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This is the second of our many quizzes on Redox. Click on this to access more such competitive quizzes on Physical Chemistry.

Redox Quiz 2

chemistry

 Fill in the blank: Salt bridge is used to maintain  ____________ in the solutions of the two half-cells.

 Salt Bridge is used to balance the ions in the reactions.

 Salt bridge is used to maintain the electroneutrality in the solutions of the two half-cells.

 Select the correct set showing the overall charge of the following: $A = MnO_{4}^{-}$, $B = {{[Fe{{(CN)}_{6}}]}^{4-}}$, $C = C{{O}_{2}}$, $D = C{{e}^{4+}}$ 

 If there is no charge on the molecule we take it as 0 because it is in its elemental form.

 The overall charge in $MnO_{4}^{-}$ is -1.The overall charge on ${{[Fe{{(CN)}_{6}}]}^{4-}}$ is -4. The overall charge on $C{{O}_{2}}$ is 0. The overall charge on $C{{e}^{4+}}$ is +4.

 You are given a complex compound: $YbB{{a}_{2}}C{{u}_{3}}{{O}_{7}}$. This compound can show superconductivity. So, what will be the oxidation state of copper? $(\text{Take the ytterbium’s oxidation state as +3})$

 Oxidation number of Yb is +3, the oxidation number of barium is +2, and the oxidation number of oxygen is -2.

 The given compound is $YbB{{a}_{2}}C{{u}_{3}}{{O}_{7}}$. The oxidation number of Yb is +3, the oxidation number of barium is +2, and the oxidation number of oxygen is -2. We can write: $+3+2(+2)+3(x)+7(-2)=0 \\ 3x-7=0 \\ x=\dfrac{7}{3}$. The oxidation number will be $\dfrac{7}{3}$ 

 We can predict the oxidation number of an element by its structure. The structure of a compound is given below:<img  src="https://cmds-vedantu.s3.ap-southeast-1.amazonaws.com/prod/question-sets/44a165ad-e5a3-407a-9146-6c0520318df11205565535620944936.png"/>The oxidation number of central atom (A) and (B) are:

 By counting the number of bonds we can calculate the oxidation number.

 There is only one central atom in the given compound, which is bromine, but there are two forms of bromine. The oxidation number can be calculated by counting the number of bonds. The oxidation number of (A) bromine is +4 because it is attached to two oxygen atoms through four bonds. The oxidation number of (B) bromine is +6 because it is attached to three oxygen atoms through six bonds.

 We are given a redox reaction below: $xBi{{(OH)}_{3}}+3SnO_{2}^{2-}\to 2Bi+ySnO_{3}^{2-}+3{{H}_{2}}O$. Find the value of x and y in the above:

 With the support of the opposite hand, determine the significance of variables, and then align all of the atoms in the reaction.

 The given reaction is: $xBi{{(OH)}_{3}}+3SnO_{2}^{2-}\to 2Bi+ySnO_{3}^{2-}+3{{H}_{2}}O$. On the product side, there are 2 bismuth atoms, so we can put the value of x as 2. On the reactant side, there are 3 tin atoms, so we can put the value of y as 3. $2Bi{{(OH)}_{3}}+3SnO_{2}^{2-} \to 2Bi+3SnO_{3}^{2-}+3{{H}_{2}}O$. Now count all the number of atoms in the reaction. There are 2 bismuth atoms, 3 tin atoms, 12 oxygen atoms, and 6 hydrogen atoms on both sides. So, we don’t have to balance the reaction.