Question

Experiment 5 Prelaboratory Assignment Percent Water in a Hydrated Salt chloride, a deliquescent salt, is used as a desiccant in laboratory desiccators to maintain a dry environment Date ab SecName Desk No. Explain. 1sb 2. Experimental Procedure, Part A.1. What is the purpose of firing the crucible? 3. A 1.803-g sample of gypsum, a hydrated salt of calcium sulfate, Caso., is heated at a temperature greater than 120 C in a crucible until a constant mass is reached. The mass of the anhydrous CaSO, salt is 1.426 Calculate the percent by mass of water in the hydrated calcium sulfate salt. 4. The gravimetrie analysis of this experiment is meant to be quantitative; therefore, all precautions should be made to minimize errors in the analysis. a. The crucible and lid are handled exclusively with crucible tongs in the experiment. How does this tochnique maintain the integrity of the analysis? b. Mass measurements of the crucible, lid, and sample are performed only at room temperature. Why is this technigue necessary for a gravimetric analysis? Experiment 5 87 85

Answer 1

Deliquescence is the property of a substance due to which it can absorb moisture (water) from air till it itself becomes a liquid. Calcium chloride is a deliquescent salt as it readily absorbs moisture from the air. So it is used as a laboratory dessicant to maintain a dry environment. For example, when some substances or reactions can be affected due to moisture in air, dessicants like calcium chloride, silica gel etc. are used to remove moisture from the container where the substance is kept or the reaction is carried out.