Question

What is the molecular formula for a compound with empirical formula K2SO4 and a molecular mass of 696g

Answer 1

Answer:

Molecular formula = K₈S₄O₁₆

Explanation:

$\diamond$ Empirical formula is defined as the simplest formula of a compound where the common factors between number of atoms is cancelled out

$\diamond$ For example,

butane $\implies$ C₄H₁₀ (Molecular formula)

empirical formula $\implies$ C₂H₅ (Common factor 2 is cancelled)

$\diamond$ We know that,

Common factor = n = $\dfrac{Molecular \ formula \ mass}{Empirical \ Formula \ Mass}$

Molecular Formula = n * (Empirical Formula)

$\diamond$ Given that,

Empirical Formula = K₂SO₄

Molecular Formula Mass = 696g

Hence,

Empirical Formula Mass = (2*40) + (32) + (4*16)

                                        = 80 + 32 + 64

                                        = 176g

Therefore,

n = $\dfrac{Molecular \ formula \ mass}{Empirical \ Formula \ Mass}$

n = $\dfrac{696}{176} = 3.9 \approx 4$

Hence,

Molecular Formula = 4 * (K₂SO₄)

Molecular Formula = K₈S₄O₁₆