Basic Concepts in Chemistry MCQs – IV

301)10 ml of a gaseous hydrocarbon was mixed with 100 ml of oxygen and exploded in an eudiometer tube. The volume of the residual gases was 95 ml of which 20 ml was absorbed by caustic soda and the reminder by pyrogallol. The molecular formula of the gas is

302)9.0 ml of a mixture of methane and ethylene
was exploded with 30 ml (excess) of oxygen. After cooling, the volume was 21.0 ml. Further treatment with caustic potash reduced the volume to 7.0 ml. The amounts of methane and ethylene in the mixture respectively are


303)If two compounds have the same empirical formula
but different molecular formulae, they must have

a) Different percentage composition
b) Different molecular weights
c) the same viscosity
d) the same vapour density

304)If 0.2 g of an organic compound on complete combustion
produces 0.18 g of water, then the percentage
of hydrogen in it is

a) 5
b) 10
c) 15
d) 20

305) Which one of the following is false about compounds of lithium ?
a) The hydroxide, carbonate and nitrate decompose to give the oxide on heating
b) It is the most electronegative element of group IA
c) The hydrogen carbonate cannot be isolated as a stable solid
d) It forms an oxide and a super oxide

306)Cinnabar is an ore of
a) Hg
b) Cu
c) Pb
d) Zn

307)The purification method of bauxite containing iron oxide as impurity is known

d) Electrolytic process

308)The structure of white phosphorus is
a) Square planar
b) Pyramidal
c) Tetrahedral
d) Trigonal planar

309) Hypo is used in photography for
a) Developing the picture
b) Picture printing
c) forming the colour of a picture
d) The fixation of the picture


312)The density of mercury in kg/L if it is 13.6 g/ml
a) 1.36
b) 0.136
c) 0.0136
d) 13.6

313)The number of electrons that could be filled in the first 5 shells of an atom if they are filled to capacity
a) 50
b) 10
c) 100
d) 110

314)The maximum number of electrons in the third shell of an atom with (1) no electrons in the fourth shell and (2) with some electrons in the fourth shell is respectively
a) 8 and 18
b) 18 and 8
c) 32 and 8
d) 32 and 18

315)A salt contains 36% water of crystallisation. If the molecular mass of anhydrous salt is 160, the number of moles of water of crystallisation present in 1 mole of the hydrated salt is
a) 2
b) 3
c) 4
d) 5

316)Which amoung the following is not a derived unit ?
a) newton
b) pascal
c) candela
d) joule

317)The mass of 0.2 mol of chlorine molecules is
a) 0.71 g
b) 7.1 g
c) 1.42 g
d) 14.2 g

318)Hydrogen is manufactured by passing steam over red hot iron. The number of moles of iron that will react with one mole of steam and the number of moles of H2 formed respectively are
a) 1.33 and 1
b) 0.75 and 1
c) 1 and 0.75
d) 1.33 and 0.75

319)1.2g of metal gives 2g of oxide. The weight of sulphate formed from the same weight of metal is (in g)
a) 10.8
b) 9.6
c) 4.8
d) 6

320)The volumes of N/10 and N / 40 solutions to be mixed so as to prepare 2L of N/20 solution is
a) (1/3)L,(2/3)L
b) (4/3)L and (1/3)L
c) (2/3)L, (4/3)L
d) (1/3)L,(3/4)L

321)2H2S + SO2® 2H2O +3S. If 1 mol each of H2S and SO2 are mixed , the maximum number of moles of S formed
a) 1.5
b) 2
c) 2.5
d) 3

322)The number of unpaired electrons present in Ti metal and T12 + ion is
a) 0,2
b) 0,0
c) 2,0
d) 2,2

323)Reactions take place in terms of
a) no. of gram moles
b) no. of gram equivalents
c) grams
d) both and b

324)The chemist’s scale for measuring the quantity of a substance is
a) mole
b) gram
c) kg.
d) a.m.u

325)The number of electrons present per mole of water molecules
a) N
b) 18N
c) 10N
d) 4N

326)Which of the following is an iso electronic pair?
a) H,He+
b) Na,Mg++
c) H2O,CH4
d) He2+,K+

327)Rutherford’s model of the atom collapses as the electron must continuously emit radiation and finally fall into the nucleus. The time taken by an electron to spiral in to the nucleus would be
a) 10-10s
b) 1010s
c) 10-2s
d) 104s

328)The number of unpaired electrons in the element with atomic number 24 is
a) 2
b) 3
c) 4
d) 6

329)The nucleon number of 17CI35 is
a) 17
b) 35
c) 18
d) 52

330)The Rydberg constant has dimensions of
a) s-1
b) cm-1
c) cm s-1
d) J an-1

331)The distance of a planet from earth is 67,000,000 km. The number of significant figures is
a) 8
b) 5
c) 2
d) 1

332)The correct expression to four significant figures for the number 2.65986 x 103 is

a)2.660 x 103
b)2.659 x 103
c)2.661 x 103
d)2.6598 x 103

333)One torr is equal to
a) 1 cm of Hg
b) 1 atm pressure
c) 1mm of Hg
d) 1 m/sec

334)One second is defined to be equal to
a) 9192631770 period of cesium clock
b) 1650763.73 periods of cesium clock
c) 1650763.73 periods of krypton clock
d) 652189. 63 periods of Krypton clock

335)How many wavelengths of Kr86 are there in one metre?

a) 1553164. 13
b) 1650763. 73
c) 652189. 631
d) 2348123. 73

336)One-gram mole of a gas at NTP occupies 22.4 litres. This fact was derived from
a) the law of gaseous volumes
b) Avogadro’s hypothesis
c) Berzelius hypothesis
d) Dalton’s atomic theory

337)At STP 2. 8 litre O2 contains ……. of oxygen

a) 0.25 g atom
b) 0.125 g mol
c) 0.125 g
d) 0.40 g

338)The number of molecules in 89. 6 litres of a gas at 0 deg C and one atmosphere are
a)2.408 x 1023
b)12.04x 1023
c)240.8 x 1023
d)24.8 x 1023

339)The number of moles of SO2 Cl2 in 13.5 gm of a sample is (S = 32, O = 16, Cl = 35.5)          

a) 0.1
b) 0.2
c) 0.3
d) 0.4

340)The number of electrons in a mole of hydrogen molecules is
a)12.046 x 1023
b)6.023 x 1023
c)3.0115 x 1023
d) 2

341)6.02 x 1022 molecules of nitrogen will occupy at NTP a volume of

 a) 22.4 liters
b) 2.24 liters
c)6.02 x 1022 liters
d) 0.224 liters

342)The volume of 6 gm of H2 at 1.5 atom and 273 deg C is
a) 89.9 litres
b) 8.96 litres
c) 8.96 ml
d) 89.6 ml

343) The volume occupied by one molecule of water is (density of water = 1 g ml -1) water

a) 3.0 x 10 -23 ml
b)6.02 x 10 23 ml
c)1.0x 10 -24 ml
d)6.02 x 10 -23 ml

344) If 1021molecules are removed from 200 mg of CO2, then the number of moles of CO2 left is

a)2.88 x 10-3
b)28.8 x 10-3
c)0.288x 10-3
d)1.66 x 10-2

345)How many moles of helium gas occupy 22.4 L at 0 deg C and 1 atm pressure?
a) 0.11
b) 0.90
c) 1.0
d) 1.11

346)Air contains nearly 20% oxygen by volume. The volume of air needed for the complete combustion of 100 cc of acetylene will be
a) 1.25 cc
b) 12.5 cc
c) 125 cc
d) 1250 cc

347)The amount of zinc (atomic weight 65) required to produce 224 ml of H2 at STP on treatment with dilute H is

a) 0.65 gm
b) 6.5 gm
c) 65 gm
d) 0.065 gm

348) 100 ml of PH3 when decomposed, produced phosphorus and hydrogen. The change in volume is 

a) 50 ml increase
b) 500 ml decrease
c) 900 ml decrease
d) Zero

349)2.76 gm of silver carbonate on being strongly heated yields a residue weighing

a) 2.48 g
b) 2.16 g
c) 2.32 g
d) 2.64 g

350)The simplest formula of a compound containing 50% of element X (atomic mass 10 ) and 50% of element Y ( atomic mass 20 ) is




d)X 2Y3

351)0. 45 gms of an acid of molecular mass 90 was neutralised by 20 ml of 0. 5N caustic potash. The basicity of the acid is
a) 1
b) 2
c) 3
d) 4

352)If 0.5 mole of BaCl2 is mixed with 0.2 mole of Na3 PO4, the maximum number ofmoles of Ba3   (PO4) 2 that can be formed is
a) 0.7
b) 0.5
c) 0.30
d) 0.10

353) What quantity of limestone (Ca CO3) on heating will give 56 kg of Ca O?

a) 1000 kg
b) 10 kg
c) 50 kg
d) 100 kg

354) The ratio of the amounts of H2 S needed to precipitate all the metal ions from 100 c. c of 1 M AgNO3 and 100 c. c of 1 M CuSO4 will be

a) 1:1
b) 2:1
c) 1:2
d) Indefinite

355)23 gm of sodium will react with ethyl alcohol to give

a) One mole of hydrogen
b) One mole of oxygen
c) One mole of Na OH
d) 1/2 mole of hydrogen

356) The percentage of P2 O5 in diammonium hydrogen phosphate (NH4) HPO4 is (Atomic mass of H = 1, 0  = 16; P = 31; N  = 14)

a) 77.58
b) 46.96
c) 53.78
d) 23.48

357) When 1.0 g of zinc is treated separately with excess of H2 SO4 and excess of NaOH, the ratio of volumes of H2 evolved is

 a) 1:1
b) 1:2
c) 2:1
d) 3:4

358)A phosphorus oxide has 43. 6% phosphorus. The empirical formula of the compound is





359)The amount of ethyl magnesium bromide (C2 H5 Mg Br) produced from 21. 8 gms of ethyl bromide will be

a) 0.266 gm
b) 2.66 gm
c) 26.6 gm
d) 266 gm

360)The equivalent mass of potassium dichromate as an oxidising agent in acidic medium is
a) 2/3 rd of its molecular weight
b) 1/3 rd of its molecular weight
c) 1/6 th of its molecular weight
d) Half of its molecular weight

361)The temperature at which real gases obey the ideal gas laws over a wide range of pressure is called the
a) Critical temperature
b) Boyle’s temperature
c) Inversion temperature
d) Reduced temperature

362)The density of a gas is given by the relation
a) n P
b) PM / RT
c) P / RT
d) M / V

363)The temperature at which Celsius and Fahrenheit scales represent the same reading is
a) 0 deg C
b) 32 F
c) -40 deg C
d) 40 deg C

364)Torr is a unit of
a) Heat
b) Pressure
c) Volume
d) Flux

365)At absolute zero
a) Water freezes
b) Molecular motion ceases
c) Vibrational motion ceases
d) All gases become liquid

366)A gas diffuses 1/ 5 times as fast as hydrogen. Its molar mass is
a) 25
b) 50
c) 75
d) 100

367)The vapour density of pure ozone would be
a) 48
b) 42
c) 24
d) 0.01

368)If the mean free path is l at one atom pressure then its value at 5 atom pressure is
a) 5 l
b) 50 l

369) The molecules of which of the following gases have the largest average K. E at 250 deg C?

a) Ar
b) Co
c) He
d) Ar, Co, He, have the same K.E


The total kinetic energy of 44 g of CO2 gas at temperature T is

a) RT
c) 2/3 RT
d) 22 KJ

371)If 4 g of oxygen diffuse through a very narrow hole, how much hydrogen would have diffused, under identical conditions?
a) 16 g
b) 1 g
c) 1/4 g
d) 64 g

372)The atomicity of a gas of molecular wt. 40 whose specific heat at constant volume is 0. 075 is
a) One
b) Two
c) Three
d) Four

373) The approximate temperature at which 1 mol L-1 of a sample of pure ideal gas exhibits a pressure of 101. 325 K Pa is

a) 12.2 k
b) 122 k
c) 24.4 k
d) 48.8 k

374) Sulphur forms two chlorides S2Cl2 and SCl2 . The  equivalent mass of sulphur in SCl2 is 16 g / mole. The equivalent mass of sulphur in S2Cl2 is

a) 8 g / mole
b) 16 g / mole
c) 48 g / mole
d) 32 g / mole

375)Compounds having the same molecular formula but different properties are called
a) Isotops
b) Isomers
c) Isobars
d) Allotropes

376)The number of moles of Zn required to produce sufficient H2 from HCI so as to reduce 1 mole of CuO to Cu
a) 3
b) 2
c) 1
d) 0.5

377)1L of 0.1M AgNo3 is added to 500 ml of 0.01 M BaCI2. The maximum number of moles of AgCI that will be precipitated is
a) 0.1
b) 0.05
c) 0.01
d) 0.025


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