Question

Which of the following statements concerning balanced chemical equations are true? There may be more than one true statement. a. Atoms are neither created nor destroyed. b. The coefficients indicate the mass ratios of the substances used. c. The sum of the coefficients on the reactant side always equals the sum of the coefficients on the product side.

Short answer

The true statements concerning balanced chemical equations are (a) Atoms are neither created nor destroyed, based on the Law of Conservation of Mass and (b) The coefficients indicate the mass ratios of the substances used, as the coefficients represent the number of moles which relates to the mass of the substances. Statement (c) The sum of the coefficients on the reactant side always equals the sum of the coefficients on the product side is false, as the main goal of balancing is to keep the number of atoms of each element the same on both sides, not necessarily the sums of coefficients.

Step-by-step solution

Analyzing Statement a

Atoms are neither created nor destroyed. This statement is based on the Law of Conservation of Mass, which states that in a chemical reaction, the total mass of the reactants must equal the total mass of the products. Since atoms make up the mass of substances, the number of each type of atom in the reactants and products must remain the same. Therefore, this statement is true.

Analyzing Statement b

The coefficients indicate the mass ratios of the substances used. Coefficients in a balanced chemical equation represent the number of moles of each substance, not their masses directly. However, since the number of moles of a substance is related to its mass, the coefficients in a balanced equation provide information about the ratio of the masses involved in a reaction. Therefore, this statement is also true.

Analyzing Statement c

The sum of the coefficients on the reactant side always equals the sum of the coefficients on the product side. The main goal of balancing a chemical equation is to make sure that the number of atoms of each element remains the same on both sides of the equation. However, it is not necessary for the sum of the coefficients on the reactant side to equal the sum of the coefficients on the product side. In many cases, these sums will not be equal. Therefore, this statement is false. So, the statements (a) and (b) are true, while the statement (c) is false.

Key concepts

Law of Conservation of Mass

When you mix vinegar and baking soda and observe the fizzing reaction, it seems like magic. However, it's powered by a fundamental scientific principle: the Law of Conservation of Mass. Put simply, this law asserts that mass cannot be created or destroyed in a chemical reaction.

For instance, imagine you have a sealed container where this vinegar and baking soda reaction occurs. If you were to weigh it before and after the reaction, you'd find the mass to be the same, despite the transformation of reactants into new products. This is because the atoms present in the vinegar and baking soda rearrange to form the products but their total count remains unchanged.

Hence, when you write a balanced chemical equation, you're actually giving a nod to this law by ensuring the number of each type of atom is equal on both the reactants and products sides. Statement (a) from our exercise, 'Atoms are neither created nor destroyed,' directly reflects this timeless principle of chemistry and is, indisputably, true.

Chemical Reaction

Imagine baking a cake. You mix ingredients like flour, sugar, and eggs, put the mixture in the oven, and get a delicious cake. Likewise, a chemical reaction takes substances, known as reactants, and converts them into new substances called products. But unlike baking, where ingredients can change into something wholly different in form and taste, atoms in a chemical reaction retain their identity even as they form new compounds.

Such transformations are encapsulated in chemical equations, a shorthand for describing a chemical reaction. These equations reveal the reactants, the products, and in a balanced state also indicate the precise proportion in which these substances react and form. Statement (b) from the exercise, 'The coefficients indicate the mass ratios of the substances used,' alludes to the relation between the coefficients and the amount of matter participating in the reaction. Although the statement is a simplification, understanding this can be crucial when predicting product quantities or scaling reactions for industrial applications.

Stoichiometry

Stoichiometry could be described as the 'recipe' part of chemistry—it deals with the measurement and calculation of reactants and products in a chemical reaction.

To cook a delicious meal, it's essential to follow the recipe quantities. Similarly, in a chemical equation, stoichiometry is like a recipe telling us the amounts of each substance involved. Coefficients in a balanced chemical equation do the heavy lifting here. They represent the ratios of the moles of reactants used and the moles of products formed. But it is crucial to note that these coefficients do not necessarily indicate the same quantities when talking about the mass; they are mole ratios.

Understanding Ratios

For example, the equation 2H₂ + O₂ → 2H₂O shows that two moles of hydrogen gas (H₂) react with one mole of oxygen gas (O₂) to form two moles of water (H₂O). Here, stoichiometry helps us grasp that for every single reaction sequence, you need twice as much hydrogen as oxygen.

Moreover, while statement (b) from our exercise is correct in linking coefficients to ratios, another key concept of stoichiometry, statement (c), 'The sum of the coefficients on the reactant side always equals the sum of the coefficients on the product side,' is a common misconception and is not supported by stoichiometry. The truth is that the sum of the coefficients is not what must balance; it is the count of atoms of each element that must do so, ensuring adherence to the Law of Conservation of Mass.