Question

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

Answer 1

`\boxed {\boxed {\sf 10.3 \ moles \ of \ ammonia}}`

Step-by-step explanation:

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

• 6.022*10²³

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.

`6.022*10^(23) \ molecules \ NH_3 / mol \ NH_3`

Use Avogadro's number as a ratio.

`(6.022*10^(23) \ molecules \ NH_3)/(1 \ mol \ NH_3)}`

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

`6.21*10^(24) \ molecules \ NH_3 *(6.022*10^(23) \ molecules \ NH_3)/(1 \ mol \ NH_3)}`

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

`6.21*10^(24) \ molecules \ NH_3 *(1 \ mol \ NH_3)/( 6.022*10^(23) \ molecules \ NH_3)}`

`6.21*10^(24)*(1 \ mol \ NH_3)/( 6.022*10^(23))`

Multiply to make 1 fraction.

`(6.21*10^(24) \ mol \ NH_3)/( 6.022*10^(23))`

Divide.

`10.31218864 \ mol \ NH_3`

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.

`10.3 \ mol \ NH_3`

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