Question

The molar mass of copper(II) chloride (CuCl2) is 134.45 g/mol. How many formula units of CuCl2 are present in 17.6 g of CuCl2

Answer 1

MM of CuCl₂ = 134.45 g/mol
Weight of CuCl₂ = 17.6 g
Number of moles of CuCl₂ is 17.6/134.45
Number of formula units of CuCl₂ in one mole equals avogadro number, i.e. 6.022×10²³. Number of formula units of CuCl₂ in this case = 17.6/134.45×6.022×10²³ = 7.883×10²²

Answer 2

Given ⇒
Molar mass of the copper chloride =  134.5 g/mole.
Mass of the Copper chloride = 17.6 g.

Now, Using the Formula,
 No. of Moles = Mass/Molar mass.
∴ No. of moles of the Copper chloride = 17.6/134.5
   = 0.13 moles.

We know, number of the formula units is equal to the number of the molecules,

∴ No. of Formula units = No. of moles × Avogadro's number.
    = 0.13 × 6.022 × 10²³
    = 0.783 × 10²³
    = 7.83 × 10²².


Thus, the formula units of the copper chloride is 7.83 × 10²².



Hope it helps.