RelativeResourceManager(9) - 2. Normality Calculate the pH...

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9 of 17 Logarithms to the base 10 are called common logarithms, and the symbol "log" is then used without indicating the base. Another base for logarithms that is widely used is the Napier or natural base, e = 2.71828. Natural logarithms are indicated by the symbol "ln". Since logarithms are exponents, the rules for multiplication using logarithms are: - logx = log x 1 log (xy) = log x + log y log(x/y) = log x - log y log 10 0 = log 1 = 0 log(x n ) = nlog x C. Examples It is possible to calculate the pH from the concentration of a compound. It is important to note whether the concentration is in molarity or normality. This becomes important whenever there is more than one hydroxide anion per mole. 1. Molarity ; Calculate the pH of 0.0003 M Ca(OH) 2 [OH] = ) Ca(OH mole 1 OH 2 L 1 moles .0003 2 (there are 2 OH - anions per mole of Ca(OH) 2 ) [OH] = 0.0006 or 6 x 10 -4 M - log of 6 x 10 -4 = - log 6 + (-log 10 -4 ) = -0.778 + 4 pOH = 3.22 pH = 14 - pOH = 10.78
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Unformatted text preview: 2. Normality Calculate the pH of 0.0003 N Ca(OH) 2 Remember, normality describes the moles of change per liter of solution, not the moles of a particular compound or ion. [OH] = 0.0003 N = 0.0003 M = 3 x 10-4 M (there are two moles of hydroxide anions per mole of Ca(OH) 2 but only one per mole of charge, or equivalent). - log of 3 x 10-4 = - log 3 + - (log 10-4 ) = -0.477+ 4 = 3.52 pOH = 3.52 pH = 14- pOH = 10.48 IV. ACID-BASE REACTIONS (NEUTRALIZATION) The formation of a salt by the addition of an acid to a base is called neutralization. In a neutralization reaction, we are primarily interested in determining the amount of an acid or base that is present. This is accomplished by adding known amounts of a base or an acid to the solution until an endpoint is reached. This process is called titration. When the endpoint is reached, the following relationship exists:...
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