Question

An organic dibasic acid is used in volumetric analysis. The percentage of elements are \(\mathrm{C}=26.7 \%, \mathrm{H}=2.2 \%\) and \(\mathrm{O}=71.1 \%\). Find the empirical formula of the acid. (a) \(\mathrm{CH}_{2} \mathrm{O}\) (b) \(\mathrm{CHO}_{2}\) (c) \(\mathrm{C}_{2} \mathrm{H}_{2} \mathrm{O}_{2}\) (d) \(\mathrm{CH}_{4} \mathrm{O}\)

Short answer

The empirical formula of the acid is \( \mathrm{CHO}_2 \) (option b).

Step-by-step solution

Convert Percentages to Grams

Assume a 100 g sample of the acid. This will allow direct conversion of percentages to grams: - For Carbon (C), we have 26.7 g - For Hydrogen (H), we have 2.2 g - For Oxygen (O), we have 71.1 g.

Find Moles of Each Element

Use the molar mass to convert grams to moles:- Moles of C: \( \frac{26.7}{12.01} = 2.22 \) moles- Moles of H: \( \frac{2.2}{1.008} = 2.18 \) moles- Moles of O: \( \frac{71.1}{16.00} = 4.44 \) moles.

Determine Molar Ratios

Divide all mole values by the smallest number of moles calculated to find the simplest ratio:- Ratio of C: \( \frac{2.22}{2.18} \approx 1.02 \)- Ratio of H: \( \frac{2.18}{2.18} = 1 \)- Ratio of O: \( \frac{4.44}{2.18} \approx 2.04 \).Approximate the ratios to whole numbers: C = 1, H = 1, O = 2.

Write the Empirical Formula

Using the whole number ratios from Step 3, the empirical formula is \( \mathrm{CHO}_2 \).

Key concepts

Volumetric Analysis

Volumetric analysis is a crucial technique in chemistry that involves measuring volumes of solutions needed to react with a given sample. This method primarily helps in determining the concentration of a substance in a solution. It's akin to a detective's toolkit, allowing chemists to uncover the amount or mass of an unknown reactant.
One common application of volumetric analysis is in titrations, where a solution of known concentration is used to determine the concentration of an unknown solution. Here are a few key points:

• Standard Solutions: These solutions have a known concentration and are critical for precise volumetric analysis.
• Indicators: Substances that signal the end point of a reaction through a physical change, such as a color shift.
• End Point vs. Equivalence Point: In a titration, the endpoint is when the indicator shows the end of the reaction, whereas the equivalence point is the actual point where reactants are stoichiometrically balanced.

This method is not only efficient but also a precise way to analyze various compounds, including organic dibasic acids, allowing complete exploration of their chemical properties.

Organic Dibasic Acid

An organic dibasic acid is a type of organic compound characterized by having two carboxylic acid (-COOH) groups. These acids play vital roles in industrial processes and biochemical reactions.
A few essential aspects include:

• Carboxylic Groups: The two -COOH groups allow these acids to participate in a wide variety of chemical reactions, often making them versatile in forming salts and esters.
• Applications: These acids are commonly used in polymer production, like creating polyesters, as well as in pharmaceuticals.

When analyzing their properties through volumetric analysis, the focus is often on their ability to donate protons (H+ ions) in solutions, which is crucial for reactions such as neutralization.

Molar Ratios

Molar ratios are crucial in chemistry as they explain the stoichiometric relationships between reactants and products in a balanced chemical equation. They act as conversion factors that enable chemists to predict the quantities needed or produced.
For instance, when calculating an empirical formula, it's essential to find the simplest whole number molar ratio of elements in a compound. Here's how it typically works:

• Converting Mass to Moles: Start by converting the percentage composition of each element to grams, assuming a 100 g sample, and then convert grams to moles using molar mass.
• Ratio Determination: Divide the moles of each element by the smallest number of moles obtained from the previous step to find the simplest ratio.
• Empirical Formula: Use these ratios to write the empirical formula of the compound, providing a simple representation of its composition.

Molar ratios are not just numbers; they represent fundamental relationships among elements in chemical reactions and compounds, vital for predicting outcomes and understanding molecular chemistry.