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 29c

Chapter 3, Problem 29c

(a) Write “true” or “false” for each statement. (c) The mass of 1 ammonia molecule is 17.0 g.

Verified step by step guidance

Understand the context: The problem is asking whether the statement about the mass of an ammonia molecule is true or false.

Recall the chemical formula for ammonia, which is NH₃. This means one molecule of ammonia consists of one nitrogen atom and three hydrogen atoms.

Calculate the molar mass of ammonia: Use the periodic table to find the atomic masses of nitrogen (approximately 14.01 g/mol) and hydrogen (approximately 1.01 g/mol).

Add the atomic masses to find the molar mass of ammonia: Multiply the atomic mass of hydrogen by 3 (since there are three hydrogen atoms) and add it to the atomic mass of nitrogen.

Compare the calculated molar mass of ammonia to the given mass in the statement (17.0 g) to determine if the statement is true or false. Remember, the mass of a single molecule is not expressed in grams but in atomic mass units (amu) or as a molar mass in g/mol.

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Key Concepts

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

Molecular Mass

Molecular mass is the sum of the atomic masses of all atoms in a molecule, expressed in atomic mass units (amu). For ammonia (NH3), the molecular mass is calculated by adding the mass of one nitrogen atom (approximately 14.0 amu) and three hydrogen atoms (approximately 1.0 amu each), resulting in a total of about 17.0 amu.

Mass of a Molecule vs. Mass of a Mole

The mass of a single molecule is typically expressed in atomic mass units (amu), while the mass of a mole of molecules is expressed in grams. One mole of any substance contains Avogadro's number of molecules (approximately 6.022 x 10^23). Therefore, the mass of one ammonia molecule is about 17.0 amu, not grams.

Unit Conversion

Unit conversion is the process of converting a quantity expressed in one unit to another unit. In this context, it is crucial to distinguish between grams and atomic mass units. While the molecular mass of ammonia is 17.0 amu, it is incorrect to state that the mass of one ammonia molecule is 17.0 g, as this conflates the two different units of measurement.

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Conversion Factors

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