Under the condition of constant temperature, the most feasible method is () A. Evaporate 10g water from 20g saturated potassium nitrate solution B. evaporate 10g water from 20g unsaturated potassium nitrate solution C. add 5g 40% potassium nitrate solution to 10g 10% potassium nitrate solution D. add 10g solid potassium nitrate to 10g unsaturated potassium nitrate solution

Under the condition of constant temperature, the most feasible method is () A. Evaporate 10g water from 20g saturated potassium nitrate solution B. evaporate 10g water from 20g unsaturated potassium nitrate solution C. add 5g 40% potassium nitrate solution to 10g 10% potassium nitrate solution D. add 10g solid potassium nitrate to 10g unsaturated potassium nitrate solution

A. Under the condition of constant temperature, the 20g saturated solution of potassium nitrate evaporates 10g of water, and the solute potassium nitrate of evaporated water precipitates, and the solution is still saturated solution; under the condition of constant temperature, the solubility of potassium nitrate remains unchanged, and the solute mass fraction of saturated solution remains unchanged; therefore, a is not feasible; B. when the 20g unsaturated solution of potassium nitrate evaporates 10g of water, and no crystals are precipitated, the quality of the solution after evaporation is affected The results show that the mass fraction of solute increases by twice as much as that of the original solution if the mass fraction of solute decreases by half while the mass fraction of solute remains unchanged; however, if potassium nitrate precipitates during evaporation, the mass fraction of the solution obtained will not be twice as much as that of the original solution; therefore, B is not feasible; C. in 10 g 10% potassium nitrate solution, 5 g 40% potassium nitrate solution is added, and the mass fraction of solute in the mixed solution is 10 g × 10% + 5 g × 40% 10 G + 5 g × 100% = 20%, It is twice as much as 10% of the original solution; therefore, C is correct; D. It is impossible to accurately determine the solute mass fraction of the obtained solution because it is uncertain whether all the added potassium nitrate is dissolved and the solute mass fraction of the original solution is not clear; therefore, D is not feasible; therefore, C is selected

In the solubility curve, the solubility of a increases with the increase of temperature, while that of B decreases with the decrease of temperature. At a certain degree centigrade (the solubility of a is greater than that of B), the solubility of a in 100 g saturated solution of a and B is higher than that of B
Compare solute of a solute of B solute of a solvent of B

Solute of a (>) solute of B
A solvent（

I want to ask, for example, "at 20 ℃, 36g sodium chloride can be dissolved in 100g water at most". Can we microcosmically think that 100g water molecules have gaps, and when sodium chloride is added to water, sodium chloride molecules are in the gaps of water molecules, and the gaps of 100g water molecules can accommodate 36g sodium chloride molecules at most, just like the smaller volume of water and alcohol mixture, isn't that the reason for the gap between molecules?
Is that understandable?

Suppose you are right, that is to say, the gap between 100g water molecules can hold 36g sodium chloride molecules at most. In this way, why can more sodium chloride be dissolved when the temperature rises? If you can explain, you should remember that in your knowledge, there is an ignorant person whose solubility decreases with the increase of temperature, calcium hydroxide. How can you explain that, So your explanation doesn't work
(absolutely original, shameless plagiarism)

Characteristics and principles of keyhole imaging?

Principle: straight line propagation of light this experiment puts forward at least three questions to us: why is the image made of small holes upside down? What factors are related to the size of the image? What factors are related to the clarity of the image? In order to explain these problems, we regard the flame of a candle as composed of many small luminous points, each of which is