List of top Questions asked in CBSE CLASS XII

________________________ cultures can be maintained for a prolonged period of time by repeated sub-culturing.

Assertion (A): During plant tissue culture, the explants are treated with sodium hypochlorite.
Reason (R): Sodium hypochlorite helps in acclimatization of the regenerated plants.

Assertion (A): Some experts believe that there must be more than 30,000 genes in human genome.
Reason (R): Unreliability of in silico gene prediction is responsible for reporting lesser number of genes in human genome.

An example of secondary metabolites produced by microbial cells include:

When a transgene from a Genetically Modified crop escapes through pollen to a related plant species, it is known as:

Embryonic stem cells derived from the blastocyst stage of the embryo are ________________________ in nature.

A protein ion with a molecular weight of 10,000 Daltons carried a charge of 5+ and was subjected to mass spectrometric analysis. Calculate its mass to charge ratio.

Single nucleotide polymorphisms usually occur in ______________ regions.

Identify the vector that infects E. coli cells containing F-plasmid and that has a single-stranded circular genome:}

Severe combined immunodeficiency disease is caused due to the absence of:

Artificial seeds are produced by encapsulating the somatic embryos at the ______________ stage in a protective coating.

The peptide hormones and growth factors to promote healthy growth of animal cells in vitro are often derived from:}

The natural source of enzyme barnase and barstar, a system used to achieve male sterile plant is:

Which of the following compounds will not react with benzene sulphonyl chloride?
 

Assertion (A): Phenol on reaction with aqueous NaOH gives sodium phenoxide.
Reason (R): This reaction supports the acidic nature of phenol.

Complete and balance the following chemical equations: \( 3 \text{MnO}_4^- + 4 \text{H}^+ \longrightarrow ? \)
\( \text{Cr}_2 \text{O}_7^{2-} + 14 \text{H}^+ + 6 \text{Fe}^{2+} \longrightarrow ? \)

Which halogen compound in the following pair will react faster in \( \text{S}_\text{N}2 \) reaction and why?

Give the structures of A, B, and C in the following reactions:

Give the structures of A, B, and C in the following reactions:

Write the major product(s) in the following reactions: 

Give simple chemical tests to distinguish between the following pairs of compounds: (1) \( \text{C}_6\text{H}_5\text{COCH}_3 \text{ and } \text{C}_6\text{H}_5\text{COCH}_2\text{CH}_3 \)

Write the hybridization and magnetic character of the complex \([Ni(CO)_4]\) on the basis of valence bond theory.
[Atomic No. Ni = 28]

Out of \([CoF_6]^{3-}\) and \([Co(C_2O_4)_3]^{3-}\), which complex is:} 
(i) More stable? 
(ii) The high-spin complex? 
 

Write the electronic configuration of \(d^5\) in terms of \( t_{2g} \) and \( e_g \) in an octahedral field as: 
\( \Delta_o>P \)