1 Solutions of cyanide salts are still widely used in the extraction of gold metal from its ores. It is therefore necessary to regularly monitor the quality of the reagents used to make such solutions. The purity of a sample of solid potassium cyanide is determined as follows: 5.00 g of the impure potassium cyanide is weighed off, and quantitatively transferred into a 100.00 mL volumetric flask, dissolved and made up to the mark. A 10.00 mL portion of this solution is pipetted into a conical flask, and titrated with a 0.200 M KMNO4 solution. The endpoint of the titration is determined when the colourless solution in the conical flask turns a bright pink due to the presence of excess permanganate ions. • The average titration value is 20.69 mL of the KMNO4 solution. The reaction stoichiometry is as follows: 2KMN04(aq) + 3KCN(aq) + H20(P) → 2MnO2(s) + 3KOCN(aq) + 2K0H(aq) 1.1 Determine the percentage purity of the potassium cyanide. Naturally occurring manganese consists of only the 55Mn isotope. Determine the moles of the precipitate formed, and then calculate the total number of neutrons present in all the manganese ions in the precipitate. 1.2

1 Solutions of cyanide salts are still widely used in the extraction of gold metal from its ores. It is therefore necessary to regularly monitor the quality of the reagents used to make such solutions. The purity of a sample of solid potassium cyanide is determined as follows: 5.00 g of the impure potassium cyanide is weighed off, and quantitatively transferred into a 100.00 mL volumetric flask, dissolved and made up to the mark. A 10.00 mL portion of this solution is pipetted into a conical flask, and titrated with a 0.200 M KMNO4 solution. The endpoint of the titration is determined when the colourless solution in the conical flask turns a bright pink due to the presence of excess permanganate ions. • The average titration value is 20.69 mL of the KMNO4 solution. The reaction stoichiometry is as follows: 2KMN04(aq) + 3KCN(aq) + H20(P) → 2MnO2(s) + 3KOCN(aq) + 2K0H(aq) 1.1 Determine the percentage purity of the potassium cyanide. Naturally occurring manganese consists of only the 55Mn isotope. Determine the moles of the precipitate formed, and then calculate the total number of neutrons present in all the manganese ions in the precipitate. 1.2

Chemistry for Engineering Students

4th Edition

ISBN:9781337398909

Author:Lawrence S. Brown, Tom Holme

Publisher:Lawrence S. Brown, Tom Holme

Chapter4: Stoichiometry

Section: Chapter Questions

Problem 4.98PAE

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Without consulting your textbook, list and explain the main postulates of the kinetic molecular theory for gases. How do these postulates help us account for the following bulk properties of a gas: the pressure of the gas and why the pressure of the gas increases with increased temperature; the fact that a gas tills its entire container; and the fact that the volume of a given sample of gas increases as its temperature is increased.
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