Select the correct answer.
A compound has an empirical formula of $C _2 H _5$. What is true about this empirical formula?
A. It models the structure of the compound.
B. It shows the ratio of elements in the compound.
C. It gives the mass of each atom in the compound.
D. It indicates the number of atoms in the compound.
E. It describes only this one compound.
Answer (2)
An empirical formula represents the simplest whole number ratio of elements in a compound.
It does not model the structure, give atomic masses, indicate the actual number of atoms, or uniquely describe a compound.
The empirical formula C 2 H 5 shows the ratio of carbon to hydrogen atoms.
Therefore, the correct answer is B: It shows the ratio of elements in the compound. B
Explanation
Understanding Empirical Formula The empirical formula of a compound is the simplest whole number ratio of atoms of each element present in the compound. It does not represent the actual number of atoms in a molecule, nor does it model the structure of the compound.
Analyzing the Options Now, let's examine each option: A. It models the structure of the compound. - This is incorrect. Empirical formulas do not show the structure. B. It shows the ratio of elements in the compound. - This is correct. The empirical formula gives the simplest ratio of elements. C. It gives the mass of each atom in the compound. - This is incorrect. It provides the ratio of atoms, not their masses. D. It indicates the number of atoms in the compound. - This is incorrect. It shows the simplest ratio, not the actual number of atoms. E. It describes only this one compound. - This is incorrect. Different compounds can have the same empirical formula.
Conclusion Therefore, the correct answer is that the empirical formula shows the ratio of elements in the compound.
Examples
Understanding empirical formulas is crucial in various fields. For instance, in environmental science, knowing the empirical formula of pollutants helps in assessing their composition and potential impact. In materials science, it aids in characterizing new materials and predicting their properties. Imagine you're analyzing a new air pollutant and find its empirical formula to be N O 2 . This tells you the simplest ratio of nitrogen to oxygen atoms, which is vital for understanding its chemical behavior and designing effective control measures.
The empirical formula C 2 H 5 indicates the simplest whole number ratio of carbon to hydrogen (2:5). It does not model the structure, indicate the actual number of atoms, give masses of atoms, or uniquely identify a compound. Therefore, the correct answer is B: It shows the ratio of elements in the compound.
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