Redox Reactions - Online Test

Answer : Option D
Explaination / Solution:

In free or uncombined state each element has zero oxidation state.

Answer : Option A
Explaination / Solution:

By definition, the oxidation number of an atom is the charge that atom would have if the compound was composed of ions.

 The oxidation number of simple ions is equal to the charge on the ion. The oxidation number of sodium in the Na+ ion is +1, for example, and the oxidation number of chlorine in the Cl- ion is -1.

Answer : Option D
Explaination / Solution:

Calcium is a silvery-white metal; it is relatively soft, but much harder than sodium metal.  Calcium is a member of the alkaline-earth metals (Group II on the periodic table); these metals react vigorously with water, although not as violently as the Group I metals such as sodium or potassium:

Ca(s)  +  2H2O(l)  ——>  Ca(OH)2(aq)  +  H2(g)

Answer : Option A
Explaination / Solution:

Alkali metals have +1 oxidation state. Because they have only one electron in their outer most shell and by losing that one they can achieve stable configuration, that's why they have +1 oxidation state.

Answer : Option B
Explaination / Solution:

The alkali metals (Group 1) have 1 valence electron. Alkali metals looses this electron to achieve noble gas configuration, and so alkali metals have oxidation number +1.

Answer : Option C
Explaination / Solution:

This is according to the rules of assigning oxidation number i.e. Metal hydrides, such as NaH, LiH, etc., in which the oxidation state for H is -1.

Answer : Option D
Explaination / Solution:

This is according to the rules of assigning oxidation number i.e. Chlorine, Bromine, Iodine have positive oxidation numbers when combined with oxygen, for example in oxoacids and oxoanions.

Answer : Option C
Explaination / Solution:

as oxygen is more electronegative than Cl,Br and I. So they have positive oxidation state.

Answer : Option B
Explaination / Solution:

The more positive the value of E0, the greater is the tendency of the species to get reduced, therefore Ag+/Ag = +0.80 is strongest oxidising agent.

Answer : Option C
Explaination / Solution:

Because in electrochemical series Cu is above all in sequence I2, Ag and Br2, therefore, Cu will reduce Br2.