Question

Calculate the amount of moles in 1.17 x 1016 molecules of H2S.

Answer 1

Answer:

$\boxed {\boxed {\sf About \ 1.94 *10^{-8} \ mol \ H_2S}}$

Explanation:

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

• 6.022* 10²³

This number tells us how many particles (atoms, ions, molecules, etc.) are in 1 mole of a substance. For this problem, it is moles of hydrogen sulfide.

• 6.022*10²³ molecules of hydrogen sulfide in 1 mole.

We can use the number as a fraction.

$\frac { 6.022 *10^{23} \ molecules \ H_2S}{1 \ mol \ H_2S}$

Multiply by the given number of molecules.

$1.17*10^{16} \ molecules \ H_2S *\frac { 6.022 *10^{23} \ molecules \ H_2S}{1 \ mol \ H_2S}$

Flip the fraction so the molecules of hydrogen sulfide will cancel out.

$1.17*10^{16} \ molecules \ H_2S *\frac {1 \ mol \ H_2S }{ 6.022 *10^{23} \ molecules \ H_2S}$

$1.17*10^{16} *\frac {1 \ mol \ H_2S }{ 6.022 *10^{23} }$

$\frac {1.17*10^{16} \ mol \ H_2S }{ 6.022 *10^{23} }$

$1.94287612*10^{-8} \ mol \ H_2S$

The original measurement of molecules had 3 significant figures so we must round our answer to that.

For the number we calculated, that is the hundredth place. The 2 in the thousandth place tells us to leave the 4 in the hundredth place.

$1.94 *10^{-8} \ mol \ H_2S$

There are about 1.94*10⁻⁸ molecules of hydrogen sulfide.