Gold has fascinated humans for thousands of years. From ancient Egyptian civiliz

Question

Gold has fascinated humans for thousands of years. From ancient Egyptian civilization to the modern day, gold has been including money, jewelry, and even food! In fact, gold foil chocolate quite tasty. Determine how many protons, electrons, and neutrons a stable atom of gold has. Use this information to write the electron configuration for gold. India is the largest global con of gold. The nation imports nearly 25% of the world's mined gold- approximately 800 tons every year! If one gold necklace contains 0.04 moles of gold, how many necklaces could India make in one year? (1 lb. = 0.45 kg, 1 ton = 2000 lbs.) While shopping, you find a sixteen (16) gram ring that you want to purchase. The seller is a big Indians fan you met on the corner of 9th and Prospect (the guy was wearing a really nice trench coat and had a HUGE selection of it is Rolex watches too.) Skeptical chemist that you are, you doubt whether it is true gold. So, you test the ring to determine whether it is real gold. You remember that gold has a density of 19.3 g/mL. Describe how you would determine whether the ring is pure gold.

Explanation / Answer

(a) Gold atomic number is 79.

SO, number of protons = number of electrons = 79

GOld mass number for stable isotope = 198

so, Number of neutrons = 119

Au (Z=79) electronic configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6/4f146s1 5d10

(b) 800 tons = 800 tons * 2000 lbs/ton * 0.45 kg/lb * 1000 g./kg = 7.2 * 108 g.

Moles of gold = 7.2 * 108 / 197 = 3.65 * 106 mol

0.04 mole make a necklace

then, 3.65 * 106 mol can make 3.65 * 106 * 1 / 0.04 = 9.12 * 107 necklaces

(c)

You please drop the gold ring in a glass full of water. The it replaces certain amount of water. Measure the amount of that is replaced by the ring, if tis amount equals to 19.3 g., then the ring is pure otherwise it is impure.

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