Benzene ring in phenol is expected to give the characteristic substitution or replacement reactions i.e. halogenation, nitration, sulphonation, alkylation etc. In these reactions, the attacking reagent is electrophile. The phenolic group activates the ortho and para positions in the ring due to conjugation. Disubstitution reactions are quite fast as the electron density in the ring has increased considerably. Phenols do not respond to nucleophilic substitution reactions as it is influenced by phenolic group.

Conversion of freshly prepared precipitate into the colloidal solution is known as

The half life for radioactive decay of C-14 is 5730 years.
A sample of tree had only 80% of C-14 left.
Estimate the age of the tree.
(log 5 = 0.698) (log 4 = 0.602)

Why do the actinoids exhibit a higher number of oxidation states than lanthanoids?

When methyl bromide is treated with sodium tert-butoxide, the compound formed is:

Answer the question on basis of passage given below :
Look at the following chemical reactions and answer the following question :
(A) \(C_7H_8 \xrightarrow{\text{Conc. HNO}_3, 0^\circ C}
(B) \xrightarrow{Sn/HCl}
(C) \xrightarrow{NaNO_2/H_3O^+}
(D) \xrightarrow{H_2O, Heat}(E)\)
(E) \(CH_3I \xrightarrow{KMnO_4/H^+}
(F) \xrightarrow{H_3O^+}
(G) \xrightarrow{NaOH} (H)\)
Which are water soluble ?

Read the passage carefully and answer the following questions
There are mainly four series of the transition metals, \(3 d\) series ( \(S c\) to Zn), \(4 d\) series (Y to Cd), \(5 d\) series (La and Hf to Hg ) and 6d series which has Ac and elements from Rf to Cn . The two series of the inner transition metals; \(4 f\) ( Ce to Lu ) and \(5 f\) (Th to Lr ) are known as lanthanoids and actinoids respectively. Their chemical properties are transitional between those of \(s\) and \(p\) block elements. The transition metals (with the exception of Zn, Cd and Hg) are very hard and have low volatility. Their melting and boiling points are high. Transition metals have incomplete d subshell either in neutral atom or in their ions. With partly filled d orbitals these elements exhibit certain characteristic properties such as display of a variety of oxidation states, formation of coloured ions and entering into complex formation with a variety of ligands. The transition metals and their compounds are known for their catalytic activity.
In general the electronic configuration of outer orbitals of transition metals is \((n - 1)d^{1-10}ns^{1-2}\) but Pd shows an exceptional electronic configuration as......

Which of the following are autosomal recessive trait/ disorder?
(A) Thalassemia
(B) Haemophilia
(C) Sickle cell anaemia
(D) Phenylketonuria
Choose the correct answer from the options given below:

Inactive protoxins is converted into its active toxin by:

Two cylindrical wires of the same material have their lengths in the ratio 2: 1 and their diameters in the ratio \(1: 3\). The ratio of the resistance of thinner wire to that of thicker wire is:

Identify the features developed by flowering plants to discourage self-pollination:
(A) Self incompatibility
(B) Synchronized pollen release and stigma receptivity
(C) Different positions of anther and stigma in a flower
(D) Producing bisexual flowers
Choose the correct answer from the options given below:

Transmission of HIV infection occurs by:
(A) By transfusion of contaminated blood
(B) By sharing infected needles
(C) Sexual contact with HIV infected person
(D) From an infected mother to her child through the placenta
Choose the correct answer from the options given below:

Read the passage carefully and answer the questions based on the passage:
Species diversity on earth is not uniformly distributed. It is generally highest in the tropics and decreases towards the poles. Earth's fossil history reveals the incidences of mass extinctions in the past. Earth's rich biodiversity is vital for the very survival of mankind. It is believed that communities with high diversity tend to be less variable and more productive. The reasons of conserving biodiversity are narrowly utilitarian, broadly utilitarian and ethical. Biodiversity conservation may be in-situ as well as ex-situ.
How many episodes of mass extinction of species have occurred since the origin and diversification of life on earth?