Law of Definite Proportions Different

Law of definite proportions Different samples of the same compound always contain the same proportion by mass of each element. 

Law of Definite Proportions Different samples of any pure compound contain the same elements in the same proportions by mass ako known as the Law of Constant Composition. 

Elements and Compounds—Chemical Symbols—Molecules—Atoms —Electrons—How Electrons Form Atoms—Explanation of Chemical Activity—Chemical Formulas—Speed of Chemical Reactions—Physical and Chemical Changes—The Law of Definite Proportions—Different Kinds of Chemical Reaction —Classification of Chemical Compounds—The Law of Combining Weights—Solutions—Acids and Bases—Neutral Substances—Organic and Inorganic Chemistry—Electrochemistry —Experiments in Electrochemistry, Pages 7-39... 

The second hypothesis suggests that, in order to form a certain compound, we not only need atoms of the right kinds of elements, but specific numbers of these atoms as weU. This idea is an extension of a law published in 1799 by Joseph Proust, a French chemist. According to Proust s law of definite proportions, different samples of a given compound always contain the same elements in the same mass ratio. Thus, if we were to analyze samples of carbon dioxide gas obtained from different sources, such as the exhau.st from a car in Mexico City or the air above a pine forest in northern Maine, each sample would contain the same ratio by mass of oxygen to carbon. Consider the following results of the analysis of three seimples of carbon dioxide, each from a different source ... 

Ans. The compounds have different ratios of hydrogen to oxygen atoms, and thus different mass ratios. The law of definite proportions applies to each compound individually, not to the two different compounds. H20 and H202 each follow the law of definite proportions (and together they also follow the law of multiple proportions). 

Lattice Points positions in a unit cell occupied by atom, molecules, or ions Law of Definite Proportion law that states that different samples of the same compound always contain elemental mass percentages that are constant Law of Mass Action mathematical expression based on the ratio between products and reactants at equilibrium, an equation to determine the equilibrium rate constant Law of Multiple Proportions law that states when two elements combine to form more than one compound that the mass of one element compared to the fixed mass of... 

Each element is characterized by the mass of its atoms. Atoms of the same element have the same mass, but atoms of different elements have different masses. Dalton realized that there must be some feature that distinguishes the atoms of one element from those of another. Because Proust s law of definite proportions showed that elements always combine in specific mass ratios, Dalton reasoned that the distinguishing feature between atoms of different elements must be mass. 

Chemical combination of elements to make different substances occurs when atoms join together in small whole-number ratios. Only if whole numbers of atoms combine will different samples of a pure compound always contain the same proportion of elements by mass (the law of definite proportions). Fractional parts of atoms are never involved in chemical reactions. 

The reasoning is similar for the law of multiple proportions. Suppose that one atom of A can combine with two atoms of B in forming an entirely different, but none the less definite, compound. Let us designate this compound AB2. The law of definite proportions would hold for this compound as well as for the first. Furthermore, if we should take such amounts of each compound that each contained the same number of atoms of A then the second would contain twice as many atoms of B as the first. The weight of B in the second would, therefore, be exactly twice the weight of B in the first compound. Thus the law of multiple proportions is also a necessary deduction from the atomic theory. 

Besides forming molecular compounds with water (hydrates) certain salts have the property of combining with a second salt either with or without water. In these combinations the character of the individual salts is somewhat modified but not completely changed. Hence the name, double salts . In physical properties such as crystalline form, solubility, and, in some cases, color, the crystals of the double salt differ from those of the simple salts. These compounds follow the law of definite proportions. 

Law of definite proportions The law of definite proportions is derived from Dalton s fourth hypothesis and states that different samples of the same compound always contain the same proportion by the mass of each element. Water (H2O) always has a ratio of 2 grams of hydrogen to 16 grams of oxygen regardless of the sample size. 

Insulin is a complex protein molecule produced by the pancreas in all vertebrates. This hormone regulates carbohydrate metabolism. Inability to produce insulin results in diabetes mellitus. Diabetes is treated by injections of insulin. Given the law of definite proportion, would you expect any differences in chemical activity between human insulin extracted from pancreatic tissue and human insulin produced by genetically engineered bacteria Why or why not ... 

There you have it H2O, H2O2, OH, HjO". Not much difference typographically. But chemically, they re worlds apart, which exemplifies a principle called the law of definite proportions. It is not just the elements that determine the nature of a compound but the proportions, too. The ramifications of the conservation of mass and the law of definite proportions are the subjects we tackle next. 

As may be recalled from our discussion of the law of definite proportion, isomers are molecules that have been built from the same number and type of atoms but arranged in a different order. We cited, as examples, fulminic acid, cyanic acid, and isocyanic acid HONC, HOCN, and HCNO, respectively. We saw that this simple rearrangement of elements made the first explosive, the second a poison, and the third a pacific participant in several, more constructive, organic syntheses. Isomers that differ only by being mirror images of each other are termed chiral isomers (pronounced kiral, with a hard c sound, the way chemist is pronounced kemisf). 

Now let s suppose you analyzed 500.0 g of sucrose isolated from a sample of sugar cane. The analysis is shown in Table 3-5. Note in Column 2 that the percent by mass values equal those in Column 2 in Table 3-4. According to the law of definite proportions, samples of a compound from any source must have the same mass proportions. Conversely, compounds with different mass proportions must be different compounds. Thus, you can conclude that samples of sucrose always will be composed of 42.2% carbon, 6.50% hydrogen, and 51.30% oxygen. 

Furthermore, we may say that a compound is a pure substance consisting of two or more different elements in a fixed ratio. Water is 11.1% hydrogen and 88.9% oxygen by mass. Similarly, carbon dioxide is 27.3% carbon and 72.7% oxygen by mass, and calcium oxide (the white solid A in the previous discussion) is 71.5% calcium and 28.5% oxygen by mass. We could also combine the numbers in the previous paragraph to show that calcium carbonate is 40.1% calcium, 12.0% carbon, and 47.9% oxygen by mass. Observations such as these on innumerable pure compounds led to the statement of the Law of Definite Proportions (also known as the Law of Constant Composition) ... 

Compounds were first recognized as distinct substances because of their different physical properties and because they could be separated from one another by physical methods. Once the concept of atoms and molecules was established, the reason for these differences in properties could be understood Two compounds differ from each other because their molecules are different. Conversely, if two molecules contain the same number of the same kinds of atoms, arranged the same way, then both are molecules of the same compound. Thus, the atomic theory explains the Law of Definite Proportions (see Section 1-5). 

Fluorine reacts with hydrogen (FI) and deuterium (D) to form hydrogen fluoride (FIF) and deuterium fluoride (DF), where deuterium (jIT) is an isotope of hydrogen. Would a given amount of fluorine react with different masses of the two hydrogen isotopes Does this violate the law of definite proportion Explain. 

Chlorine has two natural isotopes 17CI and ifCI. Hydrogen reacts with chlorine to form the compound HCI. Would a given amount of hydrogen react with different masses of the two chlorine isotopes Does this conflict with the law of definite proportion Why or why not ... 

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