Question

In combustion analysis, is the combined mass of the products \(\left(\mathrm{CO}_{2}\right.\) and \(\mathrm{H}_{2} \mathrm{O}\) ) less than, equal to, or greater than the combined mass of the compound that is combusted and the \(\mathrm{O}_{2}\) that reacts with it? Explain.

Short answer

The combined mass of products is equal to the combined mass of the reactants.

Step-by-step solution

Define the Problem

In the given problem, a compound is combusted in the presence of oxygen ( \(\mathrm{O}_{2}\) ) to form combustion products: carbon dioxide ( \(\mathrm{CO}_{2}\) ) and water ( \(\mathrm{H}_{2}\mathrm{O}\) ). We need to determine the relation between the combined mass of the products and the initial reactants, which includes the combusted compound and the reacting oxygen.

Apply the Law of Conservation of Mass

According to the Law of Conservation of Mass, in a chemical reaction, the total mass of reactants equals the total mass of products. Therefore, the mass of the combusted compound plus the mass of the oxygen used in the reaction should be equal to the mass of the resulting \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2}\mathrm{O}\) after combustion.

Solution Conclusion

Since the total mass of the reactants is conserved during the reaction and equals the total mass of the products, the combined mass of the products \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2}\mathrm{O}\) is equal to the combined mass of the initial compound and the oxygen \(\mathrm{O}_{2}\) that react with it.

Key concepts

Combustion Analysis

Combustion analysis is a technique used to determine the composition of a chemical compound, particularly those containing carbon and hydrogen. This process involves burning the compound in the presence of oxygen (\(\mathrm{O}_2\)). As a result, the products carbon dioxide (\(\mathrm{CO}_2\)) and water (\(\mathrm{H}_2\mathrm{O}\)) are formed, which can be measured to infer the initial composition of the compound.

Understanding combustion analysis involves recognizing that this process systematically measures the relative amounts of \(\mathrm{CO}_2\) and \(\mathrm{H}_2\mathrm{O}\) produced. By capturing these products, scientists can back-calculate to determine the amounts of carbon and hydrogen in the original substance. This method is particularly helpful in organic chemistry for identifying unknown compounds. Additionally, combustion analysis provides insight into the elemental makeup and stoichiometry of the compounds involved.

In any practice dealing with combustion analysis, considering the precision of measurement is crucial. This precision allows chemists to correctly deduce the molecular formula and offers valuable data about the substance combusted. Overall, it provides a strong foundation for analyzing reactions based on the principle that the composition of the reactants defines the products formed.

Chemical Reaction

A chemical reaction involves transforming one set of chemical substances, known as reactants, into another set, known as products. In the context of combustion, the main substances are typically hydrocarbons (like the compound being combusted) and oxygen (\(\mathrm{O}_2\)).

In a combustion reaction, a chemical change occurs when these reactants produce energy in the form of heat and light, along with new substances like carbon dioxide (\(\mathrm{CO}_2\)) and water (\(\mathrm{H}_2\mathrm{O}\)). These reactions are typically exothermic, meaning that they release energy. The fundamental essence of any combustion reaction is the rearrangement of atoms, where atoms from the reactants are reorganized to form new bonds in the products.

Key characteristics of a chemical reaction include:

• Reactants transform into different substances known as products.
• Different chemical bonds are formed in the process, often releasing energy.
• Chemical reactions follow specific equations that are balanced to obey the law of conservation of mass.

Understanding the basics of chemical reactions helps to grasp how substances combine and rearrange themselves during combustion, emphasizing that no atoms are lost in the process. Instead, they are merely redistributed, forming new compounds.

Mass of Reactants and Products

The mass of reactants and products in a chemical reaction must always adhere to the Law of Conservation of Mass. This fundamental principle states that mass can neither be created nor destroyed in a chemical reaction. Instead, the total mass of the reactants is always equal to the total mass of the products.

In combustion reactions, this principle is particularly straightforward: the combined mass of the substance being combusted and the oxygen provided together equals the mass of the resulting \(\mathrm{CO}_2\) and \(\mathrm{H}_2\mathrm{O}\). In simple terms, all the mass you start with in the reactants will be present in some form in the products.

This balance can be represented through balanced chemical equations, which illustrate that the mass on either side of the reaction equals. Thus:

• If you start with a specific mass of a hydrocarbon and a certain mass of oxygen, the products will collectively weigh the same.
• Balancing equations ensures that molecular amounts of products and reactants maintain the conservation of mass.
• It reminds us that even though substances change form, their total mass remains consistent throughout the reaction.

By comprehending how reactants and products relate through their mass, you grasp a key aspect of chemistry that underscores the harmony and predictability of chemical transformations.