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Potassium ion in a 250.0 (±0.1) mL water sample was precipitated with sodium tetraphenylborate:

K++(C6H5)4B-→KB(C6H5)4(s)

The precipitate was filtered, washed, dissolved in an organic solvent, and treated with excess Hg (EDTA)2-:

4HgY2-+(C6H5)4B-+4H2O→H3BO3+4C6H5Hg++4HY3-+OH-

The liberated EDTA was titrated with 28.73 (±0.03) mL of 0.043 7 (±0.000 1) M Zn2+. Find [K+] (and its absolute uncertainty) in the original sample.

Short Answer

Expert verified

The amount of K+ in the original sample will be 1.256(±0.003) mM

Step by step solution

01

Given information

Amount of water sample = 250 mL

For each mole of K+ involved in the first reaction , 4 moles of EDTA generated in the second reaction .

Amount of Zn2+ used for EDTA titration=28.73 (±0.03) mL of 0.043 7 (±0.000 1) M

02

EDTA

EDTA also known as Ethylenediaminetetraacetic acid is one type of chelating agent used in different industries, medications and laboratory applications. It is generally used to treat heavy metal toxicity, lead poisoning, coronary artery disease, neurotoxicity etc.

03

Determine K+

K+=14molesofZn2+Volumeofsample=1428.73±0.03mL0.0437±0.0001M250±0.1=14±0%28.73±0.104%0.0437±0.229%250±0.040%=1.256±0.265×10-3M=1.256±0.003mM

Therefore, the amount of K+ in the original sample will be 1.256(±0.003) mM.

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Most popular questions from this chapter

Sulfide ion was determined by indirect titration with EDTA. To a solution containing 25.00 mL of 0.04332 M Cu(ClO4)2 plus 15 mL of 1 M acetate buffer (pH 4.5) were added 25.00 mL of unknown sulfide solution with vigorous stirring. The CuS precipitate was filtered and washed with hot water. Ammonia was added to the filtrate (which contained excess Cu2+) until the blue color of Cu(NH3)42+ was observed. Titration of the filtrate with 0.039 27 M EDTA required 12.11 mL to reach the murexide end point. Calculate the molarity of sulfide in the unknown.

According to Appendix I, Cu2+ forms two complexes with acetate:

Cu2++CH3CO2−⇌Cu(CH3CO2)+ â¶Ä‰â¶Ä‰â¶Ä‰â¶Ä‰â¶Ä‰â¶Ä‰Î²1(=K1)Cu2++2CH3CO2−⇌Cu(CH3CO2)2 â¶Ä‰â¶Ä‰â¶Ä‰â¶Ä‰â¶Ä‰â¶Ä‰Î²2

(a) Referring to Box 6-2, find K2 for the reaction

Cu(CH3CO2)++CH3CO2−⇌Cu(CH3CO2)2(aq) â¶Ä‰â¶Ä‰K2

(b) Consider 1.00 L of solution prepared by mixing 1.00 × 10-4 mol Cu(ClO4)2 and 0.100 mol CH3CO2Na. Use Equation 12-16 to find the fraction of copper in the form Cu2+


Consider the titration of 25.0 mL of 0.020 0 M MnSO4 with 0.010 0 M EDTA in a solution buffered to pH 8.00. Calculate pMn2+ at the following volumes of added EDTA and sketch the titration curve:

(a) 0 mL (b) 20.0 mL (c) 40.0 mL (d) 49.0 mL (e) 49.9 mL (f) 50.0 mL (g) 50.1 mL

(h) 55.0 mL (i) 60.0 mL

Consider the titration of 25.0 mL of 0.020 0 M MnSO4 with 0.010 0 M EDTA in a solution buffered to pH 8.00. Calculate pMn2+ at the following volumes of added EDTA and sketch the titration curve:

(a) 0 mL (b) 20.0 mL (c) 40.0 mL (d) 49.0 mL (e) 49.9 mL (f) 50.0 mL (g) 50.1 mL

(h) 55.0 mL (i) 60.0 mL

A 50.0-mL sample containing Ni2+ was treated with 25.0 mL of 0.050 0 M EDTA to complex all the Ni2+ and leave excess EDTA in solution. The excess EDTA was then back-titrated, requiring 5.00 mL of 0.050 0 M Zn2+. What was the concentration of Ni2+ in the original solution?

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