15. Which statement is correct? of protons and neutrons. a. Electrons have a muc

Question

15. Which statement is correct? of protons and neutrons. a. Electrons have a much smaller mass than that b. Protons are much more massive than neutrons. protons and neutrons. c. Electrons have a much larger mass than that of d. Electrons, protons, and neutrons have about the same mass. e. Neutrons are much more massive than protons. 16. A hypothetical element has two stable isotopes: one isotope has a mass of 106.9051 amu with an abundance of 48.183%, the other isotope has a mass of 108.9048 amu with an abundance of 51.825%. What is the average atomic mass of this element? d. 107.970 amu a. 107.950 amu. e. 107.940 amu. b. 107.980 amu c. 107.960 amu

Explanation / Answer

15. Generally, protons and neutrons have nearly the same mass while electrons are much less massive. If we assume that a neutron has a mass of 1, then the relative masses are:

Neutron = 1; Proton = 0.99862349; Electron = 0.00054386734

So, correct option: (a)

16.

Average atomic mass = (mass of isotope × relative abundance)   ----------- (1)

Sum of abundances of both isotopes = 48.183 + 51.825 = 100

1st isotope: mass = 106.9051 and abundance = 48.183%

Relative abundance = 48.183% / 100.00 = 0.48183

2nd isotope: mass = 108.9048 and abundance = 51.825%

Relative abundance = 51.825% / 100 = 0.51825

From equation (1):

Average atomic mass = (106.9051 x 0.48183) + (108.9048 x 0.51825)

Average atomic mass = 51.5100 + 56.4399

Average atomic mass = 107.9499

Or Average atomic mass = 107.950 (option a)

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