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Chapter 3: Problem 1

What is an atomic mass unit? Why is it necessary to introduce such a unit?

Short Answer

Expert verified
An atomic mass unit, or amu, is one-twelfth of the mass of an atom of carbon-12, approximately equal to 1.660539040 x \(10^{-27}\) kilograms. It's necessary as it allows us to express the extremely small masses of atoms and molecules in a more practical way, provides a common scale for comparing the masses of different atoms, and simplifies stoichiometric calculations in chemistry.

Step by step solution

01

Definition of atomic mass unit

An atomic mass unit, often abbreviated as amu, is defined as one-twelfth (1/12) of the mass of an atom of carbon-12. It is approximately equal to 1.660539040 x \(10^{-27}\) kilograms.
02

Explaining the necessity of atomic mass unit

Atomic mass unit is necessary for the following reasons: \n\n1. It allows us to express very small masses (such as those of atoms and molecules) in a more practical and convenient way. Dealing with such minute quantities in standard SI units like kilograms would be difficult as the masses of atoms and molecules are extremely small.\n\n2. It provides a common scale to compare the masses of different atoms. The atomic masses of all elements are measured relative to the atomic mass of carbon-12.\n\n3. It simplifies stoichiometric calculations in chemistry. By using atomic masses in terms of amus, the number of atoms, ions, or molecules can easily be calculated from a given mass of an element or compound.

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Most popular questions from this chapter

Tin (Sn) exists in Earth's crust as \(\mathrm{SnO}_{2}\). Calculate the percent composition by mass of \(\mathrm{Sn}\) and \(\mathrm{O}\) in \(\mathrm{SnO}_{2}\).

A sample containing \(\mathrm{NaCl}, \mathrm{Na}_{2} \mathrm{SO}_{4},\) and \(\mathrm{NaNO}_{3}\) gives the following elemental analysis: Na: 32.08 percent; O: 36.01 percent; Cl: 19.51 percent. Calculate the mass percent of each compound in the sample.

Carbon has two stable isotopes, \({ }_{6}^{12} \mathrm{C}\) and \({ }_{6}^{13} \mathrm{C},\) and fluorine has only one stable isotope, \({ }_{9}^{19} \mathrm{~F}\). How many peaks would you observe in the mass spectrum of the positive ion of \(\mathrm{CF}_{4}^{+}\) ? Assume that the ion does not break up into smaller fragments.

A certain metal oxide has the formula MO, where \(\mathrm{M}\) denotes the metal. A 39.46-g sample of the compound is strongly heated in an atmosphere of hydrogen to remove oxygen as water molecules. At the end, \(31.70 \mathrm{~g}\) of the metal is left over. If \(\mathrm{O}\) has an atomic mass of 16.00 amu, calculate the atomic mass of \(\mathrm{M}\) and identify the element.

The annual production of sulfur dioxide from burning coal and fossil fuels, auto exhaust, and other sources is about 26 million tons. The equation for the reaction is $$ \mathrm{S}(s)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{SO}_{2}(g) $$ How much sulfur (in tons), present in the original materials, would result in that quantity of \(\mathrm{SO}_{2} ?\)
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