Q. In Lassaigne’s test, a blue colour is obtained if the organic compound contains nitrogen. The blue colour is due to

NTA AbhyasNTA Abhyas 2022 Report Error

$K_{4}\left[\right.Fe\left(\right.CN\left(\left.\right)_{6}\left]\right.$

$Fe_{4}\left[\right.Fe\left(\right.CN\left(\left.\right)_{6}\left(\left]\right.\right)_{3}$

$Na_{3}\left[\right.Fe\left(\right.CN\left(\left.\right)_{6}\left]\right.$

$Cu_{2}\left[\right.Fe\left(\right.CN\left(\left.\right)_{6}\left]\right.$

Solution:

In Lassaigne’s test, a blue colour is obtained if the organic compound contains nitrogen. The Prussian blue is due to $Fe_{4}\left[\right.Fe\left(\right.CN\left(\left.\right)_{6}\left(\left]\right.\right)_{3}$ is formed.

Questions from NTA Abhyas 2022

1. According to the Valence bond theory, which statement is incorrect regarding bonding between two carbon atoms?

2. 3. Which of the following is not found in nucleotides?

4. Hybridisation, shape and magnetic moment of $\mathrm{K}_3\left[\mathrm{Co}\left(\mathrm{CO}_3\right)_3\right]$ is

Coordination Compounds

5. In the reaction

Chemistry Most Viewed Questions

1. If for a certain reaction $\Delta_{r}H$ is $30\, kJ\, mol^{-1}$ at $450 \,K$, the value of $\Delta_{r}S$ (in $JK^{-1}\, mol^{-1})$ for which the same reaction will be spontaneous at the same temperature is

NEET 2020 Thermodynamics

2. If $8\,g$ of a non-electrolyte solute is dissolved in $114\, g$ of n-octane to reduce its vapour pressure to $80\%$, the molar mass (in $g \,mol^{-1})$ of the solute is [Given that molar mass of n-octane is $114 \,g\, mol^{-1}]$

NEET 2020 Solutions

3. At standard conditions, if the change in the enthalpy for the following reaction is $-109 \,kJ\, mol^{-1}$ $H_{2(g)}+Br_{2(g)} \to 2HBr_{(g)}$ Given that bond energy of $H_{2}$ and $Br_{2}$ is $435\,KJ\,mol^{-1}$ and $192\,KJ\,mol^{-1}$ , respectively, what is the bond energy (in $KJ \,mol^{-1})$ of $HBr$ ?

NEET 2020 Thermodynamics

4. An organic compound contains $78 \%$ (by wt.) carbon and remaining percentage of hydrogen. The right option for the empirical formula of this compound is: [Atomic wt. of $C$ is $12, H$ is $1$]

NEET 2021 Some Basic Concepts of Chemistry

5. The density of 2 M aqueous solution of NaOH is 1.28 g/cm$^3$. The molality of the solution is
[Given that molecular mass of NaOH = 40 g mol$^{-1}$]

NEET 2019 Some Basic Concepts of Chemistry

6. Given below are half cell reactions:
$ MnO _{4}^{-}+8 H ^{+}+5 e ^{-} \rightarrow Mn ^{2+}+4 H _{2} O $
$ E _{ Mn ^{2+} / MnO _{4}^{-}}^{\circ}=-1.510\, V$
$\frac{1}{2} O _{2}+2 H ^{+}+2 e ^{-} \rightarrow H _{2} O ,$
$ E _{ O _{2} / H _{2} O }^{\circ}=+1.223 \,V$
Will the permanganate ion, $MnO _{4}^{-}$liberate $O _{2}$ from water in the presence of an acid ?

NEET 2022 The d-and f-Block Elements

7. In water saturated air the mole fraction of water vapour is $0.02$. If the total pressure of the saturated air is $1.2\, atm$, the partial pressure of dry air is :

NEET 2019 Solutions

8. Following limiting molar conductivities are given as
$\lambda^{o}_{m}\left(H_{2}SO_{4}\right) \,= \,x S\, cm^{2} mol^{-1}$
$\lambda^{o}_{m}\left(K_{2}SO_{4}\right) = y S\,cm^{2} mol^{-1}$
$\lambda^{o}_{m}\left(CH_{3}COOK\right) =z S\, cm^{2} mol^{-1} $
$\lambda^{o}_{m}\left(in \,S \,cm^{2} mol^{-1}\right)$ for $CH_3COOH$ will be-

NEET 2019 Electrochemistry

9. One atom of an element weighs $ 1.8\times 10^{-22}g$ . Its atomic mass is

Manipal 2009 Some Basic Concepts of Chemistry

10. In the following reaction,
$H_3C-C\equiv CH\xrightarrow [{873\, K}] {\text{red hot iron tube}}$A,
the number of sigma(s) bonds present in the product A is :-

NEET 2019 Hydrocarbons