1) Hydrates contain water in a stoichiometric quantity. What does this mean? 2)

Question

1) Hydrates contain water in a stoichiometric quantity. What does this mean?

2) Why can you use calcium chloride to reduce the moisture in a humid basement area?

3) Plaster of Paris is calcium sulfate monohydrate, (CaSO4)2.H2O. (A) How many total atoms of all kinds are present? (B) On heating the hydrate, how many moles of water should be driven off per mole of hydrate? (C) Calculate the percent of water in the hydrate. SHOW YOUR WORK. (D) If you heat 20.00g of hydrate and drive off the water, what is the mass of the anhydrous salt remaining? SHOW YOUR WORK.

Explanation / Answer

1). Hydrates contain water in a stochiometric quantity, this means that the water contained will be in certain integral multiple it will not be random the amount of water will be in some fixed integral multiple.

2).this can be used because it reacts with water present in the form of moisture to form calcium hydrate.

3).there are 15 total atoms of all kinds are present.

B).0.5 mole

c). % of water= 18/290*100=6.2% by weight

D).since it contains 6.2% by wt.

so mass of water lost will be 0.062*20

= 1.24 gm

so total mass of unhydrates remained will be 20-1.24

18.76 gm

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