Experiment 3 Families of Elements
Name: RAYSA M DOMINGUEZ Date: February 25, 2015
Lab Partner’s Name: T. GRIFFIN Score: _________________
I. Introduction An elements is a substance made entirely by one atom. According to the modern periodic law elements are arranged accordingly to increasing atomic number. Elements in the periodic table on the horizontal row are called periods and elements in vertical columns are called groups. The main objective of this experiment was to study the similar chemical properties of groups or elements in the periodic table by observing the reaction of barium, calcium, lithium, potassium, sodium, and strontium solutions. Also, observing the halide tests for bromide chloride and iodine solutions, then identifying the alkali or alkaline earth element and the halide in an unknown solution provided by the instructor.
The three families of elements that we will study during this experiment are the alkali metals, alkaline earth metals, and halides. Elements that belong to the same family are mostly identified by their chemical reactions. The tests performed in this experiment to study the properties of elements were the flame method test of known solutions, reactions of known solutions and halide test.
The laboratory skills learned in this experiment
The main safety precautions were reinforced as followed, always use good safety technique, and wear chemical splash approved goggles, also wear a lab coat and gloves. Conduct the flame test while your lab partner observes any reactions. No flammable chemicals near the burners.
II. Results Analysis
NOTE: please refer to the attached data sheets
1. Flame test solutions
The purpose of this procedure is to determine the color of the flame which will indicate the presence of a given element. If the compound is placed in the flame of a gas burner, there may be a characteristic color given off that is visible. A flame test is performed by placing a small amount of solution on the coiled end of a wire which will then be held in a burner flame and the flame color will be observe for identification of the element.
The elements/ions subjected to the flame test were Barium (Ba), Calcium (Ca), Lithium (Li), Potassium (K), Sodium (Na) and Strontium (Sr). The ion that makes the flame test misleading is Sodium (Na). The contamination was removed by placing the wire loop into dilute hydrochloric acid and heated the wire into red hot. The purpose of cleaning the wire after every use is to remove the substance previously used so there will be no confusion or residual of the substance when placed on the flame. If the wire is not cleaned properly the flame test will have errors on the determination of the colors of the elements/ions being tested.
The characteristic flame colors of alkali studied in this experiment were, a scarlet-red flame which indicated the presence of lithium, a bright orange/yellow which indicated the presence of sodium, a violet/purple flame which indicated the presence of potassium and alkaline earth metal, a yellow-green flame indicated the presence of barium, a bright red flame indicated the presence of strontium and a brick-red flame indicated the presence of calcium.
2. Reactions of known solutions
The purpose of this experiment was to study the reactions of elements/ions when exposed to other known solutions. As, stated before we can identify elements in the same group or family because they have similar chemical reactions. Barium, Calcium and Strontium showed a positive reaction to precipitation when exposed to ammonium carbonate and ammonium sulfate; Lithium, Potassium and Sodium had no reaction. All six elements/ions (Ba, Ca, Li, K, Na,Sr) had a negative reaction when exposed to ammonium phosphate. The family or group that showed a positive precipitation test was the alkaline earth metals.
3. Halide tests of known solutions
The purpose of this procedure was to