Soda Ash Titration Pre-Lab Flashcards

Vocabulary practice flashcards covering core chemical principles, safety rules, stoichiometry, and lab procedures for the soda ash titration experiment.

Carbonate ($\text{CO}_3^{2-}$)

A diprotic base with two distinct equivalence points.

First Endpoint (Soda Ash Titration)

The reaction stage where $\text{CO}_3^{2-} + \text{H}^+ \rightarrow \text{HCO}_3^-$, causing phenolphthalein to shift from pink to colorless.

Second Endpoint (Soda Ash Titration)

The reaction stage where $\text{HCO}_3^- + \text{H}^+ \rightarrow \text{H}_2\text{CO}_3 \rightarrow \text{H}_2\text{O} + \text{CO}_2$, causing methyl red to shift from yellow to red.

Boiling / Removal of $\text{CO}_2$

A step that removes excess $\text{CO}_2$ gas to break the carbonic acid/bicarbonate ($\text{HCO}_3^-/\text{CO}_2$) buffer system and sharpen the second endpoint.

Acid Dilution Safety Rule

Always add acid to water (never water to acid) when diluting concentrated $\text{HCl}$ ($37\,\text{wt}\%$, $d = 1.18\,\text{g\,mL}^{-1}$) to prevent exothermic splashing.

Primary Standard Preparation ($\text{Na}_2\text{CO}_3$)

Drying $\text{Na}_2\text{CO}_3$ in the oven at $160^{\circ}\text{C}$ for at least $2\,\text{hours}$, then cooling in a desiccator for at least $20\,\text{minutes}$ before weighing.

Primary Stoichiometric Ratio

The mole ratio where $1\,\text{mole}$ of $\text{Na}_2\text{CO}_3$ reacts with $2\,\text{moles}$ of $\text{HCl}$ at the complete (2nd) endpoint.

Molar Mass of $\text{Na}_2\text{CO}_3$

$$105.99\,\text{g\,mol}^{-1}$$

Percent Purity Formula ($\%\,\text{Na}_2\text{CO}_3$)

$$\%\,\text{Na}_2\text{CO}_3 = \left( \frac{\text{Mass of }\text{Na}_2\text{CO}_3}{\text{Initial mass of soda ash sample}} \right) \times 100$$

Concentrated $\text{HCl}$ Dilution Volume

Diluting approximately $8\,\text{mL}$ of concentrated $\text{HCl}$ to $1\,\text{L}$ of solution.

Pre-boiling Water

Boiling water prior to titration to remove pre-dissolved atmospheric $\text{CO}_2$, which prevents early pH drops caused by background carbonic acid.

Carbonated Drinks Titration Challenge

Drinks like Coke contain additional acids (e.g., phosphoric acid) and coloring agents that mask indicator color changes, unlike clear soda ash solutions.