Homework with Hooke's Law

As many of you have already realized, there is a mistake in the textbook excercise # 5. You should use equation 8.4 (Hooke's Law), not equation 8.5. This question is very similar to 3 & 4. Also, while I'm on the topic of Hooke's law, let me point out that the masses in the equation refer to the mass of a single atom. The most common error is to use molecular weights, rather than atomic masses. You can find atomic mass by dividing the molar mass by Avogadro's number.