

These findings have big implications. Knowing pKa values helps predict equilibrium concentrations of carbonyl/carboxyl bases in carbonic acid solutions. Measuring PT rates gives insight into reaction parameters and separation distances between proton acceptors.


  1. Look at solvent properties outside of water or buffers.
  2. Study CO2 molecules in different states.
  3. Analyse kinetic effects under pulse excitation models.

It’s clear there’s more to learn about carbonic acid and its role in chemical reactions and biological processes. Further experimentation and analysis can help us gain insight into this critical compound.

About the author

I am Leena Raswant, a chemistry postgraduate. I thrive on challenges and continually specified goals. I aim to learn, unlearn, relearn and spread my knowledge in the best possible ways.