Problem 29
What is wrong with the following statement? "The atomic mass of an atom of chlorine is \(35.453 \mathrm{u}\)."
Problem 30
The atomic number of silver, \(\mathrm{Ag}\), is 47 and it has an average atomic mass of 107.87 . Why is it impossible to determine the number of neutrons in the nucleus of a silver atom?
Problem 35
Iodine-131 is used to treat overactive thyroids; it has a mass of \(130.9061 \mathrm{u}\). Give the number of protons, neutrons, and electrons in the atom.
Problem 36
In the polyatomic ion \(\mathrm{T} \mathrm{c} \mathrm{O}_{4}^{-}, \mathrm{T} \mathrm{c}\) has a hypothetical charge of \(7+\). The \({ }^{99} \mathrm{Tc}\) isotope is used in medicine for imaging purposes. It has a mass of \(98.90625 \mathrm{u}\). Give the number of protons, neutrons, and electrons for a \(\mathrm{Tc}^{7+}\) ion.
Problem 37
One chemical substance in natural gas is a compound called methane. Its molecules are composed of carbon and hydrogen, and each molecule contains four atoms of hydrogen and one atom of carbon. In this compound, \(0.33597 \mathrm{~g}\) of hydrogen is combined with \(1.0000 \mathrm{~g}\) of carbon-12. Use this information to calculate the atomic mass of the element hydrogen.
Problem 38
Carbon tetrachloride contains one carbon and four chlorine atoms. For this compound \(11.818 \mathrm{~g}\) of chlorine combine with \(1.000 \mathrm{~g}\) of \(\mathrm{C}-12 .\) Using this information, calculate the atomic mass of chlorine.
Problem 40
One atom of \(f^{109} \mathrm{Ag}\) has a mass that is 9.0754 times that of a \({ }^{12} \mathrm{C}\) atom. What is the atomic mass of this isotope of silver expressed in atomic mass units?
Problem 42
Naturally occurring magnesium (one of the elements in milk of magnesia) is composed of \(78.99 \%\) of \({ }^{24} \mathrm{Mg}\) (atomic mass \(=23.9850 \mathrm{u}\) ) \(, 10.00 \%\) of \({ }^{25} \mathrm{Mg}\) (atomic mass \(=24.9858 \mathrm{u}\) ), and \(11.01 \%\) of \({ }^{26} \mathrm{Mg}\) (atomic mass \(=\) \(25.9826 \mathrm{u}\) ). Use these data to calculate the average atomic mass of magnesium.
Problem 43
\(\mathrm{N}_{2} \mathrm{O}\) is often called nitrous oxide or "laughing gas," and \(\mathrm{NO}_{2}\) is a well-known air pollutant. How would you explain that these molecules follow the law of definite proportions?
Problem 44
An element has 24 protons in its nucleus. (a) Identify this element. (b) Write the symbol for the element's isotope. That will have a mass closest to its average atomic mass. (c) How many neutrons are in the isotope you described in part \((b) ?\) (d) How many electrons are in neutral atoms of this element? (e) How many times heavier than \({ }^{12} \mathrm{C}\) is the average atom of this element?
