Water percent in a hydrate

Let s calculate the percent water in calcium chloride dihydrate, CaCl2-2H20. One mole of CaCl2-2H20 contains 1 mole of Ca, 2 moles of Cl, and 2 moles of HzO. The molar mass of HzO is 18.02 g. The molar masses of the elements are Ca = 40.08 g and Cl = 35.46 g. 

2 moles H20 = 2x 18.02gH2O= 36.04gH2O 1 mole CaCl2 2HZ O - 147.02gCaCl2 2H20 

The calculation of the molar mass of the hydrate shows that 36.04 g of water are in 147.02 g of the compound. The percent water in CaCl2-2H20 is  

What mass of water is in 475 g of CaCl2-2H20, knowing that 24.51% of the hydrate is water Multiplying 475 g by the decimal equivalent of 24.51% shows that 116 g of water are in 475 g of CaCl2-2H20. 

Because hydrates contain molecules of water along with the positive and negative ions, it is useful to describe the composition of hydrates only in terms of the water they contain. Of course, as with any compound, the percent composition in terms of each element can be calculated just as was done in the previous section with C02 and (NH4)3P04. 

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The prefix for six is hexa- and this compound is cobalt(II) chloride hexahy-drate. Its formula mass is that of C0CI2 plus that associated with six H2O 129.83 u -I- (6 X 18.015 u) = 237.92 u. We can speak of the mass percent water in a hydrate for C0CI2 6 H2O this is... 

The following Sample Problem shows how to find the percent by mass of water in a hydrate. It also shows how to determine the formula of a hydrate based on an incomplete chemical formula. 

In this investigation, you will find the mass percent of water in a hydrate of copper(II) sulfate hydrate, CuS04-xH2O.You will use copper(II) sulfate hydrate for an important reason The crystals of the hydrate are blue, while anhydrous copper(II) sulfate is white. 

A certain hydrate of potassium aluminum sulfate (alum) has foe formula KA1(S04)2 - xH20. When a hydrate sample weighing 5.459 g is heated to remove all foe water, 2.583 g ofKAl(S04)2 remains. What is foe mass percent of water in foe hydrate What is x ... 

The water that is trapped within the crystal structure of some ionic compounds (the water of hydration) can be removed easily by heating. The amount of the water present in a given sample can be determined by weighing the sample before and after this heating. The weight loss that occurs is the weight of the water in the sample. The percent of water in the hydrate is calculated as it is in a loss-on-drying experiment. 

Since many hydrates contain water in a stoichiometric quantity, it is possible to determine the molar ratio of water to salt. First, you would determine the weight of the water lost from the hydrate by heating a weighed sample. From the weight of the water lost, you then can calculate the percent of water in the hydrate. From the weight of the water lost you can also determine the number of water molecules in the hydrate salt and thus the molar ratio. 

Calculate the percent water in the following hydrates show your work, a. BaCl2-2H20... 

V. P. Gupta and W. J. M. Douglas [AIChE J., 13 (1967) 883] carried out the isobutylene hydration reaction with excess water in a stirred tank reactor utilizing a cationic exchange resin as the catalyst. Use the following data to determine the effectiveness factor for the ion exchange resin at 85°C and 3.9 percent conversion. 

The conventional approach to perform water vapor sorption kinetics is based on the measnrement of the film sample mass until reaching constant value corresponding to a saturation level in a hydrated environment. For each hydrated enviromnent, the mass of sample is measured allowing to obtain the mass gain, ejqtressed in percent, or, in other word, the water concentration, expressed in mass of water soibed per mass of polymer or in mmol of water soibed per mass of polymer, inside sample. The combination of mass gain at each humidity level leads to build the water vapor sorption isotherm. The water vapor sorption and the isotherm shape are depending on the moisture resistance of polymer and its ability to interact with water. 

The actual name dry scrubbing was first publicized by Teller [U.S. Patent no. 3,721,066 (1973)]. He worked both with classical Army-type soda-lime and with his patented water-activated form of the alkaline feldspar nepheline syenite as a flow agent and feedstock sorbent for HF and SO9 in hot, sticky fumes from glass melting furnaces. He claimed capture of more than 99 percent of 180 ppm HF and SO9 for more than 20 hours in a packed bed of 200 X 325 mesh hydrated nephehne syenite at 42,000/hr. 

According to results, squalene-including mixtures were able to increase the barrier to maintain hydration in a comparable manner to vernix caseosa. Five percent sodium lauryl sulfate-treated rat and human skin showed increased transepidermal water loss and riboflavin penetration. However, squalene treatment reverts the effects of sodium lauryl sulfate. 

Nitric acid is miscible with water and distillation results in an azeotrope with a concentration of 68.4 percent HN03 and a boiling temperature of 121.9°C at atmospheric pressure. Two solid hydrates are known the monohydrate (HNCh H20) and the trihydrate (HN03 3H20). 

Hydrazine is produced in the hydrated form with one mole of water added. Although a significant fraction of hydrazine is used as the hydrate, numerous applications (such as rocket propulsion) require anhydrous hydrazine. Because of the azeotrope at 68 percent hydrazine, reactive distillation or extractive distillation must be used to produce pure hydrazine. 

Figure 5.32. A. Al NMR spectra of (top) unhydrated alumina cement (principally monocalcium aluminate), and (bottom) product of full hydration with demineralised water at a cement water mass ratio of 1 1. Asterisks indicate spinning side bands. B. Change in the percentage of four-coordinated Al in alumina cement during hydration, as a function of time estimated by Al MAS NMR. Open symbols (a) hydration with demineralised water. Filled symbols (b) hydration with 0.5 mass percent Li2C03 solution. After Luong et al. (1989), by permission of the American Ceramic Society.

The dry weight of the sample is the basis in the calculations involved in the reconstruction of the sample composition. Any error in the dry weight would affect the proper ratios of the different gypsum leases since an error in free water is actually credited to or against water of hydration. Table 2 shows the manner in which an error in percent free water affects the hemihydrate content in a calcined gypsum sample. 

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