Item 12 12 of 19 Constants IPeriodic Table Part A For each of the following sclu

Question

Item 12 12 of 19 Constants IPeriodic Table Part A For each of the following sclutions, calculate the initial pH and the final pH after adding 0.010 mol of NaOH For 270.0 mL of pure water, calculate the initial plH and the final plH after adding 0010 mol of NaOH Express your answers using two decimal places separated by a comma pHainal pHn Submit Request Answer Part B For 270.0 mL of a buffer solution that is 0.245 M in HCHO2 and 0.290 M in KCH0,, calculate the initial pH and the final pH after adding 0.010 mol of NaOH Express your answers using two decimal places separated by a comma. Submit Request Answer Part C

Explanation / Answer

Part A.

Pure water has a pH of perfect 7.0. Adding a base increases its pH by the relation pH + pOH = 14 giving pH from pOH as pH = 14 - pOH. pOH is given as the concentration of hydroxide ions in the medium in terms of molarity. So when 0.1mol of NaOH, a strong base is added, there is basically 0.1mol of hydroxide ions added to the medium. Assuming no change in volume as it is absent, the final volume of the solution is also taken as 270mL to calculate the concentration of hydroxide ions in the medium in terms of molarity. Molarity = Moles*(1000/Volume) = 0.1*(1000/270) = 0.3704M. Now pH is given as -log[OH-] which now gives -log(0.3704) = 0.4313. Now as mentioned earlier, pH is found as pH = 14 - pOH = 13.5686.

So pHinitial = 7.0 and pHfinal = 13.5686

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