Answer:
[tex]\boxed {\boxed {\sf 10.3 \ moles \ of \ ammonia}}[/tex]
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.
[tex]6.022*10^{23} \ molecules \ NH_3 / mol \ NH_3[/tex]
Use Avogadro's number as a ratio.
[tex]\frac{6.022*10^{23} \ molecules \ NH_3}{1 \ mol \ NH_3}}[/tex]
Multiply by the given number of ammonia molecules (6.21*10²⁴)
[tex]6.21*10^{24} \ molecules \ NH_3 *\frac{6.022*10^{23} \ molecules \ NH_3}{1 \ mol \ NH_3}}[/tex]
Flip the fraction so the molecules of ammonia can cancel out.
[tex]6.21*10^{24} \ molecules \ NH_3 *\frac{1 \ mol \ NH_3}{ 6.022*10^{23} \ molecules \ NH_3}}[/tex]
[tex]6.21*10^{24}*\frac{1 \ mol \ NH_3}{ 6.022*10^{23}}[/tex]
Multiply to make 1 fraction.
[tex]\frac{6.21*10^{24} \ mol \ NH_3}{ 6.022*10^{23}}[/tex]
Divide.
[tex]10.31218864 \ mol \ NH_3[/tex]
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.
[tex]10.3 \ mol \ NH_3[/tex]
There are about 10.3 moles of ammonia in 6.21*10²⁴ molecules.
