MCQ
Colour of acidified $K _2Cr_2O_7$ is not changed by
- A$H_2O_2$
- B$Sn^{2+}(aq.)$
- ✓$HF$
- D$HBr$
✓
Answer
Correct option: C.
$HF$
c
The color of acidified $K _2 Cr _2 O _7$ is not changed if after reacting with a substance, the oxidation state of the transition metal, $Cr$, in the compound remains the same.
The color of acidified $K _2 Cr _2 O _7$ is not changed if after reacting with a substance, the oxidation state of the transition metal, $Cr$, in the compound remains the same.
The oxidation state of $Cr$ in $K _2 Cr _2 O _7$ is calculated as :
$2+2 x +(-2) \times 7=0$
$\Rightarrow 2+2 x -14=0$
$\Rightarrow 2 x -12=0$
$\Rightarrow 2 x =+12$
$\Rightarrow x =+6$
$\therefore$ Oxidations state of $Cr =+3$
Potassium dichromate reacts with hydrogen fluoride to produce potassium fluorotrioxochromate $(VI)$ and water. The reaction involved is :
$K _2 Cr _2 O _7+2 HF \rightarrow 2 K \left[ CrO _3 F \right]+ H _2 O$
The oxidation state of $Cr$ in $K \left[ CrO _3 F \right]$ can be calculated as follows:
$+1+ x +(-2) \times 3+(-1)=0$
$\Rightarrow+1+ x -6-1=0$
$\Rightarrow x -6=0$
$\Rightarrow x =+6$
$\therefore$ Oxidations state of $Cr =+3$
Since, there is no change in the oxidation state of $Cr$ in the reactant and in the product, the color of the solution doesn't change. Therefore, the color of acidified $K _2 Cr _2 O _7$ is not changed by $HF$.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
Which of the following unit is used to form cross linked silicone ?
$0.2\, g$ of an organic compound was subjected to estimation of nitrogen by Dumas method in which volume of $N _{2}$ evolved (at STP) was found to be $22.400 \,mL$. The percentage of nitrogen in the compound is $.......$. [nearest integer] (Given: Molar mass of $N _{2}$ is $28\, mol ^{-1}$. Molar volume of $N _{2}$ at STP : $22.4\, L$ )
→On electrical decomposition of $150\, ml$ dry and pure ${O_2}$, $10\%$ of ${O_2}$ gets changed to $O$, then the volume of gaseous mixture after reaction and volume of remaining gas left after passing in turpentine oil will be ............. $\mathrm{ml}$
→At constant volume, pressure is directly proportional to the temperature, this law is popularly known as:
For which of the reaction $\Delta H = \Delta E$
→The enthalpy change $(\Delta H)$ for the reaction,
→$N_2(g) + 3H_2(g) \to 2NH_3(g)$ is
$-\,92.38\,KJ$ at $298\,K$ . The internal energy change $\Delta U$ at $298\,K$ is.....$KJ$
Consider the partial decomposition of $A$ is
→$2A(g) \rightleftharpoons 2B(g) + C(g)$
at equilibrium $700\, mL$ gaseous mixture contains $100\, mL$ of gas $C$ at $10\, atm$ and $300\, K$. What is the value of $K_P$ for the reaction
In pyrrole the electron density is maximum on
Which of the following does not show geometrical isomerism ?
Correct $IUPAC$ name
→