How many grams do 3.9 × 1025 atoms of hydrogen weigh? Answer in units of g.

Question

how to solve the whole thing in calculator

Answer 1

The molar mass of hydrogen comes from looking it up on the periodic table. It is 1.008 and the units of that number are grams/mole. So, you need to determine how many moles you have.

There are 6.022 x 10²³ atoms in one mole (no matter what element you are talking about). So the number of moles of hydrogen you have is (3.9 × 10²⁵ atoms)/(6.022 x 10²³ atoms per mole) = 64.76 moles.

64.76 moles x 1.008 grams/mole = 65.28 grams. Considering significant figures, it is rounded to 65 grams