Difference between revisions of "En-en adult card 23 hindered calcification process"

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== Explanation ==
== Explanation ==
The constitution of limestone (calcification) is the following chemical reaction: Ca<sup>++</sup> + 2HCO<sub>3</sub>- ⇔ CaCO<sub>3</sub> + H<sub>2</sub>O + CO<sub>2</sub>
The formation of limestone (calcification) follows the chemical reaction Ca<sup>++</sup> + 2HCO<sub>3</sub><sup>-</sup> ⇔ CaCO<sub>3</sub> + H<sub>2</sub>O + CO<sub>2</sub>


It requires the presence of bicarbonate HCO3- ions. However, the quantity of these ions in water depends on the pH: In water, carbon dioxide, carbonic acid, bicarbonate ion and carbonate ion are in equilibrium, depending on the pH :
It requires the presence of bicarbonate ions (HCO<sub>3</sub><sup>-</sup>). However, the quantity of these ions in water depends on the pH: in water, carbon dioxide, carbonic acid, bicarbonate ions and carbonates ion are in equilibrium, depending on the pH :


CO<sub>2</sub> + H<sub>2</sub>O ⇔ H<sub>2</sub>CO<sub>3</sub> ⇔ H<sup>+</sup> + HCO<sub>3</sub><sup>-</sup> ⇔ 2 H<sup>+</sup> + CO<sub>3</sub><sup>2-</sup>.
CO<sub>2</sub> + H<sub>2</sub>O ⇔ H<sub>2</sub>CO<sub>3</sub> ⇔ H<sup>+</sup> + HCO<sub>3</sub><sup>-</sup> ⇔ 2 H<sup>+</sup> + CO<sub>3</sub><sup>2-</sup>.


The addition of an acid shifts the equilibrium to the left.
The addition of an acid shifts the equilibrium towards the left of the equation. In other words, if the pH drops, there are fewer bicarbonate ions, making it more difficult for organisms to build their shells.  
 
In other words, if the pH drops, the bicarbonate ions are in less quantity. Hence the difficulty of making limestone for the organisms that need it.


[[fr:Fr-fr_adulte_carte_23_problèmes_de_calcification]]
[[fr:Fr-fr_adulte_carte_23_problèmes_de_calcification]]

Revision as of 16:23, 21 March 2021

Card #23: Hindered Calcification Process

Causes Consequences
Front of the card "Hindered Calcification Process"


When the pH drops, the formation of calcium carbonate (and more specifically, of calcified shells) becomes more difficult.

Explanation

The formation of limestone (calcification) follows the chemical reaction Ca++ + 2HCO3- ⇔ CaCO3 + H2O + CO2

It requires the presence of bicarbonate ions (HCO3-). However, the quantity of these ions in water depends on the pH: in water, carbon dioxide, carbonic acid, bicarbonate ions and carbonates ion are in equilibrium, depending on the pH :

CO2 + H2O ⇔ H2CO3 ⇔ H+ + HCO3- ⇔ 2 H+ + CO32-.

The addition of an acid shifts the equilibrium towards the left of the equation. In other words, if the pH drops, there are fewer bicarbonate ions, making it more difficult for organisms to build their shells.