Question

Please complete the lab report

Please Danate EXPERIMENT 6 ther Water in Hydrates MATERIALS AND EQUIPMENT Golids: finely ground eopper I) sulfate pentahydrate (Cuso, 5H,0), and unknown hydrate Cobalt chloride test paper, clay triangle, erucible and cover, 25x 200 mm ignition test tube, watch glass DISCUSSION any salts form compounds in which a definite number of moles of water are combined with each mole of the anhydrous salt. Such compounds are called hydrates. The water which is ther two ane ly eombined in a hydrate is referred to as water of crystallization or water of hydration. The following are representative examploes In a hydrate the water molecules are distinet parts of the compound but are joined to it by bonds that are weaker than either those forming the anhydrous salt or those forming the water molecules. In the formula of a hydrate a dot is commonly used to separate the formulsa of the anhydrous salt from the number of molecules of water of crystallization. For example, the formula of calcium sulfate dihydrate is written CaSO, 2H,0 rather than Caso,H Hydrated salts can usually be converted to the anhydrous form by eareful heating hich are not Hydrated SaltAnhydrous salt + water Hydrated salts can be studied qualitatively and quantitatively. In the qualitative part of this experiment we will observe some of properties of the liquid (water) driven off by heating the sample. In the quantitative part of the experiment we will determine how much water was in the hydrate by measuring the amount of water driven off by heating To make certain that all of the water in the original sample has been driven of, chemists ase a technique known as heating to constant weight. Since time expended for this is lim- ited, constant weight is essentially achieved when the sample is heated and weighed in suc- essive heatings until the weight differs by no more than 0.05 g. Thus, if the second weighing no more than 0.05 g less than the first beating, a third beating is not necessary because the mple has been heated to constant weight (almost). This is a very good reason to follow direc- ions meticulously when heating, If the sample is not beated long enough or at the correet mrature all of the water may not be driven off completely in the first heating Hence it is possible to determine the percentage of water in a hydrated salt by determin- ng the amount of mass lost (water driven to constant weight. off when a known mass of the hydrate is hea Mass lost (100) Percentage water Mass of 59

Answer 1

1.

(a) A properly dried test paper of cobalt chloride (CoCl₂) colour was blue. but when I place a drop of the collected liquid on the dried test paper, it changes its color from blue to red. This change is due to hydration of anhydrous cobalt chloride to hydrated cobalt chloride.

(b) Second evidence is that anhydrous copper sulfate (CuSO₄) has white color in appearance. But when some drops of the collected liquid was added to it, its color starts to change from white to blue slowly due to formation of hydrated copper sulfate.

These two evidences confirms that collected liquid is water obviously.

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2. the obtained anhydrous salt was divided into two parts.

(a)   The first one (anhydrous white color salt) was treated with the collected liquid which is obtained from hydrate. White color of salt was converted to blue color.

(b) the second part was treated with water and the same thing was observed as with the first one. This confirms that the same type of chemical reaction is happened in both cases. This chemical reaction is the hydration of the anhydrous copper sulphate salt.

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3.-----------------------------------------------------------------------------------------------------------------------------------------------------

Decom Posifion penta hyclzadle 2 I b lack alsr) ack calox

4. Yes, If a unknown salt was heated at excessively high temperatures than temp. required only for dehydration then it is possible that mass loss could be due to the loss of some substance other than water. If copper sulfate pentahydrate is heated at low temperatures only water will be removed but at >600^oC it decomposes into sulfur trioxide and copper(II) oxide (Black color). So it is possible that mass loss could be due to other substance other than water.

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5.

Suupoose aftez nehealing the ahtainel total mass loss-487024-30(4 Censtant Wc = 4.3702 -1.8040 + mhI num mass % of water, in oniginal Sam Massof Sample ー37.06 L870 2