Name Part 2. MS (Mass spectrometry) 9. What does the superscript to the left of
ID: 1038556 • Letter: N
Question
Name Part 2. MS (Mass spectrometry) 9. What does the superscript to the left of each atom label tell you (e.g., the 12 in "C)? The number sf pro tens 10. What is the mass of the most common isotope of carbon?__a 11. What is the mass of the next most common ion of carbon? C 12. How many protons and neutron are in3C? protons 13. Indicate the molecular ion peak [MI with an arrow in the following mass spectra, and show S , neutrons the formula and m/z value (e.g. [M], CaH9 . mz 53). The structure of molecules are provided in the spectra. Show all calculation work to add atomic masses 80 60 40 30 O m/z 20 70 30 0 100 80 40 20 m/z Exp. 11 Exp. 11Explanation / Answer
9) The superscript to the left of an atom , for example, 12 in 12C denotes the mass number of the atom. The mass number of an atom is the sum of the number of protons and neutrons present in the nucleus of the atom.
10) The most common isotope of carbon is 12C and the mass of the most common isotope of carbon is 12 u (u = atomic mass unit).
11) The next common isotope of carbon is the naturally occurring 13C and the mass of the 13C isotope is 13 u.
12) The atomic number (number of protons present in the nucleus of an atom) of carbon is 6. Therefore, there are 6 protons in 13C. The sum of the protons and neutrons present in the nucleus of the atom is 13; hence, there are (13 – 6) = 7 neutrons present in 13C.
13a) We have cyclohexane, the molecular formula of which is C6H12. The molecular ion peak [M]+ corresponds to the loss of one electron from the neutral molecule to form a charged positive ion. Therefore, the molecular ion peak derived from cyclohexane has the molecular formula C6H12+ and has a mass same as the neutral molecule (since an electron is considered to be massless). The molecular formula of C6H12 is (6*12.011 + 12*1.008) u = 84.162 u. Therefore, we have the following information about the molecular ion peak:
[M]+, C6H12+, .m/z = 84.162 ? 84 (ans)
b) We have cyclohexanone, the molecular formula of which is C6H10O. The molecular ion peak [M]+ corresponds to the loss of one electron from the neutral molecule to form a charged positive ion. Therefore, the molecular ion peak derived from cyclohexanone has the molecular formula C6H10O+ and has a mass same as the neutral molecule (since an electron is considered to be massless). The molecular formula of C6H10O is (6*12.011 + 10*1.008 + 1*15.999) u = 98.145 u. Therefore, we have the following information about the molecular ion peak:
[M]+, C6H10O+, m/z = 98.145 ? 98 (ans)
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.