1. A sample of potassium hydrogen phthalate (KHC 8 H 4 O 4 ), which is an acid,

Question

1. A sample of potassium hydrogen phthalate (KHC8H4O4), which is an acid, with a mass of 0.1728 g is dissolved in water and used to standardize a solution of strontium hydroxide. An endpoint is reached when 25.03 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 27.03 mL of a solution of acetic acid (CH3COOH). An endpoint is reached when 28.62 mL of strontium hydroxide has been added. Determine the molarity (in mol/L) of the acetic acid solution. Report your answer to four significant figures.

Explanation / Answer

1)

KHP

MW = 204.22

mol = mass/MW = 0.1728/204.22 = 0.00084614 mol of KHP

SrOH + KHP = H2O + SrKP

mol of acid = 0.00084614

then mol of acid = mol of base = 0.00084614

mol of base = M*V = 25.03*M

0.00084614 = 25.03/1000 * M

M = (0.00084614 *1000)/(25.03) = 0.03380503395 M of SrOH

2)

V = 28.62 ml of SrOH

M = 0.03380503395

V = 27.03 acid

M = ?

M1*V1 = M2*V2

0.03380503395 * 28.62 = 27.03 * M

M = 0.03380503395 * 28.62 /27.03 = 0.035793 M of HAc

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