How would you test a colorless crystalline compound to determine if it was a hyd
ID: 960293 • Letter: H
Question
How would you test a colorless crystalline compound to determine if it was a hydrate? A sample of a crystalline compound, when heated in an open test tube, produced several droplets of water on the cool upper region of the tube. The residue dissolved in water forming a yellow-brown solution, while the original compound formed a colorless solution in water. Why should you conclude that the compound is not a true hydrate? What is the meaning of the numeral represented by X in the general formula for a hydrate, salt middot X H_2O? Cobalt(II) chloride is commonly obtained from chomical supply houses as a hydrate with the formula CoCl_2 middot 6 H_2O. An analysis showed that 25.0 g of this hydrate contains 11.3 g of water. What is the percent water by weight in this hydrate? Please show your calculations below.Explanation / Answer
a)FIrst we Record its mass,then we put it in a test tube and heat it with burner. If the compound is a hydrate, the water in the compound will release in the form of water vapor. After few around 10 -15 minutes, take it out of the test tube and weigh it again. If the mass is now less, that means that there was water present that has now evaporated, and the initial compound was a hydrate.
b) it is quite simple when we dissolve original compound to water it form colourless solution in water , similarly the unhydrated form(residue ) of the original compound when dissolve in water must produce colourless solution in water , but in actual it is forming a yellow brown solution that means the original compound is not a true hydrate .
c) the letter X shows the no of water molecule that are bind in the form of water of crystallization .
d) molar mass of COVl2 .6H2O = 238 g
wight of water / weight of COVl2 .6H2O * 100 = 11.3 g / 238 *100= 4.748
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