JEE Chemistry - Some basic concepts in chemistry

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Question - 1

The number of significant figures in 0.04520 is _____________.

  • A 2
  • B 4
  • C 10
  • D 15

Question - 2

lf law of conservation of mass was to hold true, then 18.80 g of BaCl2 on reaction with 11.80 g of H2SO4 will produce 7.30 g of HCI and BaSO4 equal to __________ g.
  • A 23.3
  • B 13.3
  • C 24.4
  • D 14.1

Question - 3

In an acid-base titration, student records burette readings as 20.1 mL, 20.20 mL,20.3 mL. The number of significant figures in average burette reading is ______ mL.
  • A 2
  • B 1
  • C 3
  • D 4

Question - 4

Copper sulphate pentahydrate contains 25.45 % of copper and 36.08 % of water. If the law of constant proportions is true, then the weight of copper required to produce 20 g of copper sulphate pentahydrate will be _____ g.
  • A 5.09
  • B 6.01
  • C 3.02
  • D 2.05

Question - 5

In the crystalline solid MSO4.nH2O of molar mass 288 g mol-1, the percentage of anhydrous salt is 56.25 by weight. The value of 'n' is _______.
  • A 7
  • B 5
  • C 2
  • D 9

Question - 6

The empirical formula and molecular mass of a compound are CH2O and 150 g/mol respectively. The molecular formula of the compound can be given as CxHyOx. The value of 'x' is _____.
  • A 2
  • B 5
  • C 1
  • D 3

Question - 7

2.4 g of sample of magnesium when burnt in excess of O2 gives 3.84 g of magnesium oxide. The percentage purity of magnesium in the sample is ______%
[Molar mass of MgO = 40 g mol-1]
  • A 70
  • B 56
  • C 96
  • D 25

Question - 8

Potassium chlorate decomposes on heating. When 4.96 g of potassium chlorate is heated, the weight loss of 0.96 g is observed. The mass of potassium chlorate decomposed is _____ g.
[Molar mass of KCIO3= 122.5 g mol-1]
  • A 2.45
  • B 1.5
  • C 2.54
  • D 5.54

Question - 9

The number of molecules present in 0.032 mg of O2 is given as 6.022 x 10x. Find 'X'.
  • A 17
  • B 15
  • C 11
  • D 13

Question - 10

If 1021 molecules are removed from 140 mg of N2, then the number of moles of N2 left is 3.34 x 10x moles. The value of 'X' is _______.

  • A 3
  • B -3
  • C 0
  • D -5
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