Question

how many moles are in 25mg of O2? (molar mass of O= 16g/mol)
The answer is 7.8x10^4 but I don't know to do it

Answer 1

moles = grams/molecular mass

Answer 2

use this formula

Answer 3

1000mg = 1g

Answer 4

25mg converted to grams is just 25mg(1g/1000mg) = 0.25g

Answer 5

.025g/16 gives me 1.5625x10^-3 not 7.8x10^-4 @australopithecus

Answer 6

You need the molecular mass of O2, you probably divided by just the molecular mass of a single oxygen atom, there are 2 oxygen atoms in O2