In chemical formulas, there are often subscript numbers (such as the 2 in H2O, or the 6, 12, and 6 in C6H12O6).
1 answer:
Answer : The correct option is, Subscript numbers tell us how many of the element to their upper-left there are in the molecule.
Explanation :
Subscript number : It indicates that the total number of atoms of an element present in a molecule.
While witting a chemical formula, first we have to write the symbol of an element and then write the number in the bottom of the symbol.
For example :
is the chemical formula of the glucose molecule. The glucose molecule is made up of six carbon atoms, twelve hydrogen atoms and 6 oxygen atoms.
The number 6 of carbon atom is written after and in the bottom (lower-right) of the symbol of carbon element (C). Similarly, the number 12 is written lower-right of the symbol of hydrogen element (H) and the number 6 is written lower-right of the symbol of oxygen element (O).
Therefore, the subscript numbers tell us how many of the element to their upper-left there are in the molecule.
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Considering the definition of empirical formula, the empirical formula is C₃H₈.
<h3>Definition of empirical formula</h3>The empirical formula is the simplest expression to represent a chemical compound, which indicates the elements that are present and the minimum proportion in whole numbers that exist between its atoms, that is, the subscripts of chemical formulas are reduced to the most integers. small as possible.
<h3>Empirical formula in this case</h3>In this case, in first place you know the percent composition:
- C: 81.71 %
- H: 18.29%
Assuming a 100 grams sample, the percentages match the grams in the sample. So you have 81.71 grams of carbon and 18.29 grams of hydrogen H.
Then it is possible to calculate the number of moles of each atom in the molecule, taking into account the corresponding molar mass:
- C:
= 6.81 moles
- H:
= 18.29 moles
The empirical formula must be expressed using whole number relationships, for this the numbers of moles are divided by the smallest result of those obtained. In this case:
- C:
= 1
- H:
= 2.68 ≅
To express this relationship in the form of simple integers, it is necessary to multiply by a simple number to achieve this:
- C: 1×3 =3
- H:≅
×3= 8
Therefore the C: H mole ratio is 3: 8
Finally, the empirical formula is C₃H₈.
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