Answer: [tex]7.7\times 10^{22}[/tex] molecules of [tex]Ba(OH)_2[/tex]
Explanation:
According to avogadro's law, 1 mole of every substance occupies 22.4 L at STP and contains avogadro's number [tex]6.023\times 10^{23}[/tex] of particles.
To calculate the moles, we use the equation:
[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text {Molar mass}}=\frac{21.9g}{171g/mol}=0.128moles[/tex]
1 mole of [tex]Ba(OH)_2[/tex] contains = [tex]6.023\times 10^{23}[/tex] molecules
0.128 mole of [tex]Ba(OH)_2[/tex] contains = [tex]\frac{6.023\times 10^{23}}{1}\times 0.128=7.71\times 10^{22}[/tex] molecules
Thus there are [tex]7.7\times 10^{22}[/tex] molecules of [tex]Ba(OH)_2[/tex]
