Emission transitions in the Paschen series end at orbit n = 3 and start from orbit n and can be represented as v = 3.29 × 1015 (Hz) [1/32 – 1/n2]
Calculate the value of n if the transition is observed at 1285 nm. Find the region of the spectrum.
V = c/λ = 3x108/1285x10-9
= 3.29 x 1015(1/32 – 1/n2)
= 1/n2 = 1/9 - 3x108/1285x10-9 x (1 / 3.29 x 1015)
= 0.111- 0.071 = 0.04 or 1/25
Or
n2 = 25,
n= 5
The spectrum lies in the infra-red region.
The mass of an electron is 9.1 × 10–31 kg. If its K.E. is 3.0 × 10–25 J, calculate its wavelength.
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(i) 1 mole of carbon is burnt in air.
(ii) 1 mole of carbon is burnt in 16 g of dioxygen.
(iii) 2 moles of carbon are burnt in 16 g of dioxygen.
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(c) H2O2 (aq) + Fe 2+ (aq) → Fe3+ (aq) + H2O (l) (in acidic solution)
(d) Cr2O7 2– + SO2(g) → Cr3+ (aq) + SO42– (aq) (in acidic solution)
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(ii) 2 mol A + 3 mol B
(iii) 100 atoms of A + 100 molecules of B
(iv) 5 mol A + 2.5 mol B
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(iii) 1 g Li (s)
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