The percentage of concentration in solution is called percentage concentration, which is called concentration for short. The problem of concentration belongs to percentage application. The main quantitative relationship of concentration problem is: the weight of solution = the weight of solute+the weight of solvent, and concentration = the quality of solute? Solution weight? 100%。 Let's analyze it through some typical examples.

Example 1

When salt is added to brine, the weight of salt changes, while the weight of water remains the same. When solving this kind of problems, first find out the invariants in the topic, find out the invariants, and then find out the changing amount of solution (salt water).

Example 2

The key to solve the problem of changing water into salt is that the salt in the original salt water has not changed after evaporation (or adding a certain amount of water). Generally, the salt quantity is calculated first, and then the salt water quantity is calculated according to the current concentration, so the difference between the original salt water and the current salt water is evaporated water.

Example 3

The weight of mixed salt is the sum of the original salt in each solution, the weight of mixed brine is the sum of the original salt, and the concentration of mixed brine is divided by the weight of mixed salt.

Example 4

The unknown number is set according to the equality of mixed solution, and then the equation is set according to the equality of solute before and after mixing.