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At t.degree. C.,200 g of a solution is evaporated,20 g of water is evaporated,8 g of crystal is precipitated, and 20 g of water is evaporated, and 12 g of crystal is precipitated. The solubility of a substance at t.degree. C. is () A.40 g B.50 g C.60 g D.100 g
According to the meaning of the title,8 g of crystal is precipitated after evaporating 20 g of water, and 12 g of crystal is precipitated after evaporating 20 g of water, indicating that the original solution is an unsaturated solution. Otherwise,12 g of crystal should be precipitated after evaporating 20 g of water for the first time.
After evaporation of 20 g of water,12 g of crystal is precipitated, indicating that 12 g of crystal is dissolved in 20 g of water to form a saturated solution; according to the definition of solubility, at a certain temperature, the mass dissolved when a substance is saturated in 100 g of solvent, if the solubility of a substance is x at t.d egree. C.,20 g
12 G =100 g
X x =60g.
Therefore, C.
At t degree, KNO3 solution 200 g, evaporating 20 g of water precipitates 8 g of crystal; after evaporating another 20 g of water precipitates 12 g of crystal, then at t degree, KON3 solubility How much is it?
Analysis:
The amount of crystals precipitated after the first evaporation of water is not important, it mainly tells us that the saturated solution is obtained after the first evaporation of water.
What can really be used to calculate is the mass of the precipitated crystals after the second evaporation of water. For example, if 20g of water is evaporated for the second evaporation and 12g of crystals are precipitated, we can know that 20g of water corresponds to 12g of crystals, i.e.20g of water can dissolve up to 12g of solute.
If the solubility of KON3 is S at t, then
S/100g =12g/20g
S=60g
Can you understand? I don't understand. I can ask again.
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