Potassium Dichromate

Q.

Some chemical reactions give off distinctive smells. Give one example

Q. The equilibrium :
$C{r}_2{O}_7^{2-}{}_{\leftarrow }^{\to }2Cr{O}_4^{2-}$ exists in

1. Acidic Medium
2. Basic Medium
3. Neutral Medium
4. Does not exist

Q. Which of the statements is not true?

1. $K_{2}C{r}_2{O}_7$ solution in acidic medium is orange
2. $K_{2}C{r}_2{O}_7$ solution becomes yellow on increasing the pH beyond 7
3. On passing $H_{2}S$ through acidified $K_{2}C{r}_2{O}_7$ solution, a milky colour is observed
4. $N{a}_{2}C{r}_2{O}_7$ is preferred over $K_{2}C{r}_2{O}_7$ in volumetric analysis

Q. When $FeC{r}_2{O}_4$ is fused with Sodium Carbonate in the presence of air, we get

1. Sodium dichromate
2. Sodium oxide
3. Sodium chromate
4. Mixed oxide of Sodium and Chromium

Q. Acidified $K_{2}C{r}_2{O}_7$ oxidizes $H_{2}S$ to

1. $S{O}_2$
2. $S{O}_3$
3. $S$
4. $H_{2}S{O}_4+S$

Q.

Concentrated aqueous sodium hydroxide can separate mixture of

1. $A{l}^{3+}andF{e}^{3+}$

2. $A{l}^{3+}andS{n}^{2+}$

3. $A{l}^{3+}andZ{n}^{3+}$

4. $Z{n}^{3+}andP{b}^{2+}$

Q. In the reaction $C{u}_{3}P+K_{2}C{r}_2{O}_7+H_{2}S{O}_4\to CuS{O}_4+H_{3}P{O}_4+C{r}_2(S{O}_4{)}_3+H_{2}O$.
What is the n-factor of $C{u}_{3}P$?

1. 8
2. 3
3. 11
4. 1

Q. In the standardization of $N{a}_2{S}_2{O}_3$ using $K_{2}C{r}_2{O}_7$ by iodometry, the equivalent weight of $K_{2}C{r}_2{O}_7$ is:

1. $\frac{\text{Molecular weight}}{2}$
2. $\frac{\text{Molecular weight}}{6}$
3. $\frac{\text{Molecular weight}}{3}$
4. $\text{Same as its molecular weight}$

Q. Number of moles of $K_{2}C{r}_2{O}_7$ reduced by one mole of $S{n}^{2+}$ ions (in acidic medium) is:

1. $\frac{1}{3}$
2. $3$
3. $6$
4. $\frac{1}{6}$

Q. Consider the following list of reagents, acidified $K_{2}C{r}_2{O}_7$, alkaline $KMn{O}_4,CuS{O}_4,H_2{O}_2,C{l}_2,O_3,FeC{l}_3,HN{O}_3$ and $N{a}_2{S}_2{O}_3$. The total number of reagents that can oxidise aqueous iodide to iodine is:___

Q.

$Cr{O}_3$ dissoloves in aqueous NaOH to give :

1. $C{r}_2{O}_7^{2-}$

2. $Cr{O}_4^{2-}$

3. $Cr(OH{)}_3$

4. $Cr(OH{)}_2$

Q. $C{l}_2$ gas is obtained by various reactions but not by:

1. $KMn{O}_4+\text{conc.}HCl\stackrel{\Delta }{\to }$
2. $KCl+K_{2}C{r}_2{O}_7+\text{conc.}{H}_{2}S{O}_4\stackrel{\Delta }{\to }$
3. $Mn{O}_2+\text{conc.}HCl\stackrel{\Delta }{\to }$
4. $KCl+F_2\to$

Q. When $K_{2}C{r}_2{O}_7$ is heated with conc. $H_{2}S{O}_4$ in the presence of a soluble metal chloride, orange red vapours are produced. These are due to

1. $CrC{l}_3$
2. $CrOC{l}_2$
3. $Cr{O}_{2}C{l}_2$
4. $Cr{O}_4^{2-}$

Q.

$FeC{r}_2{O}_4+N{a}_{2}C{O}_3+O_2⟶X+Y+C{O}_2$
Mention X and Y.

1. $X=N{a}_{2}C{r}_2{O}_7;Y=F{e}_3{O}_4$

2. $X=N{a}_{2}C{r}_2{O}_4;Y=F{e}_3{O}_4$

3. $X=N{a}_{2}Cr{O}_4;Y=F{e}_2{O}_3$

4. $X=N{a}_{2}C{r}_2{O}_7;Y=F{e}_3{O}_3$

Q. The yellow colored solution of chromate salt changes to orange colour on acidification due to the formation of

1. $C{r}^{3+}$
2. $C{r}_2{O}_7^{2-}$
3. $Ti{O}_4^{-}$
4. $C{r}_2{O}_3$

Q. Ammonium dichromate is used in some fireworks. The green-coloured powder blown in the air is (IIT JEE, 1997)

1. $Cr{O}_3$
2. $C{r}_2{O}_3$
3. Cr
4. $CrO\left(O_2\right)$

Q. When potassium dichromate crystals are heated with conc. $H_{2}S{O}_4$, we get

1. oxygen
2. Hydrogen
3. Sulphur Dioxide
4. Hydrogen sulphide

Q. Which one of the following statements is correct when $S{O}_2$ is passed through acidified $K_{2}C{r}_2{O}_7$ solution?

1. $S{O}_2$ is reduced.
2. Green $C{r}_2(S{O}_4{)}_3$ is formed.
3. The solution turns blue.
4. The solution is decolourised.

Q. Which of the following gases is obtained when ammonium dichromate is heated?

1. Ammonia
2. Oxygen
3. Nitrogen
4. Nitrous oxide

Q. $C{r}_2{O}_7^{2-}\stackrel{pH=x}{\to }Cr{O}_4^{2-}\stackrel{pH=y}{\to }C{r}_2{O}_7^{2-}$.The `pH` values of x and y can be:

1. 4 and 5
2. 4 and 8
3. 8 and 4
4. 8 and 9

Q. When $K_{2}C{r}_2{O}_7$ is heated with conc. $H_{2}S{O}_4$ in the presence of a soluble metal chloride, orange red vapours are produced. These are due to

1. $CrC{l}_3$
2. $CrOC{l}_2$
3. $Cr{O}_{2}C{l}_2$
4. $Cr{O}_4^{2-}$

Q.

In acidic medium (Conc. H₂SO₄), Hydrogen peroxide reacts with K₂Cr₂O₇ in the presence of ether forms a deep violet coloured chromium peroxide. The Oxidation state of chromium in chromium pentoxide is

1. +2

2. +3

3. +5

4. +6

Q. When potassium dichromate is heated with conc.$H_{2}S{O}_4$ and NaCl, orange vapours are evolved due to

1. $Cr{O}_{2}C{l}_2$
2. $CrC{l}_3$
3. $C{l}_2$
4. $Cr{O}_5$

Q. Ammonium dichromate is used in some fireworks. The green-coloured powder blown in the air is (IIT JEE, 1997)

1. $Cr{O}_3$
2. $C{r}_2{O}_3$
3. Cr
4. $CrO\left(O_2\right)$

Q. In aqueous solutions, the Chromate ion can exist only under acidic conditions while the dichromate ion can exist only in neutral/alkaline conditions – True or false?

1. True
2. False

Q.

Pottasium dichromate is used .

1. in leather industry

2. in textile industry

3. as germicide

4. as a bleaching agent

Q. When $S{O}_2$ is passed through an acidic solution of potassium dichromate, chromium sulphate is formed. The change in oxidation number of chromium is:

1. +6 to +2
2. +6 to +3
3. +5 to +3
4. +6 to +4

Q. What is the hybridization of $Cr$ if $C{O}_2$ gas is passed into an aqueous chromate (VI) solution?

1. $s{p}^3$
2. $d^{3}s$
3. $s{p}^2$
4. $ds{p}^2$

Q. What is the hybridization of $Cr$ if $C{O}_2$ gas is passed into an aqueous chromate (VI) solution?

1. $s{p}^3$
2. $d^{3}s$
3. $s{p}^2$
4. $ds{p}^2$

Q. Potassium peroxochromate $K_{3}Cr{O}_8$ is a red-brown paramagnetic solid prepared from the following reaction.
$Cr{O}_4^{2-}+H_2{O}_2+O{H}^{-}\to [Cr{O}_8{]}^{3-}+H_{2}O+O_2$
If oxidation state of $Cr$ in product is $X$, number of peroxide bonded $O$ in product is $Y$ and number of electrons in d orbital of $Cr$ is $Z$ then what is value of $X+Y+Z$?