Thekey difference在恒定组成的法律和多比例的法律之间according to the law of constant composition, the same proportion of samples always consists of the same proportion of elements by mass, whereas according to the law of multiple proportions, if two elements bind with each other forming more than one chemical compound, then the ratio between the masses of the second element that combines with a fixed mass of the first element has ratios of small whole numbers.
The law of constant compositions and law of multiple proportions are theories in physical chemistry that are used to explainstoichiometryin chemistry. Stoichiometry is the measure of the relative quantities ofreactants and productsin a chemical reaction.
内容
1.Overview and Key Difference
2.What is Law of Constant Composition
3.What is Law of Multiple Proportions
4.Side by Side Comparison – Law of Constant Composition vs Law of Multiple Proportions in Tabular Form
5.概括
What is Law of Constant Composition?
The law of constant composition states samples of a compound will always contain the same proportion of elements by mass. We can name this law as the law of definite proportions as well. This law describes that a given compound will always contain the same elements in the same proportions by mass.
例如，无论是自来水还是海水，水分子始终以以下比例包含氢和氧元素。水分子的化学公式为H2O，并且molar massof this molecule is 18 g/mol. Therefore, one mole of water contains 18 g of H2O. The ratio between H and O in the water molecule is 2:1. Accordingly, the mass fraction of hydrogen in water = (2g / 18g) x 100% = 11.11% and the mass fraction of oxygen = (16g/18g) x 100% = 88.89%. These fractions are constant and do not alter according to the source of water and the method of separation.
The law of constant composition depends on the fact that any atom of the same element (atoms having the same atomic number) is similar to each other. Considering the above example, the assumption is that any hydrogen atom is similar to another hydrogen atom and vice versa. But there can be some exceptions as well. E.g. the isotopic composition of an element can vary depending on the source. Therefore, stoichiometry shows variations depending on the source of elements.
多数的法律是什么？
The law of multiple proportions states that when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.
We can call this law Dalton’s law as well because the law was developed by John Dalton in 1803. Let us understand this law using an example.
氮的氧化物由氮和氧原子组成。我们可以识别存在存在的五种不同的氮氧化物：n2o，不，n2O3, NO2和n2O5. Considering the mass ratios of N and O in these oxide compounds, 14 grams of nitrogen atom combines with 8, 16, 24, 32 and 40 grams of oxygen according to the mass ratio, respectively. If we take these numbers as small, whole numbers, then the ratios can be given as 1:1, 1:2, 1:3, 1:4 and 1:5.
What is the Difference Between Law of Constant Composition and Law of Multiple Proportions?
根据恒定组成定律，相同比例的样品始终由质量元素组成相同的元素，而根据多比例的定律，如果两个元素彼此互相结合形成多个化合物，则该比率为比例。在第二个元素的质量与固定质量的第一元素之间的质量之间具有较小的整数比。因此，这是恒定组成法与多比例定律的关键区别。
概括– Law of Constant Composition vs Law of Multiple Proportions
根据恒定组成定律，相同比例的样品始终由质量元素组成相同的元素，而根据多比例的定律，如果两个元素彼此互相结合形成多个化合物，则该比率为比例。在第二个元素的质量与固定质量的第一元素之间的质量之间具有较小的整数比。Thus, this is the difference between law of constant composition and law of multiple proportions.
Reference:
1. Helmenstine, Anne Marie. “Law of Constant Composition in Chemistry.” ThoughtCo, Aug. 26, 2020,Available here.
Image Courtesy:
1. “Demonstration of the Law of Multiple Proportions” By Kenji Agari – Own work(CC BY-SA 3.0)viaCommons Wikimedia
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