By knowing the natural abundance of minor isotopes, it's possible to calculate the relative heights of M+ and M+1 peaks. If natural abundances are 12C - 98.9% and 13C - 1.10%, what are the relative heights, to the nearest 0.1%, of the M+ and M+1 peaks in the mass spectrum of cholesterol, C27H48O? Ignore the contributions of isotopes like 2H (deuterium; 0.015% natural abundance) and 17O (0.04% natural abundance) that are small. The relative heights are, in order of increasing mass: 100 to

the relative height of M⁺ : M+1 is; 0.7418 : 0.2228

The relative heights are; In order of increasing mass 100 : 30

Explanation:

Given the data in the question;

The M⁺ peak comes from all ¹²₆C atoms

so, the probability in cholesterol, C₂₇H₄₈O is ( 98.9% )²⁷ = ( 0.989 )²⁷ = 0.7418

The M+1 peak comes from the isotopic carbon ¹³₆C.

so, the probability in cholesterol is ⇒ 1.10% × ( 98.9% )²⁶ = 0.011 × ( 0.989)²⁶

The probability for 27 carbons is ⇒  27 × 0.011 × ( 0.989)²⁶ = 0.2228

Therefore, the relative height of M⁺ : M+1 is; 0.7418 : 0.2228

The relative heights are; In order of increasing mass 100 : 30  

i think it is true since you can test the answer and can use observations to complete it.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.