Exam Review **Textbooks and Practice Questions**

Why isn’t there anyone smarter to solve this? I’ve thought about it for a whole day, but I still can’t figure it out. First of all, concentration refers to the proportion of a certain species within the total amount. 　　Common ways to express concentration include: Weight percent concentration: This is the most commonly used method. 　　Volume percent concentration: commonly used to indicate alcohol content in beverages. 　　Volume molar concentration: commonly used in chemistry. 　　Molality  Mole fraction: Since the volume of a solution changes with temperature, the molar concentration also changes with temperature. In rigorous thermodynamic calculations, in order to avoid the influence of temperature on the data, molality is often used instead of molar concentration. Molality is defined as the amount of solute per 1 kg of solvent; it is denoted by m and its unit is mol/kg. That is:  mB ≡ nB/wA = nB/(nA·MA). I think this method should also be used for calculations, but it might not be correct either. Additionally, regarding the solubility of oxygen in water, at 0°C, up to 0.049 volumes of oxygen can dissolve in 1 volume of water, while at 20°C and 1 standard atmosphere, the solubility of oxygen is 0.031. Still can’t figure it out,... OP, don’t you have a job? :) This post was last edited by 361350036 on 2009-4-15 15:20 ]

The first thing that needs to be corrected is that the substance that dissolves is ammonia, not oxygen. The unit is indeed not specified in the problem, but based on the answer, it should be mol/kg. 16/17 = 0.941 mol. This question is not well formulated; it’s recommended to avoid delving too deeply into it.

The answer should be mol/L, right? :) :)