Assertion : NaHCO 3 cannot be estimated by titration with standard HCl solution using phenolphthalein as indicator. However, it can be estimated under identical conditions after heating. Reason : On

Question

Assertion : NaHCO 3 ​ cannot be estimated by titration with standard HCl solution using phenolphthalein as indicator. However, it can be estimated under identical conditions after heating. Reason : On heating NaHCO 3 decomposes to Na 2 CO 3 which can be estimated using phenolphthalein indicator.

TestHub · Accepted Answer

Phenolphthalein remains colorless in the titration of NaHCO₃ versus HCl and does not change color at the endpoint. However, heating NaHCO₃ yields Na₂CO₃, which can be estimated using phenolphthalein as an indicator.

$2 N a H C O_{3} ⟶ N a_{2} C O_{3} + H_{2} O ↑$

$N a_{2} C O_{3} + H Cl ⟶ N a H C O_{3} + N a Cl$

(upto phenolphthalein endpoint.)

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