Raising the boiling point

The vapour pressure of a liquid increases with increasing temperature. When the vapour pressure of the liquid reaches the external pressure on the surface of the liquid, usually atmospheric pressure, the liquid boils. When a non-volatile solute is dissolved in the liquid, the vapour pressure is lowered and particles of solvent find it harder to escape from the liquid surface. The solution has to be heated more to push the vapour pressure up to the outside pressure, leading to a boiling point for the solution which is higher than that of the pure solvent. 

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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... 

When casting large blocks, the exotherm problem is more severe and it may be necessary to polymerise inside a pressure vessel and thus raise the boiling point of the monomer. 

As in the freezing-point method, the molecular weight is calculated from the weight of substance lequired to raise the boiling-point of too grams of solvent i°, and the result multiplied by a coefficient which depends upon the nature of the solvent. The following is a list of solvents commonly employed and their coefficients and boiling-points —... 

Solutes raise the boiling point and lower the freezing point... 

Calculate the number of grams of glycerol, C3H5(OH)3 (MW = 92.1 g/mol), that must be dissolved in 520. grams of water to raise the boiling point to 102.00°C. 

Various alcohols and glycols can be used as antifreezes and are effective freeze point depressants for water. However, because glycols raise the boiling point of water while alcohols lower it, only glycol bases are recommended for use by engine manufacturers. 

Thus, by substituting an atom of methyl for one of hydrogen in the non-oxygenated part of the alcohol, the addition of OH, raises the boiling-point 17 6i whilst, if an atom of hydrogen in the oxygenated part be similarly displaced, the same addition only raises the boiling-point S° 6. 

AO 356 g sample of a solid organic compound, when dissolved in 9 15 ml of carbon tetrachlonde (density = 1 595 g/ml), raises the boiling point of the carbon tetrachlonde by 0 560°C When analyzed, this compound is found to be 55 0% C, 2 75% H, 12 8% N, and 29 4% O What is the true formula of this compound9... 

Explain in thermodynamic terms why a solute raises the boiling point and lowers the freezing point of a solution. 

How many grams of KBr dissolved in 125 g of water is needed to raise the boiling point of water to 103.2°C ... 

The semimicro Kjeldahl-Gunning method (ASTM D-3179 ISO 333) has become a widely used method for determining nitrogen in coal, but there is some doubt about whether or not nitrogen recovery is complete by this procedure. In fact, the fate of nitrogen in the Kjeldahl method depends on its chemical form in the coal, the inorganic compounds added to catalyze the hydrolysis, and the amounts and types of compounds used to raise the boiling point of the mixture. 

The reactivity of titanium dioxide toward acid is dependent on the temperature to which it has been heated. Freshly precipitated titanium dioxide is soluble in concentrated hydrochloric acid. However, titanium dioxide that has been heated to 900°C is almost insoluble in acids except hot concentrated sulfuric, in which the solubility may be further increased by the addition of ammonium sulfate to raise the boiling point of the acid, and hydrofluoric acid. Similarly, titanium dioxide that has been calcined at 900°C is almost insoluble in aqueous alkalies but dissolves in molten sodium or potassium hydroxide,... 

There has been no effort to study systematically a series of compounds. The lower dioxoles and oxathioles are liquids, insoluble in water but soluble in most organic solvents. 1,3-Dioxole boils at 51 °C at atmospheric pressure, while 2,2-dimethyl substitution raises this to 72-73 °C. No boiling point has been reported for 1,2-dioxolane and the only report for 1,2-oxathiolane indicates that it codistills with chloroform at 20 °C (0.1 mmHg). 1,3-Dioxolane boils at 75 °C (760 mmHg) and the introduction of sulfur raises the boiling point such that 1,3-oxathiolane boils at 132-136 °C (760 mmHg). 

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