Chapter 1, Problem 47GQ

A few years ago a young chemist in Vienna, Austria, wanted to see just how permanent the gold was in his wedding band. The ring was 18-carat gold. (18-carat gold is 75% gold with the remainder copper and sliver) One week after his wedding day he took off the ring, cleaned it carefully, and weighed it. It had a mass of 5.58387 g. He weighed it weekly from then on,and after 1 year it had lost 6.15 mg just from normal wear and tear. He found that the activities that took the greatest toll on the gold were vacationing on a sandy beach and gardening.

(a) What are the symbol of the elements that make up 18-carat gold?

(b) The density of gold is 19.3 g/cm³. Use one of the periodic tables on the Internet (such as www.ptable.com) to find out if gold is the most dense of all of the known elements. If it is not gold, then what element is the most dense [considering only the elements from hydrogen (H) through uranium (U)]?

(c) If a wedding band is 18-carat gold and has a mass of 5.58 g, what mass of gold is contained within the ring?

(d) Assume there are 56 million married couples in the United States, and each person has an 18-carat gold ring. What mass of gold lost by all the wedding rings in the United States in 1 year (in units of grams) if each ring loses 6.15 mg of mass per year? Assuming gold is $1620 per troy ounce (where 1 troy ounce = 31.1 g), what is the lost gold worth?