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601.

Atomic numbers of few elements are given below which of the pairs belongs to s-block?A. 7,4B. 3,20C. 8,15D. 9,17

Answer» Correct Answer - B
Z=3,`1s^(2)2s^(1)`,Z=20,`1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(2)`
Discussion
602.

Which of the following transitions involves maximum amount of energy?A. `M `to`M^(+)+e^(-)`B. `M^(-)`to`M^(+)+2e^(-)`C. `M^(2+)`to`M^(3+)+e^(-)`D. `M^(+)`to`M^(2+)+e^(-)`

Answer» Correct Answer - C
`M^(2+)`to`M^(3+)+e^(-),IE_(2)gtIE_(1)`
Discussion
603.

Among the elements with atomic number 9, 12, 16 and 36 which is highly electropositive ?A. Element with atomic number 9B. Element with atomic number 12C. Element with atomic number 16D. Element with atomic number 36

Answer» Correct Answer - B
Z=9,`1s^(2)2s^(2)2p^(5)`
`Z=12,1s^(2)2s^(2)2p^(6)3s^(2)`
`Z=16,1s^(2)2s^(2)2p^(6)3s^(2)3p^(4)`
`Z=36,1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(10)4s^(2)4p^(6)`
Electropositivity decreases along the period while it increases going down the group.
Discussion
604.

Which of the following metals has the highest thermal cnductivity?A. CopperB. SilverC. MaganeseD. Gold

Answer» Correct Answer - B
Metals show a similar range of thermal conductivities, silver being the highest and copper the second highest. It it because of its high thermal conductivity that copper is the preferred metal for cooking pots. The thermal conductivity of manganese is only `2%` of that of silver.
Discussion
605.

In any atoms, the outermost electrons are those that have the highest value of theA. principal quantum numberB. azimuthal quantum numberC. magnetic quantum numberD. spin quantum number

Answer» Correct Answer - A
The outermost electrons have the greatest influence on the properties of elements. Adding an electron influence `d`-orbital results in less striking changes in properties than adding an electron to an outer `s-` or `p-`orbital.
Discussion
606.

Evaluate dy/dx = tan2 (x + y).

Answer»

dy/dx = tan2 (x + y)

put v = x + y

dv/dx = 1 + (dy/dx) = 1 + tan2 v = sec2 v

∫ dv/sec2 v = ∫ dx

= ∫ cos2 v.dv = x + c

∫ (1 + cos 2v/2) dv = x + c

∫ (1 + cos 2v) dv = 2x + 2c 

v + (sin 2v/2) = 2x + 2c 

2v + sin 2v = 4x + c' 

2(x + y) + sin 2(x + y) = 4x + c' 

x – y – (1/2) sin [2(x + y)] = c
Discussion
607.

Which of the following contains the maximum number of unpaired electrons?A. `Fe^(2+)`B. `Fe^(3+)`C. `Co^(2+)`D. `Co^(3+)`

Answer» Correct Answer - C
Discussion
608.

In the long form of periodic table all the non-metals are placed underA. s-blockB. p-blockC. d-blockD. f-block

Answer» Correct Answer - B
Discussion
609.

Indicate the wrong statement on the basis of the periodic table.A. The most electronegative element in the periodic table is fluorine.B. Scandium is the first transition element and belongs to fourth period.C. There are four transition series in the periodic table each containing 10 elements.D. Along a period halogens have maximum negative electron gain enthalphy.

Answer» Correct Answer - C
There are three transition series,each containing 10 elements.The fourth has incomplete position hence discussed with f-Block elements
Discussion
610.

Examples of elements belonging to s,p,d or block are given below.Identify the wrong example.A. s-block element-CaesiumB. p-block element-BariumC. d-block element-ChromiumD. f-block element-Thorium

Answer» Correct Answer - B
Barium belongs to s-block with an outer configuration `6s^(2)`
Discussion
611.

Which of the following two elements in the periodic table are expected to combine in the most violent fashion?A. `Cs`and `F`B. `P`and `O`C. `Mg`and `N`D. `C1`and `F`

Answer» Correct Answer - A
`Cs`, the most electropositive element, is expected to combine with `F`, the most electronegative element, in the most violent fashion.
Discussion
612.

What are beats? When do they occur? Explain their use if any.

Answer»

Two sound waves of nearly same frequency are travelling in the same direction and interfere to produce a regular waxing (maximum) and waning (minimum) in the intensity of the resultant sound waves at regular intervals of time is called beats.

It two vibrating bodies have slightly difference in frequencies, beats can occur.

No. of beats can be heard ∆υ = υ1 ∼ υ2

Importance :

1. It can be used to tune musical Instruments

2. Beats are used to detect dangerous gases.

Explanation for tuning musical instruments with beats :

Musicians use the beat phenomenon in tuning their musical instruments. If an instrument is sounded against a standard frequency and tuned until the beats disappear then the instrument is in tune with the standard frequency.
Discussion
613.

Define Modulation.

Answer»

Modulation : The process of combining low frequency audio signal with high frequency carrier wave is called modulation.
Discussion
614.

Why are household appliances connected in parallel?

Answer»

In parallel, the voltage (V) across each appliance is same. The current (I) through them depends upon the power (P) of the appliance. The higher power appliance draws more current and lower power appliance draws less current.

(∵ P = VI or I ∝ P)
Discussion
615.

Distinguish between ammeter and voltmeter.

Answer»
AmmeterVoltmeter
(1) It is used to measure current.(1) It is used to measure P.D between two points.
(2) Resistance of an ideal Ammeter is zero.(2) Resistance of ideal volt meter is infinity.
(3) It is connected in series in the circuits. (3) It is connected in parallel in the circuits.
Discussion
616.

Magnetic lines from continous closed loops. Why?

Answer»

Magnetic lines of force always start from north pole and forming curved path, enter south pole and travel to north pole inside the magnet. Thus lines of force are forming closed loops.
Discussion
617.

Write the expression for the reactance of (i) an inductor and(ii) a capacitor.

Answer»

(i) Inductive reactance (XL) = ωL

(ii) Capacitive reactance (Xc) = ωC
Discussion
618.

All eukaryotic unicellular organisms belong toA. MoneraB. ProtistaC. FungiD. Bacteria

Answer» Correct Answer - B
Discussion
619.

Match the following columns:

Answer» Correct Answer - a-p,q; b-t; c-r; d-p
Discussion
620.

Match the following columns:

Answer» Correct Answer - a-r,s; b-p; c-q,s
Discussion
621.

Which one of the following is correct order of the size of iodine species ?A. `IgtI^(-)gtI(+)`B. `I^(+)gtI^(-)gtI`C. `IgtI^(+)gtI(-)`D. `I^(-)gtIgtI^(+)`

Answer» Correct Answer - D
Cation is smaller and anion is larger in size than its parent atom.
Discussion
622.

The amount of energy when million atoms of iodine are completely converted into `I^(-)` ions in the vapour state according to the equation,`I_((g))+e^(-)`to`I^(-)_((g)) ` is `4.9X10^(-13)` J.What would be the electron gain enthalpy of iodine in terms of KJ `mol^(-1)` and eV per atom?A. `295,3.06`B. `-295-3.06`C. `439,5.09`D. `-356,-7.08`

Answer» Correct Answer - B
The electron gain enthalpy of iodine is equal to the energy released when 1 mole of iodine atoms in vapour state is converted into `I^(-)` ions `Delta_(eg)H=(4.9)xx(10)^(-13)xx6.023xx10^(23)/(10)^(6)=29.5xx10^(4) J mol^(-1)
295 KJ mol^(-1)`
Thus,electron gain enthalpy of iodine=`-295 KJ mol^(-1)` We know that ` eV per atom=96.49 KJ `mol^(-1)`
`therefore`Electron gain enthalpy of iodine in eV per atom
`=-(295)/(96.49)=3.06 eV per atom.
Discussion
623.

`K^(+)` and `Cl^(-)` ions are isoelectronic.Which of the statement is not correct?A. Both `K^(+)` and `Cl^(-)` ions have same configuration.B. Both `K^(+)` and `Cl^(-)` ions have same configuration.C. `K^(+)` ions is bigger than `Cl^(-)` ion in ionic size.D. `Cl^(-)` ions is bigger than `K^(+)` ion in size.

Answer» Correct Answer - C
Cation is smaller than the anion.
Discussion
624.

Consider the isoelectronic species, `Na^(+),Mg^(2+),F^(-)` and `O^(2-)`. The correct order of increasing length of their radii is:A. `F^(-)O^(2-)ltMg^(2+)ltNa^(+)`B. `Mg^(2+)ltNa^(+)ltF^(-)ltO^(2-)`C. `O^(2-)ltF^(-)ltNa^(+)ltMg^(2+)`D. `O^(2-)ltF^(-)ltMg^(2+)ltNa^(+)`

Answer» Correct Answer - B
For isoelectronic species,ionic radii decrease with increase in nuclear charge(I.e.,no. of protons).Thus,the cation with greater +Ve charge will have a smaller radius and the anion with greater -Ve charge will have a larger radius.Thus,the correct order of increasing ionic radii is `Mg^(2+)ltNa^(+)ltF^(-)ltO^(2-)`
Discussion
625.

Which of the following statements regarding the variation of atomic radii in the periodic table is not true?A. In a group,these is continuous decrease in size with icrease in atomic number.B. The size of inert gases is larger than halogens.C. The size of inert gases is larger than halogens.D. In `3^(rd)` period,the size of atoms increase with increase in atomic number.

Answer» Correct Answer - D
Size of atoms decreases with increases in atomic number in a period.
Discussion
626.

Which of the following statements regarding an anion is not true?A. The gain of an electron leads to the formation of an anion.B. The radius of the anion is larger than the atomic radius of its parent atom.C. The effective nuclear charge increases when an anion is formedD. Electron cloud expands due to increased repulsion among the electrons.

Answer» Correct Answer - C
The effective nuclear charge decreases when an anion is formed due to increase in number of electrons
Discussion
627.

Which of the following properties of isotopes of an element is different?A. First ionisation enthalpyB. Effective nuclear chargeC. Electron affinityD. Melting point and noiling point

Answer» Correct Answer - D
Isotopes differ in physical properties.
Discussion
628.

Which is correct increasing order of their tendency of the given elements to from `M^(3-)` ion?A. BigtsbgtAsgtPgtNB. BiltSbltAsltPltNC. NltPltSbltBiltAsD. NigtSb~N~PgtAs

Answer» Correct Answer - B
On moving down the group,the stability of -3 oxidation state decreases this is due to the following reasons(i) On descending a group the size of the atom or ion increases.As a result,attraction of the nucleus per newly added electron decreases.(ii)A large anion cannot fir easily into lattice of asmall cation.(iii)As the negative charge on the ion increases.it becomes more and more susceptible to polarisation.
Discussion
629.

Why is the electron gain enthalpy of O or F less than that of S or Cl?A. O and F are more electronegative than S and Cl.B. When an electron is added to O or F,it goe to a smaller(n=2) level and suffers more repulsion than the electron in S or Cl in larger level(n=3)C. Adding an electron to 3p-orbital leads to more rpulsion than 2p-orbital.D. Electron gain enthalpy depends upon the electron affinity of the atom.

Answer» Correct Answer - B
There is more repulsion for the incoming electron when the size of atom is smaller.
Discussion
630.

The most electropositive element isA. NAB. CuC. CsD. Ca

Answer» Correct Answer - C
The element that belongs to group 1 is the most electropositive.Electropositive character increases down the group
Discussion
631.

Which of the following noble gases has the maximum positive electron gain enthalpy?A. It is difficult to add an electron due to small size.B. It is difficult to add an electron due to high electronegativity.C. It is difficult to add an electron due to stable configuration.D. It is difficult to add an electron due to high electron affinity.

Answer» Correct Answer - C
Due to stable configuration they do not accept an electron and hence they have positive electron gain enthalpy.
Discussion
632.

When we move from left to right in a period electropositive charcterA. The basic nature of the oxides increaseB. The basic nature of the oxides decreasesC. There is no regular trend in the nature of oxidesD. Oxides of ony first two group are basic in nature.

Answer» Correct Answer - B
The basic nature of the oxides decreases from left to right in a period.e.g,in third period.`underset("Strongly basic")`(Na_(2)O)`ltunderset("Basic")(MgO)ltunderset("Amphoteric")(Al_(2)O_(3))ltunderset("Weakly acidic")(SiO_(2))ltunderset("Weakly acidic")(P_(4)O_(10))ltunderset("Acidic")(SO_(2))ltunderset("Strongly acidic")(Cl_(2)O_(7))`
Discussion
633.

which of the following elements has the highest value of second ionization energy?A. `1s^(2)2s^(2)2p^(6)3s^(2)`B. `1s^(2)2s^(2)2p^(6)3s^(1)`C. `1s^(2)2s^(2)2p^(6)3s^(2)`D. `1s^(2)2p^(6)3s^(2)3p^(3)`

Answer» Correct Answer - B
After losing one electron,the atom will get a stable configuration and its second ionisation energy will be very high,Hence,option (b)Is correct.
Discussion
634.

Which one of the following arrangements represents the correct order of electron gain enthalpy of the given atomic species?A. `OltSltFltCl`B. `ClltFltSltO`C. `SltOltCiltF`D. `FltClltOltS`

Answer» Correct Answer - A
Electron gain enthalpy becomes more negative across a period while it becomes less negative in a group However,electron gain enthalpy of O or F is less than that of the succeding element.When electron is added to n=2,the repulsion is more than when it is added to n=3 in case of Cl or S.
Discussion
635.

There are many elements in the periodic table which exhibit variable valency.This is a particular characteristic ofA. Respresentative elementsB. Transition elementsC. Noble gasesD. Non-metals.

Answer» Correct Answer - B
Transition elements show variable valency due to the presence of vacant d-orbitals.
Discussion
636.

The first ionisation enthalpy of the elements C,N,P,Si are in the order ofA. CltNltSiltpB. NltSiltCltPC. SiltPltCltND. PltSiltNltC

Answer» Correct Answer - C
Discussion
637.

Which group of elements shows lowest ionisation enthalpy?A. Alkali metalsB. Alkaline earth metalsC. HalogensD. Noble gases

Answer» Correct Answer - A
Discussion
638.

The oxidation state of an element in a particular compound can be defined asA. The charge aquired by its atom on the basis of electronegative consideration from other atoms in the molecule.B. The residual charge acquired by its atom after removing all electronagative atoms from the molecule.C. The valency of the most electronegative atom present in the moleculeD. Total number of electrons accepted by an atom to form a molecule.

Answer» Correct Answer - A
Discussion
639.

The ionisation energy of nitrogen is more than that of oxygen becauseA. Extra stability of half filled orbitalsB. More number of energy levelsC. Less number of valence electronsD. Smaller size.

Answer» Correct Answer - A
Ionisation enthalpy of nitrogen is more than oxygen due to extra stability of half filled orbitals.
Discussion
640.

Assertion:Oxidation state of oxygen in `OF_(2)` and `Na_(2)O` is +2 and -2 respectively.A. If both assertion and reason is the correct explanation of assertion.B. If both assertion and reason is the correct explanation of assertion.C. If both assertion and reason is the correct explanation of assertion.D. If both assertion and reason is the correct explanation of assertion.

Answer» Correct Answer - B
Discussion
641.

The first ionisation potential of `Na,Mg,Al` and `Si` are in the orderA. `Na lt Mg gt Al lt Si`B. `Na gt Mg gt Al gt Si`C. `Na lt Mg lt Al gt Si`D. `Na gt Mg gt Al lt Si`

Answer» Correct Answer - A
`Mg` is `3s^(2)` stable configuration.
`:. Na lt Mg gt Al lt Si`.
Discussion
642.

Which among the following elements have the lowest value of `IE_(1)`?A. `Pb`B. `Sn`C. `Si`D. `C`

Answer» Correct Answer - B
The ionisation energy of tin `{Sn}` is less than that of lead (pb). It is due to the poor shielding of `d-` and `f-` electron in `Pb` due to which it feels greater attraction from nucleus.
Discussion
643.

The first ionisatin potential is maximum forA. `B`B. `N`C. `O`D. `Be`

Answer» Correct Answer - B
Ionisation potential generally increases when we more in a period from left to right but `IE_(1)` of `N_(2)` is greater than that of `O_(2)`. It is due to the more stable (half-filled orbitals) configurations of `N`.
Discussion
644.

The IUPAC name of acetyl acetone is:A. Pentane-2-,5-dioneB. Pentane-2-,4-dioneC. Hexane-2-,4-dioneD. Butane-2-,4-dione

Answer» Correct Answer - B
Discussion
645.

Among rust, smut and mushroom, all the threeA. are pathogensB. are saprobesC. bear ascocarpsD. bear basidiocarps

Answer» Correct Answer - D
Discussion
646.

Myxomycetes areA. saprobes or parasites, having mycelia, asexual reproduction by fragmentationB. slimy mass of multinucleate protoplasm, having pseudopodia-like structures fro engulfing food, reproduction through fragmentation or zoosporesC. prokaryotic organisms, cellular or acellular, saprobes or autotrophic, reproduce by binary fissionD. eukaryotic, single-celled or filamentous, saprobes or autotrophic, asexual reproduction by division of haploid individuals, sexual reproduction by fusion of two cells or their nuclei

Answer» Correct Answer - B
Discussion
647.

Myxomycetes areA. Saprobes or parasites, having mycelia, asexual reproduction by fragmentation, sexual reproduction by fusion of gametes.B. Slimy mass of multinucleate protoplasm, having pseudopodia-like structures for engulfing food, reproduction through fragmentation or zoospores.C. Prokaryotic organisms, cellular or acellular, saprobes or autotrophic, reproduce by binary fission.D. Eukaryotic, single-celled or filamentous, sprobes or autotrophic, asexual reproduction by fusion of two cells or their nuclei.

Answer» Correct Answer - B
Discussion
648.

Among rust, smut and mushroom, all the threeA. are pathogensB. are saprobesC. bear ascocarpsD. base basidiocarps

Answer» Correct Answer - A
Discussion
649.

Which of the following organisms are known as chief producers in the oceans ?A. DinoflagellatesB. DiatomsC. CyanobacteriaD. Duglenoids

Answer» Correct Answer - B
Diatoms are known as chief producers in the oceans.
Discussion
650.

Correct statement about given ketoxime is: A. (A) is named as syn-p-tolylphenyl ketoximeB. (A) is named as anti-phenyl-p-tolyl ketoximeC. Compound (A) is Z isomerD. Compound (A) is E isomer

Answer» Correct Answer - A::B::C
Discussion