1. What conditions should be used as a benchmark?
Answer: (1) High purity, above 99.9% (2) Composition and chemical formula are completely consistent (3) Good stability, not easy to absorb water, not easily oxidized by air, etc. (4) Molar mass is large, weighing is large, and the weighing error can be reduced.
2. What are the general methods for expressing the concentration of a solution?
A: mass percent concentration, volume percent concentration, mass percent by volume.
3. Briefly description of two changes occur in the dissolution process.
A: One is that solute molecules (or ions) overcome their mutual attraction to diffuse between water molecules, that is, physical changes, and the other is that solute molecules (or ions) and water molecules attract each other and combine into hydrated molecules. chemical reaction.
4. How will the solution stored in glass bottles change regularly?
A: The solution will contain sodium, calcium, silicate impurities or some ions in the solution will be adsorbed on the glass surface to reduce the concentration of the ions in the solution.