Question

Name Isis Collier Lab Section REPORT ON EXPERIMENT 3 Introduction to Gravimetrie Analysis Date 1919 Assigned Salt USALL CHLORIDEHYDRATE Formula Weight Locle X HD DATA AND RESULTS Trial 1 Trial 43.8119- 43.4019 mass of crucible, cover, and hydrated salt tared-mass mass of hydrated salt 43.8179 mass of crucible, cover, and residue after heating mass of anhydrous salt 0.5219 moles of anhydrous salt 0.00407445/wCelle mass of water lost 0.926 percent by mass of water in hydrate 80.53% moles of water lost 0.02364 moho DY mole ratio of H 0 to anhydrous salt probable formula for hydrate X-6 Show the details of all calculations: use extra sheets if necessary. QUESTIONS (Submit your answers on a separate sheer if necessary.) Specify whether the calculated mass percent of water would be too high, too low, or unchanged as a result of each of the following experimental conditions. Justify your answers. a. The heating was insufficient to remove all of the water from the hydrated salt. b. Some of the sample spattered out of the crucible onto the laboratory bench during the heating. 2. Briefly explain the reasons for the use of the following techniques in this experiment. a. The hydrate salt is heated with the crucible cover in an ajar position rather than in a fully seated position or having the crucible completely uncovered. b. The crucible cover is fully seated during cooling and weighing of the residue. A hydrate of cerium (III) sulfate, Ce:(SO.). contains 20.2% water by mass. Deduce the formula for this hydrate. Show your calculations. 3. 4. What did you observe when water was added to the anhydrous salt? Experiment 3 Introduction to Gravimetric Analysis

Answer 1

1. a) If the water of crystallization is not removed completely, then while calculating number of water molecules present in the sample, we would get a negative error as the answer will yield less number of water molecules than actually present in the molecule.

b) If some of the sample spattered out of the crucible, and yet we are computing all the results using the old data, then we will get an error which may be less or more than the actual number of water molecules present. It is an uncertainty. But if we redo the experiment using the leftover sample in the crucible amd get a new set of data and then proceed for calculation, our result will be approximately close to the original value.

2. a) While heating the sample to get rid of every amount of moisture, it may happen that the sample bursts or cracks leaving some of the sample spattered out of the crucible. This is why it is advised to keep the crucible ajar with the lid provided and do the experiment.

b) If after heating the sample nd removing any water of crystallization, we open the lid of the crucible and then weigh it, there is a high probability of the sample regaining its moisture content level, much more than the theoretical error expected, or any impurity may drop in to that crucible. To avoid all these, gravimetric experiments are done with great care and precaution, for the doer and the sample, both.