Liter molarity

When a solution is diluted, it is useful to know the resulting concentration of the diluted solution in moles per liter, molarity (M). When a solution is diluted, the moles of solute remain constant. Therefore, the volume (V) in liters times the concentration (M) of the original solution (o) equals the volume (V) times the concentration (M) of the final solution (f). In equation form, M0 V0 = Mf Vf. Take 10.0mlofa0.10M copper sulfate solution. Add 2.0 ml of water to the original solution and calculate the molarity of this new solution. Continue to add 2.0 ml of water to each subsequent solution until no color is visible. Calculate the molarity of the final solution. Explain how colored particles can be present in a colorless solution. 

Because virtually all stoichiometric calculations involve moles (abbreviated mol) of material, molarity is probably the most common concentration unit in chemistry. If we dissolved 1.0 mol of glucose in enough water to give a total volume of 1.0 L, we would obtain a 1.0 molar solution of glucose. Molarity is abbreviated with a capital M. Notice that, because molarity has units of moles per liter, molar concentrations are conversion factors between moles of material and liters of solution. 

Prefixes can be used with all of the primary and secondary units to change their values by powers of ten (Table 1.2). Note the abbreviations for the units. Capitalization is important meters and moles per liter (molar), or mill- and mega-, differ only by capitalization. There are prefixes for some of the intermediate values (for example, centi- is 10-2) but the common convention is to prefer these prefixes, and write 10 mm or.01 m instead of 1 cm. 

Note When converting from one concentration unit to another, it is convenient to assume one of the following (1) the solution has a volume of one liter molarity molality), (2) the total amount of solvent and solute is one mole mole fraction o molality), or (3) the mass of the solvent in the solution is one kilogram molality mole fraction). 

Debye and Huckel used liter molarity in deriving their equations. Molarity and molality are the expressions favored in American publications. A proper representation of concentration can not be decided upon until the so-called hydration effect shall have been studied quantitatively. 

The concentration of ions in solution may be represented in a variety of ways. The most common include moles per liter (molarity) and equivalents per liter. 

Dilution is often used to prepare less concentrated solutions. The expression for this calculation is (M])(l/,) = (MiKVi). Knowing any three of these terms enables one to calculate the fourth. The concentration of ions in solution may be represented as moles per liter (molarity) or any other suitable concentration units. However, both concentrations must be in the same units when using the dilution equation. 

Here, cs denotes the concentration in mol/kg (molality scale), and [s] is the concentration in mol/liter (molarity scale). Both units are related in that [s] = pwcs where pw= 1 kg/dm3 is the density of water. Its variation with temperature causes the molarity scale to depend on temperature, whereas the molality scale does not. In the temperature range 0-25°C, however, the density of water differs from unity by less than 0.3%, so that [s] = cs with reasonable accuracy. Most Henry coefficients are less well known. From the definitions in Eqs. (8-7) and (8-8), the coefficients involved are related by... 

Moles = (moles/liter) X liters = molarity X liters... 

When a solution is desaibed in terms of mass percent, the amount of solution is given in terms of its mass. However, it is often more convenient to measure the volume of a solution than to measure its mass. Because of this, chemists often describe a solution in terms of concentration. We define the concentration of a solution as the amount of solute in a given volume of solution. The most commonly used expression of concentration is molarity (Af). Molarity describes the amount of solute in moles and the volume of the solution in liters. Molarity is the number of moles of solute per volume of solution in liters. That is... 

Microgram (pg) Very large and very small quantities Milligram (mg) Very large and very small quantities mmol/1 or mmol/liter Molar concentration Molar concentration... 

Chemists often find it necessary to dilute solutions from one concentration to another by adding more solvent to the solution. If a solution is diluted by adding pure solvent, the volume of the solution increases, but the number of moles of solute in the solution remains the same. Thus the moles/liter (molarity) of the solution decreases. Always read a problem carefully to distinguish between (1) how much solvent must be added to dilute a solution to a particular concentration and (2) to what volume a solution must be diluted to prepare a solution of a particular concentration. 

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