In the Results section of this handout, the table does not allow you to make entries for some of the reactions (Cl₂ with KCI; Br₂ with KBr; and 1₂ with KI). Why do you think this is the case?
Objectives:
- Determine which halogens are the strongest oxidants and if there is a periodic trend in oxidation strength.
- Learn the proper use of negative controls to determine whether a reaction has occurred.
Introduction:
The chemical elements are arranged in a systematic manner that we know as the Periodic Table of the Elements. The Periodic Table places elements with the same chemical properties in the same column in ascending order of mass. These columns are known as families or groups. For example, the first column (left-most) of the Periodic Table is known as the alkali metals or Group 1. Physical properties usually form a consistent trend down a group. For example, the boiling points of the alkali metals are as follows:
Li: 1317 °C Na: 892 °C K: 774 °C Rb: 701 °C Cs: 685 °C
The trend is a decrease in boiling point as we move down the group, that is, as the molar mass of the metals increase (why might that be?). A major goal of chemists is to explain these trends and to account for any deviations.
Elements in the same row of the Periodic Table are said to be in the same period. Moving across the period one observes trends in the physical and chemical properties of the elements, although anomalies are more frequently observed. For example, note the following trend in the electronegativities of the third period elements:
Na: 1.0, Mg: 1.3, Al: 1.5, Si: 1.8, P: 2.1, S: 2.4, Cl: 2.9
Periodic Trends of the Halogens
The elemental form of the halogens is X2, for example, elemental fluorine is F2. In this form, the halogens often behave as oxidants, that is, they will take electrons from other substances and form the corresponding halide ion. For example, F2 is an oxidant that can form fluoride (F–) ions. The simplest of these reactions is when a halogen of one element reacts with a halide of another element. For example:
F2 + 2 Br– → 2 F– + Br2
In this reaction molecular fluorine, F2, is a stronger oxidant than molecular bromine, Br2, and so F2 removes an electron from each Br– ion forming F– ions and molecular bromine (Br2). Bromine (Br2) is orange and so its formation can be detected by the appearance of its orange color.
In this set of laboratory experiments, not every combination of halogen and halide will result in a
Using the lab description, please answer the below question
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