All India NEET Group

A car covers the first half of the distance between two places at the speed of 40 km per hour and the second half at 60 km per hour. what is the average speed of the car?

Juhe Shanofar answered
Time taken in travelling the first distance x will be t1 =
x/40 and time taken in travelling the second distance x
will be t2 = x/60
Now the average velocity can be calculated as
V = total distance/total time
2x/t1+t2 = 2x/x/40 +x/60
= 48km/hr

The ignition powder in aluminothermite process contains a mixture of
  • a)
    Magnesium powder and BaO2
  • b)
    Magnesium powder, aluminium and BaO2
  • c)
    Magnesium and aluminium powder
  • d)
    Magnesium and aluminium oxide
Correct answer is option 'A'. Can you explain this answer?

EduRev JEE answered
Alumino thermite process, contain oxides of Mn, Cr, that is not reduced by carbon due to very high melting point. They are reduced by Al. Its mixture consists of Mg powder along with BaO2​ or KClO3​.
A mixture of magnesium powder and BaO2 is used as ignition powder.

Roasting process is applied to which of the following ores?
  • a)
    Galena
  • b)
    Iron pyrites
  • c)
    Copper glance
  • d)
    All of these
Correct answer is option 'D'. Can you explain this answer?

EduRev JEE answered
Generally sulphide ores are subjected to roasting.
Galena: 2PbS+3O2 ⟶ 2PbO + 2SO2
Iron pyrites: 2FeS2 + 3O2 ⟶ 2FeO + 2SO2
Copper glance: 2Cu2S + 3O2 ⟶ 2Cu2O + 2SO2

Which of the following has longest C−O bond length? (Free C−O bond length in CO is 1.128Å.)
  • a)
    [Fe(CO)4]2−
  • b)
    [Mn(CO)6]+
  • c)
    Ni(CO)4
  • d)
    [Co(CO)4]
Correct answer is option 'A'. Can you explain this answer?

EduRev JEE answered
The greater the negative charge on the carbonyl complex, the more easy it would be for the metal to permit its electrons to participate in the back bonding, the higher would be the M−C bond order and simultaneously there would be larger reduction in the C−O bond order. Thus, [Fe(CO)4]2− has the lowest C−O bond order means the longest bond length.

An example of a sigma bonded organometallic compound is
  • a)
    Grignard's reagent
  • b)
    ferrocene
  • c)
    cobaltocene
  • d)
    ruthenocene.
Correct answer is option 'A'. Can you explain this answer?

EduRev JEE answered
An example of a sigma bonded organometallic compound is grignard's reagent. Grignard's reagent is represented by R−MgX. An example is methyl magnesium iodide. A sigma bond is present between C atom and Mg atom.

The basicity of H3PO4 may be
  • a)
    1
  • b)
    2
  • c)
    3
  • d)
    4
Correct answer is option 'C'. Can you explain this answer?

EduRev JEE answered
The structure of H3PO4 is as
From the structure it is clear that it has 3 P - OH bonds which can produce three H+ ions per molecule of H3PO4 in aqueous solution. Hence, basicity is three.

Aluminium oxide is not reduced by chemical reactions since
  • a)
    Aluminium oxide is reactive
  • b)
    Reducing agents contaminate
  • c)
    Aluminium oxide is highly stable
  • d)
    The process pollutes the environment
Correct answer is option 'C'. Can you explain this answer?

EduRev JEE answered
Aluminium oxide is a highly stable oxide of aluminium. Thus, it is chemically inert. Metal oxides can be reduced to the corresponding metal by using a suitable reducing agent. But the choice of the reducing agent depends upon the reactivity of the metal. If the metal to be produced is a very reactive metal like alkali metals, alkaline earth metals and aluminium, then the reduction of the oxide can be done by only the electrolytic method.
The oxides of less reactive metals like zinc, iron etc. are reduced by a number of reducing agents like carbon or coke or carbon monoxide.
This is why aluminium is extracted from its ore bauxite by electrolytic reduction. The bauxite ore is first converted into alumina which is then converted into aluminium by the electrolysis of mixture of alumina and cryolite via the Hall and Heroult process.

Which of the following statements is correct with respect to the property of the elements with increase in atomic number in the carbon family?
  • a)
    Their metallic character decreases.
  • b)
    The stability of +2 oxidation state increases.
  • c)
    Their ionisation energy increases.
  • d)
    Their atomic size decreases.
Correct answer is option 'B'. Can you explain this answer?

EduRev JEE answered
Reluctance in tendency of s-electrons to participate in bonding is called inert pair effect and due to this stability of higher oxidation state increases down the group and that of lower oxidation state increases down the group. Lower oxidation state in carbon family is +2 while higher oxidation state is +4. Thus, stability of +2 oxidation state decreases while that of +4 oxidation state increases... more

Among the following which is the strongest oxidising agent?
  • a)
    Br2
  • b)
    I2
  • c)
    Cl2
  • d)
    F2
Correct answer is option 'D'. Can you explain this answer?

EduRev JEE answered
The halogen which has higher value of standard reduction potential will be the strongest oxidizing agent. Standard reduction potentials of halogens are positive and decrease from fluorine to iodine. So, F2 is the strongest oxidizing agent.

Which element is used in preparation of Pesticides?
  • a)
    Nitrogen
  • b)
    Antimony
  • c)
    Bismuth
  • d)
    Arsenic
Correct answer is option 'A'. Can you explain this answer?

EduRev JEE answered
Most pesticides contain elements, the type and number of which depend on the pesticide desired. Chlorine, oxygen, sulfur, phosphorus, nitrogen, and bromine are most common. Inert ingredients can be many substances, dependent on the type of pesticide. Liquid pesticides have traditionally used kerosene or some other petroleum distillate as a carrier, though water has recently begun to replace kerose... more

Aqueous solution of borax acts as a buffer because :
  • a)
    It contains weak acid and its salt with strong base
  • b)
    It contains tribasic acid and strong base
  • c)
    It contains number of neutral water molecules
  • d)
    None of these
Correct answer is option 'A'. Can you explain this answer?

EduRev JEE answered
A buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa.
Aqueous solution of borax tribasic acid (H3BO3) and strong base. It contains weak acid and its salt with strong base.Hence borax act as buffer.

HNO3 acts as
  • a)
    Acid
  • b)
    Oxidising agent
  • c)
    Reducing agent
  • d)
    Both (acid) and (oxidising agent)
Correct answer is option 'D'. Can you explain this answer?

EduRev JEE answered
HNO3 is a strong acid in which N-atom is in its maximum oxidation state +5, so it can act only as oxidising agent not as reducing agent.

Assertion (A): Noble gases have very low boiling points.
Reason (R): All noble gases have general electronic configuration of ns2 np6 (except He)
  • a)
    Both (A) and (R) are true but (R) is correct explanation of (A)
  • b)
    (A) is false but (R) is true
  • c)
    (A) is true but (R) is false
  • d)
    Both (A) and (R) are true but (R) is not the correct explanation of (A)
Correct answer is option 'D'. Can you explain this answer?

EduRev JEE answered
Both (A) and (R) are true but (R) is not the correct explanation of (A)
The melting and boiling points of noble gases are very low in comparison to those of other substances of comparable atomic and molecular masses. This indicates that only weak van der Waals forces or weak London dispersion forces are present between the atoms of the noble gases in the liquid or the solid state.
The van der Waals force increases with the increase in the size of the atom, and therefore, in general, the boiling and melting points increase from He to Rn.
Helium boils at −269 C. Argon has larger mass than helium and have larger dispersion forces. Because of larger size the outer electrons are less tightly held in the larger atoms so that instantaneous dipoles are more easily induced resulting in greater interaction between argon atoms. Therefore, its boiling point (−186 C) is more than that of He.
Similarly, because of increased dispersion forces, the boiling and melting points of monoatomic noble gases increase from helium to radon.
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