NEET
Today’s Test
Previous Next

Select the correct statements :
I.Cs+ is more highly hydrated that the other alkali metal ions
II.Among the alkali metals Li, Na, K and Rb, lithium has the highest melting point
III.Among the alkali metals only lithium forms a stable nitride by direct combination with nitrogen

  • Solution

    Amongst alkali metal Li ions are highly hydrated.

Borax is used as cleansing agent because on dissolving in water it gives

  • Solution

    Borax is Na2B24O7.10H2O. It gives alkaline solution ondissolution in water as it is asalt of strong base and weak acid.
    Na2B4O7+ 7H2O→4H3BO3+ 2NaOH

  • Solution

    For a spontaneous process,total ?Stotal is always positive.

  • Solution

Which one of the following is correctly matched?

  • Solution

    Butter is an example of gel.

The alkali metals form salt-like hydrides by the direct synthesis at elevated temperature. The thermal stability of these hydrides decreases in which of the following orders ?

  • Solution

    The stability of alkali metal hydrides decreases from Lito Cs. It is due to the fact that M–H bonds become weaker with increase in size of alkali metals as we move down the group from Li to Cs. Thus the order of stability of hydrides is
    LiH > NaH > KH > RbH > CsH
    i.e. option(d) is correct answer.

The pollutants which came directly in the air from sources are called primary pollutants. Primary pollutants are sometimes converted into secondary pollutants. Which of the following belongs to secondary air pollutants?

The probability factor for the replacement of hydrogen atom during chlorination/bromination is

  • Solution

    More is the reactivity of a free radical, lesser is its selectivity for different type of H atoms (1º, 2º, or3º)and hence the probability factor will be more in such reagent. Since Cl• is more reactive, it is less selective and hence it will be more influenced by the probability factor.

Which of the following is true regarding the physical science?

The reaction of tert-butyl bromide with sodium methoxide produces mainly –

  • Solution

In BrF3 molecule, the lone pairs occupy equatorial positions to minimize

  • Solution

    In BrF3, both bond pairs as well as lone pairs of electrons are present. Due to the presence of lone pairs of electrons (lp) in the valence shell, the bond angle is contracted and the molecule takes the T-shape. This is due to greater repulsion between two lone pairs or between a lone pair and a bond pair than between the two bond pairs.

The values of heat of formation of SO2 and SO3 are –298.2kJ and –98.2 kJ. The heat of formation of the reaction SO2(1/ 2)O2→SO3 will be

  • Solution

    SO2+1⁄2O2→SO3

    ΔH=\(\Delta H_{F(SO_{3})}^{^{\circ}}-\Delta H_{F(SO_{2})}^{^{\circ}}\)

    = –98.2 + 298.2= 200 kJ/mole

The oxide of an element contains 67.67% oxygen and the vapour density of its volatile chloride is 79. Equivalent weight of the element is:

  • Solution

    Equivalent weight of an element is its weight which reacts with 8 gm of oxygen to form oxide.

    Thus eq. weight of the given element \(\frac{32.33}{67.67} \times 8 = 3.82\)

Which one of the following will dissolve in water most readily?

  • Solution

    KF being highly ionic compound will dissolve most readily in water. (Like disolves like).

Which is correct about physical adsorption?

  • Solution

    Physical adsorption involves weak forces, physical in nature with small heat of adsorption. Thus low temperature and high pressure favours physical adsorption.

Which of the following compounds does not follow Markownikoff’s law ?

  • Solution

    As per Markovnikoff’s law, the positive part (e.g. H of HX) or the less negative part of the reagent adds to that carbon atom of alkene which has more number of hydrogen atoms (the rich gets richer). So(c) is the correct optionas the two carbons containing the double bond have one H atom each i.e. symmetric.

Acetyl bromide reacts with excess of CH3MgI followed by treatment with a saturated solution of NH4Cl gives

  • Solution

Tin cry refers to

  • Solution

    Tin cry is the emission of sound on bending the tin.

Among the following options, the sequence of increasing first ionisation potential will be

  • Solution

    1st l.P. increases from left to right in a period.

Propionamide on Hofmann degradation gives –

  • Solution

UnAttempted

0

Attempted

0

Correct

0

Wrong

0

Attempted     
Correct
UnAttempted
Wrong