CONCENTRATION PROBLEM
Concentration, mixing & dilution.
Random salt-water mixing and dilution problems asking for the final concentration, with solute-conservation solution steps — a classic elementary olympiad topic.
Everything runs locally in your browser
Solution animation · solute conservation
Pouring ①: 0 g in (salt 0 g), current conc = 0%.
What is this?
Concentration problems rely on solute conservation: the amount of salt stays the same before and after mixing or diluting. Concentration = solute ÷ solution × 100%. Mixing: (X×A% + Y×B%) ÷ (X+Y). Diluting: X×A% ÷ (X+Y_water). Hold on to "salt is unchanged" and every problem falls into place.
示例与注意事项Example & notes
一个例子A worked example
20% 糖水 200 克再加水 50 克：溶质仍是 40 克、溶液变成 250 克，浓度降到 16%。200 g of 20% syrup plus 50 g of water keeps 40 g of solute in 250 g of solution — a 16% concentration.
注意事项Things to watch
- 稀释与混合题的抓手永远是「溶质守恒」，先算溶质再算浓度。Dilution and mixing always reduce to conserving solute — find the solute first.
- 百分比指质量分数而非体积分数，配液时要看清题目单位。Percentages here are mass fractions, not volume — check the units in the question.
- 两液混合后的浓度必在两者之间，可用来快速检错。A mixture always lands between the two concentrations — a quick sanity check.
相关问答More Q&A
能反求加多少水吗？Can it solve for the water needed?
可以，输入目标浓度即可反解需要加入的水量或溶质。Yes — enter the target concentration and it works out the water or solute required.
有动画演示吗？Is there an animation?
有，混液动画会展示颜色随浓度收敛的过程。Yes — the mixing animation shows the colour converging as concentration settles.