Question

Determine if any of the following data sets on chemical reactions are inconsistent with the law of conservation of mass and therefore erroneous. a. 8 grams of natural gas react with 38 grams of oxygen gas to form 17 grams of carbon dioxide and 19 grams of water. b. \(5.7\) grams of sodium react with \(8.9\) grams of chlorine to produce \(14.6\) grams of sodium chloride.

Short answer

Data set (a) does not follow the law of conservation of mass since the mass of the reactants (46 grams) does not equal the mass of the products (36 grams) and is therefore erroneous. Data set (b) conserves mass (both reactants and products are 14.6 grams) and is consistent with the law.

Step-by-step solution

Understanding the Law of Conservation of Mass

The Law of Conservation of Mass states that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations. Therefore, the mass of the reactants must equal the mass of the products in a chemical reaction.

Analyzing data set (a)

Calculate the total mass of the reactants and the products for data set (a). For the reactants, the sum of the mass of natural gas and oxygen gas is 8 grams + 38 grams = 46 grams. For the products, the sum of the mass of carbon dioxide and water is 17 grams + 19 grams = 36 grams.

Checking for mass conservation in data set (a)

Compare the mass of the reactants with the mass of the products in data set (a). If there is a discrepancy, the data is inconsistent with the law of conservation of mass. Here, the mass of reactants is 46 grams and the mass of products is 36 grams, which are not equal. Therefore, data set (a) does not conserve mass and is erroneous.

Analyzing data set (b)

Calculate the total mass of the reactants and the products for data set (b). For the reactants, the sum of the mass of sodium and chlorine is 5.7 grams + 8.9 grams = 14.6 grams. For the products, the mass of sodium chloride is already given as 14.6 grams.

Checking for mass conservation in data set (b)

Compare the mass of the reactants with the mass of the products in data set (b). Since the mass of reactants is 14.6 grams and the mass of products is also 14.6 grams, data set (b) conserves mass and is consistent with the law of conservation of mass.

Key concepts

Chemical Reactions

At the heart of chemistry lies the study of chemical reactions, the processes in which substances, known as reactants, transform into different substances, called products. A simple analogy to understand a chemical reaction is following a recipe to bake a cake - you start with specific ingredients (reactants) and end up with a cake (product). But in the realm of chemistry, instead of flour and eggs, we have elements and compounds that interact.

During a chemical reaction, the molecules of the reactants break apart and reorganize themselves to create new molecules as products. These reactions can involve anything from a simple combination of hydrogen and oxygen to form water to the complex series of reactions during photosynthesis in plants. It's fascinating to note that while these molecules change, the actual atoms involved are conserved, meaning they are neither created nor destroyed - they merely rearrange themselves.

Mass Conservation

The principle of mass conservation is a cornerstone in the scientific community, articulated by Antoine Lavoisier in the 18th century. Simply put, during a chemical reaction, the total mass of the system must remain constant over time, as system mass cannot change quantity if it is not added or removed. This principle, also known as the Law of Conservation of Mass, implies that mass can neither be created nor destroyed.

The law aligns beautifully with the concept of atoms being the basic building blocks that are indestructible in any chemical reaction. In our exercise example, if the mass of the starting materials, which are the reactants, does not equal the mass of the resulting substances, which are the products, it suggests an error in the experimental procedure or in measuring the quantities. This discrepancy in dataset (a) hints at such a mistake since the reactant mass (46 grams) doesn't match the product mass (36 grams).

Stoichiometry

Diving deeper, stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. The term 'stoichiometry' from Greek origins translates to 'measuring elements'. Essentially, it is the calculation of the quantities of chemical elements to satisfy the Law of Conservation of Mass in a given chemical reaction.

Stoichiometry not only involves the mass of reactants and products but also their moles, which are a measure of the number of particles. It considers the ratios of the amounts of each substance involved and is governed by the balanced chemical equation for the reaction. For example, in dataset (b), the strict adherence to stoichiometric principles means that the masses before and after the reaction must be equal, illustrated by the mass balance of 14.6 grams for both reactants and products. This balance showcases stoichiometry at work, ensuring that the chemical equation is not only qualitatively but also quantitatively correct.