What happens when you combine two NP-complete problems and make them three-dimensional? Pure mathematical torture. This unholy hybrid of a Rubik's cube and Sudoku would keep even Fields Medal winners occupied for decades. The real challenge isn't solving it—it's explaining to your therapist why you voluntarily subjected yourself to this punishment. Mathematicians call this "recreational" the same way they call proving Fermat's Last Theorem "an interesting afternoon exercise."

Content Me panic-reviewing gas law calculations at 2 AM for my 7 AM exam. Because n is constant, we can use Equation 10.8. Solve: Rearranging Equation 10.8 to solve for V2 gives ½ = 4 x - (6.0 L) 1.0 atm /252 K 295 K, = 11L 0.45 atm/ check: The result appears reasonable. Notice that the felt temperatures moles, fits the initial voltaebya ratio of pressures endle volume connect sim, the expect that alecreasing pressure will cause the yetuense. increase Sintany, we expect that decre sion id cause the volume to decrease afore st at the dister. in pressures is raote aramatic than the difference in temperateres Thus, we shag expect the effect of the pressure change to predominate in determining the final yo. ume, as it does. PRACTICE EXERCISE A 0.50-mol sample of oxygen gas is confined at 0 °C in a cylinder with a morade piston, such as that shown in Figure 10.12. The gas has an initial pressure of 10 at. The piston then compresses the gas so that its final volume is halt the initial volume The final pressure of the gas is 2.2 atm. What is the final temperature of the gas in degrees Celsius? 10.5 FURTHER APPLICI OF THE IDEAL-GAS EQUATION The ideal-gas equation can be used to determine many relationships involving the physical properties of gases. In this section we use it first to define the rela tionship between the density of a gas and its molar mass, and then to calculate the volumes of gases formed or consumed in chemical reactions Gas Densities and Molar Mass The ideal-gas equation allows us to calculate gas density from the molar mas pressure, and temperature of the gas. Recall that density has the units of me per unit volume (d = m/V). a (Section 1.4) We can arrange the gas equat to obtain similar units, moles per unit volume, n/V: P V RT If we multiply both sides of this equation//// @ sergM,