50g of potassium iodide is added to 1,500g of water What is the molality of the resulting solution in .NET framework

Encode EAN-13 Supplement 5 in .NET framework 50g of potassium iodide is added to 1,500g of water What is the molality of the resulting solution

Calculate the mole fraction of each component in a solution containing 275 mol ethanol and 625 mol water

Calculating molality is no more or less difficult than calculating molarity, so you may be asking yourself why all the fuss Is it even worth adding another quantity and another variable to memorize Yes! While molarity is exceptionally convenient for calculating concentrations and working out how to make dilutions in the most efficient way, molality is reserved for the calculation of several important colligative properties, including boiling point elevation Boiling point elevation refers to the tendency of a solvent s boiling point to increase when an impurity (a solute) is added to it In fact, the more solute that is added, the greater the change in the boiling point Boiling point elevations are directly proportional to the molality of a solution, but chemists have found that some solvents are more susceptible to this change than others The formula for the change in the boiling point of a solution, therefore, contains a proportionality constant, abbreviated Kb, which is a property determined experimentally and must be read from a table such as Table 13-2 The formula for the boiling point elevation is Tb = Kb m Note the use of the Greek letter delta ( ) in the formula to indicate that you re calculating a change in boiling point, not the boiling point itself You ll need to add this number to the boiling point of the pure solvent to get the boiling point of the solution The units of Kb are typically given in degrees Celsius per molality

13: Playing Hot and Cold: Colligative Properties Table 13-2

307 253 595 495 279 119 356 0512

1181 801 2040 767 807 784 1817 1000

Boiling point elevations are a result of the attraction between solvent and solute particles in a solution Adding solute particles increases these intermolecular attractions because more particles are around to attract one another Solvent particles must therefore achieve a greater kinetic energy to overcome this extra attractive force and boil, which translates into a higher boiling point (See 10 for full information on kinetic energy)

What is the boiling point of a solution containing 452g of menthol (C10H20O) dissolved in 350g of acetic acid 1207 C The problem asks for the boiling point of the solution, so you know that first you have to calculate the boiling point elevation This means you re required to know the molality of the solution and the Kb value of the solvent (acetic acid) Table 13-2 tells you that the Kb of acetic acid is 307 To calculate the molality, you must convert 452g of menthol to moles 452g menthol 1 mol menthol = 029 mol 1 156g menthol You can now calculate the molality of the solution, taking care to convert grams of acetic acid to kilograms

m = 029 mol menthol = 083 0350 kg acetic acid Now that you have molality, you can plug it and your Kb into the formula to find the change in boiling point Tb = 307 C m 083m = 25 C

Remember, however, that you re not quite done because the problem asks for the boiling point of the solution, not the change in it Luckily, the last step is just simple arithmetic You must add your Tb to the boiling point of pure acetic acid which, according to Table 13-2, is 1181 C This gives you a final boiling point for the solution of 1181 C + 26 C = 1207 C

What is the boiling point of a solution containing 158g sodium chloride (NaCl) and 12 kg of water What if the same number of moles of calcium chloride (CaCl2) is added to the solvent Explain why there is such a great difference in the boiling point elevation

A clumsy chemist topples a bottle of indigo dye (C16H10N2O2) into a beaker containing 450g of ethanol If the boiling point of the resulting solution is 792 C, how many grams of dye were in the bottle