If NaOH is added to an aqueous solution of Zn²⁺ ions, a white precipitate appears and on adding excess NaOH, the precipitate dissolves. In this solution zinc exists in the :

cationic part
anionic part
both in cationic and anionic parts
there is no zinc left in the solution

Solution

What is the function of potassium nitrate in gun powder ?

It is a sublime substance
It is added to act as instant explosive
It is added to provide oxygen
It reacts with sulphur to form another compound that is highly explosive in nature

Solution

KNO₃ is included in gun powder to provide a supply of oxygen.

The general formula of an alum is M₂SO₄.M'(SO₄)₃.24H₂O
where M is univalent and M’ is a trivalent metal which of the following does not form alum ?

Li
Na
K
all of these form alum

Solution

Li does not form alum because of its small size.

Which of the following statement is false ?

Strontium decomposes water readily than beryllium
Barium carbonate melts at a higher temperature than calcium carbonate
Barium hydroxide is more soluble in water than magnesium hydroxide
Beryllium hydroxide is more basic than barium hydroxide

Solution

Be(OH)₂ is amphoteric, but the hydroxides of other alkaline earth metals are basic. The basic strength increases gradually.

Among the following oxides, which one is most basic

ZnO
MgO
Al₂O₃
N₂O₅

Solution

MgO. N₂O₅ is strongly acidic,ZnO and Al₂O₃ are amphoteric, therefore, MgO is most basic.

Which of the following is neither deliquescent nor efflorescent and is used for wool washing ?

NaOH
KOH
NaHCO₃
Na₂CO₃.NaCO₃.2H₂O

Solution

Sodium sesquicarbonate (Na₂CO₃.NaCO₃.2H₂O) is neither deliquescent nor efflorescent and is used for wool washing.

All of the following substances react with water. The pair that gives the same gaseous product is

K and KO₂
Na and Na₂O₂
Ca and CaH₂
Ba and BaO₂

Solution

Which one of the following has minimum value of cation/anion ratio ?

NaCl
KCl
MgCl₂
CaF₂

Solution

Atomic size of K⁺ > Ca²⁺ > Mg²⁺ and that of Cl–> F^–.Therefore, Mg²⁺/Cl^- ratio has the minimum value.

Which one out of the NaOH and KOH, is a better absorber of CO₂ ?

NaOH
KOH
both absorb CO₂ equally
can not be predicted

Solution

KOH is better absorber of CO₂ because K₂CO₃ formed is more soluble and does not separate out.

Lithium can not be stored in kerosene oil because

it is an alkali metal
it reacts with kerosene oil
it floats to the surface of kerosene oil
none of the above is correct

Solution

Because of its very low density lithium floats to the surface of kerosene oil.

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