How many moles of ammonia , NH3 , are contained in 6.21 times 10^24 molecules of ammonia

Explanation:

To convert from molecules to moles, we must Avogadro's Number.

This number is how many particles (atoms, molecules, ions, etc.) in 1 mole of a substance. In this case, it is molecules of ammonia in 1 mole of ammonia.

Use Avogadro's number as a ratio.

Multiply by the given number of ammonia molecules (6.21*10²⁴)

Flip the fraction so the molecules of ammonia can cancel out.

Multiply to make 1 fraction.

Divide.

The original measurement of molecules had 3 significant figures (6,2 and 1). Therefore we must round our answer to 3 sig figs.

For the answer we found, 3 sig figs is the tenth place. The 1 in the hundredth place tells us to leave the 3 in the tenth place.

There are about 10.3 moles of ammonia in 6.21*10²⁴ molecules.