Chemistry MCQs for NEET — Practice Questions with Answers

group 2 elements will show +2 only, 

its OXYGEN, whose OX no is different in per oxide, normal oxide and super oxide.

3.

0 to +5, in elementary state ox no is 0

3.

 can lose all valence electron, which is  4s¹ ,3d⁵ = 6 electron

Chromium is hexavalent in this compound - each one has an oxidation state of +6 to balance out the 7 x-2 oxygen ions and the 2 x +1 potassium ions (the net total has to be zero for a neutral compound). oxidation state of Cr in K2Cr2O7 is +6.

2 -ve charge is shared by 2 oxygen , so each oxygen will have -1 charge.

The permanganate ion (MnO4-) is the oxidizing agent and hydrogen peroxide the reducing agent in the given reaction.

The oxidation number of manganese in MnO4- ion is +7, which gets reduced to +2 in the Mn2+ ion. The oxidation number of oxygen in H2O2 is -1, which gets increased to zero in free elemental oxygen, O2. So, it can easily be seen that the permanganate ion oxidizes H2O2 to O2. The oxidation number of hydrogen remains the same (+1) in the reaction.

Hydrogen peroxide is also strong oxidizing agent, but the permanganate ion is a more powerful oxidant than the former. So, H2O2 acts as a reductant when it encounters the MnO4- ion.

fluorineThe strongest oxidizing agent is fluorine with the largest positive number for standard electrode potential..

Nitrogen compounds, on the other hand, encompass oxidation states of nitrogen ranging from -3, as in ammonia and amines, to +5, as in nitric acid.

The balanced chemical reactions (ionic reactions)for reduction of K2Cr2O7 by Sn2+are:
Cr2O72- + 14H++ 6e-→2Cr3+ + 7H2O
( ​Sn2+ → Sn4+ + 2e- )    × 3

Balanced Net reaction : 3Sn2++ Cr2O72- + 14H+ → 3 Sn4+ + 2Cr3+ + 7H2O​

Thus according to the balanced reaction : 1 mole of Cr2O72- will be reduced by 3 moles of Sn2+
Thus 1 mole of Sn2+  will reduce = 1/3 moles of Cr2O72-
                                                            = 0.33 moles of Cr2O72-

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In the given reaction: Cu + 2AgNO3 → 2Ag + Cu(NO3)2, copper metal (Cu) is oxidized to copper(II) ion (Cu2+), while silver ions (Ag+) are reduced to silver metal (Ag). This involves a transfer of electrons, which is characteristic of a redox (reduction-oxidation) reaction.