Experiment 6 - Thermal Decomposition of Sodium Bicarbonate, Lab Reports of Chemistry

Download Experiment 6 - Thermal Decomposition of Sodium Bicarbonate and more Lab Reports Chemistry in PDF only on Docsity! 28 Experiment 6 - Thermal Decomposition of Sodium Bicarbonate NaHCO3 (s) is commonly called sodium bicarbonate. When NaHCO3 is heated above 110 oC (but not heated to "red heat") it has been observed that both H2O (g) and CO2 (g) are evolved by some chemical change, and that after this decomposition is complete, a white solid residue remains. Among possible reactions, the two following unbalanced reactions seem the ones that are most likely to explain these facts: NaHCO3 (s) → Na2CO3 (s) + H2O (g) + CO2 (g) (reaction A) sodium bicarbonate sodium carbonate water vapor carbon dioxide NaHCO3 (s) → Na2O (s) + H2O (g) + CO2 (g) (reaction B) sodium oxide You are to choose between reactions (A) and (B) on the basis of your laboratory work, which will involve heating a weighed sample of sodium bicarbonate in a crucible and weighing the residue left in your crucible after heating. From the mass of the solid product ("residue"), you should be able to decide if the product of the reaction is Na2CO3 or Na2O. Safety Precautions: • Wear your safety goggles. • Use care when handling HCl (aq). If any HCl splashes on your skin or clothes, rinse it off immediately with plenty of water. Waste Disposal: • The solid waste may be discarded in one of the regular garbage cans. Procedure 1. Obtain a clean, dry crucible that has no cracks. 2. Place the crucible in a clay triangle, on a ring attached to a ring stand. Make certain that the crucible hangs securely in the triangle; ask for help if it seems shaky. Put the cover on the crucible. 3. Heat the crucible and cover for 10 minutes with a high flame, until the bottom of the crucible glows red hot. Allow the crucible to cool in the clay triangle. (This step is to clean out the crucible.) 4. When they have reached room temperature, weigh the crucible and cover. 5. Add sodium bicarbonate to the crucible until it is 3/4 full. Weigh the crucible, sample, and cover. Obtain the mass of the sample by subtraction. 6. Using a medium-sized flame, heat the sample for 15 minutes. Do NOT heat the sample until it is red hot. Cool it in place as before, and then weigh it. (While you are waiting for the sample to heat and cool, you may start on the calculations.) 7. Heat again, this time for 10 minutes, then cool and weigh as before. If the crucible, cover, and sample weigh the same, then we can be reasonably confident