Determination of %Mgo in Unknown

Determination of %MgO

using a Compleximetric Titration

Procedure:

The procedure for this experiment is taken from the laboratory manual referenced below. There were no significant deviations from that procedure.

Data Table

 Mass of Na2EDTA*2H2O _0.9864 g

Molar Mass of Na2EDTA*2H2O 372.25 g/mol

Estimated Morality of EDTA solution ____0.0088M_________________

Standardization of EDTA Solution

Concentration of Zn2+ 0.0112M

| Trial #1 | Trial #2 | Trial #3 |

Final Buret Reading | 10.50 ml | 9.20 ml | 26.50 ml |

Initial Buret reading | 3.00 ml | 2.00 ml | 18.50 ml |

Volume used, EDTA | 7.50 ml | 7.20 ml | 8.00 ml |

Morality of EDTA Solution | 0.0149M | 0.0155M | 0.0140M |

Average Morality of Standard ETDA solution = (0.0149M+0.0155M+0.0140M)/3= 0.0148M |

Determination of %MgO of Unknown

Uknown No. __1W__

| Sample #1 | Sample #2 | Sample #3 |

Mass of sample | 0.2100 g | 0.1951g | 0.1933g |

Final buret reading, EDTA | 45.30ml | 38.50ml | 39.70ml |

Initial buret reading, EDTA | 6.50ml | 0.20ml | 1.00ml |

Volume used, EDTA | 38.80ml | 38.30ml | 38.70ml |

 Measurement of water blank

Final Buret Reading, EDTA ______39.80ml_____________

Initial Buret Reading, EDTA ______39.80ml_____________

| Sample #1 | Sample # 2 | Sample #3 |

Moles of Mg2+ | 5.7424*10-4 mol | 5.6684*10-4mol | 5.7276*10-4mol |

%MgO in sample | 11.0213% | 11.7101% | 11.9426% |

Average %MgO in sample: ( 11.0213% +11.7101%+11.9426%)/3 = 11.5580% |

Sample Calculations:

Estimated morality of EDTA solution

M = [(0.9864gEDTA) / (372.25gNa2EDTA/mol)]/0.300L sol’n=0.0088M

Molarity of EDTA solution:

Since Zn2+ and EDTA react in 1:1 molar ration, morality and volume of Zn2+ are used to determine the molar mass of EDTA solution.

M = (0.010L Zn2+) * (0.0112M Zn2+) = 1.12*10-4 mol Zn2+ = 1.12*10-4 mol EDTA

M(EDTA) from Trial #1:

M= 1.12*10-4 mol EDTA/0.0075L EDTA = 0.0149M EDTA...