Chapter 2

Which substance in each of the following pairs of quantities contains more moles of oxygen? a. \(2 \mathrm{mol} \mathrm{N}_{2} \mathrm{O}\) or \(1 \mathrm{mol} \mathrm{N}_{2} \mathrm{O}_{5}\) b. \(1 \mathrm{mol} \mathrm{NO}\) or \(1 \mathrm{mol} \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}\) c. \(2 \mathrm{mol} \mathrm{NO}_{2}\) or \(1 \mathrm{mol} \mathrm{NaNO}_{2}\)

Aluminum, silicon, and oxygen form minerals known as aluminosilicates. How many moles of aluminum are in 1.50 moles of the following? a. pyrophyllite,\(\mathrm{Al}_{2} \mathrm{Si}_{4} \mathrm{O}_{10}(\mathrm{OH})_{2}\) b. \(\operatorname{mica}, \mathrm{KAl}_{3} \mathrm{Si}_{3} \mathrm{O}_{10}(\mathrm{OH})_{2}\) c. albite, \(\mathrm{Na} \mathrm{AlSi}_{3} \mathrm{O}_{8}\)

The uranium used for nuclear fuel exists in nature in several minerals. Calculate how many moles of uranium are in 1 mole of the following. a. carnotite, \(\mathrm{K}_{2}\left(\mathrm{UO}_{2}\right)_{2}\left(\mathrm{VO}_{4}\right)_{2}\) b. uranophane, \(\mathrm{CaU}_{2} \mathrm{Si}_{2} \mathrm{O}_{11}\) c. autunite, \(\mathrm{Ca}\left(\mathrm{UO}_{2}\right)_{2}\left(\mathrm{PO}_{4}\right)_{2}\)

Calculate the molar masses of the following gases. (a) \(\mathrm{SO}_{2}\) (b) \(\mathrm{O}_{3} ;\) (c) \(\mathrm{CO}_{2} ;\) (d) \(\mathrm{N}_{2} \mathrm{O}_{5}\)

Determine the molar masses of the following minerals. a. rhodonite, \(\mathrm{MnSiO}_{3}\) b. scheelite, CaWO \(_{4}\) c. ilmenite, FeTiO \(_{3}\) d. magnesite, \(\mathrm{MgCO}_{3}\)

Flavors Calculate the molar masses of the following common flavors in food. a. vanillin, \(\mathrm{C}_{8} \mathrm{H}_{8} \mathrm{O}_{3}\) b. oil of cloves, \(\mathrm{C}_{10} \mathrm{H}_{12} \mathrm{O}_{2}\) c. anise oil, \(\mathrm{C}_{10} \mathrm{H}_{12} \mathrm{O}\) d. oil of cinnamon, \(\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}\)

Calculate the molar masses of the following common sweeteners. a. sucrose, \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\) b. saccharin, \(\mathrm{C}_{7} \mathrm{H}_{5} \mathrm{O}_{3} \mathrm{NS}\) c. aspartame, \(\mathrm{C}_{14} \mathrm{H}_{18} \mathrm{N}_{2} \mathrm{O}_{5}\) d. fructose, \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\)

How many moles of carbon are there in 500.0 grams of carbon?

How many moles of gold are there in 2.00 ounces of gold?

How many moles of \(\mathrm{Ca}^{2+}\) ions are in 0.25 mol \(\mathrm{CaTiO}_{3} ?\) What is the mass in grams of the \(\mathrm{Ca}^{2+}\) ions?

How many moles of \(\mathrm{O}^{2-}\) ions are in \(0.55 \mathrm{mol} \mathrm{Al}_{2} \mathrm{O}_{3} ?\) What is the mass in grams of the \(\mathrm{O}^{2-}\) ions?

Suppose pairs of balloons are filled with \(10.0 \mathrm{g}\) of the following pairs of gases. Which balloon in each pair has the greater number of particles? (a) \(\mathrm{CO}_{2}\) or \(\mathrm{NO} ;\) (b) \(\mathrm{CO}_{2}\) or \(\mathrm{SO}_{2} ;(\mathrm{c}) \mathrm{O}_{2}\) or \(\mathrm{Ar}\)

If you had equal masses of the substances in the following pairs of compounds, which of the two would contain the greater number of ions? (a) \(\mathrm{NaBr}\) or \(\mathrm{KCl} ;\) (b) \(\mathrm{NaCl}\) or \(\mathrm{MgCl}_{2} ;(\mathrm{c}) \mathrm{CrCl}_{3}\) or \(\mathrm{Na}_{2} \mathrm{S}\)

How many moles of \(\mathrm{NaCl}\) are there in a crystal of halite that has a mass of \(6.82 \mathrm{g} ?\)

The density of uranium \(\left(\mathrm{U} ; 19.05 \mathrm{g} / \mathrm{cm}^{3}\right)\) is more than five times as great as that of diamond \(\left(\mathrm{C} ; 3.514 \mathrm{g} / \mathrm{cm}^{3}\right) .\) If you have a cube ( \(1 \mathrm{cm}\) on a side) of each element, which cube contains more atoms?

Aluminum \(\left(d=2.70 \mathrm{g} / \mathrm{cm}^{3}\right)\) and strontium \(\left(d=2.64 \mathrm{g} / \mathrm{cm}^{3}\right)\) have nearly the same density. If we manufacture two cubes, each containing 1 mol of one element or the other, which cube will be smaller? What are the dimensions of this cube?

How does mass spectrometry provide information on the molecular mass of a compound?

Would you expect the mass spectra of \(\mathrm{CO}_{2}\) and \(\mathrm{C}_{3} \mathrm{H}_{8}\) to have molecular ions with the same mass (to the nearest amu)?

Would you expect the mass spectra of \(\mathrm{CO}_{2}\) and \(\mathrm{C}_{3} \mathrm{H}_{8}\) to be the same?

Many of the explosive materials of concern to airport security contain nitrogen and oxygen. Calculate the masses of the molecular ions formed by (a) \(\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{N}_{6} \mathrm{O}_{6},\) (b) \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{N}_{8} \mathrm{O}_{8},\) (c) \(\mathrm{C}_{5} \mathrm{H}_{8} \mathrm{N}_{4} \mathrm{O}_{12},\) and (d) \(\mathrm{C}_{14} \mathrm{H}_{6} \mathrm{N}_{6} \mathrm{O}_{12}\)

Mass spectrometry has proven useful in analyzing the gases emitted from landfills. The principal component is methane \(\left(\mathrm{CH}_{4}\right),\) but small amounts of dimethylsulfide \(\left(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{S}\right)\) and dichloroethene \(\left(\mathrm{C}_{2} \mathrm{H}_{2} \mathrm{Cl}_{2}\right)\) are often present, too. Calculate the masses of the molecular ions formed by these three compounds in a mass spectrometer.

In April \(1897,\) J.J. Thomson presented the results of his experiment with cathode-ray tubes in which he proposed that the rays were actually beams of negatively charged particles, which he called "corpuscles." a. What is the name we use for the particles today? b. Why did the beam deflect when passed between electrically charged plates? c. If the polarity of the plates were switched, how would the position of the light spot on the phosphorescent screen change?

There are three stable isotopes of magnesium. Their masses are \(23.9850,24.9858,\) and 25.9826 amu. If the average atomic mass of magnesium is 24.3050 amu and the natural abundance of the lightest isotope is \(78.99 \%,\) what are the natural abundances of the other two isotopes?

Some newer television sets utilize nanoparticles of cadmium sulfide (CdS) and cadmium selenide (CdSe), called "quantum dots," to produce the colors on the screen. Different-sized quantum dots lead to different colors. a. Calculate the formula masses of \(\mathrm{CdS}\) and \(\mathrm{CdSe}\). b. If a nanoparticle of CdSe contains \(2.7 \times 10^{7}\) atoms of Cd, how many atoms of Se are in the particle? c. If a nanoparticle of CdS weighs \(4.3 \times 10^{-15} \mathrm{g}\), how many grams of Cd and how many grams of S does it contain?

Samples of air are collected daily at the Mauna Loa Observatory in Hawaii and analyzed for \(\mathrm{CO}_{2}\) content. During January 2016 the average result of these analyses was \(402.5 \mu\) moles \(\left(10^{-6} \text {moles }\right)\) of \(\mathrm{CO}_{2}\) per mole of air. If the average molar mass of the gases in air is \(28.8 \mathrm{g} / \mathrm{mol},\) how many \(\mu \mathrm{g}\) of \(\mathrm{CO}_{2}\) per gram of air were in these samples?

Suppose we know the atomic mass of each of the three stable isotopes of an element to six significant figures, and we know the natural abundances of the isotopes to the nearest \(0.01 \% .\) How well can we know the average atomic mass - that is, how many significant figures should be used to express its value?