61. The mass of one Avogadro number of helium atom is
A. 1.00 gram
B. 4.00 gram
C. 8.00 gram
D. 4 x 6.02 x 1023 gram
✅ The correct answer is option B.
Chemistry MCQs
62. The gas used for artificial ripening of green fruit is
A. ethylene
B. ethane
C. carbon dioxide
D. acetylene
✅ The correct answer is option A.
63. The first metal used by man was
A. iron
B. copper
C. gold
D. bronze
✅ The correct answer is option B.
64. The metal does not give H2 on treatment with dilute HCL is
A. Zn
B. Fe
C. Ag
D. Ca
✅ The correct answer is option C.
65. The oldest rocks in the earth’s crust were once molten, and came from deep inside the earth. The molten rock, called magma, spewed out in volcanic eruptions during the earth;s early life and solidified into hard rock’s called
A. granite
B. basalt
C. igneous rocks
D. sedimentary rocks
✅ The correct answer is option C.
66. The luster of a metal is due to
A. its high density
B. its high polishing
C. its chemical inertness
D. presence of free electrons
✅ The correct answer is option D.
67. The ionisation energy of hydrogen atom in the ground state is x KJ. The energy required for an electron to jump from 2nd orbit to 3rd orbit is
A. 5x/36
B. 5x
C. 7.2 x
D. x/6
✅ The correct answer is option A.
68. The mass number of a nucleus is
A. always less than its atomic number
B. the sum of the number of protons and neutrons present in the nucleus
C. always more than the atomic weight
D. a fraction
✅ The correct answer is option B.
69. The number of water molecules present in a drop of water (volume 0.0018 ml) at room temperature is
A. 1.568 x 103
B. 6.023 x 1019
C. 4.84 x 1017
D. 6.023 x 1023
✅ The correct answer is option B.
70. The main buffer system of the human blood is
A. H2CO3 – HCO3
B. H2CO3 – CO32-
C. CH3COOH – CH3COO-
D. NH2CONH2 – NH2CONH+
✅ The correct answer is option A.