Shanxian Chemical
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HydrogenPeroxideTitrationwithPotassiumPermanganateLabReport
Experimental report on potassium permanganate titration of hydrogen peroxide
1. Experimental purpose
Master the principle and method of determining hydrogen peroxide content by potassium permanganate method, and further proficiency in titration operation.
Second, experimental principle
Hydrogen peroxide is a widely used disinfectant in the medical and health industries. It can be quantitatively oxidized by $KMnO_ {4} $in acidic solution to generate oxygen and water. The reaction is as follows:
$2MnO_ {4} ^ {-} + 5H_ {2} O_ {2} + 6H ^ {+} = 2Mn ^ {2 + } + 5O_ {2}\ uparrow + 8H_ {2} O $
The reaction can proceed smoothly at room temperature. The reaction speed is slow at the beginning of titration, and it accelerates with the formation of $Mn ^ {2 +} $. $MnO_ {4} ^ {-} $itself is purple in the solution and can be used as an indicator. After the stoichiometry point, a slight excess of $MnO_ {4} ^ {-} $makes the solution appear pink and indicates the end point.
III. Experimental instruments and reagents
1. ** Instruments **: acid burette, pipette, volumetric flask, conical bottle, analytical balance, measuring cylinder, etc.
2. ** Reagents **: $KMnO_ {4} $standard solution ($0.02mol/L $), $H_ {2} SO_ {4} solution ($3mol/L $), $H_ {2} O_ {2} $sample.
IV. Experimental steps
1. ** $KMnO_ {4} $Calibration of standard solution **
- accurately weigh 0.15 dollars - 0.20g $reference material $Na_ {2} C_ {2} O_ {4} $in a $250mL $conical flask, add $30mL $distilled water and $15mL 3mol/L H_ {2} SO_ {4} $solution, cover the surface dish, heated to 75 dollars - 85 ^ {\ circ} C $on a water bath.
- Titration with $KMnO_ {4} $solution to be calibrated while hot. Start the titration slowly. After $Mn ^ {2 +} $is generated in the solution, the titration speed can be appropriately accelerated, but it must still be added dropwise. Titration until the solution is reddish and keeps $30s $without fading is the end point. Record the volume of the consumed $KMnO_ {4} $solution. Calibrate three times in parallel to calculate the exact concentration of the $KMnO_ {4} $standard solution.
2. ** Determination of hydrogen peroxide content **
- Pipette the $10.00mL H_ {2} O_ {2} $sample solution, place it in a $250mL $volumetric flask, dilute it to scale with water, and shake well.
- Pipette the above diluted $H_ {2} O_ {2} $solution $25.00mL $into a $250mL $conical flask, add $3mol/L H_ {2} SO_ {4} $solution $15mL $.
- Titrate with $KMnO_ {4} $standard solution until the solution is reddish and keeps $30s $fading is the end point. Record the volume of the solution consumed $KMnO_ {4} $. Parallel measurement three times, calculate the sample $H_ {2} O_ {2} $content.
5, experimental data recording and processing
1. ** $KMnO_ {4} $Calibration of standard solution **
| times | $m (Na_ {2} C_ {2} O_ {4})/g $| $V (KMnO_ {4})/mL $| $c (KMnO_ {4})/(mol/L )$ | $\ overline {c} (KMnO_ {4})/(mol/L) $| Relative mean deviation |
|---|---|---|---|---|---|
| 1 | | | | | |
| 2 | | | | | |
| 3 | | | | | |
$c (KMnO_ {4}) =\ frac {2m (Na_ {2} C_ {2} O_ {4}) } {5M (Na_ {2} C_ {2} O_ {4}) V (KMnO_ {4}) } $
where: $m (Na_ {2} {2} O_ {4}) $C_ mass of reference substance $Na_ {2} C_ {2} O_ {4} $, $g $; $M (Na_ {2} C_ {2} O_ {4}) $Na_ {2} | | | |< { 2} O_ {4} $molar mass, $134.00g/mol $; $V (KMnO_ {4}) $is the titration consumed $KMnO_ {4} $solution volume, $L $.
2. ** Determination of hydrogen peroxide content **
| times | $V_ {total} (H_ {2} O_ {2})/mL $| $V (H_ {2} O_ {2})/mL $| $V (KMnO_ {4})/mL $| $w (H_ {2} O_ {2 })/\%$ | $\ overline {w} (H_ {2} O_ {2 })/\%$ | relative mean deviation |
|---|---|---|---|---|---|---|
| 1 | | | | | | |
| 2 | | | | | | |
| 3 | | | | | | |
$w (H_ {2} O_ {2}) =\ frac {\ frac {5} {2} c (KMnO_ {4}) V (KMnO_ {4}) M (H_ {2} O_ {2}) } {m_ {like}}\ times100\% $
where: $c (KMnO_ {4}) $is the concentration of $KMnO_ {4} $standard solution, $mol/L $; $V (KMnO_ {4} ) $is the volume of the solution consumed by titration $KMnO_ {4} $, $L $; $M (H_ {2} O_ {2}) $is the molar mass of $H_ {2} O_ {2} $, $34.02g/mol $; $m_ {sample} $is the mass of the sample taken, $g $ (in this experiment $m_ {sample} =\ rho V $, $\ rho $is $H_ {2} O_ {2} $The density of the sample solution, $V $is the volume of the absorbed $H_ {2} O_ {2} $sample solution, where $V = 10.00mL $, since $H_ {2} O_ {2} $The sample solution is dilute, it can be approximated that its density is $1g/mL $).
6. Precautions
1. When calibrating the $KMnO_ {4} $solution, the temperature should be controlled at 75 dollars - 85 ^ {\ circ} C $, if the temperature is too high, $H_ {2} C_ {2} O_ {4} $will partially decompose; if the temperature is too low, the reaction speed will be slow.
2. The titration rate should start slowly, otherwise the added $KMnO_ {4} $solution will not have time to react with $C_ {2} O_ {4} ^ {2 -} $and decompose in hot acidic solution.
$4MnO_ {4} ^ {-} + 12H ^ {+} = 4Mn ^ {2 + } + 5O_ {2}\ uparrow + 6H_ {2} O $
3. When titrating $H_ {2} O_ {2} $with a $KMnO_ {4} $solution, it cannot be heated because $H_ {2} O_ {2} $is easy to decompose when heated.
4. The end point judgment is based on the solution being reddish and keeping $30s $without fading. If the solution fades after a long time, it is due to the slow decomposition of $MnO_ {4} ^ {-} $due to impurities such as reducing gases and dust in the air, which does not affect the analysis results.
VII. Experimental results and discussion
1. Calculate the content of $H_ {2} O_ {2} $according to the experimental data, compare it with the theoretical value or the labeled value on the product label, and analyze the reasons for the error.
2. Discuss the factors that may affect the accuracy of the measurement results during the experimental process, such as titration speed, temperature control, endpoint judgment, etc., and think about how to improve the experimental operation to improve the accuracy of the measurement.
1. Experimental purpose
Master the principle and method of determining hydrogen peroxide content by potassium permanganate method, and further proficiency in titration operation.
Second, experimental principle
Hydrogen peroxide is a widely used disinfectant in the medical and health industries. It can be quantitatively oxidized by $KMnO_ {4} $in acidic solution to generate oxygen and water. The reaction is as follows:
$2MnO_ {4} ^ {-} + 5H_ {2} O_ {2} + 6H ^ {+} = 2Mn ^ {2 + } + 5O_ {2}\ uparrow + 8H_ {2} O $
The reaction can proceed smoothly at room temperature. The reaction speed is slow at the beginning of titration, and it accelerates with the formation of $Mn ^ {2 +} $. $MnO_ {4} ^ {-} $itself is purple in the solution and can be used as an indicator. After the stoichiometry point, a slight excess of $MnO_ {4} ^ {-} $makes the solution appear pink and indicates the end point.
III. Experimental instruments and reagents
1. ** Instruments **: acid burette, pipette, volumetric flask, conical bottle, analytical balance, measuring cylinder, etc.
2. ** Reagents **: $KMnO_ {4} $standard solution ($0.02mol/L $), $H_ {2} SO_ {4} solution ($3mol/L $), $H_ {2} O_ {2} $sample.
IV. Experimental steps
1. ** $KMnO_ {4} $Calibration of standard solution **
- accurately weigh 0.15 dollars - 0.20g $reference material $Na_ {2} C_ {2} O_ {4} $in a $250mL $conical flask, add $30mL $distilled water and $15mL 3mol/L H_ {2} SO_ {4} $solution, cover the surface dish, heated to 75 dollars - 85 ^ {\ circ} C $on a water bath.
- Titration with $KMnO_ {4} $solution to be calibrated while hot. Start the titration slowly. After $Mn ^ {2 +} $is generated in the solution, the titration speed can be appropriately accelerated, but it must still be added dropwise. Titration until the solution is reddish and keeps $30s $without fading is the end point. Record the volume of the consumed $KMnO_ {4} $solution. Calibrate three times in parallel to calculate the exact concentration of the $KMnO_ {4} $standard solution.
2. ** Determination of hydrogen peroxide content **
- Pipette the $10.00mL H_ {2} O_ {2} $sample solution, place it in a $250mL $volumetric flask, dilute it to scale with water, and shake well.
- Pipette the above diluted $H_ {2} O_ {2} $solution $25.00mL $into a $250mL $conical flask, add $3mol/L H_ {2} SO_ {4} $solution $15mL $.
- Titrate with $KMnO_ {4} $standard solution until the solution is reddish and keeps $30s $fading is the end point. Record the volume of the solution consumed $KMnO_ {4} $. Parallel measurement three times, calculate the sample $H_ {2} O_ {2} $content.
5, experimental data recording and processing
1. ** $KMnO_ {4} $Calibration of standard solution **
| times | $m (Na_ {2} C_ {2} O_ {4})/g $| $V (KMnO_ {4})/mL $| $c (KMnO_ {4})/(mol/L )$ | $\ overline {c} (KMnO_ {4})/(mol/L) $| Relative mean deviation |
|---|---|---|---|---|---|
| 1 | | | | | |
| 2 | | | | | |
| 3 | | | | | |
$c (KMnO_ {4}) =\ frac {2m (Na_ {2} C_ {2} O_ {4}) } {5M (Na_ {2} C_ {2} O_ {4}) V (KMnO_ {4}) } $
where: $m (Na_ {2} {2} O_ {4}) $C_ mass of reference substance $Na_ {2} C_ {2} O_ {4} $, $g $; $M (Na_ {2} C_ {2} O_ {4}) $Na_ {2} | | | |< { 2} O_ {4} $molar mass, $134.00g/mol $; $V (KMnO_ {4}) $is the titration consumed $KMnO_ {4} $solution volume, $L $.
2. ** Determination of hydrogen peroxide content **
| times | $V_ {total} (H_ {2} O_ {2})/mL $| $V (H_ {2} O_ {2})/mL $| $V (KMnO_ {4})/mL $| $w (H_ {2} O_ {2 })/\%$ | $\ overline {w} (H_ {2} O_ {2 })/\%$ | relative mean deviation |
|---|---|---|---|---|---|---|
| 1 | | | | | | |
| 2 | | | | | | |
| 3 | | | | | | |
$w (H_ {2} O_ {2}) =\ frac {\ frac {5} {2} c (KMnO_ {4}) V (KMnO_ {4}) M (H_ {2} O_ {2}) } {m_ {like}}\ times100\% $
where: $c (KMnO_ {4}) $is the concentration of $KMnO_ {4} $standard solution, $mol/L $; $V (KMnO_ {4} ) $is the volume of the solution consumed by titration $KMnO_ {4} $, $L $; $M (H_ {2} O_ {2}) $is the molar mass of $H_ {2} O_ {2} $, $34.02g/mol $; $m_ {sample} $is the mass of the sample taken, $g $ (in this experiment $m_ {sample} =\ rho V $, $\ rho $is $H_ {2} O_ {2} $The density of the sample solution, $V $is the volume of the absorbed $H_ {2} O_ {2} $sample solution, where $V = 10.00mL $, since $H_ {2} O_ {2} $The sample solution is dilute, it can be approximated that its density is $1g/mL $).
6. Precautions
1. When calibrating the $KMnO_ {4} $solution, the temperature should be controlled at 75 dollars - 85 ^ {\ circ} C $, if the temperature is too high, $H_ {2} C_ {2} O_ {4} $will partially decompose; if the temperature is too low, the reaction speed will be slow.
2. The titration rate should start slowly, otherwise the added $KMnO_ {4} $solution will not have time to react with $C_ {2} O_ {4} ^ {2 -} $and decompose in hot acidic solution.
$4MnO_ {4} ^ {-} + 12H ^ {+} = 4Mn ^ {2 + } + 5O_ {2}\ uparrow + 6H_ {2} O $
3. When titrating $H_ {2} O_ {2} $with a $KMnO_ {4} $solution, it cannot be heated because $H_ {2} O_ {2} $is easy to decompose when heated.
4. The end point judgment is based on the solution being reddish and keeping $30s $without fading. If the solution fades after a long time, it is due to the slow decomposition of $MnO_ {4} ^ {-} $due to impurities such as reducing gases and dust in the air, which does not affect the analysis results.
VII. Experimental results and discussion
1. Calculate the content of $H_ {2} O_ {2} $according to the experimental data, compare it with the theoretical value or the labeled value on the product label, and analyze the reasons for the error.
2. Discuss the factors that may affect the accuracy of the measurement results during the experimental process, such as titration speed, temperature control, endpoint judgment, etc., and think about how to improve the experimental operation to improve the accuracy of the measurement.
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