Science (English Medium) Class 11 - CBSE Question Bank Solutions for Chemistry

Nucleophiles and electrophiles are reaction intermediates having electron-rich and electron-deficient centres respectively. Hence, they tend to attack electron-deficient and electron-rich centres respectively. Classify the following species as electrophiles and nucleophiles.

(i) H₃CO^– 

(ii) \[\begin{array}{cc}
\phantom{.}\ce{O}\\
\phantom{.}||\\
\ce{H3C - C - O-}
\end{array}\]

(iii) \[\ce{\overset{\bullet}{C}l}\]

(iv) Cl₂C:

(v) (H₃C)₃C⁺ 

(vi) Br^– 

(vii) H₃COH

(viii) R – NH – R

Write hydrocarbon radicals that can be formed as intermediates during monochlorination of 2-methylpropane? Which of them is more stable? Give reasons.

0.3780 g of an organic chloro compound gave 0.5740 g of silver chloride in Carius estimation. Calculate the percentage of chlorine present in the compound.

In the estimation of sulphur by Carius method, 0.468 g of an organic sulphur compound afforded 0.668 g of barium sulphate. Find out the percentage of sulphur in the given compound.

Discuss the principle of estimation of halogens present in an organic compound.

\[\ce{CO}\] is isoelectronic with

(i) \[\ce{NO+}\]

(ii) \[\ce{N2}\]

(iii) \[\ce{Sncl2}\]

(iv) \[\ce{NO^{-}2}\]

Give reasons for the following:

Ethyne molecule is linear.

Assertion (A): Among the two \[\ce{O - H}\] bonds in \[\ce{H2O}\] molecule, the energy required to break the first \[\ce{O - H}\] bond and the other \[\ce{O - H}\] bond is the same.

Reason (R): This is because the electronic environment around oxygen is the same even after breakage of one \[\ce{O - H}\] bond.

Assertion (A): Sulphur present in an organic compound can be estimated quantitatively by Carius method.

Reason (R): Sulphur is separated easily from other atoms in the molecule and gets precipitated as light yellow solid.

Assertion (A): Toluene on Friedal Crafts methylation gives o– and p–xylene.

Reason (R): CH₃-group bonded to benzene ring increases electron density at o– and p– position.

Discuss the principle of estimation of sulphur present in an organic compound.

The ionisation constant of an acid, K_a, is the measure of strength of an acid. The K_a values of acetic acid, hypochlorous acid and formic acid are 1.74 × 10^–5, 3.0 × 10^–8 and 1.8 × 10^–4 respectively. Which of the following orders of pH of 0.1 mol dm^–3 solutions of these acids is correct?

Discuss the principle of estimation of phosphorus present in an organic compound.

Determine the solubilities of silver chromate, barium chromate, ferric hydroxide, lead chloride and mercurous iodide at 298K from their solubility product constants. Determine also the molarities of individual ions.

What is the maximum concentration of equimolar solutions of ferrous sulphate and sodium sulphide so that when mixed in equal volumes, there is no precipitation of iron sulphide? (For iron sulphide, K_sp = 6.3 × 10^–18).

The ionization constant of nitrous acid is 4.5 × 10^–4. Calculate the pH of 0.04 M sodium nitrite solution and also its degree of hydrolysis.

Hydrogen bonds are formed in many compounds e.g., \[\ce{H2O, HF, NH3}\]. The boiling point of such compounds depends to a large extent on the strength of hydrogen bond and the number of hydrogen bonds. The correct decreasing order of the boiling points of above compounds is ______.

In which of the following substances will hydrogen bond be strongest?

Structures of molecules of two compounds are given below :

(I)	(II)

1. Which of the two compounds will have intermolecular hydrogen bonding and which compound is expected to show intramolecular hydrogen bonding.
2. The melting point of a compound depends on, among other things, the extent of hydrogen bonding. On this basis explain which of the above two compounds will show higher melting point.
3. Solubility of compounds in water depends on power to form hydrogen bonds with water. Which of the above compounds will form hydrogen bond with water easily and be more soluble in it.

Arrange the following in increasing order of \[\ce{pH}\].

\[\ce{KNO3 (aq), CH3COONa (aq), NH4Cl (aq), C6H5COONH4 (aq)}\]