Figure 14-10 is necessary to get the solubility of KNO 3 at both temperatures (s

Question

Figure 14-10 is necessary to get the solubility of KNO3 at both temperatures (shown on the graph).

At 0 °C, sKNO3 = 15 g KNO3 /100 g H2O
At 25 °C, sKNO3 = 38 g KNO3 /100 g H2O

The solution to the problem can be done in 2 steps: 1) evaporate the water and calculate the amount of KNO3 that precipitates and 2) reduce the temperature and calculate again. There are several ways to achieve the same results. It’s best to convert the mass of sample to mass of water in the sample.

sKNO3 = 38 g KNO3/100 g H2O can be rewritten as
sKNO3 = 38 g KNO3/138 g solution
sKNO3 = (38 g KNO3) / (100 g H2O + 38 g KNO3)
         = 0.275 (g KNO3/g soln)

or as

cH2O = 100 g H2O/138 g solution

So, the mass of KNO3 in the 355 g of solution is

mKNO3 = 0.275 (g KNO3/g soln) x 335 g soln
           = 92.3 g KNO3 dissolved at 25 °C

and the mass of water in the 355 g of solution is
mH2O = (100 g H2O / 138 g soln) x 335 g soln
         = 242.8 g H2O

Now, remove 55 g of H2O, lower the temperature, and recalculate the mass of dissolved KNO3:

mKNO3 = 187.8 g H2O x (15 g KNO3 / 100 g H2O)
               = 28.2 g KNO3 dissolved at 0 °C

Almost done: calculate the amount of KNO3 that precipitates after the temperature change from the amounts remaining in solution

mKNO3 ppt = 92.3 g originally – 28.2 remaining
               = 64.1 g KNO3 ppt

Explanation / Answer

please explain understandable and only do if you sure can do that

Part A Exercise 14.42 If 55 g H20 is evaporated from the solution at the same time as the temperature is reduced from 25.0 to 0.0° C, what mass of KNO3(s) will recrystallize? (Refer to the figure below.) One way to recrystallize a solute from a solution is to the temperature. Another way is to evaporate solvent from the solution. A 355 g sample of a saturated solution of KNOa(s) in water is prepared at 25.0°C. page ) Section 141 You may want to reference ( while completing this problem. Liso, 66 NaCl NH,CI FIGURE 14-10 Aqueous solubility of several salts as a function of temperature Solubilities can be expressed in many ways: molarities, mass percent, or, as in this figure, grams of solute per 100 g H2O. For each solubility curve (as shown here for KCIO). points on e curve (S) represent saturated KCIO to s solutions and below the curve (2), 20 30 40 60 to unsaturated solutions. 19.12.2017 DOLL

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