Ch.3 - Chemical Reactions and Reaction Stoichiometry

Brown - Chemistry: The Central Science 14th Edition

Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook

Brown 14th Edition

Ch.3 - Chemical Reactions and Reaction Stoichiometry

Problem 53c

Chapter 3, Problem 53c

Determine the empirical and molecular formulas of each of the following substances: (c) Monosodium glutamate (MSG), a flavor enhancer in certain foods, contains 35.51% C, 4.77% H, 37.85% O, 8.29% N, and 13.60% Na, and has a molar mass of 169 g/mol.

Verified step by step guidance

Step 1: Calculate the moles of each element in the compound by dividing the percentage by the atomic mass of each element. Use the atomic masses: C (12.01 g/mol), H (1.008 g/mol), O (16.00 g/mol), N (14.01 g/mol), and Na (22.99 g/mol).

Step 2: Determine the simplest whole number ratio of the moles of each element by dividing each value by the smallest number of moles calculated in step 1.

Step 3: Use the mole ratios to write the empirical formula by assigning these ratios as subscripts to the respective elements.

Step 4: Calculate the molar mass of the empirical formula. Sum the masses of all the atoms in the empirical formula.

Step 5: Determine the molecular formula by dividing the given molar mass of the compound (169 g/mol) by the molar mass of the empirical formula calculated in step 4. Multiply the subscripts in the empirical formula by this ratio to get the molecular formula.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Empirical Formula

The empirical formula represents the simplest whole-number ratio of the elements in a compound. To determine it, the percentage composition of each element is converted to moles, and then the mole ratios are simplified to the smallest integers. This formula provides insight into the basic composition of the substance without indicating the actual number of atoms in a molecule.

Molecular Formula

The molecular formula indicates the actual number of atoms of each element in a molecule of a compound. It can be derived from the empirical formula by multiplying the subscripts by a whole number, which is determined by dividing the compound's molar mass by the molar mass of the empirical formula. This formula gives a complete picture of the molecular structure and composition.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all the atoms in a molecule based on the molecular formula. Knowing the molar mass is essential for converting between grams and moles, which is crucial for determining both empirical and molecular formulas in chemical analysis.

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Related Practice

Textbook Question

Determine the empirical and molecular formulas of each of the following substances: (a) Styrene, a compound used to make Styrofoam® cups and insulation, contains 92.3% C and 7.7% H by mass and has a molar mass of 104 g/mol.

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Textbook Question

Determine the empirical and molecular formulas of each of the following substances: (a) Ibuprofen, a headache remedy, contains 75.69% C, 8.80% H, and 15.51% O by mass and has a molar mass of 206 g/mol.

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Textbook Question

Determine the empirical and molecular formulas of each of the following substances: (b) Caffeine, a stimulant found in coffee, contains 49.5% C, 5.15% H, 28.9% N, and 16.5% O by mass and has a molar mass of 195 g/mol.

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Textbook Question

What is the molecular formula of each of the following compounds? (b) empirical formula C₂H₄O, molar mass = 88.0 g/mol

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Textbook Question

(a) Combustion analysis of toluene, a common organic solvent, gives 5.86 mg of CO₂ and 1.37 mg of H₂O. If the compound contains only carbon and hydrogen, what is its empirical formula?

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Textbook Question

Determine the empirical and molecular formulas of each of the following substances: (b) Cadaverine, a foul-smelling substance produced by the action of bacteria on meat, contains 58.55% C, 13.81% H, and 27.40% N by mass; its molar mass is 102.2 g/mol.

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