## MOLE CONCEPT PART H

**PART****–****III : 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.

**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

**Statement****–****2 : **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

**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.

**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, ^{24}Mg, ^{25}Mg and ^{26}Mg, of Mg are found in nature.

**Statement-1 :**A molecule of butane, 0_{4}H_{10}has a mass of 58.12 amu.

**Statement-2 : **One mole of butane contains 6.022 x 10^{23} molecules and has a mass of 58.12 g.

**Statement-1 :**Both 12 g. of carbon and 27 g. of aluminium will have 6.02 x 10^{2}‘ atoms.

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

**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.

**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

**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.**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.**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**

- The nonstoichiometry compound “titanium monoxide” has a continuous range of composition from Ti
_{o75}0 to

Ti0_{0}_{ 69}. What are the maximum and minimum values of the percent by weight of oxygen in this compound? [At. wt of Ti = 48]

- 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.

- 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 cm^{3}/g. If the virus is considered to be a single partical, find its molecular weight.

- 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 CO_{2} and water) by 1.1 g. Calculate % of chalk (CaCO_{3}) in the sample. [Hint : Chalk (CaCO_{3}) release CO_{2} on heating]

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

XeF_{6}+ ±CH_{2}-C1-1.7t, _________________ + HF + XeF_{4}.

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

- (i) K
_{4}Fe(CN)_{3}+ 3H_{2}SO_{4 ______________ }) 2K_{2}SO_{4}+ FeSO_{4}+ 6HCN

- 6HCN + 12H
_{2}0 > 6HCOOH + 6NH - (a) 6NH
_{3}+ 3H_{2}SO_{4}3(NI^{–}1_{4})_{2}SO_{4}(b) 6HCOOH H2s04 > 6C0 + 6H_{2}0

Above steps of reactions occur in a container starting with one mole of K_{4}[Fe(CN)_{6}], 5 mole of H_{2}SO_{4}and enough water. Find out the limiting reagent in step (i) and calculate maximum moles of CO gas and (NI-1_{4})_{2}SO, that can be produced.

3

- A
_{2}+ 2B_{2}A_{2}B_{4}^{ }^{–}_{2}A_{2}+ 28_{2 __________ }> A_{3}B_{4}

Two substance A_{2} & B_{2} react in the above manner. When A_{2} is limited it gives A_{2}B_{4} in excess gives A_{3}B_{4}. A_{2}B_{4} can be converted to A_{3}13_{4} when reacted with A_{2}, Using this information calculate the composition of the final mixture when the mentioned amount of A_{2} & B_{2} are taken

(a) 4 moles A_{2} & 4 moles B_{2}** ****(b) ^{–}_{2 }**moles A

_{2}& 2 moles B

_{2}(c) 1.25 moles A

_{2}& 2 moles B

_{2}

1 1

- When 1 mol of A reacts with –
_{2}mol of B_{2}(A + –_{2}B_{2 __________ }> AB), 100 Kcal heat is liberated and when 1 mol of

A reacted with 2 mol of B_{2} (A + 2B_{2 ___ }> AB_{4}) , 200 Kcal heat is liberated. When 1 mol of A is completely

reacted with excess of B_{2} to form AB as well as AB_{4}, 140 Kcal heat is liberated Calculate the mol of B_{2} used. [Write your answer as (No. of moles of B_{2} used x 1000)]

- In a gravimetric determination of P. an aqueous solution of dihydrogen phosphate ion H
_{2}P0,^{–}is treated with a

mixture of ammonium and magnesium ions to precipitate magnesium ammonium phosphate, Mg(NH_{4})PO_{4} . 6H_{2}0. This is heated and decomposed to magnesium pyrophosphate , Mg_{2}P_{2}0_{7} , which is weighed. A solution of H_{2}PO_{4}^{–} yielded 1.054 g of Mg_{2}P_{2}0_{7}. What weight of NaH_{2}PO_{4} was present originally? (Na = 23 , H = 1 , P = 31 , 0 = 16 Mg = 24)

- 1 g of dry green algae absorbs 4.7 x 10
^{-3}moleof CO_{2}per hour by photosynthesis. If the fixed carbon atoms

were all stored after photosynthesis as starch (C_{6}1^{–}1_{10} 0_{5}), how long would it take for the algae to double their own weight assuming photosynthesis takes place at a constant rate ?

- Cl
_{2}+ KOH^{60%}> KCI + KCIO + H_{2}O KCIO^{50%}> KCI + KCIO_{3}

K0103 ^{80%}> KCIO_{4} + KCI

112 L 01_{2} 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)

- The ‘roasting’ of 100.0 g of a copper ore yielded 71.8 g pure copper. If the ore is composed of Cu
_{2}S and CuS with 4.5 % inert impurity, calculate the percent of Cu_{2}S in the ore.

The reactions are

Cu_{2}S + 0_{2 ____ } > 2Cu + SO_{2} and CuS + 0, -> CL SO_{2} [Atomic mass Cu = 63.5, S = 32]

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

Fe + Br_{2} > FeBr_{2}

FeBr_{2} + Br_{2} Fe, Br_{a} (not balanced)

Fe_{3}Br_{8} + Na_{2}CO_{3 __________ }> NaBr + CO_{2} + Fe_{3}0, (not balanced)

How much Fe, in kg, is consumed to produce 2.50 x 10^{3} kg NaBr ?

- How many grams of 90% pure Na
_{9}SO_{4}can be produced from 250 g of 95% pure NaCI. - Find the sum of average oxidation number of S in H
_{2}S0_{5}(peroxy monosulphuric acid) and Na_{2}S_{2}0_{3}(sodium thiosulphate). - The reaction C1
_{2}(g) + S_{2}0_{3}^{2- ______ }> SO_{4}^{2-}+ Cl^{–}is to be carried out in basic medium. Starting with 0.15

mole of C1_{2}, 0.01 mole S_{2}0_{3}^{2-}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. - 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.
- What volume (in ml) of 0.2 M H
_{2}SO_{4}solution should be mixed with the 40 ml of 0.1 M NaOH solution such that the resulting solution has the concentration of H_{2}SO_{4}as_{5}^{6}_{5} - 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 + H_{2}O > NaA10_{2} + H_{2} (At.wt. Na = 23, 0 = 16, H = 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:**

- 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

- A sample of ammonium phosphate (NH
_{4}),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

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

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

- 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

- One mole of a mixture of N
_{2}, NO_{2}and N_{2}0_{4}has a mean molar mass of 55.4. On heating to a temperature at

which all the N_{2}0_{4} may be presumed to have dissociated : N_{2}0_{4} 2NO_{2}, the mean molar mass tends to

the lower value of 39.6. What is the mole ratio of N_{2} NO_{2} : N_{2}0_{4} 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

- 0 mL of NO
_{2}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 NO_{2}(At. wt. of N = 14)

(A) 0.10 mL and 3.01 x 10^{22} (B) 0.20 mL and 3.01 x 10^{21}

(C) 0.20 mL and 6.02 x 10^{23} (D) 0.40 mL and 6.02 x 10^{21}

- 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

- 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

- Formation of polyethene from calcium carbide takes place as follows :

CaC_{2}+H_{2}0 Ca(OH)_{2} + C_{2}H_{2} ; C_{2}H_{2}+ H_{.} C_{2}H_{4}

n(C_{2}H_{4}) (-CH_{2}-C1-1_{2}-)_.

The amount of polyethylene possibly obtainable from 64.0 kg CaC_{2} can be

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

- The hourly energy requirement of an astronaut can be satisfied by the energy released when 34 g of sucrose

(C_{12}H_{22}0,_{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.

- If a piece of iron gains 10% of its weight due to partial rusting into Fe
_{2}O_{3}the percentage of total iron that has

rusted is :

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

- If 10 g of Ag reacts with 1 g of sulphur , the amount of Ag
_{2}S formed will be [Atomic weight of Ag = 108,

S = 32] ?

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

- 100 g impure CaCO
_{3}on heating gives 5.6 It. CO_{2}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

- When a 12 g mixture of carbon and sulphur is burnt in air, then a mixture of CO
_{2}and SO_{2}is produced, in which

the number of moles of SO_{2}is half that of 00_{2}. 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

- 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.

- XeF
_{6}fluorinates 1_{2}to IF, and liberates Xenon(g). 210 mmol of XeF_{6}can yield a maximum of mmol of IF,

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

- 1 mol of iron (Fe) reacts completely with 0.65 mol 0
_{2}to give a mixture of only FeO and Fe_{2}0_{3}. Mole ratio of

ferrous oxide to ferric oxide is :

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

- Composition of a sample is Fe
_{o 93}0_{1 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%

- The following equations are balanced atomwise and chargewise.

- Cr
_{2}0_{7}^{2-}+ 8H+ + 3H_{2}0_{2 ____________ }> 20r^{3}+ + 7H_{2}0 + 30_{2} - Cr
_{2}0_{7}^{2}+ 8H’ + 5H_{2}0_{2 ________ }> 2Cr^{3}+ + 9H_{2}0 + 40_{2} - Cr
_{2}0_{7}^{2-}+ 8H+ + 7H_{2}0_{2 ____________ }> 2Cr^{3}+ + 11 H_{2}0 + 50_{2}

The precise equation/equations representing the oxidation of H_{2}0_{2}is/are :

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

**xNO**_{3}^{–}**+**+ zH^{+}—> 2NO + 31_{2}+ 4H_{2}0 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

- Molarity of H
_{2}SO_{4}is 18 M. Its density is 1 .8 g/cm^{3}, hence molality is

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

- 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

- Mole fraction of ethyl alcohol in aqueous ethyl alcohol (C
_{2}H_{5}OH) solution is 0.25. Hence percentage of ethyl

alcohol by weight is :

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

- 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

- 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.

- 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 H_{2}SO_{4} and having a density of 1.96 g/ ml. (molecular weight of H_{2}SO_{4} = 98). Take reaction SO_{3} + H_{2}O H_{2}SO_{4}

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

- On mixing 15.0 ml of ethyl alcohol of density 0.792 g m1
^{-1}with 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**

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

(A) N_{2}0 and CO (B) N_{2} and 0_{3}0_{2} (C) N_{2} and CO (ID) N_{2}0 and CO_{2}

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

4 Ag + 8 KCN + 0_{2} + 2H_{2}0 _________ > 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**

**If 27 g of Carbon is mixed with 88 g of Oxygen and is allowed to burn to produce CO**_{2}, then :

**(A) Oxygen is the limiting reagent. ****(B) Volume of **CO_{2}** gas produced at NTP is 50.4 L.**

**(C) C and 0 combine in mass ratio 3 : 8. (ID) Volume of unreacted **0_{2}** at STP is 11.2 L.**

**A + B A**_{3}B_{2}(unbalanced)

**A _{3}B_{2} + C **

**A**

_{3}B_{2}C_{2}(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 A _{3}B_{2}C_{2} is formed **

**(B) 1/2 mole of A**

_{3}B_{2}C_{2}is formed(C) 1/2 mole of A_{3}B_{2}** is formed (D) 1/2 mole of A _{3}B_{2} is left finally**

**Consider the redox reaction 2S**_{2}0_{3}^{2-}+ 1_{2 _____________ }**> S**_{4}0_{6}^{2-}+ 2 1^{–}:

**(A) S _{2}0_{3}^{2-} gets reduced to **S

_{4}0

_{6}

^{2-}(B) S

_{2}0

_{3}

^{2-}

**gets oxidised to S**

_{4}0_{6}^{2-}(C) 1_{2}** gets reduced to 1 ^{–} **

**(D) 1**

_{2}gets oxidised to I^{–}**35.* If 100 ml of 1M H _{2}SO_{4} solution is mixed with 100 ml of 9.8%(wlw) H_{2}SO_{4} solution (d = 1 g/ml) then :**

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

**(C) mass of H _{2}SO_{4} in the solution is 98 gm **

**(D) mass of H**

_{2}SO_{4}in the solution is 19.6 gm**Equal volume of 0.1 M NaCI and 0.1 M FeCl**_{2}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) [Fe ^{2}1 = 0.05M (C) [CI^{–}] = 0.3M (D) [CI^{–}] = 0.15M**