① solution quality = solute quality+solvent quality

② concentration = solute mass/solution mass

③ Solution mass = solute mass/concentration

④ Solute mass = solution mass × concentration

Questions and answers of attention concentration in civil servants written examination;

① Problem 1: The increase or decrease of solvent causes the change of concentration.

Idea: No matter whether the solvent increases or decreases, the solute is always the same.

② Question 2: The increase of solute causes the change of concentration.

Idea: Solute and concentration increased, but solvent remained unchanged.

③ Question 3: The ratio of two or more solutions with different solubility.

Idea: The problem can be solved by grasping that the solute mass before mixing of each solution is equal to that after mixing.

You can check the review materials of the civil servant's test and understand the problem-solving skills.