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o. Particles in a gold ring. You have a pure (24-karat) gold ring with mass 17.7

ID: 2283043 • Letter: O

Question

o. Particles in a gold ring. You have a pure (24-karat) gold ring with mass 17.7 g. Gold has an atomic mass of 197 g/mol and an atomic number of 79. (a) How many protons are in the ring, and what is their total positive charge? (b) If the ring car- 1 ries no net charge, how many electrons are in it? ries no net charge. how many electrons are in i? ·Two equal point charges of +3.00 × 10-6 C are placed 0.200 m apart. What are the magnitude and direction of the 1 force each charge exerts on the other? .At what distance would the repulsive force between two electrons have a magnitude of 2.00 N? Between two protons?

Explanation / Answer

1.

N(no of gold atoms in17.7g)=m/mw x NA=17.7/197 x 6.022x1023=0.54xx1023

(a) No of protons=NZ=0.54xx1023x79=42.66xx1023

charge of protons=NZe=42.66xx1023x1.6x10-19=6.826x105C

(b)No of electrons for zero net charge=NZ=0.54xx1023x79=42.66xx1023

2.

F=kq1q2/d2

F=9x109x(3x10-6/0.2)2

F=2.025N

force is going to be repulsive so each will exert force in the direction of another

3

F=kq1q2/d2

2=9x109x(1.6x10-19/d)2

d=1.6x10-19sqrt(9x109/2)

d=1.07x10-14m(for both electrons and protons since charge on both are same)