Science (English Medium) Class 12 - CBSE Question Bank Solutions

Give reasons CH₃NH₂ is more basic than C₆H₅NH₂.

An element has atomic mass 93 g mol⁻¹ and density 11.5 g cm^–3. If the edge length of its unit cell is 300 pm, identify the type of unit cell. (N_A = 6.023 × 10²³ mol⁻¹)

Calculate the number of unit cells in 8.1 g of aluminium if it crystallizes in a f.c.c. structure. (Atomic mass of Al = 27 g mol^–1)

Give reason for the following:

Red phosphorus is less reactive than white phosphorus.

Write the reaction involved in the Stephen reduction

Account for the following: 

Zn, Cd and Hg are soft metals.

Write the IUPAC name of the following coordination compound:

K₃[Fe(CN)₆]

Write the IUPAC names of the following coordination compounds: 

[CoBr₂(en)₂]⁺, (en = ethylenediamine)

Give reasons for the following :

Aquatic animals are more comfortable in the cold water than in warm water.

Write the chemical reactions involved in the process of extraction of Gold. Explain the role of dilute NaCN and Zn in this process.

Give reason (CH₃)₂NH is more basic than (CH₃)₃N in an aqueous solution.

An element 'X' (At. mass = 40 g mol^-1) having f.c.c. the structure has unit cell edge length of 400 pm. Calculate the density of 'X' and the number of unit cells in 4 g of 'X'. (N_A = 6.022 × 10²³ mol^-1)

 Arrange the following in the increasing order of their pK_b values:

C₆H₅NH₂, C₂H₅NH₂, C₆H₅NHCH₃

Which allotrope of sulphur is thermally stable at room temperature ?

Write down the IUPAC name of the following complex :

[Cr(en)₃]Cl₃

What is the role of dilute NaCN in the extraction of gold ?

Illustrate the following reactions giving suitable example in each case 

Ammonolysis

Write the structures of main products when benzene diazonium chloride (C6 H5 N+2CI−)C6 H5 N2+CI- reacts with the  :  HBF₄/∆

 Write the structures of main products when benzene diazonium chloride (C6 H5 N+2CI−)C6 H5 N2+CI- reacts with the :Cu/HBr

Which reducing agent is employed to get copper from the leached low-grade copper ore?