Question

How many moles are in 4.3 x 1024 molecules of H20?

Answer 1

Answer:

$\boxed {\boxed {\sf About 7.1 \ mol \ H_2O}}$

Explanation:

To convert from molecules to moles, we must use Avogadro's Number: 6.022*10²³. This tells us the amount of particles (atoms, molecules, etc.) in 1 mole of a substance. In this case, the particles are molecules of water.

$\frac {6.022*10^{23} \ molecules \ H_2O} {1 \ mol \ H_2O}$

Multiply by the given number of molecules.

$4.3 *10^{24} \ molecules \ H_2O *\frac {6.022*10^{23} \ molecules \ H_2O} {1 \ mol \ H_2O}$

Flip the fraction so the molecules of water cancel.

$4.3 *10^{24} \ molecules \ H_2O *\frac {1 \ mol \ H_2O} {6.022*10^{23} \ molecules \ H_2O}$

$4.3 *10^{24} *\frac {1 \ mol \ H_2O} {6.022*10^{23} }$

$\frac {4.3 *10^{24}\ mol \ H_2O} {6.022*10^{23} }$

$7.140484889 \ mol \ H_2O$

The original measurement of atoms has 2 significant figures ( 4 and 3), so our answer must have the same. For the moles we calculated, that is the tenth place. The 4 in the hundredth place tells us to leave the 1.

$7.1 \ mol \ H_2O$

There are about 7.1 moles of water.