Oxidation Number Method

Q.

How many moles of ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ is required to oxidise one mole of$\mathrm{Fe}\left({\mathrm{C}}_2{\mathrm{O}}_4\right)$ in an acidic medium.

1. $2$

2. $3$

3. $1/2$

4. $1/3$

Q. Balance the following chemical equation in basic medium:$\underset{\left(aq\right)}{Mn{O}_4^{-}}+\underset{\left(aq\right)}{B{r}^{-}}\to \underset{\left(s\right)}{Mn{O}_2}+\underset{\left(aq\right)}{Br{O}_3^{-}}$

1. $Mn{O}_4^{-}+2B{r}^{-}+H_{2}O\to Mn{O}_2+2Br{O}_3^{-}+2O{H}^{-}$
2. $2Mn{O}_4^{-}+B{r}^{-}+H_{2}O\to 2Mn{O}_2+Br{O}_3^{-}+2O{H}^{-}$
3. $Mn{O}_4^{-}+B{r}^{-}+H_{2}O\to 2Mn{O}_2+Br{O}_3^{-}+2O{H}^{-}$
4. $2Mn{O}_4^{-}+B{r}^{-}+H_{2}O\to Mn{O}_2+Br{O}_3^{-}+2O{H}^{-}$

Q. A 4 mol mixture of Mohr’s salt and $F{e}_2(S{O}_4{)}_3$ requires 400 ml of $0.5{\text{M KMnO}}_4$ for complete oxidation in an acidic medium. The percentage of Mohr’s salt in the mixture is:

1. 40 %
2. 5 %
3. 50 %
4. 25 %

Q.

Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.

(d) ethene is burnt in the presence of oxygen to form carbon dioxide, and water and releases heat and light.

Q.

Balance the chemical equation ${\mathrm{CaC}}_2\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to \mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+{\mathrm{C}}_2{\mathrm{H}}_2\left(\mathrm{g}\right)$

Q.

The equivalent weight of Mohr’s salt is

Q. The reaction of the permanganate ion with the oxalate ion in acidic solution forms manganese(II) ion and carbon dioxide. What is the stoichiometric coefficient in front of manganese(II) in the balanced redox equation?
$Mn{O}_4^{-}+C_2{O}_4^{2-}\to M{n}^{2+}+C{O}_2$

1. 2
2. 1
3. 3
4. 5

Q.

Balance the following equation by ion electron method

_{Na2S2O3+I2=Na2S4O6+NaI}

Q.

Solid calcium carbonate is heated to produce solid calcium oxide and carbon dioxide gas is released

(a) Translate the following chemical change in the form of a chemical equation

(b) Make it informative

(c) Balance it if required

Q.

Assign oxidation numbers to the underlined elements in each of the following species:
$Na{H}_{2}P{O}_4$

$NaH\underset{–}{S}{O}_4$

$H_4{\underset{–}{P}}_2{O}_7$

$K_2\underset{–}{Mn}{O}_4$

$Ca{\underset{–}{O}}_2$

$Na\underset{–}{B}{H}_4$

$H_2{\underset{–}{S}}_2{O}_7$

$KAl\underset{–}{S}{O}_4{)}_2.12H_{2}O$

Q.

Balance the reaction : ${\mathrm{H}}_2\mathrm{S}+{\mathrm{SO}}_2\to \mathrm{S}+{\mathrm{H}}_2\mathrm{O}$ and identify the Oxidizing and Reducing agents

Q. RCONH2 when treated with LiAlH4 /H2O yield

Q.

$\mathrm{PbS}$ reacts with ozone$\left({\mathrm{O}}_3\right)$ to form lead sulphate$\left({\mathrm{PbSO}}_4\right)$ and oxygen$\left({\mathrm{O}}_2\right)$. As per the balanced equation, molecules of ozone required for every molecule of $\mathrm{PbS}$ are:

1. 4

2. 3

3. 2

4. 1

Q. The oxidation number of carbon is zero in :

1. $HCHO$
2. $C{H}_{2}C{l}_2$
3. $C_6{H}_{12}{O}_6$
4. All of the above

Q.

How to calculate the equivalent weight of ferrous ammonium sulphate?

Q. Balance the following chemical equation:$C{r}_2{O}_7^{2-}\left(aq\right)+S{O}_3^{2-}\left(aq\right)\to C{r}^{3+}\left(aq\right)+S{O}_4^{2-}\left(aq\right)$ (Acidic medium)

1. $C{r}_2{O}_7^{2-}\left(aq\right)+3S{O}_3^{2-}\left(aq\right)+H^{+}\left(aq\right)\to 2C{r}^{3+}\left(aq\right)+3S{O}_4^{2-}\left(aq\right)+4H_{2}O\left(aq\right)$
2. $C{r}_2{O}_7^{2-}\left(aq\right)+S{O}_3^{2-}\left(aq\right)+8H^{+}\left(aq\right)\to 2C{r}^{3+}\left(aq\right)+3S{O}_4^{2-}\left(aq\right)+4H_{2}O\left(aq\right)$
3. $C{r}_2{O}_7^{2-}\left(aq\right)+3S{O}_3^{2-}\left(aq\right)+8H^{+}\left(aq\right)\to 2C{r}^{3+}\left(aq\right)+3S{O}_4^{2-}\left(aq\right)+4H_{2}O\left(aq\right)$
4. $C{r}_2{O}_7^{2-}\left(aq\right)+3S{O}_3^{2-}\left(aq\right)+8H^{+}\left(aq\right)\to C{r}^{3+}\left(aq\right)+3S{O}_4^{2-}\left(aq\right)+4H_{2}O\left(aq\right)$

Q.

Why ${\mathrm{V}}_2{\mathrm{O}}_5$ is used in Contact Process?

Q. In which of the following has the average oxidation number of oxygen been arranged in increasing order ?

1. $O{F}_2<K{O}_2<Ba{O}_2<O_3$
2. $Ba{O}_2<O_3<O{F}_2<K{O}_2$
3. $K{O}_2<O{F}_2<O_3<Ba{O}_2$
4. $Ba{O}_2<K{O}_2<O_3<O{F}_2$

Q.

An unbalanced chemical equation is called_________ equation.

Q. Molecular wt of mohr’s salt is 392. Its equivalent weight, when it is oxidized by $KMn{O}_4$ in acidic medium is

1. $M$
2. $\frac{M}{2}$
3. $\frac{M}{4}$
4. $2M$

Q. 8. If phenol is treated with HCN, HCl and Aluminium chloride what will be the product?

Q.

Write the balanced chemical equations for the following reactions

Magnesium burns in carbon dioxide to form magnesium oxide and carbon.

Q. A soliution of NaOH is 4g/L . What volume of HCl gas at STP will neutralize , 50ml of the alkali solution

Q. Which ordering of compounds is according to the decreasing order of the oxidation state of nitrogen?

1. $HN{O}_3,NO,N{H}_{4}Cl,N_2$
2. $NO,HN{O}_3,N{H}_{4}Cl,N_2$
3. $HN{O}_3,NO,N_2,N{H}_{4}Cl$
4. $HN{O}_3,N{H}_{4}Cl,NO,N_2$

Q. Balance the following equations.
(i) $KMn{O}_2+HCl\to KCl+MnC{l}_2+H_{2}O+C{l}_2$
(ii) $N{H}_3+O_3\to NO+H_{2}O$

Q.

Balance this reaction using the ion-electron method in the shortest way possible:

${\mathrm{Fe}}^{2+}+{{\mathrm{MnO}}_4}^{-}+{\mathrm{H}}^{+}\to {\mathrm{Fe}}^{3+}+{\mathrm{Mn}}^{2+}+{\mathrm{H}}_2\mathrm{O}$

Q. What is Q in equilibrium

Q. Consider the following redox reaction :

$S_4{O}_6^{2-}\left(aq\right)+Al\left(s\right)\to H_{2}S\left(aq\right)+A{l}^{3+}\left(aq\right)$

What will be the net balanced equation in an acidic medium (by oxidation number method).

1. $2S_4{O}_6^{2-}\left(aq\right)+6Al\left(s\right)+15H^{+}\to 2H_{2}S\left(aq\right)+6A{l}^{3+}\left(aq\right)+6H_{2}O\left(l\right)$
2. $S_4{O}_6^{2-}\left(aq\right)+6Al\left(s\right)+20H^{+}\to 4H_{2}S\left(aq\right)+6A{l}^{3+}\left(aq\right)+6H_{2}O\left(l\right)$
3. $3S_4{O}_6^{2-}\left(aq\right)+6Al\left(s\right)+2H^{+}\to 3H_{2}S\left(aq\right)+6A{l}^{3+}\left(aq\right)+6H_{2}O\left(l\right)$
4. $S_4{O}_6^{2-}\left(aq\right)+5Al\left(s\right)+20H^{+}\to 4H_{2}S\left(aq\right)+5A{l}^{3+}\left(aq\right)+4H_{2}O\left(l\right)$

Q. Match List-I (Compounds) with List-II (Oxidation states of nitrogen) and select answer using the codes given below the lists.

	List -I		List-II
$\left(a\right)$	$Na{N}_3$	$\left(1\right)$	$+5$
$\left(b\right)$	$N_2{H}_2$	$\left(2\right)$	$+2$
$\left(c\right)$	$NO$	$\left(3\right)$	$-\frac{1}{3}$
$\left(d\right)$	$N_2{O}_5$	$\left(4\right)$	$-1$

1. a$\to$1, b$\to$4, c$\to$2, d$\to$1
2. a$\to$4, b$\to$3, c$\to$2, d$\to$1
3. a$\to$3, b$\to$4, c$\to$1, d$\to$2
4. a$\to$3, b$\to$4, c$\to$2, d$\to$1

Q. What will be the correct balanced redox reaction for the given equation? (Use oxidation number method)
$T{l}_2{O}_3\left(s\right)+N{H}_{2}OH\left(aq\right)\to TlOH\left(s\right)+N_2\left(g\right)$

1. $T{l}_2{O}_3\left(s\right)+4N{H}_{2}OH\left(aq\right)\to 2TlOH\left(s\right)+2N_2\left(g\right)+5H_{2}O$
2. $T{l}_2{O}_3\left(s\right)+2N{H}_{2}OH\left(aq\right)\to 2TlOH\left(s\right)+N_2\left(g\right)+5H_{2}O$
3. $T{l}_2{O}_3\left(s\right)+2N{H}_{2}OH\left(aq\right)\to 2TlOH\left(s\right)+N_2\left(g\right)+5H_{2}O$
4. $2T{l}_2{O}_3\left(s\right)+4N{H}_{2}OH\left(aq\right)\to 4TlOH\left(s\right)+2N_2\left(g\right)+5H_{2}O$