Friday, September 27, 2013

Calculate pH of 100 ml solution containing 0.012 g sodium hydroxide (NaOH).

General information:
NaOH is a strong base that accepts a proton from water to produce sodium (Na+) and hydroxyl (OH-) ions in solution. The following equation can be used to accurately calculate pH of a strong base solution with concentrations above 10-5 M:

pH = 14 + log [OH-]

Molecular weight (molar mass) of NaOH = 40.00 g/ mole

Calculations:
Number of moles of NaOH in solution =  0.012 g ÷ 40.00 (g/ mole) = 0.0003 mole
Volume of NaOH solution in liters = 100 ml × 0.001 (liter/ ml) = 0.1 liter

Molar concentration of NaOH solution = 0.0003 mole ÷ 0.1 liter = 0.003 mole/ liter
pH = 14 + log (0.003) = 14 - 2.52 = 11.48

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Online pH calculator
pH of strong base
pH of strong acid

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