Potassium hydrogencarbonate

Dissociation constant

Link to relevant study record(s)

Reference

Reference 1

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

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^- <=> CO_{3^{2 -}).}

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^- <=> CO_{3^{2 -}}).

Reference 2

Endpoint:

dissociation constant

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Principles of method if other than guideline:

Apparent molar volumes VΦ and apparent molar heat capacities Cp, Φ of aqueous potassium carbonate and potassium bicarbonate solutions were determined. Corrections for speciation due to hydrolysis and disproportionation in solution were applied using Young's rule, and semi-empirical equations were fitted to the experimental results. Based on the results several thermodynamic properties were determined. The pK2 for potassium hydrogencarbonate determined at several temperatures.

GLP compliance:

not specified

Dissociating properties:

yes

No.:

#2

pKa:

10.34

Temp.:

25 °C

The pK2 of potassium hydrogencarbonate is reported to be 10.335 at 25 ^oC.

Conclusions:

The pK2 of potassium hydrogencarbonate is reported to be 10.335 at 25 °C.

Executive summary:

The pK2 of potassium hydrogencarbonate is reported to be 10.335 at 25 °C.

Description of key information

 Potassium hydrogencarbonate 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:

6.35

Additional information

The pK of potassium hydrogencarbonate at 25 °C is 6.35 (pK1) and 10.33 (pK2).

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^-=> CO_3^2-).