List of top Chemistry Questions asked in UP Board XII

$[NiCl_4]^{2-}$ is paramagnetic while $[Ni(CO)_4]$ is diamagnetic even though both are tetrahedral. Why?

For which of the following ions will the magnetic moment ($\mu$) be maximum?

(A) Write the electronic configuration of the element with atomic number 24.
(B) Find the number of unpaired electrons in $Co^{2+}$ ion.
(C) Why is the range of oxidation states greater in the actinoid series compared to the lanthanoid series?

Write the structures of (A), (B), and (C) in the following reaction:
\[ C_6H_5NO_2 \xrightarrow{Fe/HCl} (A) \xrightarrow[\text{273 K}]{NaNO_2 + HCl} (B) \xrightarrow[\Delta]{H_2O/H^+} (C) \]

Write the structures of (A), (B), and (C) in the following reaction:
Reaction Scheme: \[ (C) \xleftarrow{\text{conc. } HNO_3} \text{Phenol} \xrightarrow{\text{dil. } HNO_3} (A) + (B) \]

What happens when aniline reacts with the following:
(A) Bromine water
(B) $(CH_3CO)_2O$ / Pyridine
(C) $HNO_2 + HCl (0^\circ - 5^\circ C)$

What is a peptide bond? Explain with an example.

Write the mechanism of bimolecular nucleophilic substitution reaction ($S_N2$) of alkyl halide.

Write the IUPAC nomenclature of the following organic compounds:
(A) $CH_3 - CH_2 - \overset{\text{O}}{\overset{||}{\text{C}}} - CH_2 - \underset{\text{CH}_3}{\underset{|}{\text{CH}}} - CH_3$
(B) $Ph - CH = CH - CHO$

Write the definition of electrode potential and cell electromotive force (emf).

Does the half-life of a first-order reaction depend on the initial concentration of the reaction? Explain.

The increasing order of reactivity of the following compounds in $S_N1$ reaction is:
Compounds:
A. $(CH_3)_3CBr$
B. $CH_3CH_2CH_2CH_2Br$
C. $(CH_3)_2CHCH_2Br$
D. $CH_3CH(Br)CH_2CH_3$

If the rate law of a reaction is Rate $= K[A]^2 [B]^0$, then what will be the order of the reaction?

In \( 2A \rightarrow \) Product, the reaction concentration of A remains 0.4 mol\(^{-1}\) from 0.5 mol\(^{-1}\) in 10 minutes.
Calculate the velocity of reaction for this period of time.

What happens when — (write chemical equation only):
i) Phenol reacts with Br$_2$ water?
ii) Acetylation of phenol happens in the presence of pyridine?
iii) Phenol is heated with PCl$_5$?
iv) Phenol reacts with NaOH?
v) Vapour of the mixture of phenol and methyl alcohol is passed through hot thoria (ThO$_2$)?

Compound of which transition metal ion is colourless?

Explain with reason:
(i) Cr^{2+} is a reducing agent while Mn^{3+} is an oxidising agent, while both have \(d^4\) configuration.}

Magnetic moment of a bivalent ion in aqueous solution will be, if its atomic number is 25:

Explain the following:
(i) Lanthanoid contraction
(ii) Oxidation states in Lanthanoids and Actinoids

100 ml of 10 M HCl is mixed with 75 ml of 10 M Na$_2$CO$_3$. The resulting solution would be –

Write IUPAC names of the following compounds:
(i)\; \includegraphics[height=10pt]{dummy} (ring with –CHO and adjacent –CH$_3$)
(ii)\; (CH$_3$)$_2$CHCOCH(CH$_3$)$_2$
(iii)\; CH$_3$CH(OCH$_3$)CHO
(iv)\; HOOC–(CH$_2$)$_4$–COOH
(v)\; \includegraphics[height=10pt]{dummy} (benzene–CH$_2$COOH)

A cell in which the following reaction occurs:
\[ \text{Zn}_{(s)} + \text{Cu}^{2+}_{(aq)} \rightarrow \text{Zn}^{2+}_{(aq)} + \text{Cu}_{(s)} \] has standard electrode potential \(E^\circ_{\text{cell}} = 1.1~\text{V}\) at \(298~\text{K}\). Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction.