Elevation, boiling point

Beckmann thermometer A very sensitive mercury thermometer with a small temperature range which can be changed by transferring mercury between the capillary and a bulb reservoir. Used for accurate temperature measurements in the determination of molecular weights by freezing point depression or boiling point elevation. 

Boiling point elevation. A solute which does not enter the vapor phase to any significant extent raises the boiling point of the solvent. As above, the solute lowers the activity of the solvent, which, in turn, lowers the vapor pressure. Therefore the solution must be raised to a higher temperature before its vapor pressure reaches 1.0 atm. At equilibrium... 

Boiler yater treatment Boiling point elevation Bois de Rose oil Bois de rose oil Boll weevil Bollworm Bologna Bolometer Bolometers... 

May be inferior for systems with high boiling point elevations (high vacuum levels requited). 

The coUigative properties of antifreeze chemicals may also result in boiling point elevation. As the chemical is added to water, the boiling point of the mixture increases. Unlike the freeze depression, the boiling elevation does not experience a maximum the boiling point versus concentration curve is a smooth curve that achieves its maximum at the 100% antifreeze level. The boiling point elevation can be another important characteristic for antifreeze fluids in certain heat-transfer appHcations. 

Estimate temperature distribution in the evaporator, taking into account boiling-point elevations. If all heating surfaces are to be equal, the temperature drop across each effect will be approximately inversely proportional to the heat-transfer coefficient in that effect. 

Siedepunkt, m. boiling point, -bestimmuug, /. boiling-point determination, -(s)erhohimg, /. boiling-point elevation. 

Lower boiling point elevation than vertical units. 

M depends not on the molecular sizes of the particles but on the number of particles. Measuring colligative properties such as boiling point elevation, freezing point depression, and vapor pressure lowering can determine the number of particles in a sample. 

The properties of a solution differ considerably from those of the pure solvent Those solution properties that depend primarily on the concentration of solute particles rather than their nature are called colligative properties. Such properties include vapor pressure lowering, osmotic pressure, boiling point elevation, and freezing point depression. This section considers the relations between colligative properties and solute concentration, with nonelectrolytes that exist in solution as molecules. 

Boiling Point Elevation and Freezing Point Lowering... 

When a solution of a nonvolatile solute is heated, it does not begin to boil until the temperature exceeds the boiling point of the solvent. The difference in temperature is called the boiling point elevation, ATb. 

Boiling point elevation is a direct result of vapor pressure lowering. At any given temperature, a solution of a nonvolatile solute has a vapor pressure lower than that of the pure solvent. Hence a higher temperature must be reached before the solution boils, that is, before its vapor pressure becomes equal to the external pressure. Figure 10.8 (p. 270) illustrates this reasoning graphically. 

The freezing point lowering, like the boiling point elevation, is a direct result of the lowering of the solvent vapor pressure by the solute. Notice from Figure 10.8 that the freezing point of the solution is the temperature at which the solvent in solution has the same vapor pressure as the pure solid solvent. This implies that it is pure solvent (e.g., ice) that separates when the solution freezes. 

Boiling point elevation and freezing point lowering, like vapor pressure lowerings are colligative properties. They are directly proportional to solute concentration, generally expressed as molality, m. The relevant equations are... 

Click Coached Problems for a self-study module on boiling point elevation. 

When the concentration of sugar reaches 66%, you are at the maple syrup stage. The calculated boiling point elevation (660 g of sugar, 340 g of water)... 

Key Terms boiling point elevation molality osmotic pressure... 

Boiling point elevation (ATb) Increase in the boiling point caused by addition of a nonvolatile solute, 269-271 Bomb calorimeter Device used to measure heat flow, in which a reaction is carried out within a sealed metal container, 202-203... 

Because the presence of a nonvolatile solute lowers the vapor pressure of the solvent, the boiling point of the solvent rises. This increase is called boiling-point elevation. The elevation of the boiling point has the same origin as vapor-pressure lowering and is also due to the effect of the solute on the entropy of the solvent. 

Hence the water in the solution freezes at —0.2°C. A similar expression (boiling-point elevation = kb X molality) is used to relate the elevation of boiling point to the molality of the solute. 

Bohr frequency condition, 13 Bohr radius, 23 boiling, 314 boiling point, 314 alkanes, 737 anomalous, 184 boiling point prediction, 180 boiling point trends, 183 boiling-point elevation, 332 Boltzmann, L., 276 Boltzmann formula, 276 bomb calorimeter, 224... 

In physical chemistry, we apply the term colligative to those properties that depend upon number of molecules present. The principal colligative properties are boiling point elevation, freezing point depression, vapour pressure lowering, and osmotic pressure. All such methods require extrapolation of experimental data back to infinite dilution. This arises due to the fact that the physical properties of any solute at a reasonable concentration in a solvent are... 

Boiling-point elevation and freezing-point depression measurements have demonstrated that at all concentrations in THF and at low concentrations in ether (up to 0.1M) Grignard reagents prepared from alkyl bromides and iodides are monomeric, that is, there are few or no molecules with two magnesium atoms. Thus, part of the Schlenk equilibrium is operating... 

A = Kj- Cflj A 7b = Ki) Cflj We use molality in these equations because they describe temperature changes. The constant Zf is called the freezing point depression constant, and is called the boiling point elevation constant. These constants are different for different solvents but do not depend on the identity of the solutes. For water, Zf is 1.858 °C kg/mol and is 0.512 °C kg/mol. 

Like freezing point depression and boiling point elevation, osmotic pressure is proportional to the concentration of solute molecules. Experiments show that osmotic pressure is proportional to both concentration (expressed as... 

In 1910 Stobbe and Posnjak drew the conclusion that polystyrene is a colloidal body after noting that boiling point elevations of its solutions are negligible. They proposed cyclic formulas composed of four, five, or possibly more structural units, e.g. 

The depression of the activity may be measured in various ways. The most obvious would involve a measurement of the vapor pressure lowering, but this method is superseded by others both in accuracy and in simplicity of execution. The boiling point elevation and freezing point depression methods relegated vapor pressure measurement... 

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