1. A sample of potassium hydrogen phthalate (KHC8H4O4), which is an acid, with a

Question

1. A sample of potassium hydrogen phthalate (KHC8H4O4), which is an acid, with a mass of 0.8356 g is dissolved in water and used to standardize a solution of strontium hydroxide. An endpoint is reached when 34.22 mL of strontium hydroxide has been added. Determine the molarity (in mol/L) of the strontium hydroxide solution. Report your answer to four significant figures.

2. The standardized strontium hydroxide solution is then used to titrate 24.28 mL of a solution of chlorous acid (HClO2). An endpoint is reached when 21.23 mL of strontium hydroxide has been added. Determine the molarity (in mol/L) of the chlorous acid solution. Report your answer to four significant figures.

Explanation / Answer

KHP + SrOH = KSrP + H2O

mol of KHP = mass/MW = 0.8356/204.22 = 0.0040916 mol of KHP

if V= 34.22 ml of SrOH are needed then

M = mol/V = 0.0040916/(34.22 /1000) = 0.11956 M of SrOH are present

2)

if then we use

V = 24.28 ml of HClO2

find new molarity M of HClO

V = 21.23 ml of SrOH used

MV = 21.23*0.11956 = 2.5382 mmol of SrOH

then we have 2.5382 mmol of HClO2

then:

M = mmol/V = 2.5382/24.28 = 0.1045 M of HClO2

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