How would I solve these atoms/mass/mole problems?
Find the # of atoms of phosphorus (P) in 3.44 moles of phosphorus.
What is the mass of 0.38 moles of cobalt(Co)?
How many moles of nickel (Ni) is 3.88 x 10^25 atoms of nickel?
There are two basic relationships that you need to learn and remember and then mole/mass/atoms problems will be easy to do.
First, one mole of any substance, whether it is an element or a compound contains Avogardro's number of atoms or molecules of that substance. Avogadro's number being 6.023 x 10^23.
Thus, in one mole of hydrogen there are 6.023 x 10^23 atoms of hydrogen. In one mole of HCl there are 6.023 x 10^23 molecules of HCl. To find the number of atoms in a given number of moles, just multiply the number of moles by Avogardro's number. Let's do an example using Potassium (K) and assume you have 2.6 moles of potassium. 2.6 x 6.023 x 10^23 = 1.566 x 10^24 atoms of potassium.
If instead you are given the number of atoms of the substance, just divide the number of atoms given by Avogadro's number to get the number of moles. Let's do an example and assume we have 14 x 10^25 atoms of Calcium. How many moles do we have?
14 x 10^25 atoms divided by 6.023 x 10^23 atoms /mole = 2.324 x 10^2 moles of calcium.
Second, one mole of any element is equal in mass to the atomic mass of that element. Thus, one mole of iron has a molar mass of 55.847g/mole. To find the actual mass of the substance, you multiply the molar mass by the number of moles. Using iron as the example, if you had 0.2 moles of iron you would have 0.2 moles x 55.847 g/mole = 11.169 g of iron.
Using these two relationships you can solve everyone of these mole/mass/atom problems.