Chapter 6.3, Problem 6RQ

Interpretation Introduction

Interpretation: The empirical formula of sugar needs to be determined with the help of given information.

Concept Introduction: The molecular mass of compound is the sum of atomic mass of all the atoms present in the given chemical compound. Here the molecular formula represents the exact number of all bonded atoms in the compound.

Whereas empirical formula can be defined as the simplest positive integer ratio of all bonded atoms in the compound.

Answer to Problem 6RQ

The empirical formula of sugar must be CHO₂.

Explanation of Solution

Given:

Mass percentage of O = 51.42 %

Mass percentage of C = 42.10%

Mass percentage of H = 6.48 %

Let the total mass be 100 g thus, mass of O, C and H will be 51.42 g, 42.10 g and 6.48 g respectively.

Calculate moles of each with the help of atomic mass:

  $\begin{array}{l}\text{O = }\frac{\text{51}\text{.42}}{\text{16}\text{.00 }}\text{=3}\text{.214}\\ \text{C = }\frac{\text{42}\text{.10}}{\text{12}\text{.00 }}\text{=3}\text{.5}\\ \text{H=}\frac{\text{6}\text{.48}}{\text{1}\text{.00 }}\text{=6}\text{.48}\end{array}$

Divide by least moles to get the whole number ratio:

  $\begin{array}{l}\text{O = }\frac{\text{3}\text{.214}}{\text{3}\text{.214}}\text{= 1}\\ \text{C = }\frac{\text{3}\text{.5}}{\text{3}\text{.214 }}\text{= 1}\\ \text{H=}\frac{\text{6}\text{.48}}{\text{3}\text{.214 }}\text{= 2}\end{array}$

Thus the empirical formula of sugar must be CHO₂.

Conclusion

The empirical formula of sugar must be CHO₂.