Question

2. When the following equation is balanced with the smallest possible integer coefficients, what is the coefficient of H'? _Cr* __H __ Cr +_ He A) 3 B) 5 C6 D)2 E) 4 3. The following reaction occurs in acidic aqueous solution: H.AsO + Zn = AsH, + Zn? H.ASO. is a[n) agent in which the oxidation number of Asis C ) reducing. 13 A) reducing 5 D) oxidizing, +3 B) oxidizing, + 5 E) reducing. +2 When the following equation for a reaction, which occurs in acidic solution is correctly balanced sing the smallest possible whole numbers, the coefficient of His: Sn+NO, =SnO, NO B) 4 A) O C) 8 D) 16 E) 12 __to_ 5. In the following reaction, the oxidation number of Fe changes from FeO, + 3C0 - 2Fe + 3CO, c' doesn't change A) 0, +3 D) 0, +2 B) E +3,0 +2,0 6. In the reaction: Fe2O3 + 3C0 = 2Fe + 3CO2 the reducing agent is: A) co B) C) Fe:0; Fe D C O 7. When the oxidation half reaction is balanced (for the reaction given below which occurs in acid) using the smallest Integer coefficients possible, what is the coefficient of H20 in the balanced half reaction? MnO, +HSO,' = Mn0,2 +50,? C A) 3 B)1 c4 0)2 E) bi Palance the eaction al check the afous and change

Answer 1

2. 2Cr+ + 4H+ = 2Cr+3 + 2H2

Charge as well as no of atoms on reactant and product side must be balanced.

3. Oxidation means loss of electron or incresae in oxidation no. The species which is oxidised is called reducing agent and the one that is reduced is called oxidising agent. In this case Zn is loosing electrons to become Zn+2 thus, it is oxidised. Hence, Zn is a reducing agent.

For H3AsO4 oxidation no of As will be-

3(+1) +x + 4(-2) =0

So, x=8-3=5

For AsH3 oxidation no of As will be

y + 3(1) =0

So, y=-3

Since As is gaining electrons, it is getting reduced. Thus, H3AsO4 is oxidising agent with oxidation state of As as +5.

4. Sn + 4NO2- + 4H+ = SnO2 + 4NO + 2H2O

Balancing of both the charge and no of atoms is carried out to solve the question.

5. For Fe2O3, oxidation no of Fe is-

2x + 3(-2) =0

So, x =6/2=3

For, Fe in the product oxidation state is 0. Thus, the oxidation state changes from +3 to 0.

6. Reducing agent means the species which is getting oxidised i.e. for which loss of electron occur or for which oxidation no increases.

For Fe oxidation no decreases from +3 to 0. Thus, it undergoes reduction and is the oxidising agent. However, for C, oxidation no increases from +2 to +4. Thus, it undergoes oxidation and CO is the reducing agent.