In the mass spectrum of 1,2-dibromoethane, BrCH2CH2Br, the molecular ion cluster M : M+2 : M+4 has intensities in the approximate ratio

JEE Main levelSingle correct optionDifficulty 2 of 3si073

In the mass spectrum of 1,2-dibromoethane, $BrCH X_{2} CH X_{2} Br$ , the molecular ion cluster M : M+2 : M+4 has intensities in the approximate ratio

Bromine occurs as

^{79}

Br and

^{81}

Br in about 1:1 ratio. For two Br atoms the combinations give

(1 + 1)^{2} = 1 : 2 : 1

. The ratio

9 : 6 : 1

is for two Cl atoms (

3 : 1

squared).