Volume of a gas

The reaction between zinc and hydrochloric acid prodnces hydrogen gas. The net ionic eqnation for the reaction is 

The H2 gas evolved in the reaction is collected in the inverted gradnated cylinder. Using the balanced eqnation, we determine how mnch H2 will be prodnced. 

The vessel contains approximately 5 mL of 1.0 M HCl. A gradnated cylinder is filled with water and inverted over the tnbing to collect the gas prodnced by the reaction of zinc and acid. The temperatnre of the water is 25.0°C and the pressnre in the room is 748.0 torr. 

We adjust the level of the graduated cylinder to make the water level the same inside and outside of the cylinder. This lets us know that the pressure inside the cylinder is the same as the pressure in the room. When the water levels are the same, we can read the volume of gas collected, which is 26.5 mL. 

The pressure inside the cylinder is the sum of two partial pressures that of the collected H2, and that of water vapor. To determine the partial pressure of H2, which is what we want, we mnst subtract the vapor pressure of water from the total pressure. Table 11.5 gives the vapor pressure of water at 25.0°C as 23.8 torr. Therefore, the pressure of H2 is 748.0 - 23.8 = 724.2 torr. Using Equation 11.8(b), 

---

Ideal Gas Behavior, In 1787 it was demonstrated that the volume of a gas varies directly with temperature if the pressure remains constant. Other investigations determined complementary correlating relations from which the perfect or ideal gas law was drawn (1 3). Expressed mathematically, the ideal gas law is... 

The interaction forces which account for the value of a in this equation arise from tire size, the molecular vibration frequencies and dipole moments of the molecules. The factor b is only related to the molecular volumes. The molar volume of a gas at one atmosphere pressure is 22.414 ImoD at 273 K, and this volume increases according to Gay-Lussac s law with increasing... 

Concentration The amount of a substance present in a given volume of a gas or liquid, in parts per million (ppm) or jLg m . In the case of gases, the ppm is proportional to the molecular concentration, hence the relationship between ppm and pg m " depends on the molecular weight of the gas concerned. 

Volumetric heat The heat required to raise the temperature of a unit volume of a gas one degree Celsius. 

The volume of a gas would theoretically be zero at a temperature of approximately -273°C or -460°F. Tliis temperature, wliich lias become known as absolute zero, is tlie basis for tlie definition of two absolute temperature scales, tlie Kelvin (K) and Rankine (°R) scales. The former is defined by shifting tlie Celsius scale by 273-Celsius degrees so that 0 K is equal to -273°C. Equation (4.2.3) shows tliis relation. 

If a fixed quantity of gas is held at a constant pressure and heated or cooled, its volume will change. According to Charles law, the volume of a gas at constant pressure is directly proportional to the absolute temperature. This is shown by the following equation ... 

A gas expands uniformly to fill any container in which it is placed. This means that the volume of a gas is the volume of its container. Volumes of gases can be expressed in liters, cubic centimeters, or cubic meters ... 

Relation of gas volume (V) to number of moles (n) and temperature (7) at constant pressure (/ ). The volume of a gas at constant pressure is directly proportional to (a) the number of moles of gas and (b) the absolute temperature. The volume-temperature plot must be extrapolated to reach zero because most gases liquefy at low temperatures well above 0 K. 

It is found experimentally that the volume of a gas that dissolves in a... 

Charles s and Gay-Lussac s law Relation stating that at constant P and n, the volume of a gas is directly proportional to its absolute temperature, 106-107, 111 Chelating agent Complexing ligand that forms more than one bond with a central metal atom the complex formed is called a chelate, 411-412 natural, 424-425 synthetic, 424-425 Chemical equation Expression that describes the nature and relative amounts of reactants and products in a reaction, 60-61. See also Equation, net ionic. 

Two volumes of hydrogen fluoride gas combine with one volume of the gas dinitrogen difluoride to form two volumes of a gas G. 

Fig. 4-5. An absolute temperature scale from the change of volume of a gas with temperature.

Boyles Law states The volume of a gas is inversely proportional to its absolute pressure, at a constant temperature. PjVj — P2V2... 

Under constant temperature conditions, the volume of a gas varies inversely as the pressure p, V] = p2V2... 

In fluid flow it is important to know how the volume of a gas will vary as the pressure changes. Two important idealised conditions which are rarely obtained in practice are changes at constant temperature and changes at constant entropy. Although not actually reached, these conditions are approached in many flow problems. 

Charles and Gay-Lussac carried out a number of experiments with the hope of improving the performance of their balloons. They found that, provided the pressure is kept constant, the volume of a gas increases as its temperature is raised. In this case, a straight-line graph is obtained when the volume is plotted against the temperature (Fig. 4.10). This result implies... 

Boyle also observed that heating a gas causes it to expand in volume, but more than a century passed before Jacques-Alexandre-Cesar Charles reported the first quantitative studies of gas volume as a function of temperature. Charles found that for a fixed amount of gas, a graph of gas volume vs. temperature gives a straight line, as shown in Figure 5. In other words, the volume of a gas is directly proportional to its temperature ... 

The volume of a gas also changes when the amount of the gas changes. In this respect, gases are like liquids or solids. If we double the amount of any gas while keeping the temperature and pressure fixed, the gas volume doubles. In other words, gas volume is proportional to the amount of gas. oc igas (fixed pressure and temperature)... 

Gases and condensed phases look very different at the molecular level. Molecules of F2 or CI2 move freely throughout their gaseous volume, traveling many molecular diameters before colliding with one another or with the walls of their container. Because much of the volume of a gas is empty space, samples of gaseous F2 and CI2 readily expand or contract in response to changes in pressure. This freedom of motion exists because the intermolecular forces between these molecules are small. 

Charles s Law explains the relationship between the temperature and volume of a gas. Which graph best represents this relationship ... 

Jacques Charles first showed the relationship between temperature and volume of a gas in 1787. His work showed that gases expand in a linear manner as the temperature is increased and contract linearly as the temperature is decreased, provided the pressure is kept constant. 

The graphical plot of the temperature versus volume of a gas produces a straight line. If several different gases are studied and the temperature-volume data is plotted, the extrapolations of these graphs all intersect at the same temperature, -273°C. The Kelvin equivalent of this temperature is expressed as 0 K, or absolute zero. The mathematical expression to change Celsius temperature to Kelvin is K = C° + 273°. 

The relationship between Kelvin temperature and the volume of a gas is expressed as Charles s law The volume of a confined gas, at a constant pressure, is directly proportional to its Kelvin temperature. Mathematically, Charles s law is ... 

In this activity, you will measure the volume of a gas (air) at two different temperatures. 

Predict how the volume of a gas will change when the temperature is raised or lowered. 

Calculate what the change in volume of a gas should be when the temperature is changed. 

Read the entire laboratory activity. Form a hypothesis about how the volume of a gas will change as the temperature is changed. Record your hypothesis in the next column. 

Suppose that a series of measurements of the volume of a gas is made, as the applied pressure is varied. As an example, the original results obtained by Boyle are presented as in Table 1. 

Fig. 1 Volume of a gas (expressed as distance in a tube of constant diameter) versus pressure (a). Pressure as a function of reciprocal volume (b).

Since the molar volume of a gas is much larger than the molar volume of the liquid phase, the Clapeyron equation can be reduced to... 

Alveolar pressure (Palv) is the pressure within the alveoli. In between breaths, it is equal to 0 cmH20. Because no pressure gradient exists between the atmosphere and the alveoli, there is no airflow. However, in order for air to flow into the lungs, alveolar pressure must fall below atmospheric pressure. In other words, alveolar pressure becomes slightly negative. According to Boyle s law, at a constant temperature, the volume of a gas and its pressure are inversely related ... 

The fact that the volume of a gas varies linearly with temperature is combined with the concept of absolute temperature to give a statement of Charles law ... 

---