When same amount of zinc is treated separately with excess of sulphuric acid and excess of sodium hydroxide solution the ratio of volumes of hydrogen evolved is

1 : 1
1 : 2
2 : 1
9 : 4

Solution

Zn + H₂SO₄ ⟶ ZnSO₄ + H₂
Zn + 2NaOH ⟶ Na₂ZnO₂ + H₂
∴ Ratio of volumes of H₂ evolved is 1 : 1

Which of the following chemicals is not present in clear hard water?

MgCO₃
MgSO₄
Mg(HCO₃)₂
CaCl₂

Solution

MgCO₃ is insoluble in water.

Saline hydrides react explosively with water, such fires can be extinguished by

water
carbon dioxide
sand
None of these

Solution

Fire due to action of water on saline hydrides cannot be extinguished with water or CO₂. These hydrides can reduce CO₂ at high temperature to produce O₂.

D₂O is preferred to H₂O, as a moderator, in nuclear reactors because

D₂O slows down fast neutrons better
D₂O has high specific heat
D₂O is cheaper
None of these

Solution

H₂O absorbs neutrons more than D₂O and this decreases the number of neutrons for the fission process.

The H^– ion can be formed in ordinary chemical reaction under proper conditions, but the H⁺ ion cannot. The best explanation for this difference is due to

the radius of the H nucleus
the electronegativity of H atom.
the ionisation energy of the H-atom
the bond dissociation energy of H–H bond

Solution

Single e^- of the H atom cannot be readily removed to form H^-

Heavy water reacts respectively with CO₂, SO₃, P₂O₅ and N₂O₅ to give the compounds:

D₂CO₃, D₂SO₄, D₃PO₂, DNO₂
D₂CO₃, D₂SO₄, D₃PO₄, DNO₂
D₂CO₃, D₂SO₃, D₃PO₄, DNO₂
D₂CO₃, D₂SO₄, D₃PO₄, DNO₃

HCl is added to following oxides. Which one would give H₂O₂

MnO₂
PbO₂
BaO
None of these

Solution

MnO₂ , PbO₂ and BaO will not give H₂O₂ with HCl.MnO₂ and PbO₂ will give Cl₂ and BaO will react with HCl to give BaCl₂ and water.

Solution

Which pair does not show hydrogen isotopes ?

Ortho and para hydrogen
Protium & deuterium
Deuterium & tritium
Tritium and protium

Solution

Ortho and para hydrogens are two forms of hydrogen(₁H¹ ) which differ only in the direction of spin of proton.

At its melting point ice is lighter than water because

H₂O molecules are more closely packed in solid state
ice crystals have hollow hexagonal arrangement of H₂O molecules.
on melting of ice the H₂O molecule shrinks in size
ice froms mostly heavy water on first melting

Solution

In the structure of ice each molecule of H₂O is surrounded by three H₂O molecules in hexagonal honeycomb manner which results an open cage like structure.As a result there are a number of 'hole' or open spaces.In such a structure lesser number of molecules are packed per ml. When ice melts a large no.of hydrogen bonds are broken.The molecules therefore move into the holes or open spaces and come closer to each other than they were in solid state. This result sharp increase in the density. Therefore ice has lower density than water.

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