Investigating Stoichiometry With Carbonic Acid Salts

Investigating Stoichiometry with Carbonic Acid Salts Problem: Testing the actual yield versus the theoretical yield of NaCl when HCI is titrated into Na2C03 and NaHC03. When 0. 15g of both NaHC03 and Na2C03 are titrated with HCI, then 0. 165g of NaCl should form from the NaHC03, and 0. 104g of NaCl should form from the 0. 15g of Na2C03. Procedure: Weigh 2 samples of 0. 15g of dried unknown each, and dissolve each into 50mL of distilled water. Add 0. 5 to 1 mL of bromocresol green indicator until the solution turns blue. Titrate the HCI until it turns green. Gently heat and boil out the C02. It should turn blue again.

Continue the titration until it turns yellow. Heat the solution and let the water evaporate. Weigh the glassware with the solid formed at the bottom, NaCl. Dispose of the NaCl, rinse and dry the glassware. Weigh the empty glassware and record. Find the difference from 5 and 6. Do this for both flasks. Results: In table 1 . 1, the mixture of HCI and unknown sample 1 were combined. It took about 19. 5mL of HCI to turn the solution yellow, after heating and evaporating the water from the solution, the glassware with the NaCl weighed 92. 84g. When the glassware was weighed again after the NaCl was washed out, it was 92. 69g. There was 0. g of NaCl that had formed. In table 1. 2, the mixture of HCI and unkown sample 2 were combined. It took 40mL of HCI to turn the solution yellow, after the heating and evaporation of the water, the glassware with the NaCl weighed 76. 38g. When the glassware was weighed again after the NaCl was washed out, it was 76. 24g. There was 0. 14g of NaCl that had formed. Discussion: The results for example 2 might have been off, when titrating the solution we added too much HCI and turned the solution yellow instead of green. So instead of boiling the solution until it turned blue again, we had to boil the solution to evaporate the ater.

That may have thrown off the amount of NaCl that was supposed to form after the water evaporated. Data: The data that was collected was reasonable, the error wasn''t too large and both results were close to the theoretical values. Conclusion: We learned that the theoretical yields of a solution can be reached if all the steps are followed exactly; by over titrating sample number 2, we skipped the steps to boil the solution back to blue and then re-titrate to yellow. We have learned that over titrating can throw off your actual yield. Investigating Stoichiometry with Carbonic Acid Salts By boopidyboo