# Objectives: To determine the amount of nickel in a given salt. Calculate the weight percent of nickel in the salt and compared with theoretical. To study the gravimetric analysis

Universiti Tunku Abdul Rahman

UESB 1113 General Laboratory I

Atomic Structures & Periodicity

Bachelor of Science (Hons) Biotechnology

Year 1 Semester 1

Experiment 8:

Determination of Nickel by Gravimetric Analysis.

Name/ID: Hew Xin Hong / 05UEB02306

Low Wei Seong / 05UEB02315

Tutorial Group: Group 4

Date: 18th July 2005

Tutor: Mr. Lee Chong Yong

Experiment 8

Title: Determination of Nickel by Gravimetric Analysis.

Objectives:

• To determine the amount of nickel in a given salt.
• Calculate the weight percent of nickel in the salt and compared with theoretical.
• To study the gravimetric analysis method in determine compound in certain given unknown salt.

Theory and Background:

Gravimetric analysis is a technique through which the amount of an analyte (the ion being analyzed) can be determined through the measurement of mass. Gravimetric analyses depend on comparing the masses of two compounds containing the analyte. The principle behind gravimetric analysis is that the mass of an ion in a pure compound can be determined and then used to find the mass percent of the same ion in a known quantity of an impure compound. In order for the analysis to be accurate, certain conditions must be met:

1. The ion being analyzed must be completely precipitated.
2. The precipitate must be a pure compound.
3. The precipitate must be easily filtered.

An example of a gravimetric analysis is the determination of chloride in a compound. In order to do a gravimetric analysis, a cation must be found that forms an insoluble compound with chloride. This compound must also be pure and easily filtered.

Gravimetric analysis, by definition, includes all methods of analysis in which the final stage of the analysis involves weighing. In the most basic case, this could involve simply heating a sample to dryness and weighing to determine the amount of volatile components. In this account, however, I shall limit myself to gravimetric methods which rely on the use of precipitation reactions.

The quantitative determination of a substance by precipitation followed by isolation and weighing of the precipitate is called gravimetric analysis.

The basic method of gravimetric analysis is fairly straightforward. A weighed sample is dissolved after which an excess of a precipitating agent is added. The precipitate which forms is filtered, dried or ignited and weighed. From the mass and known composition of the precipitate, the amount of the original ion can be determined.

For successful determinations the following criteria must be met;

1. The desired substance must be completely precipitated. In most determinations the precipitate is of such low solubility that losses from dissolution are negligible. An additional factor is the "common ion" effect; this further reduces the solubility of the precipitate. When Ag+ is precipitated out by addition of Cl-

Ag+ + Cl- =<-> AgCl(s)

the (low) solubility of AgCl is reduced still further by the excess of Cl- which is added, pushing the equilibrium to the right.

1. The weighed form of the product should be of known composition.
2. The product should be "pure" and easily filtered. It is usually difficult to obtain a product which is "pure", i.e. one which is free from impurities but careful precipitation and sufficient washing helps reduce the level of impurity.

Nickel is a metallic chemical element in the periodic table that has the symbol Ni and atomic number 28.Nickel is silvery white metal that takes on a high polish. It belongs to the iron group, and is hard, malleable, and ductile. It occurs combined with sulfur in millerite, with arsenic in the mineral niccolite, and with arsenic and sulfur in nickel glance.

On account of its permanence in air and inertness to oxidation, it is used in the smaller coins, for plating iron, brass, etc., for chemical apparatus, and in certain alloys, as German silver. It is magnetic, and is very frequently accompanied by cobalt, both being found in meteoric iron. It is chiefly valuable for the alloys it forms.

Nickel is one of the five ferromagnetic elements. Because of the precise alloy used, the US "nickel" coin is not ferromagnetic, while the Canadian coin of the same name is up to and including the year 1958.The most common oxidation state of nickel is +2, though 0, +1 and +3 Ni complexes are observed.

The bulk of the nickel mined comes from two types of ore deposits. The first are laterites where the principal ore minerals are nickeliferous limonite: (Fe,Ni)O(OH) and garnierite (a hydrous nickel silicate): (Ni,Mg)3Si2O5(OH). The second are magmatic sulfide deposits where the principal ore mineral is pentlandite: ...