Chemistry: Hexamminenickel(II) Synthesis
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Questions and Answers

What is the final observable color change when the titration of sodium thiosulfate is complete?

  • Purple
  • Colorless (correct)
  • Dark blue
  • Yellow

    • How much copper sulfate solution is pipetted into the conical flask for the titration?

  • 5 mL
  • 15 mL
  • 10 mL (correct)
  • 20 mL

    • What role does starch indicator play during the titration process?

  • It indicates the presence of iodine. (correct)
  • It makes the solution yellow.
  • It stops the reaction.
  • It adds volume to the solution.

    • What is the molarity of the sodium thiosulfate solution calculated from the titration data?

    <p>0.0053 M</p> Signup and view all the answers

    Why is it important to wait for 20 seconds after stirring the flask during the titration?

    <p>To ensure accurate color measurement.</p> Signup and view all the answers

    What property of nickel solutions is measured during the estimation process?

    <p>Absorbance</p> Signup and view all the answers

    Which indicator is used in complexometric titration with EDTA for nickel detection?

    <p>Murexide</p> Signup and view all the answers

    During the absorbance measurement, which concentration corresponds to an absorbance of 3.51?

    <p>0.06 M</p> Signup and view all the answers

    What is the desired endpoint appearance in the titration process?

    <p>Bluish violet color</p> Signup and view all the answers

    How is the pH adjusted during the preparation for complexometric titration?

    <p>By adding ammonia solution</p> Signup and view all the answers

    What should be done after obtaining the cursor from the first titration?

    <p>Record the total volume of EDTA used</p> Signup and view all the answers

    What measurement is used to calculate the nickel concentration in the unknown solution?

    <p>Absorbance at 395 nm</p> Signup and view all the answers

    What is the purpose of diluting the pipetted complex solution with distilled water?

    <p>To make it easier to measure absorbance</p> Signup and view all the answers

    What is the molarity of the iodate solution calculated from a burette reading of 2.5 mL?

    <p>$4.4 \times 10^{-6}$ M</p> Signup and view all the answers

    How much iodine (in grams) is present in 1 liter of the solution?

    <p>5.6 × 10^-3 grams</p> Signup and view all the answers

    What is the concentration of iodine in parts per million (ppm) in the salt sample?

    <p>28 ppm</p> Signup and view all the answers

    Which element was involved in identifying iodate anions in the salt sample?

    <p>Iodine</p> Signup and view all the answers

    Who invented the cyanotype blue printing process?

    <p>Sir John Herschel</p> Signup and view all the answers

    In the context of blue printing, what is reduced to ferrous ions?

    <p>Fe3+ ions</p> Signup and view all the answers

    What is the total mass of iodine present in 10 grams of salt based on the provided calculations?

    <p>0.28 mg</p> Signup and view all the answers

    What was the purpose of performing iodometric titration in this context?

    <p>To determine the concentration of iodate ions and iodine</p> Signup and view all the answers

    What color change indicates the successful formation of the hexamminenickel(II) complex?

    <p>Pale green to intense violet</p> Signup and view all the answers

    Which reagent is used to facilitate the formation of [NiII(NH3)6]Cl2?

    <p>Aqueous ammonia</p> Signup and view all the answers

    What is the purpose of filtering and washing the crystals with ammonia solution?

    <p>To remove impurities</p> Signup and view all the answers

    In the spectrochemical series, which ligand has a weaker field strength compared to ammonia?

    <p>Water (H2O)</p> Signup and view all the answers

    How is the crystal field splitting parameter (Δ) quantified?

    <p>Using spectroscopic methods</p> Signup and view all the answers

    According to the Beer-Lambert Law, what does the variable 'A' represent?

    <p>Absorbance</p> Signup and view all the answers

    Which of the following bands corresponds to the highest energy absorption for [Ni(NH3)6]2+?

    <p>Band 1 at 28200 cm-1</p> Signup and view all the answers

    What method is primarily used to determine the yield of the hexamminenickel(II) complex?

    <p>Weighing the dried crystals</p> Signup and view all the answers

    What is the primary difference between Turnbull's Blue and Prussian Blue?

    <p>The positions of ferrous and ferric ions in the cyanide lattice are reversed.</p> Signup and view all the answers

    What application has Prussian Blue recently gained in technology?

    <p>Electrodes in sodium-ion batteries.</p> Signup and view all the answers

    Which of the following steps is NOT part of the experimental protocol for sensitizing paper?

    <p>Immersing the paper in the sensitizing solution for 10-15 minutes.</p> Signup and view all the answers

    What compound is formed immediately after Turnbull's Blue forms?

    <p>Prussian Blue.</p> Signup and view all the answers

    What is the primary structural characteristic of the [Fe(CN)6]4- anion in Prussian Blue?

    <p>It possesses an octahedral shape.</p> Signup and view all the answers

    Why is it essential to immerse the sensitizing paper all at once in ferric cyanide?

    <p>To avoid lines appearing on the blue field of the paper.</p> Signup and view all the answers

    What is the historical origin of the name 'Prussian Blue'?

    <p>From its application in Prussian army uniform coats.</p> Signup and view all the answers

    What is the chemical formula for Prussian Blue?

    <p>Fe4[Fe(CN)6]3.15 H2O.</p> Signup and view all the answers

    Study Notes

    Synthesis of Hexamminenickel(II) chloride

    • Reaction:
      • [NiII(OH2)6]Cl2 + 6 NH3 → [Ni(NH3)6]Cl2 + 6 H2O
    • Procedure:
      • Combine 10 mL of [NiII(OH2)6]Cl2 solution (contains 6 g of NiCl2) with 15 mL of aqueous ammonia in a 250 mL beaker.
      • Add the ammonia solution dropwise to the nickel chloride solution while stirring until the solution changes color from pale green to intense violet.
      • Allow the solution to stand at room temperature for 5 minutes, cover with a watch glass and then cool in an ice bath for 15 minutes.
      • Filter the solution and wash the resulting crystals with 3-5 mL of ammonia solution.
      • Dry the crystals using filter paper and weigh them to calculate the yield.

    Spectrochemical Series

    • The Spectrochemical Series orders ligands based on their increasing ability to split d-orbitals.
    • The splitting is determined experimentally through the crystal field splitting parameter (Δ).
    • Weak Field: I-  Br- S2- SCN- Cl- NO3- F-  C2O42- H2O NCS- CH3CN  NH3 en  bipy phen NO2- PPh3 CN- CO Strong Field
    • Example of ligands:
      • H2O < NH3 < en (Ethylenediamine)

    Spectrophotometric Analysis of Ni Complexes

    • The complex’s color is related to its measured wavelength of maximum absorbance (λmax)
    • Example:
      • [Ni(OH2)6]2+ : λmax (Band 1) = 25300 cm-1; λmax (Band 2) = 13800 cm-1
      • [Ni(NH3)6]2+ : λmax (Band 1) = 28200 cm-1; λmax (Band 2) = 17500 cm-1
      • [Ni(en)3]2+ : λmax (Band 1) = 29000 cm-1; λmax (Band 2) = 18650 cm-1

    Beer–Lambert Law

    • Relates absorbance (A) to concentration (C), path length (l), and molar absorptivity (ε):
      • A = εCl
    • Use in quantitative analysis:
      • The absorbance and concentration of a solution are directly proportional.
      • Higher concentrations lead to higher absorbance values.

    Spectrophotometric Estimation of Nickel (II) Complex

    • Procedure:
      • Measure the absorbance of solutions of known NiCl2 concentration and an unknown solution at 395 nm using a UV-Vis spectrophotometer.
      • Plot absorbance against mg/mL of nickel to create a standard curve.
      • Use the standard curve to determine the concentration of the unknown solution.

    Complexometric Titration with EDTA

    • Reaction:
      • Ni2+ + EDTA4- [Ni(EDTA)]2-
    • Indicator:
      • Murexide indicator: Yellow-green (Ni2+) to violet ([Ni(EDTA)]2-)
    • Procedure:
      • Titrate a known volume of the nickel complex solution with a standard EDTA solution.
      • Add murexide indicator and adjust pH to 7 with ammonia solution.
      • Titrate until a bluish violet endpoint is reached.
      • From the EDTA volume used, determine the amount of Ni present in the complex.

    Standardization of Sodium Thiosulfate

    • Reaction:
      • 2 Cu2+ + 4 I- Cu2I2 + I2
      • I2 + 2 S2O32- S4O62- + 2 I-
      • Net: 2 Cu2+ + 2 I- + 2 S2O32- Cu2I2 + S4O62-
    • Procedure:
      • Titrate a known volume of copper sulfate solution with sodium thiosulfate.
      • Add potassium iodide (KI) for a yellow solution and then starch indicator for a purple color.
      • Continue titration until the purple color dissipates, then add potassium thiocyanate (KSCN) and titrate again until colorless.
      • From the volume of sodium thiosulfate used, calculate its molarity.

    Estimation of Iodine

    • Reaction:
      • IO3- + 6S2O32- + 6H+ 3S4O62- + I- + 3H2O
    • Procedure:
      • Titrate a known volume of iodate solution with standardized sodium thiosulfate.
      • Use the sodium thiosulfate molarity and titration volume to calculate the iodate concentration.
      • Convert the iodate concentration to iodine concentration (ppm).

    Cyanotype Blue Printing

    • The process involves the reduction of ferric (Fe3+) ions to ferrous (Fe2+) ions by light, followed by the reaction of ferrous ions with potassium ferricyanide to form Turnbull's Blue, which subsequently converts to Prussian Blue.
    • This method was commonly used in engineering and architecture for creating blueprints of drawings.
    • Prussian Blue is a blue pigment used in various applications, including battery electrodes.

    Experimental Protocol: Cyanotype Blue Printing

    • Prepare sensitized paper by immersing it in a solution containing ferric ions, such as ammonium ferric citrate or ammonium ferric oxalate, and drying it.
    • Expose the dried sensitized paper to light for 4-6 minutes, ensuring a sharp image.
    • Develop the image:
      • Dip the exposed paper in 0.1 M ferric cyanide solution to initiate the reaction to form Turnbull’s Blue.
      • Wash the paper with 0.1 M HCl and deionized water for a clean cyanotype print.
      • After development, dry the paper.

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    Description

    This quiz covers the synthesis of hexamminenickel(II) chloride and its associated procedures. It also delves into the concepts of the Spectrochemical Series and how ligands affect d-orbital splitting. Test your knowledge of chemical reactions and coordination complexes.

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