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After a bottle of 14% potassium hydroxide solution was heated and evaporated off 100 g of water,80 mL of 28% potassium hydroxide solution was obtained at a concentration of () A.5 mol/L B.6 mol/L C.6.25mol /L D.6.5mol/L
If the mass of the 14% potassium hydroxide solution is x and the mass of the solute before and after evaporation remains unchanged, then x×14%=(x-100g)×28%, x=200g,
The amount of the substance containing potassium hydroxide in the 28% potassium hydroxide solution was 100 g×28%
56G/mol=0.5mol,
The mass concentration of the resulting solution was 0.5 mol
0.08L=6.25mol/L,
Therefore, C.
At 60.d egree. C., the solubility of sodium chloride was 55 g, and 300 g of a saturated solution of sodium chloride at this temperature was available. How many grams of sodium chloride crystals will precipitate if the temperature of the sodium chloride solution after evaporation of 60 grams of water is reduced from 60°C to 40°C? (Solubility of sodium chloride at 40°C is 49 g) At 60.d egree. C., the solubility of sodium chloride was 55 g, and 300 g of a saturated solution of sodium chloride at the existing temperature, How many grams of sodium chloride crystals will precipitate if the temperature of the sodium chloride solution after evaporation of 60 grams of water is reduced from 60°C to 40°C? (49 G solubility of sodium chloride at 40°C) At 60.d egree. C., the solubility of sodium chloride was 55 g, and 300 g of a saturated solution of sodium chloride at the present temperature, How many grams of sodium chloride crystals will precipitate if the temperature of the sodium chloride solution after evaporation of 60 grams of water is reduced from 60°C to 40°C? (Solubility of sodium chloride at 40°C is 49 g)
At 60.d egree. C., the solubility of sodium chloride was 55 g, and 300 g of a saturated solution of sodium chloride at temperature was available:
Assuming NaCl x g:
55:(100+55)= X:300
X =106.45 g
Water content =300-106.45=193.55 g
If 60 g of water is to be evaporated, the water content is 193.55-60=133.55 g
Let 133.55g water dissolve yg NaCl (60C):
55:100= Y:133.55
Y =73.45 g,
When the temperature of sodium chloride solution is reduced from 60°C to 40°C, zg of NaCl can be dissolved at 40°C:
49:100= Z:133.55
Z =65.44 g
Mass of sodium chloride crystals precipitated in this process =73.45-65.44=8.01 g
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