Answer:
[tex]\boxed {\boxed {\sf 5.1 \ mol \ H_2O}}[/tex]
Explanation:
To convert from representative particles to moles, Avogadro's Number: 6.02*10²³, which tells us the number of particles (atoms, molecules, etc.) in 1 mole of a substance.
We can use it in a ratio.
[tex]\frac {6.02*10^{23} \ molecules \ H_2O}{1 \ mol \ H_2O}[/tex]
Multiply by the given number of molecules.
[tex]3.1*10^{24} \ molecules \ H_2O*\frac {6.02*10^{23} \ molecules \ H_2O}{1 \ mol \ H_2O}[/tex]
Flip the ratio so the molecules of water cancel out.
[tex]3.1*10^{24} \ molecules \ H_2O*\frac {1 \ mol \ H_2O}{6.02*10^{23} \ molecules \ H_2O}[/tex]
[tex]3.1*10^{24} *\frac {1 \ mol \ H_2O}{6.02*10^{23} }[/tex]
[tex]\frac {3.1*10^{24} \ mol \ H_2O}{6.02*10^{23} }[/tex]
Divide.
[tex]5.14950166113 \ mol \ H_2O[/tex]
The original number of molecules has 2 significant figures: 3 and 1, so our answer must have the same. For the number we calculated, that is the tenth place. The 4 in the hundredth place tells us to leave the 1.
[tex]5.1 \ mol \ H_2O[/tex]
There are about 5.1 moles of water in 3.1*10²⁴ molecules of water.
