pH of Pure Water at 100°C | Acids & Bases

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SUMMARY

The pH of pure water at 100°C is approximately 6.87, indicating it is slightly more acidic than neutral pH 7. This change occurs due to the increase in the ionic product of water (Kw) to 1.8 x 10-14 at elevated temperatures. Additionally, higher temperatures lead to increased absorption of CO2, resulting in the formation of carbonic acid (H2CO3), further lowering the pH. Thus, both temperature and CO2 absorption significantly influence the acidity of water.

PREREQUISITES
  • Understanding of pH scale and its implications
  • Knowledge of ionic product of water (Kw)
  • Familiarity with acid-base chemistry, specifically carbonic acid formation
  • Basic principles of temperature effects on chemical equilibria
NEXT STEPS
  • Research the effects of temperature on Kw in detail
  • Study the process of CO2 absorption in water and its impact on pH
  • Learn about the implications of pH changes in aquatic environments
  • Explore the role of carbonic acid in biological systems
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Chemistry students, environmental scientists, and anyone interested in the effects of temperature on water chemistry and acid-base reactions.

Jack16
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Could You Help Me Out Please...

The Value of Kw ,the ionic product of water,increases with temperature.Will the pH of pure water be greater or less than 7 at 100*C?
 
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Hello,

It will be slightly more acidic, although H+ and OH- will be equally dissociated from water; because pH is calculated according to [H+]. Let me assume that in a higher temperature, the ionic product changes to 1,8.10-14. When you calculate the -log value of this, you'll find ca. 6,87. This shows that the pH value will be lower in higher temperatures.

In addition, in a higher temperature, the absorption of CO2 will be much higher, then the formation of carbonic acid, H2CO3, will cause the resulting aqueous solution to be even more acidic than that in the ambient temperature.

Regards, chem_tr
 
Last edited:

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