HT 05: Laboratory Mathematics

Laboratory Mathematics

424562019	percentage solutions	The percentage of concentrations may be expressed as W/V or V/V (W/W is not used). When diluting liquids, the required volume of the stock solution is diluted to 100 mL with the appropriate solvent. If the solute is a solid, the volume occupied by the solid (i.e. displacement) must be taken into consideration. 10% = 0.1 = 10/100 = 1/10 = 1:10 Part = Base X Rate Vc X Cc = Vd X Cd
424562020	gravimetric factor	A method of compensating for variances in the actual dye concentration of dry dye powder in preparing staining solutions. To use the gravimetric factor, multiply the factor by the amount of present dye required to prepare the staining solution. The answer is the amount needed of the new dye powder. gravimetric factor = Concentration of present dye / concentration of new dye.
424562021	hydrates	Frequently a hydrate other than the one specified can be used if the appropriate correction is made in the amount weighed. Would need to use more of the hydrate (compared to the anhydrous compound), because some of this weight is water. To use the hydrate factor, multiply the factor by the amount of anhydrous compound required to prepare the staining solution. The answer is the amount needed of the hydrate. hydrate factor = formula weight of hydrate / formula weight of anhydrous compound
424562022	molarity	A 1M solution contains 1 mole of a substance dissolved in enough water to give a final volume of 1 liter. A solution of concentration 1 mol/L is also denoted as "1 molar" (1 M). Weight in grams = molarity X Volume in liters X molecular weight
424562023	normality	The normality of a solution is defined as the molarity divided by an equivalence factor (the number of dissociable hydrogen ions). In many instances, the molarity and the normality are the same, as with HCl or NaOH; however in other instances they differ. For example, sulfuric acid has a normality equal to twice the molarity because it has 2 dissociable hydrogen ions. Weight in grams = normality X volume in liters X molecular weight / positive valence or number of dissociable hydrogen ions
424610024	metric prefixes	kilo (k) thousand 10(3) deci (d) tenth 10(-1) centi (c) hundredth 10(-2) milli (m) thousandth 10(-3) micro (µ) millionth 10(-6) nano (n) billionth 10(-9)
424610025	unit equivalents	1 pound = 454 g 1 inch = 2.54 cm 1 L = 1.06 qt
424610026	temperature conversion	9C + 160 = 5F