Solutions — Chemistry STD 12 Science — Question

Why is the mass determined by measuring a colligative property in case of some solutes abnormal? Discuss it with the help of Van’t Hoff factor.

Explain the general methods of preparation of amines.

1. Write the steps involved in the preparation of: 

1. K₂Cr₂O₇ from Na₂CrO_4.
2. KMnO₄ from  K₂MnO_4.
3. Calomel from corrosive sublimate.

2. What is meant by lanthanoid contraction? What effect does it have on the chemistry of the elements which follow lanthanoids?

Explain the open chain structure of glucose.

1. The elements of 3d transition series are given as:

Sc Ti V Cr Mn Fe Co Ni Cu Zn

Answer the following:

1. Which element has the highest m.p. and why?
2. Which element is a strong oxidising agent in +3 oxidation state and why?
3. Which element is soft and why?

2. Write the equations involved in the preparation of Potassium dichromate from Sodium chromate (Na₂CrO₄).

Explain the following :
(i) Fermentation
(ii) Dehydration
(iii) Hydrogen bonding in alcohols.

In the reaction
Q + R → Products
The time taken for 99% reaction of Q is twice the time taken for 90% reaction of R. The concentration of R varies with time as shown in the figure given alongside.

What is the overall order of the reaction? Give the units of the rate constant for the same. Write the rate expression for the above reaction.

Match the catalysts given in Column I with the processes given in Column II.

	Column I (Catalyst)		Column II (Process)
(i)	Ni in the presence of hydrogen	(a)	Zieglar Natta catalyst
(ii)	Cu2Cl2	(b)	Contact process
(iii)	V2O5	(c)	Vegetable oil to ghee
(iv)	Finely divided iron	(d)	Sandmeyer reaction
(v)	TiCl4 + Al (CH3)3	(e)	Haber’s Process
		(f)	Decomposition of KClO3

Explain the IUPAC method of nomenclature coordination compounds with examples.

Explain the methods of preparation of aromatic aldehydes (benzoic aldehyde) from aromatic hydrocarbons.