Please answer and fill in blanks for question 3 and 4. Typed or written. But do
ID: 554253 • Letter: P
Question
Please answer and fill in blanks for question 3 and 4. Typed or written. But do not write in cursive.
Please explain how or why you have those answers.
3. The following reaction is an example of a REDOX reaction. Assign oxidation numbers to the following atoms. Circle the element that undergoes an oxidation. Ca(s) + 2H+ (aq) Ca2 + (aq) + H2 (g) The rusting of iron is a REDOX reaction. Fill in the oxidation number for each element. Circle the element that undergoes an oxidation. 4. 4 Fe (s) + 3 O2 (g) 2 Fe3O3(s)Explanation / Answer
All elements in their elemental state are neutral and are considered to have an oxidation state of 0. Also, if two atoms are bonded to themselves, like hydrogen and nitrogen, their oxidation states are considered to be zero as that diatomic form is their elemental state. Otherwise, the oxidation state of H is taken to be +1 in all cases except in hydrides where they have -1 and oxidation of oxygen is -2 in all oxides, -1 in peroxides and -0.5 in superoxides.
3. Ca being in the elemental state has oxidation state zero in the left-side of the reaction and proton, as represented by the singly positive charge has an oxidation state of +1. Then, on the right hand side of the reaction, Ca2+ has an oxidation state of +2 and hydrogen molecule has H with zero oxidation state. In terms of redox reaction, the species losing electrons or gaining positive charge are being oxidised and the species gaining electrons or losing positive charge (or gaining negative charge) are being reduced. Thus, it can be seen that Ca is being oxidised as its going from 0 to +2 and H is being reduced as it goes from +1 to 0.
4. Here again, both Fe and oxygen molecule have zero oxidation state. In Fe2O3, the charge on each O is -2, giving a total of -6 charge to be neutralized for two Fe. Thus, we get oxidation state of Fe in the molecule as -(-6/2) = +3 (the charge is negated to counteract the negative charge of O to result in a neutral molecule. Mathematically, it can be expressed as 2x - 6 = 0 giving x = 6/2 = +3). In this reaction, Fe goes from 0 oxidation state to +3, losing three electrons thus being the oxidised species while O goes from 0 to -2, gaining two electrons, thus being the reduced species.