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Chapter 3: Problem 3

Explain clearly what is meant by the statement "The atomic mass of gold is 197.0 amu."

Short Answer

Expert verified
The statement 'The atomic mass of gold is 197.0 amu' means the mass of a gold atom is approximately 197 times the mass of a carbon-12 atom. Given that the atomic mass unit (amu) is based on the carbon-12 atom, an atom of gold has about 197 protons and neutrons within its nucleus.

Step by step solution

01

Understanding atomic mass

Atomic mass, also known as atomic weight, is a measurement of the total number of particles in an atom's nucleus - protons and neutrons. Electrons are excluded as their mass is much smaller compared to protons or neutrons. The atomic mass of an element is normally measured in atomic mass units (amu), where 1 amu is approximately equal to the mass of a single proton or neutron.
02

Introduction to amu

The amu - 'atomic mass unit' is a standard unit of mass that quantifies mass on an atomic or molecular scale. One atomic mass unit is defined as 1/12 of the mass of a carbon-12 atom, which contains six protons and six neutrons.
03

Interpreting the statement

'The atomic mass of gold is 197.0 amu' means that an atom of a gold has an atomic mass approximately equal to 197 times the mass of the carbon-12 atom. This suggests the gold atom has 197 protons and neutrons in its nucleus.

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Most popular questions from this chapter

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

When baking soda (sodium bicarbonate or sodium hydrogen carbonate, \(\mathrm{NaHCO}_{3}\) ) is heated, it releases carbon dioxide gas, which is responsible for the rising of cookies, donuts, and bread. (a) Write a balanced equation for the decomposition of the compound (one of the products is \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) ). (b) Calculate the mass of \(\mathrm{NaHCO}_{3}\) required to produce \(20.5 \mathrm{~g}\) of \(\mathrm{CO}_{2.}\)

(a) A research chemist used a mass spectrometer to study the two isotopes of an element. Over time, she recorded a number of mass spectra of these isotopes. On analysis, she noticed that the ratio of the taller peak (the more abundant isotope) to the shorter peak (the less abundant isotope) gradually increased with time. Assuming that the mass spectrometer was functioning normally, what do you think was causing this change? (b) Mass spectrometry can be used to identify the formulas of molecules having small molecular masses. To illustrate this point, identify the molecule which most likely accounts for the observation of a peak in a mass spectrum at: 16 amu, 17 amu, 18 amu, and 64 amu. (c) Note that there are (among others) two likely molecules that would give rise to a peak at 44 amu, namely, \(\mathrm{C}_{3} \mathrm{H}_{8}\) and \(\mathrm{CO}_{2}\). In such cases, a chemist might try to look for other peaks generated when some of the molecules break apart in the spectrometer. For example, if a chemist sees a peak at 44 amu and also one at 15 amu, which molecule is producing the 44 -amu peak? Why? (d) Using the following precise atomic masses: \({ }^{1} \mathrm{H}(1.00797\) amu \(),{ }^{12} \mathrm{C}(12.00000 \mathrm{amu}),\) and \({ }^{16} \mathrm{O}(15.99491 \mathrm{amu}),\) how precisely must the masses of \(\mathrm{C}_{3} \mathrm{H}_{8}\) and \(\mathrm{CO}_{2}\) be measured to distinguish between them? (e) Every year millions of dollars' worth of gold is stolen. In most cases the gold is melted down and shipped abroad. This way the gold retains its value while losing all means of identification. Gold is a highly unreactive metal that exists in nature in the uncombined form. During the mineralization of gold, that is, the formation of gold nuggets from microscopic gold particles, various elements such as cadmium (Cd), lead (Pb), and zinc \((\mathrm{Zn})\) are incorporated into the nuggets. The amounts and types of the impurities or trace elements in gold vary according to the location where it was mined. Based on this knowledge, describe how you would identify the source of a piece of gold suspected of being stolen from Fort Knox, the federal gold depository.

Calculate the number of \(\mathrm{C}, \mathrm{H},\) and \(\mathrm{O}\) atoms in \(1.50 \mathrm{~g}\) of glucose \(\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)\), a sugar.

Fermentation is a complex chemical process of wine making in which glucose is converted into ethanol and carbon dioxide: $$ \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} \longrightarrow 2 \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}+2 \mathrm{CO}_{2} $$ glucose ethanol Starting with \(500.4 \mathrm{~g}\) of glucose, what is the maximum amount of ethanol in grams and in liters that can be obtained by this process? (Density of ethanol = \(0.789 \mathrm{~g} / \mathrm{mL} .)\)
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