Deep-sea diver

Another consequence of the effect of pressure on gas solubility is the painful, sometimes fatal, affliction known as the bends. This occurs when a person goes rapidly from deep water (high pressure) to the surface (lower pressure), where gases are less soluble. The rapid decompression causes air, dissolved in blood and other body fluids, to bubble out of solution. These bubbles impair blood circulation and affect nerve impulses. To minimize these effects, deep-sea divers and aquanauts breathe a helium-oxygen mixture rather than compressed air (nitrogen-oxygen). Helium is only about one-third as soluble as nitrogen, and hence much less gas comes out of solution on decompression. 

The volume of blood in the body of a certain deep-sea diver is about 6.00 L. Blood cells make up about 55% of the blood volume, and the remaining 45% is the aqueous solution called plasma. What is the maximum volume of nitrogen measured at 1.00 atm and 37°C that could dissolve in the diver s blood plasma at a depth of 93 m, where the pressure is... 

C02-0082. One breathing mixture for deep-sea divers contains 25% moiecuiar oxygen and 75% heiium. Draw a moiecuiar picture of a sampie of this mixture that contains three moiecuies of oxygen. 

Many gases are mixtures of two or more species. The atmosphere, with its mixture of nitrogen, oxygen, and various trace gases, is an obvious example. Another ex-ample is the gas used by deep-sea divers, which contains a mixture of helium and oxygen. The ideal gas model provides guidance as to how we describe mixtures of gases. 

Suppose we pump 4.0 mol of helium into a deep-sea diver s tank. If we pump in another 4.0 mol of He, the container now contains 8.0 mol of gas. The pressure can be calculated using the ideal gas equation, with n = 4.0-1-4.0 = 8.0 mol. Now suppose that we pump in 4.0 mol of molecular oxygen. Now the container holds a total of 12.0 mol of gas. According to the ideal gas model, it does not matter whether we add the same gas or a different gas. Because all molecules in a sample of an ideal gas behave independently, the pressure increases in proportion to the increase in the total number of moles of gas. Thus, we can calculate the total pressure from the ideal gas equation, using n — 8.0 + 4.0 = 12.0 mol. 

Calculate the solubility of dinitrogen in blood that is in contact with air (78% N2 ) at atmospheric pressure and at 4.0 atm, the pressure at a sea depth of 100 feet. Determine the volume of N2 that will be released from 1 L of blood if a deep-sea diver surfaces quickly from this depth. If this escape of N2 occurs in the form of gas bubbles that are 1 mm in diameter, how many bubbles per liter is this ... 

Scuba tanks usually contain compressed air, which is essentially a mixture of nitrogen (78%) and oxygen (21%). In order to avoid a painful condition called the bends, deep-sea divers replace the nitrogen with the noble gas —... 

British chemist Henry Cavendish The most abundant element formed concurrent with the universe used in balloons, airships, and by deep-sea divers. 

Deep-sea divers routinely operate under pressures of multiple atmospheres. One malady these divers must be concerned with is the bends, a dangerous condition that occurs when divers rise too quickly from the depths, resulting in the rapid release of gas from blood and tissues. Why does the bends occur ... 

Deep-sea divers breathe compressed air. Nitrogen is not very soluble in blood at normal pressures but at great depths, when the divers bodies are exposed to very high pressures, the nitrogen becomes more soluble. The dissolved nitrogen comes out of solution rapidly when the divers return to the surface, and numerous small bubbles form in the bloodstream. These bubbles can burst the capillaries—the narrow vessels that distribute the blood—or block them and starve the tissues of oxygen... 

Helium To provide an inert atmosphere for welding As a coolant in nuclear reactors With 20% oxygen, as a breathing gas for deep-sea divers To inflate the tyres of large aircraft To fill airships and weather balloons (Figure 11.12) In the helium-neon laser In low-temperature research, because of its low boiling point... 

It is carried by mountain climbers, astronauts and deep sea divers. 

To describe the behavior of a sample of gas, we need four basic descriptors the temperature of the gas, the pressure of the gas, the volume the gas occupies, and the amount of gas, usually given in the number of moles of whatever gases are present. For instance, if I told you I had a mole of a particular gas at 25°C (77°F) and this gas had a volume of 22.4 liters (about six gallons) at ambient pressure, you would have all the information you would need to predict the behavior of that gas should the pressure or temperature change. This information would be essential for our chemical engineer, our deep-sea diver, and even our winemaker. One of the products of fermentation is carbon dioxide, and if this gas is poorly contained or controlled, the corks that pop will be unintentional. 

Pure oxygen or air enriched with oxygen may also be provided in environments where breathing may be difficult. Aircraft that fly at high altitudes, of course, are always provided with supplies of oxygen in case of any problems with the ship s normal air supply. Deep-sea divers also carry with them or have pumped to them supplies of air that are enriched with oxygen. 

Helium-laced gases are used as breathing media for deep-sea divers. Why Table 10.1 may provide useful data. 

The bends first recorded in 1841, is also known as decompression sickness. It is a very serious and potentially lethal condition. The bends occurs when there is a rapid and great change in blood pressure. Deep sea divers are especially vulnerable to this painful and sometimes fatal condition. There is a higher pressure environment under vast amounts of water such as in a sea or ocean. 

Helium is mixed with oxygen gas for deep-sea divers. Calculate the percent hy volume of oxygen gas in the mixture if the diver has to submerge to a depth where the total pressure is 4.2 atm. The partial pressure of oxygen is maintained at 0.20 atm at this depth. 

Z38 The solubility of N2 in blood at 37°C and at a partial pressure of 0.80 atm is 5.6 X 10 mol/L. A deep-sea diver breathes compressed air with the partial pressure of N2 equal to 4.0 atm. Assume that the total volume of blood in the body is 5.0 L. Calculate the amount of N2 gas released (in liters) when the diver returns to the surface of the water, where the partial pressure of N2 is 0.80 atm. 

Carbonated drinks are bottled under high CO2 pressure, permitting the gas to dissolve into aqueous solution. When the bottle is opened, the partial pressure of CO2 in the gas phase rapidly decreases to the value in the atmosphere, and the gas bubbles out of solution. When the bottle is closed again, CO2 gas pressure builds until a saturated solution at equilibrium is again obtained. The solubility of gases in a liquid also increases in the bloodstream of deep-sea divers when they experience high pressures. 

Strategy The given solubility allows us to ealeulate Henry s law eonstant k), whieh can then be used to determine the concentration of N2 at 4.0 atm. We can then compare the solubilities of N2 in blood under normal pressure (0.80 atm) and under a greater pressure that a deep-sea diver might experience (4.0 atm) to determine the moles of N2 released when the diver returns to the surface. From the moles of N2 released, we can calculate the volume of N2 released. 

Deep-sea divers sometimes substitute helium for nitrogen in the air they breathe because helium has a much lower solubility in biological fluids than N2. For example, divers working at a depth of 100 ft experience a pressure of about 4 atm. At this pressure a mixture of 95% helium and 5% oxygen gives an oxygen partial pressure of about 0.2... 

---