Question 1

The correct order of melting points of the following salts is

Accepted Answer

Smaller the size of anion, smaller is the covalent character and higher will be its melting point. Hence, the order of melting point of lithium salts is LiF LiCl LiBr .

Question 2

Which among the following is used in detergent

Accepted Answer

Sodium stearate is used in soap and sodium lauryl sulphate CH _3 ( CH _2 )_ 10 CH _2- OSO _3^ Na ^ is an anionic detergent

Question 3

Thermal decomposition of lithium nitrate gives

Accepted Answer

LiNO _3 2 Li _2 O +4 NO _2+ O _2 lithium nitrate

Question 4

Magnesium burns in CO _2 to form

Accepted Answer

Mg burns in CO _2 to give MgO and C .

Question 5

Which of the following will precipitate first when aqueous solution containing sulphate ions are added?

Accepted Answer

Down the group solubility of sulphate decreases. Thus, Ba ^ 2+ ions will precipitate out most easily.

Question 6

Which of the following compounds is thermodynamically is the most stable?

Accepted Answer

The thermal stability of carbonates increases down the group. So, the order of thermal stability of carbonates of alkaline earth metals is BaCO _3> CaCO _3> MgCO _3> BeCO _3 . Therefore, BaCO _3 is thermodynamically most stable and BeCO _3 is least stable.

Question 7

Which of the following has minimum melting point?

Accepted Answer

Ionic compounds have high melting point. Greater the ionic character, more is melting point. HCl has least ionic character because of maximum electronegativity difference between the two constituent elements, ( H and Cl ) among CsF , HCl , HF and LiF HCl has minimum melting point.

Question 8

Two elements A and B have similar chemical properties. They don't form solid hydrogencarbonates, but react with nitrogen to form nitrides. A and B, respectively, are :

Accepted Answer

Li and Mg do not form solid bicarbonate, but react with N _ 2 to give nitrides. array l 6 Li + N _ 2 2 Li _ 3 ~N \ 3 Mg + N _ 2 Mg _ 3 ~N _ 2 array

Question 9

BeF _2, is soluble in water whereas fluorides of other alkaline earth metals are insoluble because of

Accepted Answer

Be ^ 2+ being small in size is heavily hydrated and heat of hydration exceeds the lattice energy. Hence BeF _ 2 is soluble in water.

s Block Elements — Previous Year Questions & Solutions