52671 + Interview Questions in Chemistry in Class 11 Page 1012 InterviewSolution

50551.	A chemical reaction cannot occur at all if its
Answer» `DELTA H is (+) ve and Delta S is (-)ve ` `Delta H is (-) ve and Delta S is (+) ve ` `Delta H and Delta S are (+ ) ve` but ` Delta H LT T Delta S` `Delta H and Delta S"are" (-) ve butDelta H GT T Delta S` ANSWER :A

Discussion

50552.	A chemical equilibrium is :
Answer» a static EQUILIBRIUM where REACTANTS & products stop combining to give products & reactants respectively adynamicequilibriumwherethereactantsandproductscontinuetogiveproductsandreactants respectively. Rates of forward and backward reactions are equal Gibb’s FREE ENERGY CHANGE is zero Solution :Properties of equilibrium

Discussion

50553.	A chemical equation tells the actual number of moles of reactants and products.
Answer» ANSWER :F

Discussion

50554.	Chemical equation is balanced according to the law of
Answer» MULTIPLE proportions constant proportions reciprocal proportions Conservation of mass Answer :D

Discussion

50555.	A chemical equation is always balanced with respect which one of the following (i)Number of atoms (ii) Number of molecules (iii) Number of moles (iv) Mass
Answer» Only i is CORRECT Only III correct Only IV Correct Both i & iv correct ANSWER :D

Discussion

50556.	A chemical commonly called "dioxin" has been very much in the news in the past few years. (It is the by product of herbicide manufacture and is thought to be quite toxic.) Its formula is C_(12)H_(4)Cl_(4)O_(2). If you have a sample of dirt (28.3 g) that contains 1.0xx10^(-4)% dioxin, how many moles of dioxin are in the dirt sample?
Answer» Solution :`N=((28.3xx1xx10^(-4))/(100))/([12xx12+4+35.5xx4+16xx2])=8.8xx10^(-8)` mole

Discussion

50557.	A chemical A is used for the preparation of washing soda to recover ammonia . When CO_(2) is bubbled through an aqueous solution of A , the solution turns milky . It is used in white washing due to its disinfectant nature . What is the chemical formula of A ?
Answer» `Ca(HCO_(3))_(2)` `CAO` `Ca(OH)_(2)` `CaCO_(3)` Answer :C

Discussion

50558.	A chemical A is used for the preparation of washing soda. When CO_2 is bubbled through an aqueous solution of A, the solution turns milky. It is used in white washing due to disinfectant nature. What is the chemical formula of A?
Answer» `Ca(HCO_3)_2` CaO `Ca(OH)_2` `CaCO_3` Answer :C

Discussion

50559.	A chemical A is used for the preparation of washing soda to recover ammonia. When CO_(2)is bubbled through an aqueous solution of A, the solution turns milky. It is used in white washing due to disinfectant nature. What is the chemical formula of A?
Answer» `Ca(HCO_(3))_(2)` CaO `Ca(OH)_(2)` `CaCO_(3)` Solution :To recover `NH_(3)` is solvay ammonia soda process, `Ca(OH)_(2)`is USED. It is treated with `NH_(4)Cl`. `2NH_(4)Cl+Ca(OH)_(2) to 2NH_(3)+CaCl_(2)+2H_(2)O` On passing `CO_(2)` through `Ca(OH)_(2)`, lime water, which is colourless, turns milky due to the FORMATION of `CaCO_(3)`. `Ca(OH)_(2)CO_(2) to CaCO_(3) darr+H_(2)O` `Ca(OH)_(2)` is used for white washing also.

Discussion

50560.	A chamber contains 77g of CO_2. The chamber was divided into three compartments X, Y and Z as shown below. Suggest the relation between the internal energies of the gas in the three compartments X, Y and Z. X11 g CO_2 "" y 22g CO_2 "" Z 44g CO_2
Answer» Solution :Under SIMILAR conditions the INTERNAL ENERGY of a given substance depends on its quantity because it is an EXTENSIVE property. The internal energies of `CO_(2)`in the compartments X, Y and Z are in the ratio 1:2:4.

Discussion

50561.	(A): CH_(3)CH(OH)COOH is optically active (R) : CH_(3)CH(OH)COOH do not possess any element of symmetry. The correct answer is
Answer» Both A and R are TRUE and R EXPLAINS A Both A and R are true and R does not explains A A is true, R is FALSE A is false, R is true SOLUTION :Both A and R are true and R explains A

Discussion

50562.	A certain weight of sodium Iodine and sodium chloride mixture when treated with sulphuric acid was found to give the same weight (as that of mixture) of sodium sulphate. The percentage composition of NaCl is
Answer» `18.86` `52.23` `35.57` `71.14` Solution :`2NaCl+H_(2)SO_(4)rarrNa_(2)SO_(4)+2HCl` `2NaI+H_(2)SO_(4)rarrNa_(2)SO_(4)+2HI` Let the wt of the mixture = 1 g `{:(2xx58.5g NaCl" gives",142G Na_(2)SO_(4)),(XG NaCl" gives",142 xg Na_(2)SO_(4)),(,117):}` 300 g of NaI gives 142g `Na_(2)SO_(4)` (1-x)g of NaI gives `((1-x)xx142)/(300)gNa_(2)SO_(4)` `(142x)/(117)+((1-x)xx142)/(300)=1impliesx=0.7114g` % of `NaCl=(0.7114)/(1)xx100=71.14`

Discussion

50563.	A certain weak acid has K_(a)=1.0xx10^(-4). Calculate the equilibrium constant for its reaction with a strong base.
Answer» Solution :`{:(HA,+,BOH,hArr,BA,+,H_(2)O),("weak",,"strong",,,,,):}`:}` or HA+B^(+)+OH^(-) hArr B^(+)+A^(-)+H_(2)O or HA + OH^(-) hArr A^(-)+ H_(2)O` `K=([A^(-)])/([HA][OH^(-)])` ...(i) Further, for the weak acid, `HA hArr H^(+)+A^(-), K_(a) = ([H^(+)][A^(-)])/([HA])` ...(ii) Also `K_(w)=[H^(+)][OH^(-)]`...(iii) From eqns. (i), (ii) and (iii), `K=(K_(a))/(K_(w))=(10^(-4))/(10^(-14))=10^(10)`

Discussion

50564.	A certain weak acid has K_(a), = 10^(-5). If the equilibrium constant for is its reaction with a strong base is repesented as yxx 10^(y) then find the value of y.
Answer» SOLUTION :` HA+ OH^(-)hArr A^(-)+H_2O ,K` ` K= (1)/(K_b)= (K_a) /(K_w)=(10 ^(-5))/( 10^(-14))=10 ^(9) `

Discussion

50565.	A certain volume of Methane diffuses in 10 Sec through a porous partition. The time taken by an equal volume of oxygen to diffuse under the same condition is
Answer» 14.14 Sec. 7.07 Sec. 20 sec. 5 Sec Solution :`((DELTAV)/(10))/((DeltaV)/(t_2)) = SQRT(32/16) = sqrt(2)`. `(t_2)/(10) = 1.414 implies t_2 = 14.14 "sec"`.

Discussion

50566.	A certain third period element has the following successive values of ionization energies in K . J . mol^(-1){:(IE_(1),IE_(2),IE_(3),IE_(4),IE_(5)),(786,580,3230,4360,16100):}the element is
Answer» Carbon Nitrogen Aluminium Silicon ANSWER :A

Discussion

50567.	A certain transition in H spectrum from an excited state to ground state in one or more steps gives rise to total 10 lines. How many of these belong to uv spectrum?
Answer» 3 4 5 6 Answer :B

Discussion

50568.	A certain substances contains only carbon and hydrogen and has a molecular weight of 70. Photochemical chlorination gave only one monochloride. Write the structure and IUPAC name of the hydrocarbon and its monochloride.
Answer» ANSWER :`(##ALN_CHM_C02_(II)_E01_054_A01##)`

Discussion

50569.	A certain substance contains only carbon and hydrogen and its molecular mass is 70. Photochlorination gave only one monochloride. Write the structure and the IUAC name of the substance and its monochloride.
Answer» SOLUTION :The available INFORMATION suggests that the hydrocarbon with molecular MAS 70 is cyclic in NATURE. It is cyclopentane. The chemical reaction is as follows :

Discussion

50570.	A certain sample of cuprous sulphide is found to have the composition Cu_(1.92)S_(1.00) because of incorporation of Cu^(2+) and Cu^(+) ions in the crystal then ratio of Cu^(2+) and Cu^(+) ions is :
Answer» `0.08: 1.00` `1:23` `1:24` `1:1` ANSWER :B

Discussion

50571.	A certain sample of coal contain 1%of sulphur by weight. What is the weight of sulphur dioxide produced when 2'10^(6)kg of this coal isburnt?
Answer» `2xx10^(4)KG` `4xx10^(4)kg` `4xx10^(5)kg` `2xx10^(5)kg` SOLUTION :WEIGHT of sulphur present in coal `(2xx10^(6)xx1)/(100)=2xx10^(4)kg""S+O_(2)rarr SO_(2)` `32xx10^(-2)kg rarr 64xx10^(-3)kg. 2xx10^(4)kg rarr?` weight of sulphur dioxide `=(2xx10^(4)xx64xx10^(-3))/(32xx10^(-3))=4xx10^(4)kg`

Discussion

50572.	A certain salt X, givesthe followingresults.(i) Its aqueous solution isalkaline tolitmus. (ii) It swell up to a glassy materialY onstrongheating. (iii) When conc. H_(2)SO_(4)is added to a hot solution of X,white crystal of anacid Z separate out Writeequations for all the above reaction and identify X,Y and Z.
Answer» Solution :(i) Since the aqueoussolution of salt (X) is alkaline to litmus, it must be the saltof a strong base and a weak acid. (ii) Since the salt (X) swellsup to a glassy material (Y) on strong heating,therefore (X) must be borax and (Y)must be a MIXTUREOF sodium metaborate and boric anhydride. (III)When CONC. `H_(2)SO_(4)`is added to a hot solution of X, i.e, borax,white crystalsof an acid (Z)separateout, therefore(Z)must beorthobasicacid. The equations for thereactionsinvolvedin the question are : (i) `underset("Borax (X)")(Na_(2)B_(4)O_(7). 10 H_(2)O) overset("Water")rarr underset(("Strong alkali"))(2NaOH)+ underset(("Weask acid"))(H_(2)B_(4)O_(7) + 8H_(2)O` (ii) `underset((X))(Na_(2)B_(4)O_(7).10H_(2)O)overset("Heat")rarrNa_(2)B_(4)O_(7)+10H_(2)O, Na_(2)B_(4)O_(7) overset("Heat")rarrubrace(2NaBO_(2) + B_(2)O_(3))_("Glassy material")` (iii) `Na_(2)B_(4)O_(7).10H_(2)O+H_(2)SO_(4)rarrunderset(" Boric acid (Z) ")(4H_(3)BO_(3))+Na_(2)SO_(4)+5H_(2)O`

Discussion

50573.	A certain salt X gives the following results (i) Its aqueous solution shows alkaline to litmus paper (ii) It swells up to a hot glassy material Y on strong heating(iii) When conc. H_(2)SO_(4) is added to a solution of X white crystal of an acid Z separates out. Write equation for all the above reactions and identify X,Y and Z.
Answer» SOLUTION :(i) `Na_(2)B_(4)O_(7)+ 7H_(2)O rarr 2NaOH+4H_(2)BO_(3)+2H_(2)` (ii) `underset(("Borax"(x))) (Na_(2) B_(4)O_(7)) overset("heat") (rarr) 2NaBO_(2)+B_(2)O_(3)` (iii) `underset((x))(Na_(2)B_(4)O_(7))+underset(("CONE"))(H_(2)SO_(4))+5H_(2)O overset("heat") (rarr) Na_(2)SO_(4)+underset((z))(4H_(3)BO_(3))`

Discussion

50574.	A certain salt (X) gives the following tests : (a) Its aqueous solution is alkaline to litmus. (b) On strong heating, it swells up to give a glassy material (Y). (c) When conc. H_(2) SO_(4) is added to a hot concentrated solution of (X), white crystal ofa weak acid (Z) separates out. Identify (X), (Y) and (Z) and write down the chemical equations for reaction at steps a, b and c.
Answer» Solution :(i) SINCE, the alkaline solution of the given salt [X] is alkaline to litmus, it MUST be a salt of strong base and weak acid. (ii) The salt [X] on heating SWELLS up to a GLASSY material (Y). Therefore, [X] should be borax and [Y] a mixture of sodium metaborate and boric anhydride. (iii) When conc. H2SO4 is added to a hot solution of borax [A], white crystals of orthoboric acid [Z] SEPARATE out. Hence, [X] = `Na_2 B_4 O_7 . 10 H_2 O , [Y] = NaBO_2 + B_2 O_3 and [Z] = H_3 BO_3`. The reaction can be expressed as follows :

Discussion

50575.	A certain salt X, gives the following results. (i) Its aqueous solution is alkaline to litmus. (ii) It swells up to a glassy material Y on strong heating (iii) When conc. H_2SO_4 is added to a hot solution of X, white crystal of an acid Z separates out. Write equations for all the above reactions and identify X, Y and Z.
Answer» Solution : (i) The given salt is alkaline to litmus. Therefore, X is a salt of a STRONG base and a weak acid. Also, when X is strongly heated, it swells to FORM substance Y. Therefore, X MUST be borax. `underset"(X)"(Na_2B_4O_7). 10H_2O overset(H_2O) tounderset"(Strong base)"(2NaOH) + underset"(Weak acid)"(H_2B_4O_7)` (ii) When borax is heated, it loses WATER and swells to form sodium metaborate. When heating is continued, it solidifies to form a glassy material Y. Hence, Y must be a mixture of sodium metaborate and boric anhydride. `Na_2B_4O_7 . 10H_2O overset(Delta)to Na_2B_4O_7 + 10 H_2O` `Na_2B_4O_7 OVERSETDELTATO ubrace(2NaBO_2+B_2O_3)_((Y))` (iii)When concentrated acid is added to borax, white crystals of orthoboric acid (Z) are formed. `Na_2B_4O_7. 10H_2O + H_2SO_4 to underset"(Z)"(4H_3BO_3) + 5H_2O + Na_2SO_4`

Discussion

50576.	A certain salt X gives the following reactions (ii) It swells up to a glassy matter Y on heating
Answer» ANSWER :`Na_2B_4O_7.10h_2Ounderset(-H_2O)OVERSET(HEAT)rarrNa_2B_4O_overset(heat)rarr2NaBO_2+B_2O_3`

Discussion

50577.	A certain salt X gives the reaction,When Con.H_2SO_4 is added to a hot solution of X, white crystals of an acid Z separates out. Identify X,and Z.
Answer» ANSWER :`Na2B_4O_7.10H_2O+H_2SO_4rarr4H_3BO_3+Na_2SO_4+5H_2O`

Discussion

50578.	A certain salt X gives the following reactions (i) Its aqueous solution is alkaline to litmus
Answer» ANSWER :X = BORAX, Y = `NaBO_2+B_2O_3, Z = `H_3BO_3` `Na2B_4O_7+H_2Ooverset(WATER)rarr2NaOH+4H_3BO_3`

Discussion

50579.	Acertain rection has equilibrium constant 10 and 100 at 300K and 400K respectively. The ratio of Delta G^(@) at 300K and 400K respectively
Answer» `(1)/(10)` `(3)/(8)` `(1)/(2)` `(3)/(4)` Solution :`(Delta G_(1)^(@))/(Delta G_(2)^(@))=(-2.303 RT_(1) log K_(P_(1)))/(-2.303 RT_(2) log K_(P_(2)))=(T_(1))/(T_(2)) xx (log K_(P_(1)))/(log K_(P_(2)))=(300)/(400) xx (log^(10))/(log^(100))=(3)/(8)`

Discussion

50580.	A certain quantity of a gas occupies 300 mL when collected over water at 25^@C and 745 mm pressure. It occupied 182.6 mL in dry state at S.T.P. Find the vapour pressure of water at 25^@C.
Answer» Solution :Let us calculate the PRESSURE EXERTED by 182.6 mL (at S.T.P.) of the DRY GAS when its volume is 300 mL and temperature is `25^@C, i.e.`, `P_1 = 760 " mm Hg. " V_1 = 182.6 mL`, `T_1 = 273 K` (at S.T.P.) `P_2 = ?, "" V_2 = 300 ml, "" T_2 = 25 + 273 = 298 K` According to the gas equation, `(P_1V_1)/T_1 = (P_2V_2)/T_2` Substituting the values, we have `(760 xx 182.6)/273 =(P_2 xx 300)/298 or P_2 = 504.9` mm Hg Under SIMILAR conditions, the wet gas exerts a pressure of 745 mm. `:." Vapour pressure of water at " 25^@C` `= 745 - 504.9 = 240.1 mm`

Discussion

50581.	A certain quantity of a gas occupies 100ml when collected over water at 15°C and 750mm pressure. If it occupies 91.9ml in dry state at STP, the vapour pressure of water at 15°C is
Answer» 12.8mm 14.8mm 13.2mm 13.7mm Answer :C

Discussion

50582.	A certain quantity of a gas measured 500 mL at a temperature of 15^@C and 750 mm Hg What pressure is required to compress this quantity of gas into a 400 mL vessel at a temperature of 50^@C ?
Answer» SOLUTION :In the present case, `P_1 = 750 mm Hg`, `V_1 = 500 mL`, `T_1 = 273 + 15 = 288 K " and"P_2` = ? `V_2 = 400 ml`, `T_2 = 273 + 50 = 323 K` Therefore, ACCORDING to the gas equation, we have `(P_1 V_1)/(T_1) = (P_2 V_2)/(t_2) " or "(750 xx 500)/288=(P_2 xx 400)/323" or "P_2 = 1051 mm` Hence, the given gas should be compressed to 1051 mm pressure.

Discussion

50583.	A certain public water supply contained 0.10 parts per billion of chloroform CHCl_(3) How many molecules of CHCl_(3)would be contained in a 0.05 ml drop of this water ?
Answer» Solution :Volume = 0.05 mL Amount of `CHCl_(3)` in th drop `=(0.05 xx 0.1)/10^(5) = 5.0 xx 10^(-12)`g Molecule MASS of `CHCl_(3) = 12+1 + 3 xx 35.5` `=119.5 g mol^(-1)` Moles of `CHCl_(3)` PRESENT `=(5.0 xx 10^(-12))/119.5` MOLECULES of `CHCl_(3)` present in the drop `=(5.0 xx 10^(-12))/119.5 xx 6.022 xx 10^(23) = 2.5 xx 10^(19)`.

Discussion

50584.	A certain particle carries 2.5 xx 10^(-16) C of static electric charge. Calculate the number of electrons present in it.
Answer» Solution :Charge CARRIED by one electron `= 1.6022 XX 10^(-19) C` `:.` Electrons present in particle CARRYING `2.5 xx 10^(-16) C " charge" = (2.5 xx 10^(-16))/(1.6022 xx 10^(-19)) = 1560`

Discussion

50585.	A certain positive ion A^(+2)has 22 mass number of most abundant isotope of A?
Answer» 42 38 40 None of these Answer :C

Discussion

50586.	Acertainparticlecarreis2.5 xx 10^(16)C ofstaticelectriccharge.Caculatethe numberofelectronspresenctin it.
Answer» Solution :Staticelectriccharge of PARTICLE (q ) = 2.5 `XX 10^(16) C` Chargeofoneelectron =1,6022`xx 10^(19) C` `=(2.5 xx 10^(16) C)/(1.6022xx 10^(19)) `=1560 ` electrons

Discussion

50587.	A certain oxide of iron contains 2.5 grams of oxide for every 7.0grams of iron. If it is regarded as a mixture of FeO and Fe_(2)O_(3) in the weight ratio a:b, what is a:b ? (atomic weight of iron = 56)
Answer» `9:10` `9:20` `14:5` `1:1` ANSWER :A

Discussion

50588.	A certain particle carries -2.5 xx 10^(-16)C of static charge. Calculate the number of electrons present in it.
Answer» Solution :`"No.of ELECTRONS "= ("STATIC charge E")/("coulomb charge of each "e^(-))=(2.5xx10^(-16)"coulomb ")/(1.602xx10^(-19)"coulomb")` `=1.56xx10^(3)" electrons "= "1,560 electrons"`.

Discussion

50589.	A certain non-volatile substance (non-electrolyte) contains 40%C, 6.7%H, 53.3 % O. An aqueous solution containing 5% by mass of the solute boils at 100.15^(@)C. Molecular formula of the compound is :
Answer» `CH_(2)O` `C_(2)H_(4)O_(2)` `C_(6)H_(12)O_(6)` `C_(12)H_(22)O_(11)` Answer :C

Discussion

50590.	A certain metal sulphide MS_(2) is used extensively as a high temperature lubricant. If MS_(2) is 40.00% by mass sulphur, atomic mass of M is
Answer» 60 96 100 80 Solution :`%S=40=(2xx32)/(M+32)XX100` `%M=60=(M)/(M+32)xx100` `IMPLIES M=(6)/(4)xx2xx32=96`

Discussion

50591.	A certain line of the Lyman series of hydrogen and a certain line of the Balmer series of He^(+) ion have nearly the same wavelength to what transition do they belong? Small differences between their Rydberg constant may be neglected. Differences between their Rydberg constant may be neglected.
Answer» ANSWER :`{:("HYDRONGEN","HELIUM"),(2to1,4to2),(3to1,6to2),(4to1,8to2):}`

Discussion

50592.	A certain gas was found to occupy a volume of 1000 cm^(3)at 27^(@)C.Calculate the temperature at which the gas occupies a volume of 600 cm^(3) at a constant pressure.
Answer» Solution :`v_(1)=1000 cm^(3), v_(2)=600 cm^(3), T_(1)=(27+273)=300 K,T_(2)= ?` `(V_(1))/(T_(1))=(V_(2))/(T_(2)) or T_(2), =(T_(1)V_(2))/(V_(1))=(300xx600)/(1000)=180K` `:. T_(2)=180K`

Discussion

50593.	A certain gas occupies 0.418 litres at 27^@C and 740 mm of Hg. If we increase the weight of the gas to 7.5 g in the same vessel and the temperature is changed to 280 K, what would be its pressure ?
Answer» Solution :According to the gas equation `PV = NRT` Now, `n= (7.5)/(181.5),R = 0.0821L " atm " K^(-1)MOL^(-1)` `T = 280 K and V = 0.418L` `:. "" P =(7.5/181.5xx0.0821xx280)/0.418=2.27` atm HENCE, the pressure of the gas WOULD be 2.27 atm.

Discussion

50594.	A certain gas takes three times as long to effuse out as helium. Its molecular mass will be
Answer» `27 u` `36 u` `64 u` `9 u` ANSWER :B

Discussion

50595.	A certain gas occupies 0.418 litres at 27^@C and 740 mm Hg. What is the volume at S.T.P. ?
Answer» Solution :According to the gas equation `(Р_1 V_1)/T_1 =(P_2 V_2)/T_2` In the present case, `P_1 = 740 " mm Hg,"V_1 = 0.418 L` `T_1 = 27 + 273 = 300 K` `P_2 = 760 " mm Hg, " V_2 = ? "" T_2 = 273 K` (at S.T.P.) Substituting the values, we have `(740 xx 0.418)/300 =(760 xx V_2)/300` `:. "" V_2 = 0.37 L`

Discussion

50596.	A certain gas is expanded from (1L, 10atm) to (4L, 5atm) against a constant external pressure of 1 atm. If the initial temperature of gas is 300K and heat capacity for the process is 50J ""^(@)C^(-1) (use 1L atm = 100J), then
Answer» `\|W\| = 0.3kJ` `\|Q\| = 15 KJ` `Delta U = 14.7 kJ` `Delta H = 15.7 kJ` Solution :Constant, P, `W = - P_("ext") Delta V` `= -1 xx (4-1) = - 3` latern, `\|W\| = 0.3 KJ` `(P_(1)V_(1))/(T_(1)) =(P_(2)V_(2))/(T_(2)), (1 xx 10)/(300)= (4 xx 5)/(T_(2)) , T_(2) = 600K` `\|q\| = C Delta T = (50 xx 300)/(1000) = 15KJ` `Delta U = q + W = + 15 - 0.3 = 14.7` `Delta H = Delta U + Delta (PV)` `=14.7 + (5 xx 4 - 10 xx 1) xx 0.1 KJ = 15.7 KJ`

Discussion

50597.	A certain gas occupies 0.418 litres at 27^@C and 740 mm Hg. If the same gas weighs 3.00 g, what is its molecular weight?
Answer» Solution :Number of MOLES in 3.00 g of gas = `(3.00)/M`, where M is the molecular WEIGHT of the gas. According to the gas equation `PV = nRT` SUBSTITUTING the values, we have `740/760 XX 0.418 = 3.00/M xx 0.0821 xx 300` (P = 760/760 atm ) `:. ""M = 181.5`

Discussion

50598.	A certain element is a metalloid that forms an acidic oxide with the formula R_(2)O_(5). Identify the elements
Answer» Solution :Since the elements forms as axide with formula, `R_(2)O_(5)`, it must be an element of GROUP 15. Now group 1 has TWO metalloids, As and Sb. Since the acidic character of pentoxides of group 15 elements decrease while the basic character increases down the group, therefore, `As_(2)O_(5)` is acidic while `Sb_(2)O_(5)` is amphoteric. THUS, the metalloid of group 15 elements which forms an acidic pentoxide `(As_(2)O_(5))` is As.

Discussion

50599.	A certain crystal has (i) density = 0.456 cm^(-3) , (ii) a fourfold axis of symmetry and (iii) 4 molecules per unit cell. Side lengths of the unit cell are a = b = 658 pm and c = 593 pm. Calculate the molar mass in g mol^(-1).
Answer» `16.20` `17.62` `19.25` `23` ANSWER :B

Discussion

50600.	A certain compound X impats golden yellow flame. Whenzinc powder is heated with concenrated solution of X, H_(2) gas is evolved. X combines with CO_(2) to give a salt Y. Y is a hydrated salt which on reaction with HCl or ecess of CO_(2) gives another salt Z which is an important part of baking powder. identify X, Y and Z.
Answer» `X-NaOH,Y-Na_(2)CO_(3),Z-NaHCO_(3)` `X-HCl, Y-NaOH,Z-NaHCO_(3)` `X-KOH,Y-K_(2)CO_(3),Z-KHCO_(3)` `X-NACL,Y-Na_(2)CO_(3),Z-NaOH` SOLUTION :`Zn+UNDERSET((X))(2NAOH) to Na_(2)ZnO_(2)+H_(2)` `underset((X))(2NaOH)+CO_(2)tounderset((Y))(Na_(2)CO_(3))+H_(2)O` `underset((Y))(Na_(2)CO_(3))+HCl to underset((Z))(NaHCO_(3))+NaCl` ltBrgt `underset((Y))(Na_(2)CO_(3))+CO_(2)+H_(2)O to underset((Z))(2NaHCO_(3))`

Discussion

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A chamber contains 77g of CO_2. The chamber was divided into three compartments X, Y and Z as shown below. Suggest the relation between the internal energies of the gas in the three compartments X, Y and Z. X11 g CO_2 "" y 22g CO_2 "" Z 44g CO_2

(A): CH_(3)CH(OH)COOH is optically active (R) : CH_(3)CH(OH)COOH do not possess any element of symmetry. The correct answer is

A certain weight of sodium Iodine and sodium chloride mixture when treated with sulphuric acid was found to give the same weight (as that of mixture) of sodium sulphate. The percentage composition of NaCl is

A certain weak acid has K_(a)=1.0xx10^(-4). Calculate the equilibrium constant for its reaction with a strong base.

A certain weak acid has K_(a), = 10^(-5). If the equilibrium constant for is its reaction with a strong base is repesented as yxx 10^(y) then find the value of y.

A certain volume of Methane diffuses in 10 Sec through a porous partition. The time taken by an equal volume of oxygen to diffuse under the same condition is

A certain third period element has the following successive values of ionization energies in K . J . mol^(-1){:(IE_(1),IE_(2),IE_(3),IE_(4),IE_(5)),(786,580,3230,4360,16100):}the element is

A certain transition in H spectrum from an excited state to ground state in one or more steps gives rise to total 10 lines. How many of these belong to uv spectrum?

A certain substances contains only carbon and hydrogen and has a molecular weight of 70. Photochemical chlorination gave only one monochloride. Write the structure and IUPAC name of the hydrocarbon and its monochloride.

A certain substance contains only carbon and hydrogen and its molecular mass is 70. Photochlorination gave only one monochloride. Write the structure and the IUAC name of the substance and its monochloride.

A certain sample of cuprous sulphide is found to have the composition Cu_(1.92)S_(1.00) because of incorporation of Cu^(2+) and Cu^(+) ions in the crystal then ratio of Cu^(2+) and Cu^(+) ions is :

A certain sample of coal contain 1%of sulphur by weight. What is the weight of sulphur dioxide produced when 2'10^(6)kg of this coal isburnt?

A certain salt X gives the following reactions (ii) It swells up to a glassy matter Y on heating

A certain salt X gives the reaction,When Con.H_2SO_4 is added to a hot solution of X, white crystals of an acid Z separates out. Identify X,and Z.

A certain salt X gives the following reactions (i) Its aqueous solution is alkaline to litmus

Acertain rection has equilibrium constant 10 and 100 at 300K and 400K respectively. The ratio of Delta G^(@) at 300K and 400K respectively

A certain quantity of a gas occupies 300 mL when collected over water at 25^@C and 745 mm pressure. It occupied 182.6 mL in dry state at S.T.P. Find the vapour pressure of water at 25^@C.

A certain quantity of a gas occupies 100ml when collected over water at 15°C and 750mm pressure. If it occupies 91.9ml in dry state at STP, the vapour pressure of water at 15°C is

A certain quantity of a gas measured 500 mL at a temperature of 15^@C and 750 mm Hg What pressure is required to compress this quantity of gas into a 400 mL vessel at a temperature of 50^@C ?

A certain public water supply contained 0.10 parts per billion of chloroform CHCl_(3) How many molecules of CHCl_(3)would be contained in a 0.05 ml drop of this water ?

A certain particle carries 2.5 xx 10^(-16) C of static electric charge. Calculate the number of electrons present in it.

A certain positive ion A^(+2)has 22 mass number of most abundant isotope of A?

Acertainparticlecarreis2.5 xx 10^(16)C ofstaticelectriccharge.Caculatethe numberofelectronspresenctin it.

A certain oxide of iron contains 2.5 grams of oxide for every 7.0grams of iron. If it is regarded as a mixture of FeO and Fe_(2)O_(3) in the weight ratio a:b, what is a:b ? (atomic weight of iron = 56)

A certain particle carries -2.5 xx 10^(-16)C of static charge. Calculate the number of electrons present in it.

A certain non-volatile substance (non-electrolyte) contains 40%C, 6.7%H, 53.3 % O. An aqueous solution containing 5% by mass of the solute boils at 100.15^(@)C. Molecular formula of the compound is :

A certain metal sulphide MS_(2) is used extensively as a high temperature lubricant. If MS_(2) is 40.00% by mass sulphur, atomic mass of M is

A certain line of the Lyman series of hydrogen and a certain line of the Balmer series of He^(+) ion have nearly the same wavelength to what transition do they belong? Small differences between their Rydberg constant may be neglected. Differences between their Rydberg constant may be neglected.

A certain gas was found to occupy a volume of 1000 cm^(3)at 27^(@)C.Calculate the temperature at which the gas occupies a volume of 600 cm^(3) at a constant pressure.

A certain gas occupies 0.418 litres at 27^@C and 740 mm of Hg. If we increase the weight of the gas to 7.5 g in the same vessel and the temperature is changed to 280 K, what would be its pressure ?

A certain gas takes three times as long to effuse out as helium. Its molecular mass will be

A certain gas occupies 0.418 litres at 27^@C and 740 mm Hg. What is the volume at S.T.P. ?

A certain gas is expanded from (1L, 10atm) to (4L, 5atm) against a constant external pressure of 1 atm. If the initial temperature of gas is 300K and heat capacity for the process is 50J ""^(@)C^(-1) (use 1L atm = 100J), then

A certain gas occupies 0.418 litres at 27^@C and 740 mm Hg. If the same gas weighs 3.00 g, what is its molecular weight?

A certain element is a metalloid that forms an acidic oxide with the formula R_(2)O_(5). Identify the elements

A certain crystal has (i) density = 0.456 cm^(-3) , (ii) a fourfold axis of symmetry and (iii) 4 molecules per unit cell. Side lengths of the unit cell are a = b = 658 pm and c = 593 pm. Calculate the molar mass in g mol^(-1).