52671 + Interview Questions in Chemistry in Class 11

1.	Compare and contrast the chemistry of group 1 metals with that of group 2 metals with respect to
Answer» Nature of oxides Solubility and THERMAL stability of carbonates POLARISING power of cations Reactivity and reducting power Solution :(a) .Nature of oxides: Alkali metals1. They form oxide, peroxide and SUPEROXIDE, i.e. `M_(2)O,M_(2)O_(3)` and `MO_(2)` respectively. 2. Readily soluble in water to form hydroxide. They are crystalline solids. Alkaline earth metals 1.They react slowly and form oxides and peroxides, i.e. `MO` and `MO_(2)` respectively. 2. Less soluble in water and form hydroxide. Yheir insolubility is due to their large lattice enthalpy. (b). Solubility and thermal stability of carbonates: Alkali metals 1. The carbonates of alkali metals are highly soluble in water. 2. The carbonates of alkali metals are highly metals are highly stable to heat. Alkaline earth metals 1. The carbonates of alkaline earth metals are sparingly soluble in water. 2. They decompose on heating and the stability increases down the group. (c ). Polarising power of cations: Alkali metals The alkali metal ions have the LOWEST polarising power. it is because their charge//radius ratio is very LOW. `Li^(o+)` has the highest polarising power among its group. Alkaline earth metals teh alkaline earth metal ions have high polarising power because they form bivalent ions and their charge/radius ration is higher than the alkali meats. (d). Reactivity and reducing power: Alkali metals 1. Alkali metals are highly reactive due to their low ionisation enthalpy and low heat of formation which decreases down the group `(darr)`. 2. The alkali metals are highly electropositive and are strong reducing agents. The `E^(Θ)` values are very high of alkali metals. Alkaline earth metals 1. Because of their low ionisation enthalpy and high electropositive character, these metals are also very reactive but less reactive than alkali metals. 2. These metals are also strong reducing agents but less than alkali metals. They have least negative value and high enthalpy of formation.

Discussion

2.	Compare acetyleneand benzene with respect to the following: (a) hybridisationof carbon atoms, (b) percentage compositions of C and H, (c ) product of ozonolysisand (d) reaction with Baeyer's reagent.
Answer» Solution :(a) In acetylene, both carbon atoms are sp hybridised, while in benzene all carbon atoms are `sp^2` hybridised.(b) The percentage composition of carbon as well as hydrogen in both acetylene and benzene is SARE, since the empirical formula is same. Percent carbon in benzene = `(72 xx 100)(78) = 92.4` Percent carbon in acetylene = `(24 xx 100)/(26) 92.4` Percent hydrogen in benzene = `(6 xx 100)/(78) = 7.6` Percent hydrogen in acetylene = `(2 xx 100)/(26) = 7.6` (c)Both acetylene and benzene on ozonolysis give glyoxal. One mole of acetylene on ozonolysis gives one mole of glyoxal, but one mole of benzene gives three moles of glyoxal. (d) Acetylene decolourises pink colour of Baeyer.s reagent, but benzene does not. Acetylene is oxidised by Baeyer.s reagent to give oxalic acid `C_2H_2 + 4(O) overset(MnO_4^(-), OH^(-))(rarr)HOOC-COOH ` Benzene is not oxidised by Baeyer.s reagent.

Discussion

3.	Compare alkali metals and alkaline earth metals with repect to ionisation enthalpy, basicity of oxides and solubility of hydroxides.
Answer» Solution :Ionisation enthalpy of alkaline earth METALS are higher than that of CORRESPONDING ALKALI metals are more electropositive than alkaline earth metals.

Discussion

4.	Compara the relative stablilties of O_(2)^(-) and N_(2)^(-)and comment on their magnetic (paramagetic or diamagnetic ) behaviour.
Answer» Solution : M.O. Electronic CONFIGURATION of` O_(2)^(-) = KK SIGMA _(2s)^(2) sigma _(2)^(2) sigma _(2p_(z) p)^(2) pi_(2p_(x))^(2) pi_(2p_(y))^(2) pi_(2p_(x))^(2) pi_(2p_(y))^(1)` Bondorder= ` (1)/(2) (8-5) = (3)/(2) = 1.5 ` M.O. Electronic configuration of` O_(2)^(-) = KK sigma _(2s)^(2) sigma _(2)^(2)pi_(2p_(x))^(2) pi_(2p_(y))^(2)pi_(2p_(z))^(1)` Bond order`= (1)/(2) (7-2) = (5)/(2) = 2.5 `

Discussion

5.	Compar the acidic nature : (a) H_2O and H_2O_2 and (b) Co and CO_2
Answer» Solution :`H_2O` is neutral . `H_2O_2` is weakly acidic. `H_2O_2` forms SATS UPON NEUTRALISATION with alkali. `H_2O_2 + NAOH rarr NaHO_2 + H_2O` `H_2O_2 + 2NaOH rarr Na_2O_2 + 2H_2O` (b) Co is neutral while `CO_2` is acidic

Discussion

6.	Common table salt is hygroscopic due to the presence of
Answer» `MgCl_(2)+CaCl_(2)` `MGO` `MgSO_(4)` `MgCO_(3)` ANSWER :A

Discussion

7.	Common salt is crystalline.Butthe saltprepared from sea wateris wetted.Why?
Answer» SOLUTION :Sea water mainlycontains chlorides of sodium ,calcium and MAGNESIUM. Sodium chloride separated from sea watercontains`MgCl_(2) and CaCl_(2)`as impurities.these impure chlorideeasily absorb atmosphere watervapourand are HYDRATED . Becauseof thehygroscopicnature of `MgCl_(2) and CaCl_(2)`common salt NaCl prepared from sea water is WETTED .

Discussion

8.	The most common oxidation state of VI A group elements is
Answer» `+IV` `+I` `+III` `+II` ANSWER :A

Discussion

9.	Common oxidation state of IVA group clements is
Answer» `+IV` `+I` `+III` `II` ANSWER :A

Discussion

10.	Common oxidation state of elemental transition metal is
Answer» `+1` 0 `+3` `+2` Answer :B

Discussion

11.	Common name of Calcium hydroxide is......
Answer» SOLUTION :SLAKED LIME

Discussion

12.	Common impurities present in bauxite are
Answer» CuO ZnO `Fe_(2)O_3` `SiO_2` SOLUTION :CONCEPT based QUESTION

Discussion

13.	Commerical 11.2 volume of H_2O_2 solution has molarity of
Answer» 1 0.5 11.2 1.12 Solution :MOLAITY `=("VOLUME STRENGTH")/11.2`

Discussion

14.	Commercially, hydrogen peroxide is marketed as 100 V, which means it contains _______.
Answer»

Discussion

15.	Commercially available concentrated hydrochlorc acid contains 38% HCI by mass. (i) What is the molarity of this solution? The density is 1.19 g cm^(-3). (ii) What volume of concentrated HCI is required to make 1.00 L of 0.10 M HCI?
Answer» Solution :(i) Suppose, we have 1000 cm (1.0 L) of the given sample of commercial hydrochloric acid. `therefore` Density `=("Mass")/("Volume")` `therefore` Mass of `1000 cm^(3)` of the sample `=1000 xx 1.19 = 1190 g` The given sample CONTAINS 38% HCl by mass. Hence, the mass of HCl present in `1000 cm^3` (1190) g `=(1190 xx 38)/100 = 452.2 g` Hence, `w = 452.2 g, V = 1000 cm^(3), M = 35.45 + 1.008 = 36.46` `therefore 452.2 = (M xx 36.46 xx 1000)/1000` or M = 12.40 Hence, the molarity of the given commercial sample is 12.40 M. ANS. (ii) The mass of pure HCl required the make 1.0 L (`1000 cm^3`) of a solution of 0.10 M HCl is given by `w =(0.10 xx 36.46 xx 1000)/1000 = 3.6 g` `therefore` 3.6 g of pure HCl will be present in the sample having mass `=100/38 xx 3.6 = 9.5 g` Since, Volume `=("Mass")/("Density")` The volume of sample having mass 9.5 g `=9.5/1.19 = 8.0 cm^(3)` Hence, `8.0 cm^(3)` of concentrated HCl are required to make 1.00 L of 0.10 M solution.

Discussion

16.	Commercial sample of H_(2)O_(2) is labelled as 10 V. Its % strength is nearly
Answer» 3 6 9 12 Solution :Applying the FORMULA , we have , Volume STRENGTH = `5.6xx("Percentage strength")/("EQ. wt. of " H_(2)O_(2))xx10` or `10=(5.6 xx "Percentage strength")/(17)xx10` Percentage strength =`(17)/(5.6)=3.03~=3`

Discussion

17.	Commercial benzene obtained from coal-tar distillation contains 3-5% thiophene as impurity. Suggest a simple method to purify it.
Answer» Solution :It is usually not easy to SEPARATE thiophene from benzene by fractional DISTILLATION because their boiling points are very close : benzene = 353 K, thiophene = 357 K. However, thiophene can be removed from commercial benzene by extraction with conc. `H_(2)SO_(4)`. The purification is based upon the fact that thiophene undergoes sulphonation much more easily than benzene. Thus, when commercial benzene is shaken with conc. `H_(2)SO_(4)` in a separating FUNNEL, thiophene undergoessulphonation to form thiophene-2-sulphonic ACID which dissolves in conc. `H_(2)SO_(4)` while benzene does not

Discussion

18.	Commercial 11.2 volume H_2O_2 solution has a molarity of.....
Answer» `1.0` 0.5 `11.2` 0.75 Answer :A

Discussion

19.	Comment upon reactions of dihydrogen with (i) Chlorine ,(ii) Sodium and (iii) Copper(II) oxide.
Answer» Solution :(i) Dihydrogen reduces chlorine to `Cl^(-)` ION and itself GETS oxidised to `H^(+)` ions. An electron pair is then shared between these two species to form a covalent melecules of HYDROGEN chloride. `H_(2)(g) + Cl_(2)(g) to 2HCl (g)` (ii) Sodium reduces dihydrogen to form HYDRIDE ion `(H^(-))` and itself gets oxidised to sodium ion `(Na^(+))`During this reaction, an electron is completely transferred from Na to H thereby ionic sodium hydride, `Na^(+) H^(-)` `2Na(s) + H_(2)(g) overset(Delta)to 2Na^(+)H^(-)(s)` (iii) Hydrogen reduces copper (II) oxide to copper metal. (zero oxidation state) while itself gets oxidizedto form a covalent moleule of `H_(2)O` (in which H has an oxidation state of +1). `overset(+2 -2)(CuO) (s) + overset(0)H_(2)(g) to overset(0)CU(s) + overset(+1)H_(2) overset(-2)O(l)`

Discussion

20.	Comment on the thermodynamic stability of NO(g), given, (i) 1/2 N_(2)(g) + 1/2O_(2)(g) to NO(g) Delta_(r)H^(@) = 90 kJ mol^(-1) (ii)NO(g) + 1/2 O_(2)(g) to NO_(2)(g) Delta_(r)H^(@) = -74 kJ mol^(-1).
Answer» Solution :Since `Delta_(r)H^(@)` is + ve i.e., ENTHALPY of formation of NO is positive so NO(G) is unstable.But `NO_(2)(g)` is formed because ENERGY is released.

Discussion

21.	Comment on the validity of the following statements, giving reasons: (i) Thermodynamically, an exothermic reaction issometimes not spontaneous. (ii) The entropy of steamis more than that of water at its boiling point. (iii)The equilibrium constant fora reaction isone or more if Delta_(r)G^(@)for it is less than zero.
Answer» Solution :(i) Yes, the given statement is TRUE. This is because `DeltaG= Delta H -T Delta S`.For exothermic reaction, `DeltaH` is `-ve`. If `T DeltaS` is`+ve` (i.e.,entropy factor opposes the process) and `T DeltaS GT DeltaH` in magnitude, `DeltaG` will be`+ve` and process will bespontaneous. (ii) Yes, thegiven statement is true. This is becauseat the same temperature, gaseous state is more DISORDERED than the liquid state. (iii) `- DeltaG^(@) = RT`ln K. Thus, if `DeltaG^(@)` is less than ZERO, i.e., it is`-ve` , thenln KWILL be `+ve` and hence K will be greaterthan 1.

Discussion

22.	Comment on the thermodynamic stability of NO(g) ,given (1)/(2)N_(2)(g)+(1)/(2)O_(2)(g) rarr NO(g) , Delta_(r)H^(@) =90kJ mol^(-1) NO(g)+(1)/(2)O_(2)(g) rarrNO_(2)(g) , Delta_(r)H^(@) =- 74kJ mol^(-1)
Answer» SOLUTION :As energy is ABSORBED in the first reaction`NO(g)` is UNSTABLE. As energy is released in the second reaction, `NO_(2)(g)` is STABLE. Thus, unstalbe `NO(g)` changes into the stable `NO_(2)(g)`

Discussion

23.	Comment on the thermodynamic stability of NO_((g)), given: (1)/(2) N_(2(g)) , + (1)/(2) O_(2(g)) to NO_((g)), Delta_(r) H^( Theta ) = 90 "kJ mol"^(-1) NO_((g)) + (1)/(2) O_(2(g)) to NO_(2(g)), Delta_(r) H^( Theta ) = -74"kJ mol"^(-1)
Answer» SOLUTION :Heat is absorbed in FIRST reaction. So, `NO_((g))` unstable. In second reaction, heat is released, So, `NO_(2(g))` is stable. So, unstable `NO_((g))` is CONVERTED into stable `NO_(2(g))`.

Discussion

24.	Comment on the thermodynamic stability of NO(g) and NO_2(g) given : frac{1}{2}N_2(g)+frac{1}{2}O_2(g)rightarrowNO(g) , Delta_fH^o=90 kJ mol^-1 NO(g)+frac{1}{2}O_2(g)rightarrowNO_2(g) , Delta_fH^o=-74 kJ mol^-1
Answer» SOLUTION :SINCE energy is absorbed in the formation of NO, it is not very stable. Since energy is RELEASED in the second reaction, NO will be EASILY CONVERTED to the more stable `NO_2`.

Discussion

25.	Comment on the structure of beryllium chloride
Answer» Solution :Beryllium CHLORIDE has a chain structure in the solid state due to the formation of coordinate bond between Cl and Be of DIFFERENT molecules. Hybridisation of Be in it is sp. In vapour phase `BeCl_(2)` tends to form a chloro-bridged DIMER in which hybridisation of Be is `sp^(2)`. At high temperatures (above 1200K) dimer is DISSOCIATED to form LINEAR monomer. In monomer hybridisation of Be is sp. `Cl-Be-Cl`.

Discussion

26.	Comment on the statement - Green chemistry is a tool for reducing pollution.
Answer» Solution :In GREEN chemistry, the reactions are generally carried out in the presence of MILT and environment friendly reagents, such as ultraviolet light, sound waves, enzymes and MICROWAVES so that harmful chemicals are neither usedup nor released. HENCE green chemistry acts as a tool for reducing environmental pollution.

Discussion

27.	Comment on the statement - A sample of an ideal gas escapes into an evacuated container without any changes in its kinetic energy.
Answer» SOLUTION :In ideal gases there are no intermolecular forces of ATTRACTION. Therefore, when an ideal gas expands into an EVACUATED CONTAINER, no work is done by the ideal gas molecules and hence the kinetic energy remains UNCHANGED.

Discussion

28.	Comment on the statement- A sample of an ideal gas escapes into an evacuated container without any changes in its kinetic energy.
Answer» Solution :In ideal GAES there are no intermolecular FORCES of attraction. Therefore, when an ideal gas expands into an evacuated container,no work is done by the ideal gas molecules and hence the KINETIC ENERGY remains unchanged.

Discussion

29.	Comment on the spontaneity of a reaction at constant temperature and pressure in the following cases. (i)DeltaH lt 0 and DeltaS gt 0 (ii) DeltaH gt0 and Delta S lt 0(iii) DeltaH lt 0 and DeltaS lt 0 (iv)DeltaH gt 0 andDeltaS gt 0
Answer» Solution :(i) Both energy factor and randomness factor FAVOUR the PROCESS. Hene, reaction will be always spontaneous. (II)Both factors opposes the process. Hence, reaction would be always non-spontaneous. (iii) Energy factor favour but randomness factor opposes. For process to be spontaneous , opposing factor should be smaller, i.e., `T DELTAS lt DeltaH`. Hence, reaction is spontaneous at low temperature ANDNON- spontaneous at high temperature. (iv) Energy factor opposes but randomness factor . For spontaneity, `T DeltaS gt DeltaH`. Hence, reaction is spontaneous at high temperature and non-spontaneous at low temperature.

Discussion

30.	Comment on the solubility of calcium sulphate in water.
Answer» SOLUTION :CALCIUM suphate is sparingly solublein water .During in water , heat is EVOLVED .Therefore ,solubility of calcium sulphate decreases with increases in TEMPERATURE . HOWEVER ,calcium sulphate is more soluble in aqueous ammonium sulphate .This is due to the formation of a double salt calcium ammonium sulphate .

Discussion

31.	Comment on the reactions of dihydrogen with (i) chlorine, (ii) sodium, and (iii) copper (II) oxide
Answer» Solution : (i) Dihydrogen reduces chlorine into chloride `(Cl^-)` ion and itself gets oxidised to `H^+` ion by chlorine to form hydrogen chloride. An electron pair is SHARED between H and Cl leading to the FORMATION of a covalent MOLECULE. (II) Dihydrogen is reduced by sodium to form NaH. An electron is transferred from Nato H leading to the formation of an ionic compound, `Na^(+)H^(-)`. (iii) Dihydrogen reduces copper(II) oxide to copper in zero oxidation state and itself gets oxidised to `H_2O`, which is a covalent molecule.

Discussion

32.	Commenton the reactions of dihydrogen with (i) chloride (ii) sodium, and (iii) copper (II) oxide.
Answer» Solution :a) Whenhydrogen reacts with CHLORINE, an electron pain is shared between H and Cl leading to the FORMATION of hydrogen CHLORIDE. `H_(2)+Cl_(2)to2HCl` b) Dihydrogen REDUCES copper (II) oxide to copper and itself gets oxidised to WATER. `H_(2) +CuOtoCu+H_(2)O`

Discussion

33.	Comment on the following statements. SiF_(4)" and "ClO_(4)^(-) are tetrahedral
Answer» Solution :Both S in `SiF_(4)" and "Cl" in "ClO_(4)^(-)` UNDERGO `SP^(3)` hybridisation .

Discussion

34.	Comment on the following statements. HSH bond angle in H_(2)S" is "92^(@) and HOH bond angle in H_(2)O is 104.5.
Answer» Solution :Since the electronegativity of s is less than O, `H_(2)S` POSSESS a LOWER BOND ANGLE then `H_(2)O`.

Discussion

35.	Comment on the following statements. BF_(3) is planar but NH_(3) is not.
Answer» Solution :The B-in `BF_(3)` undergoes `sp^(2)` hybridisation and has a triangular planar geometry . The N-in NH3 undergoes `sp^(3)`hybridisation and has pyramidal shape with ONE lone PAIR on N -atom.

Discussion

36.	Comment on the following observationThe mobility of alkali metal ions in aqueous solution Is Li^+ lt Na^+ lt K^+ lt Rb^+
Answer» SOLUTION :A SMALLER ion is HEAVILY HYDRATED which MAKES it sloe moving.Hydration varies in the order `Li^+ gt Na^+,K^+.Rb^+ gt Cs^+` and hence mobillty is in the reverse order.

Discussion

37.	Comment on the following observationsLithium is the only alkali metal which forms nitride directly.
Answer» SOLUTION :LI forms nitride as Mg dose(DIAGONAL RELATIONSHIP).Other alkali metals do have such diagonal relationship `6Li+N_2 RARR 2Li_3N`

Discussion

38.	Comment on the colour and magnetic behaviour of dipositive ions of group 2 elements.
Answer» Solution :COLOURLESS and diamagnetic DUE to the presence of all PAIRED electrons.

Discussion

39.	Comment on electron gain enthalpy of alkaline earth metals?
Answer» Solution :Allkaline EARTH metals have nearly zero VALUES of ELECTRON AFFINITY these do not FORM anions due to their `s^2` configuration.

Discussion

40.	Comment on the bond energies of four C-Hbonds present in CH_(4).
Answer» Solution :The BOND energiesof 1st ,2ND, 3RD and 4thC-H bonds are not equal and so average value is taken.

Discussion

41.	Comment on each of the following observations : (a) The mobilities of the alkali metal ions in aqueous solution are Li^(+) lt Na^(+) lt K^(+) lt Rb^(+) lt Cs^(+). (b) Lithium is the only alkali metal which forms nitride directly . (c) E^(@) for M^(2+) (aq) + 2e^(-) to M(s)(where M = Ca , Sr or Ba) is nearly constant .
Answer» Solution :(a) Smaller the size of the ion , more highly it is hydrated and hence greater is the mass of the hydrated ion and hence lower is its ionic mobility . Since the extent of HYDRATION decreases in the order : `Li^(+) gt Na^(+) gt K^(+) gt Rb^(+) gt Cs^(+)` therefore , ionic mobility increases in the reverse order : `Li^(+) lt Na^(+) lt K^(+) lt RB^(+) lt Cs^(+)` (b) Due to samll size, `Li^(+)` has high polarising power and hence it strongly attracts the larger negatively charged nitride ion `(N_(3)^(-))`TOWARDS itself . As a result , lattice energy of `Li_(3)N` is high and due to this highlattice energy `Li_(3)N` is easily formed. The other alkali metals do not form their corresponding nitrides because their lattice energies are not only low but alsodecrease further as their sizes increase from Na to Cs. `6Li(s)+N_(2)(g) OVERSET (DELTA) to 2 Li_(3)N (s)` (c) `E^(@)` of any `M^(2+)//M` electrode depends upon three factors :(i) enthalpy of vapourization,(ii) ionization enthalpy , (iii) enthalpy of hydration . Since the combined effect of these factors is approximately the same for Ca , Sr and Ba , therefore , their electrode potential are nearly constant .

Discussion

42.	Comment on each of the following observations: (a) Lithium is the only alkali metal to form a nitride directly by combination with nitrogen.
Answer» Solution :(a) Reason : `LI^+` ION being the smallest in size will COMBINE with small `N^(3-)` ion to form the stable crystal `6Li+n_2to2Li_3N`

Discussion

43.	The mobilities of the alkali metal ions in aqueous solution are Li^(+) lt Na^(+) lt K^(+) lt Rb^(+) lt Cs^(+)because
Answer» SOLUTION :Smaller the size of alkali metal ion, GREATER is its DEGREE of hydration and lesser is its MOBILITY in aqueous solution due to greater mass. Since the size of alkali metal ions follows the order `Li^(+) lt Na^(+) lt K^(+) lt Rb^(+) lt Cs^(+)`,the ionic mobility of alkali metal ions is in the order `Li^(+) lt Na^(+) lt K^(+) lt Rb^(+) lt Cs^(+)`.

Discussion

44.	Comment on each of the following observations: (a) The mobilities of the alkali metal ions in aqueous solution are Li^(+)ltNa^(+) lt K^(+) lt Rb^(+) lt Cs^(+) (b) Lithium is the only alkali metal to form a nitride directly (c) E^(Theta) for M^(2+) (aq) +2e^(-)rarrM(s) (where M=Ca, Sr or Ba) is nearly constant
Answer» Solution :The VALUE of `E^@` for a system depends upon THREE factors (i) enthalpy of vaporisation, (ii) ionisation enthalpy and (III) hydration enthalpy. The combined effect of these three factors is approximately the same for CA, Sr and Ba. Therefore, they possess nearly the same value of STANDARD electrode potential.

Discussion

45.	Comment of the following observations : The mobilities of the alkali metal ions in aqueous solution are Li^(+) lt Na^(+) lt K^(+) lt Rb^(+) lt Cs^(+)
Answer» Solution : On moving down the alkali group, the ionic and atomic SIZES of the metals increase. The given alkali metal ions can be arranged in the INCREASING order of their ionic sizes as: `Li^(+) lt Na^(+) lt K^(+) lt Rb^(+) lt Cs^(+)` Smaller the size of an ion, the more highly is it HYDRATED. Since `Li^(+)`is the smallest, it gets heavily hydrated in an aqueous solution. On the other hand, `Cs^(+)`is the LARGEST and so it is the least hydrated. The given alkali metal ions can be arranged in the DECREASING order of their hydrations as : `Li^(+) gt Na^(+) gt K^(+) gt Rb^(+) gt Cs^(+)` Greater the mass of a hydrated ion, the lower is its ionic mobility. Therefore, hydrated `Li^(+)`ion is the least mobile and hydrated `Cs^(+)`ion is the most mobile. Thus, the given alkali metal ions can be arranged in the increasing order of their mobilities as : `Li^(+) lt Na^(+) lt K^(+) lt Rb^(+) lt Cs^(+)`

Discussion

46.	Comment of the following observations : E^("ϴ") for M_((aq))^(2+) +2e^(-) to 2e^(-) to M_((s)) (where, M = Ca, Sr or Ba) is nearly constant.
Answer» Solution : Electrode potential `(E^(0))`of any `M_(2)^(2+)//M` electrode depends upon three factors : (i) Ionization enthalpy (ii) Enthalpy of hydration, (iii) Enthalpy of VAPOURIZATION. The combined effect of these factors is approximately the same for CA, Sr, and Ba. Hence, their electrode potentials are nearly constant.

Discussion

47.	Comment of the following observations : Lithium is the only alkali metal to form a nitride directly.
Answer» Solution :Unlike the other elements of group 1, Li reacts directly with nitrogen to form lithium nitride. This is because `Li^(+)`is very SMALL in size and so its size is the most compatible with the `N^(3-)` ion.Hence, the lattice energy released is very HIGH. This energy also overcomes the high amount of energy required for the formation of the `V^(3+)` ion.

Discussion

48.	Comment about the fraction of molecules moving between 400 to 500m/sec for a gas (molecular mass =20 g/mol) if its temperature increases from 300K to 400K [25/3 J/mol/K].
Answer» FRACTION of molecules increases Fraction of molecules decreases Fraction of molecules REMAINS CONSTANT Fraction of molecuels remains constant Answer :B

Discussion

49.	Combustion of sucrose is used by aerobic organisms for providing energy for the life substaining process. If all the capturing from the reaction is done through electrical process (non P-V work) then calculate maximum available energy which can be captured by combustion of 34.2 gm of sucrose Given : Delta H_("sucrose") = -6000 kJ mol^(-1) , Delta S_("combustion") = 180 J// K mol and body temperature is 300 K.
Answer» 600kJ 594.6 kCal 144.83 k Cal 605.4 kJ Solution :Non-PV work is notihing but `Delta G` So `Delta G` per mole `= Delta H - T Delta S` `= -60000 xx 10^(3) - 300(180)` `= -6054 kJ` `Delta G` per 34.2 GR `= (-6054)/(10) = - 605.4 KJ`

Discussion

50.	Assertion (A). Combustion of all organic compounds is an exothermic reaction. Reason (R). The enthalpies of all elements in their standard state are zero
Answer» ANSWER :T

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Compare and contrast the chemistry of group 1 metals with that of group 2 metals with respect to

Compare acetyleneand benzene with respect to the following: (a) hybridisationof carbon atoms, (b) percentage compositions of C and H, (c ) product of ozonolysisand (d) reaction with Baeyer's reagent.

Compare alkali metals and alkaline earth metals with repect to ionisation enthalpy, basicity of oxides and solubility of hydroxides.

Compara the relative stablilties of O_(2)^(-) and N_(2)^(-)and comment on their magnetic (paramagetic or diamagnetic ) behaviour.

Compar the acidic nature : (a) H_2O and H_2O_2 and (b) Co and CO_2

Common table salt is hygroscopic due to the presence of

Common salt is crystalline.Butthe saltprepared from sea wateris wetted.Why?

The most common oxidation state of VI A group elements is

Common oxidation state of IVA group clements is

Common oxidation state of elemental transition metal is

Common name of Calcium hydroxide is......

Common impurities present in bauxite are

Commerical 11.2 volume of H_2O_2 solution has molarity of

Commercially, hydrogen peroxide is marketed as 100 V, which means it contains _______.

Commercially available concentrated hydrochlorc acid contains 38% HCI by mass. (i) What is the molarity of this solution? The density is 1.19 g cm^(-3). (ii) What volume of concentrated HCI is required to make 1.00 L of 0.10 M HCI?

Commercial sample of H_(2)O_(2) is labelled as 10 V. Its % strength is nearly

Commercial benzene obtained from coal-tar distillation contains 3-5% thiophene as impurity. Suggest a simple method to purify it.

Commercial 11.2 volume H_2O_2 solution has a molarity of.....

Comment upon reactions of dihydrogen with (i) Chlorine ,(ii) Sodium and (iii) Copper(II) oxide.

Comment on the thermodynamic stability of NO(g), given, (i) 1/2 N_(2)(g) + 1/2O_(2)(g) to NO(g) Delta_(r)H^(@) = 90 kJ mol^(-1) (ii)NO(g) + 1/2 O_(2)(g) to NO_(2)(g) Delta_(r)H^(@) = -74 kJ mol^(-1).

Comment on the thermodynamic stability of NO(g) ,given (1)/(2)N_(2)(g)+(1)/(2)O_(2)(g) rarr NO(g) , Delta_(r)H^(@) =90kJ mol^(-1) NO(g)+(1)/(2)O_(2)(g) rarrNO_(2)(g) , Delta_(r)H^(@) =- 74kJ mol^(-1)

Comment on the thermodynamic stability of NO_((g)), given: (1)/(2) N_(2(g)) , + (1)/(2) O_(2(g)) to NO_((g)), Delta_(r) H^( Theta ) = 90 "kJ mol"^(-1) NO_((g)) + (1)/(2) O_(2(g)) to NO_(2(g)), Delta_(r) H^( Theta ) = -74"kJ mol"^(-1)

Comment on the thermodynamic stability of NO(g) and NO_2(g) given : frac{1}{2}N_2(g)+frac{1}{2}O_2(g)rightarrowNO(g) , Delta_fH^o=90 kJ mol^-1 NO(g)+frac{1}{2}O_2(g)rightarrowNO_2(g) , Delta_fH^o=-74 kJ mol^-1

Comment on the structure of beryllium chloride

Comment on the statement - Green chemistry is a tool for reducing pollution.

Comment on the statement - A sample of an ideal gas escapes into an evacuated container without any changes in its kinetic energy.

Comment on the statement- A sample of an ideal gas escapes into an evacuated container without any changes in its kinetic energy.

Comment on the spontaneity of a reaction at constant temperature and pressure in the following cases. (i)DeltaH lt 0 and DeltaS gt 0 (ii) DeltaH gt0 and Delta S lt 0(iii) DeltaH lt 0 and DeltaS lt 0 (iv)DeltaH gt 0 andDeltaS gt 0

Comment on the solubility of calcium sulphate in water.

Comment on the reactions of dihydrogen with (i) chlorine, (ii) sodium, and (iii) copper (II) oxide

Commenton the reactions of dihydrogen with (i) chloride (ii) sodium, and (iii) copper (II) oxide.

Comment on the following statements. SiF_(4)" and "ClO_(4)^(-) are tetrahedral

Comment on the following statements. HSH bond angle in H_(2)S" is "92^(@) and HOH bond angle in H_(2)O is 104.5.

Comment on the following statements. BF_(3) is planar but NH_(3) is not.

Comment on the following observationThe mobility of alkali metal ions in aqueous solution Is Li^+ lt Na^+ lt K^+ lt Rb^+

Comment on the following observationsLithium is the only alkali metal which forms nitride directly.

Comment on the colour and magnetic behaviour of dipositive ions of group 2 elements.

Comment on electron gain enthalpy of alkaline earth metals?

Comment on the bond energies of four C-Hbonds present in CH_(4).

Comment on each of the following observations: (a) Lithium is the only alkali metal to form a nitride directly by combination with nitrogen.

The mobilities of the alkali metal ions in aqueous solution are Li^(+) lt Na^(+) lt K^(+) lt Rb^(+) lt Cs^(+)because

Comment of the following observations : The mobilities of the alkali metal ions in aqueous solution are Li^(+) lt Na^(+) lt K^(+) lt Rb^(+) lt Cs^(+)

Comment of the following observations : E^("ϴ") for M_((aq))^(2+) +2e^(-) to 2e^(-) to M_((s)) (where, M = Ca, Sr or Ba) is nearly constant.

Comment of the following observations : Lithium is the only alkali metal to form a nitride directly.

Comment about the fraction of molecules moving between 400 to 500m/sec for a gas (molecular mass =20 g/mol) if its temperature increases from 300K to 400K [25/3 J/mol/K].

Assertion (A). Combustion of all organic compounds is an exothermic reaction. Reason (R). The enthalpies of all elements in their standard state are zero