Chemistry 2010 Jamb Examination
Question 41
Caustic soda (NaOH) precipitates hardness ions (as hydroxides) and is used industrially to soften water (as given).
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Question 42
Air near the cold bottle cools; water vapour loses kinetic energy and condenses on the bottle surface, forming droplets.
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Question 43
By Boyle's law, P₁V₁ = P₂V₂. If P₂ = P₁/2 then V₂ = 2V₁, so the new volume = 2V.
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Question 44
Across a period nuclear charge (effective positive charge) increases, binding electrons more strongly and raising first ionization energy.
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Question 45
N (Z=7) has electron configuration 1s2 2s2 2p3; the three 2p electrons occupy separate p-orbitals, giving 3 unpaired electrons.
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Question 46
Noble gases have full valence shells (duplet for He, octet for others), which makes them chemically stable.
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Question 47
Blood is a complex mixture of cells, plasma (water, salts, proteins) and dissolved substances; it is not a pure compound.
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Question 48
[Ca = 40, N = 14, O = 16]
Molar mass of Ca(NO3)2 = 40 + 2×14 + 6×16 = 40 + 28 + 96 = 164 g·mol-1.
Mass of N in formula = 2×14 = 28 g·mol-1.
Percentage N = (28 / 164) × 100 = 17.073...% ≈ 17.1%.
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Question 49
Atoms (not molecules): neon is monoatomic so 6 moles neon = 6 moles atoms = 6NA atoms, which is larger than the atom-count in the other options.
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