Answer to Question #62386 in General Chemistry for Lauren Sutherland

Question

Problem 2.99 (Chapter 2)

1) Using data in the table, determine the number of significant figures that must be reported before the difference in mass of 1H
and 1H+ is significant.
Particle Mass (amu)
Proton 1.0073
Electron 5.486×10−4

2)What percentage of the mass of an 1H atom does the electron represent?
Express your answer using four significant figures.

Answer 1

1) m(1H) = me + mp = 1.0073 + 0.0005(486) = 1.0078 (amu)
Thus the difference is 1.0078 - 1.0073 = 0.0005 (amu) or 1 sig. figure.

2) w(e) = me/(me + mp)*100 % = 0.0005486/1.0078 * 100 % = 0.05444 %.