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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Dissociation constant

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
dissociation constant
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: expert judgement
Guideline:
other: review article
Principles of method if other than guideline:
The dissociation constants for CO2 in water are reported.
GLP compliance:
not specified
Dissociating properties:
yes
No.:
#1
pKa:
6.35
Temp.:
25 °C
Remarks on result:
other: fresh water
No.:
#2
pKa:
10.33
Temp.:
25 °C
Remarks on result:
other: fresh water
No.:
#1
pKa:
5.86
Temp.:
25 °C
Remarks on result:
other: seawater
No.:
#2
pKa:
8.95
Temp.:
25 °C
Remarks on result:
other: seawater

In the review article, the dissociation constants of CO2 in water systems are reported to be 6.35 (pK1) and 10.33 (pK2) at 25°C in fresh water and 5.86 (pK1) and 8.95 (pK2) at 25°C in seawater ( H2CO3 <=> HCO3- <=> CO32 -).

Conclusions:
The dissociation constants of CO2 in water systems are reported to be 6.35 (pK1) and 10.33 (pK2) at 25°C in fresh water and 5.86 (pK1) and 8.95 (pK2) at 25°C in seawater.
Executive summary:

In the review article, the dissociation constants of CO2 in water systems are reported to be 6.35 (pK1) and 10.33 (pK2) at 25°C in fresh water and 5.86 (pK1) and 8.95 (pK2) at 25°C in seawater ( H2CO3 <=> HCO3- <=> CO32 -).

Description of key information

Potassium carbonate dissociates in water completely to K+ and inorganic carbon (CO32- ions in equilibrium with HCO3- and CO2). The dissociation constants of CO2 in water systems are 6.35 (pK1) and 10.33 (pK2) at 25°C in fresh water and 5.86 (pK1) and 8.95 (pK2) at 25°C in seawater (CO2 (solv) + H2O <=> H2CO3 => HCO3- => CO32 -).

Key value for chemical safety assessment

pKa at 20°C:
10.33

Additional information

The dissociation constants of CO2 in water systems are 6.35 (pK1) and 10.33 (pK2) at 25°C in fresh water and 5.86 (pK1) and 8.95 (pK2) at 25°C in seawater ( H2CO3 => HCO3- => CO32 -).