Question

Chlorine has two isotopes, Cl- 35 and Cl-37. Their abundances are \(75.53 \%\) and \(24.47 \%,\) respectively. Assume that the only hydrogen isotope present is \(\mathrm{H}-1\). (a) How many different HCl molecules are possible? (b) What is the sum of the mass numbers of the two atoms in each molecule? (c) Sketch the mass spectrum for \(\mathrm{HCl}\) if all the positive ions are obtained by removing a single electron from an HCl molecule.

Short answer

Answer: There are two different HCl molecules formed using the given isotopes, HCl-36 and HCl-38. The sum of the mass numbers for each HCl molecule is 36 amu for HCl-36 and 38 amu for HCl-38. The mass spectrum will have two peaks corresponding to the positive ions HCl-36 and HCl-38, with HCl-36 having a higher peak due to its higher percentage abundance.

Step-by-step solution

Identify the possible HCl molecules combinations

Given the provided isotopes, there are two possibilities for forming HCl molecules: 1) combining hydrogen (H-1) with Cl-35 and 2) combining hydrogen (H-1) with Cl-37.

Calculate the sum of the mass numbers of the two atoms in each molecule

(a) H-1 + Cl-35 = HCl-36 (b) H-1 + Cl-37 = HCl-38

Analyze the mass spectrum for HCl

For the mass spectrum of HCl, we must consider the positive ions formed by the removal of a single electron from an HCl molecule. This implies that for each unique molecule, we need to analyze its percentage abundance. HCl-36 abundance: (\(75.53\%\)) HCl-38 abundance: (\(24.47\%\)) Thus, the mass spectrum will be represented by two peaks at masses 36 and 38, with the peak at 36 being approximately three times larger than the peak at 38, as its abundance is three times higher.

Write the final answers

(a) Number of different HCl molecules: 2 (HCl-36 and HCl-38) (b) Sum of the mass numbers of the two atoms in each molecule: 1. HCl-36: 36 amu 2. HCl-38: 38 amu (c) The mass spectrum will have two peaks corresponding to the positive ions HCl-36 and HCl-38, with HCl-36 having a higher peak (representing a higher percentage abundance).