In class, we did a decomposition reaction of sodium hydrogen carbonate, which makes water, carbon dioxide, and sodium carbonate. How do you know when sodium hydrogen carbonate is completely reacted?
You weigh the NaHCO3 to start, let it heat at the specified T, place in a desiccator to cool, weigh. Repeat heat and cooling. Weigh again. If the two weights after heating are the same, all of the NaHCO3 has been converted to Na2CO3.
Note: One must be careful with this because Na2CO3 can be decomposed to Na2O and CO2 and the loss of CO2 will show up as a loss in weight; the optimum T for NaHCO3 to Na2CO3 is about 275 C to 300 C. The decomposition of Na2CO3 is higher than that.
To determine when sodium hydrogen carbonate (also known as baking soda or sodium bicarbonate) is completely reacted in a decomposition reaction, you can observe the production of carbon dioxide gas. Here's how you can perform the experiment and know when the reaction is complete:
1. Set up the experiment: Place a small amount of sodium hydrogen carbonate in a test tube or a flask. Make sure to use a small quantity to observe the reaction more effectively.
2. Add acid: Add a few drops of a strong acid, such as hydrochloric acid (HCl), to the test tube containing the sodium hydrogen carbonate. When the acid reacts with the sodium hydrogen carbonate, it will produce carbon dioxide gas.
3. Observe the carbon dioxide production: As the reaction progresses, carbon dioxide gas will start to form and release into the surrounding air. You can determine the completion of the reaction by observing the rate of gas production.
4. Signs of completion: When the reaction is complete or near completion, the rate of gas production will slow down significantly. At this point, you may notice fewer or no bubbles being formed in the solution, indicating that most of the sodium hydrogen carbonate has reacted.
It is worth noting that other factors, such as temperature and the concentration of acid used, can influence the reaction rate. Therefore, it is essential to control these variables to ensure accurate observation.