Copper sulphate pentahydrate

Dissolve 3 g. of copper sulphate pentahydrate and 1 g. of sodium chloride in 12 ml. of hot water, and add a solution of 1 g. of sodium bisulphite in 10 ml. of 5 per cent, sodium hydroxide solution. Shake, cool under the tap, and wash the precipitated wlute cuprous chloride with water by decantation. Dissolve the cuprous chloride in a few ml. of concentrated ammonia solution and dilute with water to 10 ml. 

Mount a I litre bolt-head flask, fitted with a mechanical stirrer, on a water bath. Place 168 g. of powdered copper sulphate pentahydrate, 210 g. (214 ml.) of pyridine and 90 ml. of water in the flask, start the... 

A typical thermogravimetric curve, for copper sulphate pentahydrate CuS04,5H20, is given in Fig. 11.2. 

As Fig. 11.2 shows, copper sulphate pentahydrate has four distinct regions of decomposition ... 

Experimental factors. In the previous section it was stated that the precise temperature regions for each reaction of the thermal decomposition of copper sulphate pentahydrate is dependent upon experimental conditions. When a variety of commercial thermobalances became available in the early 1960s it was soon realised that a wide range of factors could influence the results obtained. Reviews of these factors have been made by Simons and Newkirk30 and by Coats and Redfern31 as a basis for establishing criteria necessary to obtain meaningful and reproducible results. 

The heating rate has only a small effect when a fast reversible reaction is considered. The points of inflexion B and C obtained on the thermogravimetric curve for copper sulphate pentahydrate (Fig. 11.2) may be resolved into a plateau if a slower heating rate is used. Hence the detection of intermediate compounds by thermogravimetry is very dependent upon the heating rate employed. 

Notes. (1) Copper sulphate pentahydrate is suitable for practice in this determination 0.4 g of this contains about 0.1 g of Cu. 

Ng et al. [1261] report that dehydration of copper sulphate pentahydrate (- CuS04 3 H20) 320—336 K, obeys the Avrami—Erofe ev equation [eqn. (6), n = 2] with E = 104 kj mole-1. Dehydration of the trihydrate (- CuS04 H20), 343.5—359 K, obeyed the same rate expression with E = 134 kJ mole 1. Activation energies are approximately equal to reaction enthalpies. 

Ammonium chloride buffer, pFH 7.5 - dissolve 400 g ammonium chloride (NH4CI), 40 g EDTA disodium salt, 40 g sodium dihydrogen phosphate dihydrate (NaH2P04.2FH20) and 0.08 g copper sulphate pentahydrate (CUSO4.5H2O) in 1400 ml previously heated water (5 min in a domestic microwave) contained in a 3-1 beaker. Adjust the pFH to 7.5 0.1 with 10% w/v NaOH and make up to 2 I. 

Copper Sulphate Pentahydrate. Calculate what amount of copper sulphate crystallohydrate (blue vitriol) has to be taken for 10 ml of water to prepare a solution saturated at60°C (see Appendix 1, Table 1). Bring the solution obtained at the indicated temperature almost up to boiling and rapidly filter it through a fluted filter on a funnel for hot filtration (the funnel must be hot). Close the test tube with the filtrate with a piece of cotton wool. If crystals have formed in the filtrate, dissolve them by careful heating. Cool the solution and introduce a minute crystal of the initial salt into it. What is observed Does the temperature of the solution change ... 

Preparation of Purified Iodine. Dissolve 32 g of potassium iodide in 100 ml of water and 25 g of copper sulphate pentahydrate in 80 ml of water. Pour the solutions together into a 200-ml glass beaker and let the solution settle. Separate the precipitate from the... 

Preparation of Copper Sulphate Pentahydrate (Copper Vitriol). Pour 20-30 ml of water into a 100-ml beaker, and transfer into it the mixture remaining in a Wurtz flask after the reaction of copper with... 

Preparation of Copper(I) Oxide. Dissolve 2.5 g of copper vitriol (copper sulphate pentahydrate) in 15 ml of warm water and add 1.5 g of glucose. Heat the solution and rapidly add 2.5 ml of a 20% sodium hydroxide solution to it. Stir the mixture and let it stand for an hour. Wash the precipitate with distilled water. Write the equations of the reactions. 

Experiment Dissolve some copper sulphate pentahydrate CuS04.5H20 in a little water. The solution is light blue, a colour caused by Cu 2+ ions with four water molecules serving as ligands. Now add some drops of concentrated ammonia. The colour will change to a dark blue shade because the NH3 molecules take up the places of the water molecules in the Cu 2+ complex. Note An ammonia solution is toxic. Make certain you work in a well ventilated place. 

Note that the formula of solid copper sulphate pentahydrate for example should be written precisely as [Cu(H20)4] [S04(H20)]. The usual formula, CuS04.5H20 does not account for the fact that there are two different types of water molecules (copper-water and sulphate-water) in the crystal structure. This can easily be proved. On heating, first four molecules of water are released from crystalline copper sulphate, at around 120°C, while the fifth molecule can only be removed at a much higher temperature, 240°C. 

Copper(II) sulphate (0-25m). Dissolve 62-42 g copper sulphate pentahydrate, CuS04.5H20, in water and dilute to 1 litre. 

Copper sulphide suspension. Dissolve 012 g copper sulphate pentahydrate CuS04.5H20 in 100 ml water, add 5 drops of 2m ammonia solution and introduce hydrogen sulphide gas until the solution becomes cloudy. The suspension must be freshly prepared. 

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