MOLE CONCEPT PART H

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MOLE CONCEPT PART H


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PARTIII : ASSERTION / REASONING

Each question has 5 choices (A), (B), (C), (D) and (E) out of which ONLY ONE is correct.

  • STATEMENT-1 is true, STATEMENT-2 is true and STATEMENT-2 is correct explanation for STATEMENT-1.
  • STATEMENT-1 is true, STATEMENT-2 is true and STATEMENT-2 is not correct explanation for STATEMENT-1.
  • STATEMENT-1 is true, STATEMENT-2 is false.
  • STATEMENT-1 is false, STATEMENT-2 is true.
  • Both STATEMENTS are false.
  1. Statement-1 : The weight percentage of a compound A in a solution is given by

Mass A

0/0 of A =                                            x100

Total mass of solution

Statement2 : The mole fraction of a component A is given by,

No. of moles of A

Mole fraction of A = Total no of moles of all components

  1. Statement-1 : The ratio of the mass of 100 billion atoms of magnesium to the mass of 100 billion atoms of

24

lead can be expressed as ___

207

Statement-2 : Atomic weights are relative masses.

  1. Statement-1 : The average mass of one Mg atom is 24.305 amu, which is not the actual mass of one Mg

Statement-2 : Three isotopes, 24Mg, 25Mg and 26Mg, of Mg are found in nature.

  1. Statement-1 : A molecule of butane, 04 H10 has a mass of 58.12 amu.

Statement-2 : One mole of butane contains 6.022 x 1023 molecules and has a mass of 58.12 g.

  1. Statement-1 : Both 12 g. of carbon and 27 g. of aluminium will have 6.02 x 102‘ atoms.

Statement-2 : Gram atomic mass of an element contains Avogadro’s number of atoms.

  1. Statement-1 : The molality and molarity of very dilute aqueous solutions differ very little.

Statement-2 : The density of water is about 1.0 g cm‘ at room temperature.

  1. Statement-1 : For calculating the molality or the mole fraction of solute, if the molarity is known, it is necessary to know the density of the solution.

Statement-2 : Molality, molarity and the mole fraction of solute can be calculated from the weight percentage and the density of the solution

  1. Statement-1 : Laboratory reagents are usually made up to a specific molarity rather than a given molality. Statement-2: The volume of a liquid is more easily measured than its mass.
  2. Statement-1 : Molality and mole fraction concentration units do not change with temperature. Statement-2 These units are not defined in terms of any volume.
  3. Statement-1 : A one moral solution prepared at 20°C will retain the same molality at 100°C, provided there is no loss of solute or solvent on heating.

Statement-2 : Molality is independent of temperature.

EXERCISE:2

PART-I : SUBJECTIVE QUESTIONS

  1. The nonstoichiometry compound “titanium monoxide” has a continuous range of composition from Tio750 to

Ti00 69. What are the maximum and minimum values of the percent by weight of oxygen in this compound? [At. wt of Ti = 48]

  1. Assume that the nucleus of the F atom is a sphere of radius 5 x 10-13 cm. Calculate the density of matter in F

nucleus.

  1. A plant virus is found to consist of uniform cylindrical particles of 150 A in diameter and 5000 A long. The

specific volume of the virus is 0.75 cm3/g. If the virus is considered to be a single partical, find its molecular weight.

  1. A sample of chalk contains clay as impurity. The clay impurity loses 11% of its weight as moisture on prolong

heating. 5 gram sample of chalk on heating shows a loss in weight (due to evolution of CO2 and water) by 1.1 g. Calculate % of chalk (CaCO3) in the sample. [Hint : Chalk (CaCO3) release CO2 on heating]

  1. Consider the following reaction involved in the preparation of teflon polymer -÷CF,-CF,t,

XeF6+ ±CH2-C1-1.7t,  _________________ + HF + XeF4.

Determine the moles of XeF,3 required for preparation of 100 g Teflon.

  1. (i) K4Fe(CN)3 + 3H2SO4 ______________ ) 2K2SO4 + FeSO4 + 6HCN
  • 6HCN + 12H20 > 6HCOOH + 6NH
  • (a) 6NH3 + 3H2SO4 3(NI14)2 SO4 (b) 6HCOOH  H2s04 > 6C0 + 6H20
    Above steps of reactions occur in a container starting with one mole of K4[Fe(CN)6], 5 mole of H2SO4 and enough water. Find out the limiting reagent in step (i) and calculate maximum moles of CO gas and (NI-14)2SO, that can be produced.

3

  1. A2 + 2B2                A2B4                              2 A2 + 282 __________ > A3B4

Two substance A2 & B2 react in the above manner. When A2 is limited it gives A2B4 in excess gives A3B4. A2B4 can be converted to A3134 when reacted with A2, Using this information calculate the composition of the final mixture when the mentioned amount of A2 & B2 are taken

(a) 4 moles A2 & 4 moles B2      (b) 2 moles A2 & 2 moles B2 (c) 1.25 moles A2 & 2 moles B2

1                       1

  1. When 1 mol of A reacts with –2 mol of B2 (A + –2 B2 __________ > AB), 100 Kcal heat is liberated and when 1 mol of

A reacted with 2 mol of B2 (A + 2B2 ___ > AB4) , 200 Kcal heat is liberated. When 1 mol of A is completely

reacted with excess of B2 to form AB as well as AB4, 140 Kcal heat is liberated Calculate the mol of B2 used. [Write your answer as (No. of moles of B2 used x 1000)]

  1. In a gravimetric determination of P. an aqueous solution of dihydrogen phosphate ion H2P0, is treated with a

mixture of ammonium and magnesium ions to precipitate magnesium ammonium phosphate, Mg(NH4)PO4 . 6H20. This is heated and decomposed to magnesium pyrophosphate , Mg2P207 , which is weighed. A solution of H2PO4 yielded 1.054 g of Mg2P207. What weight of NaH2PO4 was present originally? (Na = 23 , H = 1 , P = 31 , 0 = 16 Mg = 24)

  1. 1 g of dry green algae absorbs 4.7 x 10-3 moleof CO2 per hour by photosynthesis. If the fixed carbon atoms

were all stored after photosynthesis as starch (C61110 05), how long would it take for the algae to double their own weight assuming photosynthesis takes place at a constant rate ?

  1. Cl2 + KOH 60%> KCI + KCIO + H2O KCIO 50%> KCI + KCIO3

K0103 80%> KCIO4 + KCI

112 L 012 gas at STP is passed in 10 L KOH solution, containing 1 mole of potassium hydroxide per liter. Calculate the total moles of KCI produced, rounding it off to nearest whole number. (Yield of chemical reactions are written above the arrow (-f) of respective reaction)

  1. The ‘roasting’ of 100.0 g of a copper ore yielded 71.8 g pure copper. If the ore is composed of Cu2S and CuS with 4.5 % inert impurity, calculate the percent of Cu2S in the ore.

The reactions are

Cu2S + 02 ____  > 2Cu + SO2     and      CuS + 0, -> CL SO2 [Atomic mass Cu = 63.5, S = 32]

  1. NaBr, used to produce AgBr for use in photography can itse. ,Je prepared as follows :

Fe + Br2         > FeBr2

FeBr2 + Br2                   Fe, Bra                                                      (not balanced)

Fe3Br8 + Na2CO3 __________ > NaBr + CO2 + Fe30,                             (not balanced)

How much Fe, in kg, is consumed to produce 2.50 x 103 kg NaBr ?

  1. How many grams of 90% pure Na9SO4 can be produced from 250 g of 95% pure NaCI.
  2. Find the sum of average oxidation number of S in H2S05 (peroxy monosulphuric acid) and Na2S203 (sodium thiosulphate).
  3. The reaction C12(g) + S2032- ______ > SO42- + Cl is to be carried out in basic medium. Starting with 0.15
    mole of C12, 0.01 mole S2032- and 0.3 mole of OH, how many moles of OH will be left in solution after the reaction is complete. Assume no other reaction occurs.
  4. HCl solution (50% by mass and d = 1.25 g/ml) is used to prepare one litre 0.5 M HCI. What is the volume of sample used for this purpose.
  5. What volume (in ml) of 0.2 M H2SO4 solution should be mixed with the 40 ml of 0.1 M NaOH solution such that the resulting solution has the concentration of H2SO4 as 565
  6. To 100 ml of 5 M NaOH solution (density 1.2 g/ml) were added 200 ml of another NaOH solution which has a density of 1.5 g/ml and contains 20 mass percent of NaOH. What will be the volume of the gas (at STP) in litres liberated when aluminium reacts with this (final) solution.

The reaction is Al + NaOH + H2O > NaA102 + H2 (At.wt. Na = 23, 0 = 16, H = 1)

  1. A drop (0.05 mL) of 12 M HCI is spread over a thin sheet of aluminium foil (thickness 0.10 mm and density of Al = 2.70 g/mL). Assuming whole of the HCI is used to dissolve Al, what will be the maximum area of hole produced in foil ?

OBJECTIVE QUESTIONS

Single choice type:

  1. Which of the following will contain same number of atoms as 20g of calcium?

(A) 24g magnesium      (B) 12g carbon             (C) 8g oxygen gas     (D) 16 g oxygen atom

  1. A sample of ammonium phosphate (NH4),P0, contains 3.18 mol of H atoms. The number of mol of O atoms in the sample is :

(A) 0.265                      (B) 0.795                      (C) 1.06                       (D) 3.18

  1. The moiar mass of normal water is .. as compared to heavy water.

(A) 10% less                (B) 10% high                (C) 2% less                (ID) zero% less

  1. The ratio of the weight of one litre of a gas to the weight of 1.0 L oxygen gas both measured at S.T.P. is 2.22. The molecular weight of the gas would be :

(A) 14.002                    (B) 35.52                      (0) 71.04                      (D) 55.56

  1. One mole of a mixture of N2, NO2 and N204 has a mean molar mass of 55.4. On heating to a temperature at

which all the N204 may be presumed to have dissociated : N204       2NO2, the mean molar mass tends to
the lower value of 39.6. What is the mole ratio of N2 NO2 : N204 in the original mixture ?

(A) 0.5 : 0.1 : 0.4           (B) 0.6 : 0.1 : 0.3          (C) 0.5 : 0.2 : 0.3         (D) 0.6 : 0.2 : 0.2

  1. 0 mL of NO2 at STP was liquefied, the density of the liquid being 1.15 g mL-1. Calculate the volume and the
    number of molecules in the liquid NO2 (At. wt. of N = 14)

(A) 0.10 mL and 3.01 x 1022                             (B) 0.20 mL and 3.01 x 1021

(C) 0.20 mL and 6.02 x 1023                             (D) 0.40 mL and 6.02 x 1021

  1. A certain organic substance used as a solvent in many reactions contains carbon, hydrogen, oxygen and
    Weight % of hydrogen in the compound is 7.7. The weight ratio C : 0 : S = 3 : 2 : 4. What is the !east possible molar mass of the compound ?

(A) 86                           (B) 63                          (C) 94                          (D) 78

  1. The oxides of a certain (hypothetical) element contain 27.28%, 42.86% and 52.94% oxygen. What is the ratio
    of the valancies of the element in the 3 oxides ?

(A) 2 : 3 : 4                    (B) 1 : 3 : 4                  (C) 1 : 2 : 4                 (D) 1 : 2 : 3

  1. Formation of polyethene from calcium carbide takes place as follows :

CaC2+H20 Ca(OH)2 + C2H2 ; C2H2+ H.            C2H4

n(C2H4)              (-CH2-C1-12-)_.

The amount of polyethylene possibly obtainable from 64.0 kg CaC2 can be

(A) 28Kg                       (B) 14kg                      (C) 21 kg                    (D) 42 kg

  1. The hourly energy requirement of an astronaut can be satisfied by the energy released when 34 g of sucrose
    (C12H220,1) are burnt in his body. How many g of oxygen would be needed to be carried in space capsule to meet his requirement for one day :

(A) 916.2 gm                 (B) 91.62 gm                (C) 8.162 gm              (D) 9.162 gm.

  1. If a piece of iron gains 10% of its weight due to partial rusting into Fe2O3 the percentage of total iron that has
    rusted is :

(A) 23                           (B) 13                          (C) 23.3                       (D) 25.67

  1. If 10 g of Ag reacts with 1 g of sulphur , the amount of Ag2S formed will be [Atomic weight of Ag = 108,
    S = 32] ?

(A) 7.75 g                      (B) 0.775 g                   (C) 11 g                                (D) 10 g

  1. 100 g impure CaCO3 on heating gives 5.6 It. CO2 gas at STP. Find the percentage of calcium in the lime stone
    [At. wt. : Ca = 40 : C = 12 ; 0 = 16]

(A) 10                           (B) 20                          (C) 1                           (D) 30

  1. When a 12 g mixture of carbon and sulphur is burnt in air, then a mixture of CO2 and SO2 is produced, in which
    the number of moles of SO2 is half that of 002. The mass of the carbon in the mixture is :

(A) 4.08 g                      (B) 5.14 g                    (C) 8.74 g                   (D) 1.54 g

  1. When x grams of carbon are heated with y grams of oxygen in a closed vessel, no solid residue is left behind.
    Which of the following statements is correct ?

(A) y/x must lie between 1.33 and 2.67           (B) y/x must be greater than or equal 2.67.

(C) y/x must be less than or equal 1.33          (D) y/x must be greater than or equal 1.33.

  1. XeF6 fluorinates 12 to IF, and liberates Xenon(g). 210 mmol of XeF6 can yield a maximum of mmol of IF,

(A) 420                          (B) 180                        (C) 210                        (D) 245

  1. 1 mol of iron (Fe) reacts completely with 0.65 mol 02 to give a mixture of only FeO and Fe203. Mole ratio of
    ferrous oxide to ferric oxide is :

(A) 3 : 2                        (B) 4 : 3                       (0) 20 : 13                  (D) none of these

  1. Composition of a sample is Feo 93 01 DO If Fe is present in +2 & +3 oxidation state in this sample then % of Fe
    present in +3 oxidation state

(A) 85%                        (B) 30%                       (0) 15%                       (D) 60%

  1. The following equations are balanced atomwise and chargewise.
  • Cr2072- + 8H+ + 3H202 ____________ > 20r3+ + 7H20 + 302
  • Cr2072 + 8H’ + 5H202 ________ > 2Cr3+ + 9H20 + 402
  • Cr2072- + 8H+ + 7H202 ____________ > 2Cr3+ + 11 H20 + 502
    The precise equation/equations representing the oxidation of H202 is/are :

(A) (i) only                               (B) (ii) only                          (C) (iii) only                             (D) all the three

  1. xNO3 + + zH+—> 2NO + 312 + 4H20 x . y z respectively in the above equation are :

(A) 2, 6, 8                               (B) 1, 6 4                             (C) 0, 6 , 8                            (D) 2 3 , 4

  1. Molarity of H2SO4 is 18 M. Its density is 1 .8 g/cm3, hence molality is

(A) 18                                      (B) 100                                (0) 36                        (D) 500

  1. A solution of glucose received from some research laboratory has been marked mole fraction x and molality

(m) at 10°C. When you will calculate its molality and mole fraction in your laboratory at 24°C you will find

(A) mole fraction (x) and molality (m)                                (B) mole fraction (2x) and molality (2m)

(C) mole fraction (x/2) and molality (m12)                      (ID) mole fraction (x) and (m ± dm) molality

  1. Mole fraction of ethyl alcohol in aqueous ethyl alcohol (C2H5OH) solution is 0.25. Hence percentage of ethyl

alcohol by weight is :

(A) 54%                                  (B) 25%                              (C) 75%                              (D) 46%

  1. A mineral water sample was analysed and found to contain 1 x 10′ % ammonia (w/w). The mole of dissolved

ammonia gas in one litre water bottle is (c1„,,,e,     1 gm/ml)

(A) 5.8 x 1 0-4 mol                 (B) 1 x 10-2 mol                  (C) 0.58 x10-2 mol            (D) same as wlw

  1. What is the quantity of water that should be added to 16 g. methanol to make the mole fraction of methanol as

0.25

(A) 27 g.                                 (B) 12 g.                              (C) 18 g.                             (D) 36 g.

  1. Calculate the mass percent (w/w) of sulphuric acid in a solution prepared by dissolving 4 g of sulphur trioxide

in a 100 ml sulphuric acid solution containing 80 mass percent (w/w) of H2SO4 and having a density of 1.96 g/ ml. (molecular weight of H2SO4 = 98). Take reaction SO3 + H2O                          H2SO4

(A) 80.8%                              (B) 84%                              (0) 41.65%              (D) None of these

  1. On mixing 15.0 ml of ethyl alcohol of density 0.792 g m1-1with 15 ml of pure water at 4° C, the resulting solution

is found to have a density of 0.924 g m1-1. The percentage contraction in volume is :

(A) 8 %                         (B) 2 %                      (C) 3 %                       (D) 4 “./0

More than one choice type

  1. In which of the following pairs do 1 g of each have an equal number of molecules?

(A) N20 and CO                      (B) N2 and 0302                   (C) N2 and CO            (ID) N20 and CO2

  1. Silver metal in ore is dissolved by potassium cyanide solution in the presence of air by the reaction

4 Ag + 8 KCN + 02 + 2H20 _________ > 4 K[Ag (0N)2] + 4 KOH

  • The amount of KCN required to dissolve 100 g of pure Ag is 120 g.
  • The amount of oxygen used in this process is 0.742 g (for 100 gm pure Ag)
  • The amount of oxygen used in this process is 7.40 g (for 100 gm pure Ag)
  • The volume of oxygen used at STP is 5.20 litres.

 

CHEMISTRY-MOLE CONCEPT

  1. If 27 g of Carbon is mixed with 88 g of Oxygen and is allowed to burn to produce CO2 , then :

(A) Oxygen is the limiting reagent.            (B) Volume of CO2 gas produced at NTP is 50.4 L.

(C) C and 0 combine in mass ratio 3 : 8.    (ID) Volume of unreacted 02 at STP is 11.2 L.

  1. A + B A3B2 (unbalanced)

A3B2 + C               A3B2C2 (unbalanced)

Above two reactions are carried out by taking 3 moles each of A and B and one mole of C. Then which option is/are correct ?

(A) 1 mole of A3B2C2 is formed                                      (B) 1/2 mole of A3B2C2 is formed

(C) 1/2 mole of A3B2 is formed                    (D) 1/2 mole of A3B2 is left finally

  1. Consider the redox reaction 2S2032- + 12 _____________ > S4062- + 2 1 :

(A) S2032- gets reduced to S4062-             (B) S2032- gets oxidised to S4062-

(C) 12 gets reduced to 1                                             (D) 12 gets oxidised to I

35.* If 100 ml of 1M H2SO4 solution is mixed with 100 ml of 9.8%(wlw) H2SO4 solution (d = 1 g/ml) then :

(A) concentration of solution remains same (B) volume of solution become 200 ml

(C) mass of H2SO4 in the solution is 98 gm (D) mass of H2SO4 in the solution is 19.6 gm

  1. Equal volume of 0.1 M NaCI and 0.1 M FeCl2 are mixed with no change in volume due to mixing. Which of the

following will be true for the final solution. (No precipitation occurs). Assume complete dissociation of salts and neglect any hydrolysis.

(A) [Na] = 0.05 M         (B) [Fe21 = 0.05M           (C) [CI] = 0.3M            (D) [CI] = 0.15M


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