The heat of atomisation of methane and ethane are ‘x’ kJ mol –1 and ‘y’ kJ mol –1 respectively. The longest wavelength () of light capable of breaking the C-C bond can be expressed in SI unit as : (A)

Question

The heat of atomisation of methane and ethane are ‘x’ kJ mol –1 and ‘y’ kJ mol –1 respectively. The longest wavelength () of light capable of breaking the C-C bond can be expressed in SI unit as :

(A) hc y 6x 4
(B) A N hc 250(4y 6x)
(C) A N hc 250(y 6x)
(D) A 6x N hc y

Prashant Kotian · Accepted Answer

Correct answer: B. CH4(g)  C(g) + 4H(g); rH = x kJ/mole C2H6(g)  2C(g) + 6H(g); rH = y kJ/mole 1000x = 4 × C H   1000y = 1 × C C   + 6 × C H   C C   = 3x y        × 1000 = A hc.N    ' '  wavelength of photon    A hc N [4y 6x] 250

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