Laws of definite and multiple proportions

[Dhamnekar Win,odd]

1) A sample of compound X (a clear, colorless, combustible liquid with a noticeable odor) is analyzed and found to contain 14.13 g carbon and 2.96 g hydrogen. A sample of compound Y (a clear, colorless, combustible liquid with a noticeable odor that is slightly different from X’s odor) is analyzed and found to contain 19.91 g carbon and 3.34 g hydrogen. Are these data an example of the law of definite proportions, the law of multiple proportions, or neither? What do these data tell you about substances X and Y?

2)A sample of compound A (a clear, colorless gas) is analyzed and found to contain 4.27 g carbon and 5.69 g oxygen. A sample of compound B (also a clear, colorless gas) is analyzed and found to contain 5.19 g carbon and 13.84 g oxygen. Are these data an example of the law of definite proportions, the law of multiple proportions, or neither? What do these data tell you about substances A and B?

My answers:

1)

The data provided in the question is not an example of either the law of definite proportions or the law of multiple proportions. The law of definite proportions states that a chemical compound always contains exactly the same proportion of elements by mass. The law of multiple proportions states that when two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in a ratio of small whole numbers.

In this case, the ratio of hydrogen to carbon in compound X is 2.96 g / 14.13 g = 0.21 and the ratio of hydrogen to carbon in compound Y is 3.34 g / 19.91 g = 0.17. These ratios are not equal, so the data does not support the law of definite proportions. Additionally, the ratio of these two ratios is 0.17 / 0.21 = 0.81, which is not a small whole number, so the data does not support the law of multiple proportions either.

Based on this data alone, it is not possible to determine any additional information about substances X and Y.

2)

The data provided in the question is an example of the law of multiple proportions. This law states that when two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in a ratio of small whole numbers. In this case, the ratio of oxygen to carbon in compound A is 5.69 g / 4.27 g = 1.33 and the ratio of oxygen to carbon in compound B is 13.84 g / 5.19 g = 2.67. The ratio of these two ratios is 2.67 / 1.33 = 2, which is a small whole number.

This tells us that substances A and B are two different compounds formed by the combination of carbon and oxygen in different proportions.

[Sensei]

20 minutes ago, Dhamnekar Win,odd said:

Based on this data alone, it is not possible to determine any additional information about substances X and Y.

14.13 g carbon / 12.011 g/mol = 1.18 mol of Carbon

2.96 g hydrogen / 1.008 g/mol = 2.937 mol of Hydrogen

2.937 / 1.18 = ~ 2.5

i.e. proportions are 5 Hydrogen atoms to 2 Carbon atoms.

 

[Dhamnekar Win,odd]

1) The data provided in the question indicates that compound X and Y are two different compounds formed by the combination of carbon and Hydrogen in indefinite proportions. In this case, the ratio of hydrogen to carbon in compound X is 2.96 g / 14.13 g = 0.21 and the ratio of hydrogen to carbon in compound Y is 3.34 g / 19.91 g = 0.17. These ratios are not equal, so the data does not support the law of definite proportions. Additionally, the ratio of these two ratios is 0.17 / 0.21 = 0.81, which is a small whole number, so the data  supports the law of multiple proportions. 

 

 

 

2) The data provided in the question indicates that compounds A and B are two different compounds formed by the combination of carbon and oxygen in different proportions. Compound A has one-half as much oxygen per amount of carbon (or twice as much carbon per amount of oxygen) as compound B. This means that for a fixed amount of carbon, compound A has half the amount of oxygen compared to compound B. Similarly, for a fixed amount of oxygen, compound A has twice the amount of carbon compared to compound B. This is an example of the law of multiple proportions.

One possible pair of compounds that would fit the relationship described in the question are carbon monoxide (CO) and carbon dioxide (CO₂). Both of these compounds are formed by the combination of carbon and oxygen. In carbon monoxide, there is one oxygen atom for every carbon atom, while in carbon dioxide, there are two oxygen atoms for every carbon atom. This means that for a fixed amount of carbon, carbon monoxide has half the amount of oxygen compared to carbon dioxide. Similarly, for a fixed amount of oxygen, carbon monoxide has twice the amount of carbon compared to carbon dioxide. This is an example of the law of multiple proportions.

[Bufofrog]

11 minutes ago, Dhamnekar Win,odd said:

Additionally, the ratio of these two ratios is 0.17 / 0.21 = 0.81, which is a small whole number, so the data  supports the law of multiple proportions.

How exactly is 0.81 a whole number?

[Dhamnekar Win,odd]

2 hours ago, Bufofrog said:

How exactly is 0.81 a whole number?

[math]\frac45[/math] is a small whole number ratio that supports the law of multiple proportions. In the compound X, 0.8 atoms of carbon required compared to the carbon atoms required in the compound Y, for each atom of Hydrogen.

Edited April 23, 2023 by Dhamnekar Win,odd