5 Calculating Concentrations

• Concentration is the amount of solute in a solution.
• Solute is the part of the solution being dissolved.
• Solvent is the part of the solution that dissolves the solute.
• If same number of electrons, then no charge.
• Salt: combination of metals and nonmetal.
• Calcium Carbonate (CaCO3) has 2 factors (replaceable).
• Standard solution is one strength which have known amounts of solute and solvent in a given quantity of solution.
• Normal saline solution: 0.85 NaCl.
• Dilute or Weak solutions are of relatively low concentration and are light in color.
• Concentrated or Strong solutions are of relatively high concentration and are darker in color.
• States whether the concentration is high or low, but we don’t know how much solute is present in the solution.
• Molarity (M) is moles solute/liter solution.
• Reducing the concentration of a solution results in the total number of solutes in the solution remaining the same, but the volume of the solution becomes greater, resulting in a lower molarity, ppm, mg/L, or % concentration.
• Dimensionless quantities are pure numbers with no associated units of measurement.
• The expression “1 ppm” means a given property exists at a relative proportion of one part per million parts examined, as would occur if a water-borne pollutant was present at a concentration one-millionth of a gram per gram of sample solution.
• Parts per notation is often used in the measurement of dilutions (concentrations) for instance, for measuring the relative abundance of dissolved minerals or pollutants in water.
• One part per trillion (1ppt) is a proportion equivalent to one drop of water diluted into twenty Olympic-sized swimming pools.
• Molality (m) is moles solute/kg solvent.
• Normality (N) is equivalent weight solute/liter solution.
• Mole Fraction (xA) is moles solute/total moles solution.
• Determining mole fraction involves solving a linear equation.
• Mole fractions are dimensionless quantities.
• The final answer in mole fraction calculations is dimensionless.
• The definition of a gram equivalent varies depending on the type of chemical reaction that is discussed and can refer to acids, bases, redox species, and ions that will precipitate.
• Not all solvents are water (e.g., ethanol), and the final answer is m = 0.2 mole fraction (X).
• Normality is the only concentration unit that is reaction dependent (whether acids, bases, redox species, and ions).
• Mole percentage or molar percentage, denoted “mol %”, is equal to 100% times the mole fraction and is sometimes quoted instead of the mole fraction.
• Normality (N) is the equivalent weight solute per liter of solution.
• Molar fraction is the proportion of the total number of moles in a solution.
• In normality calculations, one equivalent (or equivalent weight) of a substance is the amount of that substance which supplies or consumes one mole of reactive species.
• Molarity (in units of mol/L, molar, or M) is also referred to as molar concentration.
• Molarity denotes the number of moles of a given substance per liter of solution.
• A capital letter M is used to abbreviate the units of mol/L.
• A 40% v/v ethanol solution contains 40mL ethanol per 100mL total volume.
• Parts-per notation is a quantity-per-quantity notation.
• Volume-volume percentage, sometimes referred to as percent volume per volume, 𝑣𝑣, describes the volume of the solute in mL per 100mL of the resulting solution.
• Mass-volume percentage is often used for solutions made from a solid solute dissolved in a liquid.
• Parts per notation is used especially to denote relative proportions in measured quantities, particularly in low-value (high-ratio) proportions at the part-per-million (ppm), part-per-billion (ppb), and parts-per-trillion (ppt) level.
• A 40% w/v sugar solution contains 40 g of sugar per 100 mL of resulting solution.
• This is the most useful when a liquid-liquid solution is being prepared, although it is used for mixtures of gases as well.