How many grams of O2 is consumed during this synthesis? What is the source of th

Question

How many grams of O2 is consumed during this synthesis? What is the source of this O2?
PROCEDURE: Synthesis of Werner Complexes • For this lab you will be working in groups of 2. Please take turns performing aspects of the synthesis. Perform the following steps in a fume hood. 1. Heat about 150 mL of water in a 250 mL beaker and maintain at a boil. 2. In an evaporating dish, combine 2.0g of Cobalt(II) Chloride Hexahydrate with 5.0 mL of distilled water. To this, add 7.5 mL of 10% (by volume) ethylenediamine (en). 2. Place the evaporating dish on top of the beaker of boiling water. Stir the mixture (using a small stir bar) over this steam bath for 40 minutes; maintain the volume of the solution at about 10mL by occasionally adding small portions of water. During this process, the Co2+ is oxidized to Co3+ by the oxygen in the air. Good agitation is necessary to promote solvation of the oxygen. 3. Add 6 mL of concentrated 12M HCl. Continue heating and stirring, without addition of water, until a thin slurry of crystals has formed. (Note: Stopping the evaporation at the right time is critical to the success of the synthesis. Stopping too soon will give a poor yield of the product; stopping too late will give an impure product.) Cool the slurry to Room Temperature by setting the evaporating dish on the lab bench. Stir occasionally for 15 minutes. 4. Filter the mixture using a Buchner funnel with Side-Arm Flask attached to an aspirator. When the draining from the Buchner funnel has essentially stopped, turn off the aspirator & add 2.5 mL of 6M HCl to the funnel and gently stir up the mixture with a spatula, taking care not to tear the filter paper. Continue to filter to remove any excess solution (Do not use Pure Water to wash your product. If you do, the complex will decompose.) If the product is still brown or blue, repeat the washing process with 6M HCl. If the product is pure green, skip the washing to avoid loss of product. 5. Transfer the moist crystals of the product to a clean watch glass. Dry the material on the steam bath. During the last stages of drying, powder the material on the watch glass by scrapping and pressing with a spatula. 6. Once the product is dry, weigh using a weigh boat. 7. Transfer the dried product to a previously weighed 3-dram vial. Label this vial with your Name(s), Product Name, Product Formula, Mass Product Obtained and the Date. Preparation of cis-[Co(en)2Cl2]Cl 1.) Make 5 ml (or 10 mL if that is the only volumetric flask available) of a 0.015 M aqueous solution of the trans isomer. 2.) Heat this green solution over a steam bath – it should turn violet. Cool the solution in ice and observe what happens; reheat the solution if necessary. Use this solution to collect a uv-vis absorbance spectrum. How many grams of O2 is consumed during this synthesis? What is the source of this O2?
PROCEDURE: Synthesis of Werner Complexes • For this lab you will be working in groups of 2. Please take turns performing aspects of the synthesis. Perform the following steps in a fume hood. 1. Heat about 150 mL of water in a 250 mL beaker and maintain at a boil. 2. In an evaporating dish, combine 2.0g of Cobalt(II) Chloride Hexahydrate with 5.0 mL of distilled water. To this, add 7.5 mL of 10% (by volume) ethylenediamine (en). 2. Place the evaporating dish on top of the beaker of boiling water. Stir the mixture (using a small stir bar) over this steam bath for 40 minutes; maintain the volume of the solution at about 10mL by occasionally adding small portions of water. During this process, the Co2+ is oxidized to Co3+ by the oxygen in the air. Good agitation is necessary to promote solvation of the oxygen. 3. Add 6 mL of concentrated 12M HCl. Continue heating and stirring, without addition of water, until a thin slurry of crystals has formed. (Note: Stopping the evaporation at the right time is critical to the success of the synthesis. Stopping too soon will give a poor yield of the product; stopping too late will give an impure product.) Cool the slurry to Room Temperature by setting the evaporating dish on the lab bench. Stir occasionally for 15 minutes. 4. Filter the mixture using a Buchner funnel with Side-Arm Flask attached to an aspirator. When the draining from the Buchner funnel has essentially stopped, turn off the aspirator & add 2.5 mL of 6M HCl to the funnel and gently stir up the mixture with a spatula, taking care not to tear the filter paper. Continue to filter to remove any excess solution (Do not use Pure Water to wash your product. If you do, the complex will decompose.) If the product is still brown or blue, repeat the washing process with 6M HCl. If the product is pure green, skip the washing to avoid loss of product. 5. Transfer the moist crystals of the product to a clean watch glass. Dry the material on the steam bath. During the last stages of drying, powder the material on the watch glass by scrapping and pressing with a spatula. 6. Once the product is dry, weigh using a weigh boat. 7. Transfer the dried product to a previously weighed 3-dram vial. Label this vial with your Name(s), Product Name, Product Formula, Mass Product Obtained and the Date. Preparation of cis-[Co(en)2Cl2]Cl 1.) Make 5 ml (or 10 mL if that is the only volumetric flask available) of a 0.015 M aqueous solution of the trans isomer. 2.) Heat this green solution over a steam bath – it should turn violet. Cool the solution in ice and observe what happens; reheat the solution if necessary. Use this solution to collect a uv-vis absorbance spectrum.
PROCEDURE: Synthesis of Werner Complexes • For this lab you will be working in groups of 2. Please take turns performing aspects of the synthesis. Perform the following steps in a fume hood. 1. Heat about 150 mL of water in a 250 mL beaker and maintain at a boil. 2. In an evaporating dish, combine 2.0g of Cobalt(II) Chloride Hexahydrate with 5.0 mL of distilled water. To this, add 7.5 mL of 10% (by volume) ethylenediamine (en). 2. Place the evaporating dish on top of the beaker of boiling water. Stir the mixture (using a small stir bar) over this steam bath for 40 minutes; maintain the volume of the solution at about 10mL by occasionally adding small portions of water. During this process, the Co2+ is oxidized to Co3+ by the oxygen in the air. Good agitation is necessary to promote solvation of the oxygen. 3. Add 6 mL of concentrated 12M HCl. Continue heating and stirring, without addition of water, until a thin slurry of crystals has formed. (Note: Stopping the evaporation at the right time is critical to the success of the synthesis. Stopping too soon will give a poor yield of the product; stopping too late will give an impure product.) Cool the slurry to Room Temperature by setting the evaporating dish on the lab bench. Stir occasionally for 15 minutes. 4. Filter the mixture using a Buchner funnel with Side-Arm Flask attached to an aspirator. When the draining from the Buchner funnel has essentially stopped, turn off the aspirator & add 2.5 mL of 6M HCl to the funnel and gently stir up the mixture with a spatula, taking care not to tear the filter paper. Continue to filter to remove any excess solution (Do not use Pure Water to wash your product. If you do, the complex will decompose.) If the product is still brown or blue, repeat the washing process with 6M HCl. If the product is pure green, skip the washing to avoid loss of product. 5. Transfer the moist crystals of the product to a clean watch glass. Dry the material on the steam bath. During the last stages of drying, powder the material on the watch glass by scrapping and pressing with a spatula. 6. Once the product is dry, weigh using a weigh boat. 7. Transfer the dried product to a previously weighed 3-dram vial. Label this vial with your Name(s), Product Name, Product Formula, Mass Product Obtained and the Date. Preparation of cis-[Co(en)2Cl2]Cl 1.) Make 5 ml (or 10 mL if that is the only volumetric flask available) of a 0.015 M aqueous solution of the trans isomer. 2.) Heat this green solution over a steam bath – it should turn violet. Cool the solution in ice and observe what happens; reheat the solution if necessary. Use this solution to collect a uv-vis absorbance spectrum. PROCEDURE: Synthesis of Werner Complexes • For this lab you will be working in groups of 2. Please take turns performing aspects of the synthesis. Perform the following steps in a fume hood. 1. Heat about 150 mL of water in a 250 mL beaker and maintain at a boil. 2. In an evaporating dish, combine 2.0g of Cobalt(II) Chloride Hexahydrate with 5.0 mL of distilled water. To this, add 7.5 mL of 10% (by volume) ethylenediamine (en). 2. Place the evaporating dish on top of the beaker of boiling water. Stir the mixture (using a small stir bar) over this steam bath for 40 minutes; maintain the volume of the solution at about 10mL by occasionally adding small portions of water. During this process, the Co2+ is oxidized to Co3+ by the oxygen in the air. Good agitation is necessary to promote solvation of the oxygen. 3. Add 6 mL of concentrated 12M HCl. Continue heating and stirring, without addition of water, until a thin slurry of crystals has formed. (Note: Stopping the evaporation at the right time is critical to the success of the synthesis. Stopping too soon will give a poor yield of the product; stopping too late will give an impure product.) Cool the slurry to Room Temperature by setting the evaporating dish on the lab bench. Stir occasionally for 15 minutes. 4. Filter the mixture using a Buchner funnel with Side-Arm Flask attached to an aspirator. When the draining from the Buchner funnel has essentially stopped, turn off the aspirator & add 2.5 mL of 6M HCl to the funnel and gently stir up the mixture with a spatula, taking care not to tear the filter paper. Continue to filter to remove any excess solution (Do not use Pure Water to wash your product. If you do, the complex will decompose.) If the product is still brown or blue, repeat the washing process with 6M HCl. If the product is pure green, skip the washing to avoid loss of product. 5. Transfer the moist crystals of the product to a clean watch glass. Dry the material on the steam bath. During the last stages of drying, powder the material on the watch glass by scrapping and pressing with a spatula. 6. Once the product is dry, weigh using a weigh boat. 7. Transfer the dried product to a previously weighed 3-dram vial. Label this vial with your Name(s), Product Name, Product Formula, Mass Product Obtained and the Date. Preparation of cis-[Co(en)2Cl2]Cl 1.) Make 5 ml (or 10 mL if that is the only volumetric flask available) of a 0.015 M aqueous solution of the trans isomer. 2.) Heat this green solution over a steam bath – it should turn violet. Cool the solution in ice and observe what happens; reheat the solution if necessary. Use this solution to collect a uv-vis absorbance spectrum.

Explanation / Answer

In the experiment,

Co2+(aq) --> Co3+(aq) + e-

The oxidation of Co from +2 state to +3 state occurs by O2 present in the atmosphere

The net balanced equation being,

4Co2+(aq) + O2(g) + 2H2O(l) --> 4Co3+(aq) + 4OH-(aq)

So,

4 Co2+ gets oxidized to 4 Co3+ by loosing 4 e-

These 4 e-'s are taken by the to O atoms in 0 oxidation state in O2 to form 2 OH- when combined with H2O.

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