Calcium fluorapatite (Cap(PO),F2, FM 1008.6) laser crystals were doped with chromium to improve their efficiency. It was suspected that the chromium could be in the +4 oxidation state.² 1. To measure the total oxidizing power of chromium in the material, a crystal was dissolved in 2.9 M HCIO, at 100 °C, cooled to 20 °C, and titrated with standard Fe2+, using Pt and Ag|AgCl electrodes to find the end point. Chromium above the +3 state should oxidize an equivalent amount of Fe² + in this step. That is, Cr4 + would consume one Fe² + and Cº + in Cr₂0 would consume three Fe2+ Cr++ Fe² + →→→→ Cr³ + + Fe³ + Cr₂0²+3 Fe²+ +3 Fe²+C++. →→→→→ Cr³ + + 3 Fe³ + 2. In a second step, the total chromium content was measured by dissolving a crystal in 2.9 M HCIO, at 100 °C and cooling to 20 °C. Excess S,Oand Ag were then added to oxidize all chromium to Cr₂0. Unreacted $,0 was destroyed by boiling, and the remaining solution was titrated with standard Fe² +. In this step, each Cr in the original unknown reacts with three Fe² + 5,0% C C₁₂O Cr₂0% +3 Fe²+Cr³++ 3 Fe³ + + In step 1, 0.4313 g of laser crystal required 0.495 ml. of 2.765 mM Fe (prepared by dissolving Fe(NH),(SO) 6H,0 in 2 M HCIO). In step 2, 0.1536 g of crystal required 0.695 ml. of the same Fe2+solution. Find the average oxidation number of Cr in the crystal and find the total micrograms of Cr per gram of crystal. Hg Cr g of crystal average oxidation number:
Calcium fluorapatite (Cap(PO),F2, FM 1008.6) laser crystals were doped with chromium to improve their efficiency. It was suspected that the chromium could be in the +4 oxidation state.² 1. To measure the total oxidizing power of chromium in the material, a crystal was dissolved in 2.9 M HCIO, at 100 °C, cooled to 20 °C, and titrated with standard Fe2+, using Pt and Ag|AgCl electrodes to find the end point. Chromium above the +3 state should oxidize an equivalent amount of Fe² + in this step. That is, Cr4 + would consume one Fe² + and Cº + in Cr₂0 would consume three Fe2+ Cr++ Fe² + →→→→ Cr³ + + Fe³ + Cr₂0²+3 Fe²+ +3 Fe²+C++. →→→→→ Cr³ + + 3 Fe³ + 2. In a second step, the total chromium content was measured by dissolving a crystal in 2.9 M HCIO, at 100 °C and cooling to 20 °C. Excess S,Oand Ag were then added to oxidize all chromium to Cr₂0. Unreacted $,0 was destroyed by boiling, and the remaining solution was titrated with standard Fe² +. In this step, each Cr in the original unknown reacts with three Fe² + 5,0% C C₁₂O Cr₂0% +3 Fe²+Cr³++ 3 Fe³ + + In step 1, 0.4313 g of laser crystal required 0.495 ml. of 2.765 mM Fe (prepared by dissolving Fe(NH),(SO) 6H,0 in 2 M HCIO). In step 2, 0.1536 g of crystal required 0.695 ml. of the same Fe2+solution. Find the average oxidation number of Cr in the crystal and find the total micrograms of Cr per gram of crystal. Hg Cr g of crystal average oxidation number:
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Transcribed Image Text:Calcium fluorapatite (Cap(PO),F2, FM 1008.6) laser crystals were doped with chromium to improve their efficiency. It was
suspected that the chromium could be in the +4 oxidation state.²
1. To measure the total oxidizing power of chromium in the material, a crystal was dissolved in 2.9 M HCIO, at 100 °C,
cooled to 20 °C, and titrated with standard Fe2+, using Pt and Ag|AgCl electrodes to find the end point. Chromium above
the +3 state should oxidize an equivalent amount of Fe² + in this step. That is, Cr4 + would consume one Fe² + and Cº +
in Cr₂0 would consume three Fe2+
Cr++ Fe² + →→→→ Cr³ + + Fe³ +
Cr₂0²+3 Fe²+
+3 Fe²+C++.
→→→→→ Cr³ + + 3 Fe³ +
2. In a second step, the total chromium content was measured by dissolving a crystal in 2.9 M HCIO, at 100 °C and cooling
to 20 °C. Excess S,Oand Ag were then added to oxidize all chromium to Cr₂0. Unreacted $,0 was destroyed
by boiling, and the remaining solution was titrated with standard Fe² +. In this step, each Cr in the original unknown reacts
with three Fe² +
5,0%
C
C₁₂O
Cr₂0% +3 Fe²+Cr³++ 3 Fe³ +
+
In step 1, 0.4313 g of laser crystal required 0.495 ml. of 2.765 mM Fe (prepared by dissolving Fe(NH),(SO) 6H,0 in
2 M HCIO). In step 2, 0.1536 g of crystal required 0.695 ml. of the same Fe2+solution. Find the average oxidation number of
Cr in the crystal and find the total micrograms of Cr per gram of crystal.
Hg Cr
g of crystal
average oxidation number:
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