Question

How many formula units are contained in 23.5 g of Sb2S3

Answer 1

The molar mass of Sb2S3 is approximately equal to 339.7 g/mol. We calculate the number of moles of Sb2S3 by dividing the given mass by the molar mass. 
                                     n = 23.5 g / (339.7 g/mol)
                                        n = 0.0692 mols
To calculate for the number of formula units, we multiply the number of mols by the Avogadro's number, 
                            number of formula units = (0.0692 mols)(6.022 x 10^3)
                                                   = 4.167 x 10^22 formula units

Answer 2

Answer: The number of formula units in given amount of $Sb_2S_3$ are $4.155\times 10^{22}$

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of $Sb_2S_3$ = 23.5 g

Molar mass of $Sb_2S_3$ = 339.7 g/mol

Putting values in above equation, we get:

$\text{Moles of }Sb_2S_3=\frac{23.5g}{339.7g/mol}=0.069mol$

According to mole concept:

1 mole of a compound contains $6.022\times 10^{23}$ number of formula units

So, 0.069 moles of $Sb_2S_3$ will contain = $(0.069\times 6.022\times 10^{23})=4.155\times 10^{22}$ number of formula units

Hence, the number of formula units in given amount of $Sb_2S_3$ are $4.155\times 10^{22}$