As was mentioned in Chapter 10 “Solids and Liquids”, all pure liquids have a characteristic vapour pressure in equilibrium with the liquid phase, the partial pressure of which is dependent on temperature. Now that this new concentration unit has been introduced, the first colligative property can be considered. Thus the mole fraction of C 6H 6 in Example 11.1 could be calculated by evaluating the definition of mole fraction a second time, or - because there are only two substances in this particular mixture - we can subtract the mole fraction of the C 10H 8 from 1 to get the mole fraction of C 6H 6. What is the mole fraction of CH 3OH in the solution?Ī useful thing to note is that the sum of the mole fractions of all substances in a mixture equals 1. The mole fraction is a number between 0 and 1 and is unitless.Ī solution is made by mixing 33.8 g of CH 3OH in 50.0 g of H 2O. Now we can calculate the mole fraction of C 10H 8: The number of moles of C 6H 6 is as follows: The number of moles of C 10H 8 is as follows: We need to determine the number of moles of each substance, add them together to get the total number of moles, and then divide to determine the mole fraction of C 10H 8. What is the mole fraction of C 10H 8 in the solution? (χ is the lowercase Greek letter chi.) The mole fraction is always a number between 0 and 1 (inclusive) and has no units it is just a number.Ī solution is made by mixing 12.0 g of C 10H 8 in 45.0 g of C 6H 6. The mole fraction of the ith component in a solution, χ i, is the number of moles of that component divided by the total number of moles in the sample: These properties are called colligative properties the word colligative comes from the Greek word meaning “related to the number,” implying that these properties are related to the number of solute particles, not their identities.īefore we introduce the first colligative property, we need to introduce a new concentration unit. The differences are proportional to the fraction that the solute particles occupy in the solution. However, some of the properties of solutions differ from pure solvents in measurable and predictable ways. This makes sense because the majority of the solution is the solvent. The properties of solutions are very similar to the properties of their respective pure solvents. Calculate the osmotic pressure of solutions.Calculate changes in vapour pressure, melting point, and boiling point of solutions.Theoretical yield - the amount of product formed from the complete conversion of a limiting reactant in a chemical reaction. Stoichiometry - the calculation of the quantities of reactants and products involved in a chemical reaction. Percent yield - the ratio of the actual yield to the theoretical yield of a material. Percent composition - the percentage by mass of each element in a compound. Molecular formula - a formula which states the exact number and type of each atom present in a molecule of a substance. Mole ratio - the ratio of moles of one substance to the moles of another substance in a balanced equation. Mole - The SI unit that measures the amount of matter a substance has one mole is equal to 6.022x10^23 representative particles, also known as Avagadro's number. Molar volume - the volume of one mole of any gas at standard temperature and pressure. Molar mass - the mass, in grams, of a mole of a substance. Limiting reactant - the reactant in a chemical reaction that limits the amount of product formed. Atomic mass unit - equals 1/12 the mass of a carbon atom.Īvagadro's number - the number of atoms in a mole, equal to 6.02x10^23 atoms.Ĭonversion factor - a ratio expressed as a fraction that equals one.ĭimensional analysis - the sequential application of conversion factors expressed as fractions and arranged so that any dimensional unit can be cancelled out until the desired set of dimensional units is obtained.Įmpirical formula - the simplest formula of a compound expressed as the smallest possible ratio of the elements.Įquivalence statement - a statement that shows the quantities and units that are equal to each other.Įxcess reactant - the reactant in a chemical reaction that remains when a reaction stops once the limiting reactant is completely consumed.
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