Answer to Question #295187 in General Chemistry for Star

Question

Calculate the number of formula units of Li2CO3 present in a 0.500g sample of lithium carbonate. Li=7, C=12, O=16

Answer 1

Solution:

Calculate the molar mass of Li₂CO₃:

Molar mass of Li₂CO₃ = 2×Ar(Li) + Ar(C) + 3×Ar(O) = 2×7 + 12 + 3×16 = 74 (g/mol)

Calculate the moles of Li₂CO₃:

Moles of Li₂CO₃ = (0.500 g Li₂CO₃) × (1 mol Li₂CO₃ / 74 g Li₂CO₃) = 0.0067568 mol Li₂CO₃

One mole of any substance contains 6.022×10²³ formula units.

Hence,

Number of formula units of Li₂CO₃ = (0.0067568 mol) × (6.022×10²³ formula units / 1 mol) = 4.069×10²¹ formula units Li₂CO₃

Answer: The number of formula units of Li₂CO₃ is 4.069×10²¹