Question

How many molecules are present in 187 grams of XeF4

Answer 1

There are 5.43 x 10²³ present in  187 grams of XeF₄

Further explanation  

The mole is the number of particles(molecules, atoms, ions) contained in a substance  

1 mol = 6.02.10²³ particles

Can be formulated

N=n x No

N = number of particles

n = mol

No = Avogadro's = 6.02.10²³

Moles can also be determined from the amount of substance mass and its molar mass

$\tt n(mol)=\dfrac{mass(m)}{MW}$

mass of XeF₄ = 187 g

mol XeF₄ (MW=207,2836 g/mol) :

$\tt mol=\dfrac{187}{207,2836 g/mol}=0.902$

Number of molecules :

$\tt N=0.902\times 6.02\times 10^{23}\\\\N=5.43\times 10^{23}$