STUDY GUIDE 8, SELF TEST 1

© Department of Physics, University of Guelph.

Click on the problem number you wish.

1. If you could somehow isolate at a single point, one gram mole of Na+ ions, what total charge would you have at the point? Recall: Avogadro's number NA = 6.02X1023 (g mol)-1

2. (a) A Na+ ion is placed one-quarter of the distance between two Ca++ ions which are 10.0 nm apart. Find the resultant force on the Na+ ion assuming that the solvent is water (k = 80.4). (You should be able to answer the question using either
Coulomb's Law or
the Field method)

(b) Where would the resultant force on the Na+ ion be zero? (There are two answers to this part.)

3. A Cl- ion is in a field of 100 NC-1. Calculate the ratio of the Coulomb force to the weight of the ion. (The weight is the gravitational force on the ion at the surface of the Earth.) Recall w = mg and g = 9.8 N/kg on the Earth's surface. Assume a chlorine mass number 35. The value of Avogadro's number is 6.02X1023 (g mol)-1