Hi, can someone help me with this question please!
The Atlantic Ocean contains about 9.0 lb (1 lb = 454g) of Gold per cubic square mile. How many moles of Gold are there per cubic mile?

Any help would be greatly appreciated.

How is a mole defined ?
How much does a mole of Gold "weigh"
This will give you what you need to answer this question.

You should know that one mole of an element has the mass equal to it's relative mass in grams.

Hydrogen gas has a relative molecular mass of 2. So, one mole of hydrogen gas will have a mass of 2 g.

Similarly, oxygen gas has an Mr (relative molecular mass) of 32, hence, one mole of oxygen gas has a mass of 32 g.

Does it help?

Post your answer. :)

EDIT: To clear up things, if you are dealing with a metal, then the mass of one mole of that metal is directly it's relative atomic mass in grams. Sodium has an Ar (relative atomic mass) of 23, so, 1 mole of Na will weigh 23 g.