3.2 Day 2 Procedure

Last updated
Save as PDF

Page ID: 212057

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

Day 2 - Synthesis of \([Co(NH_3)_5Cl]Cl_2\)

Partners should combine their products in order to perform the second synthesis.

In a 100 mL Erlenmeyer on a stir/hot plate dissolve 2 g of \([Co(NH_3)_4(CO_3)]NO_3\) in 15 mL of water and add ~3 mL of concentrated HCl dropwise until no more CO2 is expelled. Neutralize with concentrated aqueous ammonia (use pH paper to indicate neutrality – to avoid contamination of the cobalt solution, use a glass stir rod to transfer a drop of solution to the paper), and then add 2 mL of concentrated aqueous ammonia. Heat at 75-85°C for 20 minutes.

Cool the solution to about 50°C. Add 20 mL of concentrated \(HCl\) slowly while gently swirling the mixture. Reheat the mixture for 20 to 30 minutes to 75-85°C; observe the color change. Cool the solution to 5 °C in an ice bath. Collect the fine purple-red crystals of \([Co(NH3)5Cl]Cl2\) by filtration using a medium glass frit and wash twice with 3 mL of ice-cold distilled water, filtering each time. Wash twice with 3 mL of ethanol and filter. Dry in an oven at 100-120°C for one hour, cool, weigh, and calculate the percent yield. Transfer your product to a vial and return the glass frit to the Stockroom. Typical yields vary between 50 and 75%.

Obtain an IR spectrum of the product and compare it with the spectra obtained above.

Question: Where are the IR absorptions for bound ammonia?