Gases combining volumes

Boyle s law Charles s law combined gas law standard temperature and pressure, STP law of combining gas volumes Avogadro s principle... 

Experiments with many other gas reactions show that volumes of gases always react in ratios of small whole numbers. Figure 11.15 presents the combining volumes for a synthesis reaction and a decomposition reaction. The observation that at the same temperature and pressure, volumes of gases combine or decompose in ratios of small whole numbers is called the law of combining gas volumes. 

The law of combining gas volumes states that in chemical reactions involving gases, the ratio of the gas volumes is a small whole number. 

A representation of some of Gay-Lussac s experimental results on combining gas volumes. 

Adsorption (qv) of gases has been reviewed (40,50) (see also Adsorption, gas separation). Adsorption, used alone or in combination with other removal methods, is excellent for removing pollutant gases to extremely low concentrations, eg, 1 ppmv. When used in combination, it is typically the final step. Adsorption, always exothermic, is even more attractive when very large gas volumes must be made almost pollutant free. Because granular adsorbent beds ate difficult to cool because of poor heat transfer, gas precooling is often practiced to minimize adsorption capacity loss toward the end of the bed. Pretreatment to remove or reduce adsorbable molecules, such as water, competing for adsorption sites should also be considered (41). 

Oxidizers. The characteristics of the oxidizer affect the baUistic and mechanical properties of a composite propellant as well as the processibihty. Oxidizers are selected to provide the best combination of available oxygen, high density, low heat of formation, and maximum gas volume in reaction with binders. Increases in oxidizer content increase the density, the adiabatic flame temperature, and the specific impulse of a propellant up to a maximum. The most commonly used inorganic oxidizer in both composite and nitroceUulose-based rocket propellant is ammonium perchlorate. The primary combustion products of an ammonium perchlorate propellant and a polymeric binder containing C, H, and O are CO2, H2, O2, and HCl. Ammonium nitrate has been used in slow burning propellants, and where a smokeless exhaust is requited. Nitramines such as RDX and HMX have also been used where maximum energy is essential. 

Explosives and propellants are mixtures of fuel and oxidizer. The intensity of combustion is determined by the heat of combustion per pound of material, the material s density, the gas volume generated per volume of material, and the rate of deflagration or detonation. The latter, the most important variable, is determined by the speed at which fuel and oxidizer molecules combine. 

According to the combined gas law, the volume of a given mass of gas can have any value, depending on its temperature and pressure. To compare the quantities of gas present in two different samples, it is useful to adopt a set of standard conditions of temperature and pressure. By universal agreement, the standard temperature is chosen as 273 K (0°C) and the standard pressure is chosen as exactly 1 atm (760torr). Together, these conditions are referred to as standard conditions or as standard temperature and pressure (STP). While there is nothing special about STP, some authors and some instructors find it convenient to use this short notation for this particular temperature and pressure. 

The law we need here that is applied to situations where the number of moles of gas and the volume stay constant can be derived from the Combined Gas Law ... 

Plan (1) Use the Combined Gas Law to calculate the volume that 1 L of the gas would have occupied... 

C is a temperature higher than STP. This condition increases the 1.00-L volume that contains 0.44 g of the mixture at STP. We calculate the expanded volume with the combined gas law. 

Combined gas law Amount (n) Pressure, volume, and temperature (K) (PiVO/Tj = (P2V2)/T2... 

It is possible to combine Avogadro s law and the combined gas law to produce the ideal gas equation, which incorporates the pressure, volume, temperature, and amount relationships of a gas. The ideal gas equation has the form of... 

If you have a gas at a certain set of volume/temperature/pressure conditions and at least some of the conditions change, then you will probably be using the combined gas equation. If moles of gas are involved, the ideal gas equation will probably be necessary... 

The presence of two volumes (or two temperatures) is a very strong indication that we will need to use the combined gas law. To use this gas law we need subscripts to differentiate the different volumes and temperatures. Label one volume Vj and the other V2. It does not matter which volume we label 1 or 2 as long as we label all associated variables with the same subscript. 

For example, suppose a 5.0-L bottle of gas with a pressure of 2.50 atm at 20°C is heated to 80°C. We can calculate the new pressure using the combined gas law. Before we start working mathematically, however, let s do some reasoning. The volume of the bottle hasn t changed, and neither has the number of moles of gas inside. Only the temperature... 

Now substitute the known quantities into the equation. (You could substitute the knowns into the combined gas equation first, and then solve for the volume. Do it whichever way is easier for you.)... 

Most gas law experiments use either the combined gas law or the ideal gas equation. Moles of gas are a major factor in many of these experiments. The combined gas law can generate the moles of a gas by adjusting the volume to STP and using Avogadro s relationship of 22.4 L/mol at STE The ideal gas equation gives moles from the relationship n = PV/RT. 

The values of P, T, and n may be used to determine the volume of a gas. If this volume is to be used with Avogadro s law of 22.4 L/mol, the combined gas law must be employed to adjust the volume to STE This equation will use the measured values for P and Talong with the calculated value of V. These values are combined with STE conditions (0°C (273.15 K) and 1.00 atm) to determine the molar volume of a gas. 

Use the combined gas law to calculate molar volume at room temperature and atmospheric pressure. 

But when one volume of nitrogen reacted with one volume of oxygen, the result was two volumes of nitrous oxide, not one. Joseph Louis Gay-Lussac (1778-1850) had experimentally demonstrated that two volumes of nitrous gas result from combining one volume of nitrogen with one volume of... 

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