ED 4 The cncentration of the solute in solution Solubility, Miscibility, and Con

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ED 4 The cncentration of the solute in solution Solubility, Miscibility, and Concentration The term solubility refers to the maximum amount of solute that will dissolve in a 3. The temperature o there is a limit to the smount of solvent under stated conditions. At a specific temperature, there is a lpcited contai tion (a amount of solute that will dissolve in a given amount of solvent. may be verv Solubility can be expressed in a relative, qualitative way. For example a solute iven t soluble, moderately soluble, slightly soluble, or insoluble in a given solvent ata ature. Table 8.1 shows how temperature effects the amount of four different salts thm solve in 100 g of wates one u the u & Nac Table 9.1 Temperature Effeet on Solubility of Four Salts in Water, g solute/100 g 90°c 100'c 55.6 NaCI 35.735.8 36.0 36.3 36.6 370 37.3 37.8 38.4 39.0 39.8 KBr 535 595 65.2 70.6 755 80.2 85.5 90.0 95.0 99.2 104.0 55.7 58.8 The term miscibility describes the solubility of two liquids in each other. When both the 5. numb of Na tainir Baci, 316 33.3 357 382 40.7 43.6 46.6 494 52.6 56.768 solute and solvent are liquids, their solubility in each other is described as miscible (soluble) or immiscible (insoluble). For example, ethyl alcohol and water are miscible; oil and water are immiscible PRO The concentration of a solution expresses how much solute is dissolved in solution and can be expressed several ways: Wear 1. Dilute vs. Concentrated: a dilute solution contains a relatively small amount of solute in a given volume of solution; a concentrated solution contains a relatively large amount of solute per unit volume of solution. A. 2 Saturated vs. Unsaturated vs. Supersaturated: a. A saturated solution contains as much dissolved solute as possible at a given tem- persture and pressure. The dissolved solute is in equilibrium with undissolved solute. A saturated solution can be dilute or concentrated. The solutions described in Table 8.1 are Ms saturated at each temperature. See Solute(solid) == Solute (dissolved) 2. and the r 84

Explanation / Answer

1. a) At 50 0 C, the solubility of NaCl in water is 37.0 g per 100 g water.

So, at that temperature 37.0 g of NaCl is dissolved in 100 g of water to make a saturated solution of NaCl with mass of 137.0 grams.

Mass percentage of NaCl in solution = (37 g * 100 %)/ 137 g = 27 %

b) In between 20 to 30 0 C, the solubility of KCl in water increases by an equal amount per each degree of temerature rise.

At 20 C, the solubility of KCl is 34 grams/ 100 g of water and at 30 C, the solubility is 37 g/ 100 g / water

So, on increasing 10 C temeprature, solubility increases by 3 g/ 100 g of water

So, on increasing one degree C temperature solubility increases by 0.3 g / 100 water

So, at 23 C temperature ( 3 C more than 20 C) the solubility of KCl is = (34 + 3* 0.3) g / 100 g water = 34.9 g/ 100 g water

c) At 30 0 C: solubility of BaCl2 is 38.2 g/ 100 g water

So, 38.2 g of BaCl2 gets dissolved to 100 g of water to make 138.2 g of saturated solution

At 30 0 C: 100 grams of saturated solution contains (38.2*150/100) g of BaCl2 = 57.3 g of BaCl2

At 60 0C temperature, solubility of BaCl2 is 46.6 g/ 100 g water

So, at that temperature, saturated solution of 1 g of water 50 contains (46.6 * 150) / 100 grams of BaCl2 = 69.9 g BaCl2

So, you need to add additional (69.9-57.3) g = 12.6 grams of BaCl2

2. a) Solubility of KCl at 50 0 C is 42.6 g / 100 g water

So, Grams of solute in 100 grams of water is 42.6 grams

b) Total mass of solution = mass of solute + mass of water = (100 +42.6) grams = 142.6 grams

c) Mass percent of solute in the solution = (42.6 g * 100%)/ 142.6 g = 29.88 %

d) At 100 0C, the solubility of KCl is 55.6 g / 100 g water

So, at that temperature you can add (55.6-46.6) g = 9.0 grams of KCl to make the solution saturated

e)

At, 30 0C, the solubilityis 37 g/ 100 g water

On cooling from 100 to 30 0C, (55.6-37.0) g = 18.6 g of KCl is precipitated out.

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