Molecular Weight Of Nickel Dmg
Experiment 7-023: Gravimetric determination of Nickel in a Five-cent Coin
- Molecular Weight Of Nickel Dmg 1
- Molecular Weight Of Nickel Dmg In Windows 7
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- Molecular Weight Of Nickel Dmg Complex
- Molecular Weight Of Nickel Dmg 2
Transfer the unknown nickel ore sample into one weighing bottle and bring to constant weight by drying. After drying, weigh accurately by difference three samples (about 0.5 g each), into numbered 400 ml beakers. In the fume hood, add 20 mL conc. The Gravimetric Estimation of Nickel: The nickel is precipitated as nickel dimethyl glyoxime by adding alcoholic solution of dimethyl glyoxime C 4 H 6 (NOH) 2 and then adding a slight excess of aqueous ammonia solution. When the pH is buffered in the range of 5 to 9, the formation of the red chelate occurs quantitatively in a solution. Jan 09, 2008 2DMG(aq) + Ni2+(aq) - Ni(DMG)2(s) + 2H2O(l) Ni(DMG)2(s) is a red precipitate. As you can see nickel has not been oxidized, nickel is not oxidized as the Ni2+ ion only forms a complex. DMG has to be in an alcohol solution because It is the conjugate base, not dmgH2 itself, that forms the complexes. Examples of molecular weight computations: C14O162, S34O162. Definitions of molecular mass, molecular weight, molar mass and molar weight. Molecular mass (molecular weight) is the mass of one molecule of a substance and is expressed in the unified atomic mass units (u). (1 u is equal to 1/12 the mass of one atom of carbon-12). Use of the information, documents and data from the ECHA website is subject to the terms and conditions of this Legal Notice, and subject to other binding limitations provided for under applicable law, the information, documents and data made available on the ECHA website may be reproduced, distributed and/or used, totally or in part, for non-commercial purposes provided that ECHA is.
Molar mass: 116.120 gmol −1 Appearance White/Off White Powder Density: 1.37 g/cm 3: Melting point: 240 to 241 °C (464 to 466 °F; 513 to 514 K) Boiling point: decomposes. Material Safety Data Sheet Dimethylglyoxime, 1% Alcoholic - 2 - Ingestion: May cause irritation of the digestive tract. Symptoms may include headache, excitement, fatigue.
A gravimetric determination of a substance involves the separation of that substance in a form which may be weighed accurately and is of known composition. That usually means that a material dissolved in solution is completely precipitated from solution, and the solid is weighed. In the case of nickel, Ni2+ ions form an extremely insoluble bright red complex with two dimethylglyoxime (DMG) anions under mildly basic conditions. No other common metallic ion reacts in the same way, so the formation of the insoluble Ni(DMG)2 complex makes it possible to separate the Ni2+ ions from other metal ions in solution. The reaction is illustrated below; the dashed lines represent hydrogen bonds which help stabilize the complex.
The Chemistry:
2 Dimethylglyoxime + Ni2+------------> Ni(DMG)2+ 2 H+
The Ni(DMG)2 complex (MW 288.9 g/mole) is stable to heat and is unusually hydrophobic; it will dry quickly in an oven at 110-120 oC to yield a pure substance whose weight can be used to calculate the nickel content of the original sample.
A five-cent piece (a nickel) consists of copper alloyed with nickel and other metals. Before the five-cent piece can be analyzed for the nickel content, it must be cleaned, weighed and then dissolved. Reaction of the coin with the nitric acid oxidizes both the nickel and copper atoms and releases various oxides of nitrogen:
3 Cu(s) + 8 H+(aq) + 2 NO3-(aq) -------> 3 Cu2+(aq) + 2 NO(g) + 4 H2O(l) [1]
Molecular Weight Of Nickel Dmg 1
3 Ni(s) + 8 H+(aq) + 2 NO3-(aq) --------> 3 Ni2+(aq) + 2 NO(g) + 4 H2O(l) [2]
The resulting solution is acidic and contains both Ni2+ and Cu2+ ions. Before adding the DMG and separating the Ni2+ from the Cu2+ ions, the solution must be neutralized (and made weakly basic) by adding sodium acetate. To avoid interference by Cu2+, sodium tartrate is also added, as the tartrate ion wraps itself around the Cu2+ ions and prevents their precipitation when the DMG is added.
The precipitate (Ni(DMG)2 ) initially produced by adding DMG consists of very small crystals which cannot be filtered, as they penetrate or clog the filter mat. A more tractable precipitate is generated if the solution is simmered for an hour or more to encourage the growth of larger crystals. Such simmering of a precipitate to encourage flocculation (a common technique) is known as digestion. The digested precipitate is filtered and washed extensively with distilled water to remove adsorbed impurities. Extensive washing will not cause a loss of precipitate, as the Ni(DMG)2 complex is extremely insoluble (less than 1.0 mg per liter in cold water).
The Experiment:
This lab requires two weeks to complete, during the first week the nickel samples will be prepared and the Ni(DMG)2 will be precipitated. Between the two weeks, this precipitate will be allowed to digest, so that it can be filtered, dried and weighed during the second week.
Students will work individually, except when preparing the stock sample of nickel (4 students per 5-cent coin).
Week I
Students will pre-dry their crucibles (with filters), prepare the stock sample of nickel and precipitate the Ni(DMG)2 in the first week of this lab.The Ni(DMG)2 samples will be stored in your lab locker and allowed to digest for 1 week.
Week II
The Ni(DMG)2 product will be filtered, dried and weighed during week 2. Since there will be a considerable amount of downtime during this week, you will also be working on lab 7-016 while your samples are being filtered and dried (in a drying oven). After allowing your samples to dry and cool, you should mass your samples and determine the % of nickel in a 5-cent coin.
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WASTE MANAGEMENT
Molecular Weight Of Nickel Dmg In Windows 7
In this experiment you generate waste containing the toxic metal, nickel. The solid waste Ni(DMG)2 should be placed in the solid chemical waste container and all liquid waste should be placed in the liquid chemical waste container located in the Chemical Waste Hood.
Molecular Weight Of Nickel Dmg In Mac
Useful Information:
Calculations: Need some help with calculations?
Coin Specifications:The U.S. Mint coin specification web page. Check out the rest of the site, it's pretty cool.
Molecular Weight Of Nickel Dmg Complex
