What are the formulas of the following substances? (a) PCl? ; Molec. mass =137.3 amu (b) Nicotin

step 1 I'm asked to find this formula given the its molecular weight. So to do this, I'm going to find

What are the formulas of the following substances? (a) PCl?...

What are the formulas of the following substances?
(a) $\mathrm{PCl}_{?} ;$ Molec. mass $=137.3 \mathrm{amu}$
(b) Nicotine, $\mathrm{C}_{10} \mathrm{H}_{14} \mathrm{~N}_{?} ;$ Molec. mass $=162.2 \mathrm{amu}$

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Key Concepts

Molecular Mass

Molecular mass is the sum of the atomic masses of all the atoms in a molecule. It is a critical concept for determining the formula of a compound because comparing the calculated molecular mass (based on assumed formulas) with a given molecular mass helps in confirming the correct formula.

Empirical Formula Determination

Determining an empirical formula involves finding the simplest whole-number ratio of the atoms present in a compound. This process often starts with analyzing the known molecular mass in conjunction with the atomic masses of the elements, thereby guiding the identification of the number of atoms for each element in the compound.

Stoichiometry

Stoichiometry involves the quantitative relationships between reactants and products in chemical reactions and compounds. In the context of determining formulas, stoichiometry allows the calculation of the contributions of each element to the overall molecular mass, ensuring that the sum of the atomic masses aligns with the given molecular mass.

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