Question

Identify the acid and the base that form the salt Sodium Hydrogen-Carbonate and Write the chemical equation which supports your answer. State whether the compound is acidic, basic or neutral and also write its pH value.

Answer 1

Hint: Sodium Hydrogen-Carbonate: \[NaHC{{O}_{3}}\]. Now looking at the chemical composition of this salt, try and figure out the reactants required for its conception and its possible chemical properties.

Complete answer:
Sodium Hydrogen-Carbonate (\[NaHC{{O}_{3}}\]) is a salt which is conceived as the product of a chemical reaction between the strong alkali salt Sodium Carbonate (\[N{{a}_{2}}C{{O}_{3}}\], pH = 11.70 for 10 wt% solution), which itself is formed as a product of the reaction between the strong base Sodium Hydroxide (NaOH, pH = 14 for 1N solution) and the weak acid Carbonic Acid (\[{{H}_{2}}C{{O}_{3}}\], pH = 3.68 for 100 mmol per L) which is carried out as follows:

$2NaOH+{{H}_{2}}C{{O}_{3}}\to N{{a}_{2}}C{{O}_{3}}+2{{H}_{2}}O$

This Sodium Carbonate then formed is then again reacted with Carbonic acid to give out Sodium Hydrogen-Carbonate as a result of a process called the Solvay Process which goes as follows:

$N{{a}_{2}}C{{O}_{3}}+{{H}_{2}}O+C{{O}_{2}}\xrightarrow{N{{H}_{3}}}2NaHC{{O}_{3}}$

It is very important to note that while Carbonic Acid is fairly stable at room temperature, the presence of water in any form exponentially accelerates its rate of decomposition therefore resulting in \[{{H}_{2}}O\] and \[C{{O}_{2}}\].
Assuming equal concentrations of 1N each of \[N{{a}_{2}}C{{O}_{3}}\] and \[{{H}_{2}}C{{O}_{3}}\] are used in the production of \[NaHC{{O}_{3}}\], then the salt is very mildly basic as the strength of Sodium Carbonate as a base is just a little bit greater than that of Carbonic Acid as an acid, with the resultant pH of Sodium Hydrogen-Carbonate being about 8.27.

Note: Remember that Sodium Hydrogen-Carbonate is a weak basic salt and requires a weak base for its production and the usage of a strong base like Sodium Hydroxide will result in the formation of Sodium Carbonate.