Chapter 3: Problem 48

Determine the empirical formulas of the compounds with the following compositions by mass: $$ \begin{array}{l}{\text { (a) } 55.3 \% \mathrm{K}, 14.6 \% \mathrm{P}, \text { and } 30.1 \% \mathrm{O}} \\ {\text { (b) } 24.5 \% \mathrm{Na}, 14.9 \% \mathrm{Si}, \text { and } 60.6 \% \mathrm{F}} \\ {\text { (c) } 62.1 \% \mathrm{C}, 5.21 \% \mathrm{H}, 12.1 \% \mathrm{N}, \text { and the remainder O }}\end{array} $$

Short Answer

Expert verified

The empirical formulas for the given compounds are: (a) KPO₄ (b) Na₂SiF₆ (c) C₅H₀.₄₀₇N¹.₀₂₂O₂.₀₃₃

Step by step solution

Convert percentage composition to mass

Assume that each compound has a total mass of 100 grams. This assumption allows us to easily convert the percentage composition directly into grams of each element. For example, For compound (a): - 55.3% K implies 55.3 grams of K - 14.6% P implies 14.6 grams of P - 30.1% O implies 30.1 grams of O We will make similar calculations for compounds (b) and (c).

Determine moles of each element

Next, we need to determine the moles of each element in the compound. To do this, divide the mass (in grams) of each element by its respective molar mass. For compound (a): - Moles of K: $\frac{55.3}{39.10}$ (molar mass of K is 39.10 g/mol) - Moles of P: $\frac{14.6}{30.97}$ (molar mass of P is 30.97 g/mol) - Moles of O: $\frac{30.1}{16.00}$ (molar mass of O is 16.00 g/mol) Calculate the moles for elements in compounds (b) and (c) similarly.

Determine the mole ratio

To determine the mole ratio, divide all the moles calculated in Step 2 by the smallest moles value among the elements in that compound. For compound (a): - Calculate the smallest moles value: min(K, P, O) - Divide all the moles by the smallest moles value to get the mole ratio. Do this also for compounds (b) and (c).