Question

The following are actual student responses to the question: Why is it necessary to balance chemical equations? a. The chemicals will not react until you have added the correct ratios. b. The correct products will not form unless the right amounts of reactants have been added. c. A certain number of products cannot form without a certain number of reactants. d. The balanced equation tells you how much reactant you need, and allows you to predict how much product you will make. e. A ratio must be established for the reaction to occur as written.Justify the best choice, and, for choices you did not pick, explain what is wrong with them. Justify the best choice, and, for choices you did not pick, explain what is wrong with them.

Short answer

The best choice is (d): "The balanced equation tells you how much reactant you need and allows you to predict how much product you will make." This choice highlights the importance of balancing chemical equations in predicting reactant and product amounts and understanding mole-to-mole ratios. The other choices are incorrect or less specific about the importance of balancing chemical equations.

Step-by-step solution

Understanding the purpose of balancing chemical equations

Balancing chemical equations is essential in chemistry because it obeys the Law of Conservation of Mass. This law states that matter cannot be created or destroyed; it can only change forms during a chemical reaction. Thus, the atoms of each element on the reactant side must equal the atoms of each element on the product side.

Evaluate each choice

Let us now analyze each provided student response: a. "The chemicals will not react until you have added the correct ratios." This statement is not entirely accurate because chemical reactions may still occur even if the reactant ratios are not balanced. The reaction may not be complete, and the final products may differ, but a reaction can still occur. b. "The correct products will not form unless the right amounts of reactants have been added." Again, the statement is not entirely accurate, as the right products can form even without the right amounts of reactants, but not optimally or completely. c. "A certain number of products cannot form without a certain number of reactants." This statement is somewhat true as the ratio of reactants affects the formation of products. However, it does not specifically address the importance of balancing chemical equations. d. "The balanced equation tells you how much reactant you need and allows you to predict how much product you will make." This statement is true and accurate. A balanced chemical equation reflects the Law of Conservation of Mass and helps us in predicting the amounts of products formed and reactants needed. It also facilitates understanding the mole-to-mole ratio between reactants and products. e. "A ratio must be established for the reaction to occur as written." This statement is also true, but it is less specific regarding the importance of balancing chemical equations than option (d).

Justify the best choice and explain what is wrong with the other choices

The best choice among the given options is (d): "The balanced equation tells you how much reactant you need and allows you to predict how much product you will make." This choice correctly emphasizes the importance of balancing chemical equations in predicting reactant and product amounts and the use of mole-to-mole ratios. Explanation of why we did not pick the other choices: - Choice (a) is incorrect because reactions can still occur even if the reactant ratios are not balanced, just not optimally or entirely. - Choice (b) is incorrect for a similar reason, as the right products can form without the right amounts of reactants, but not optimally or completely. - Choice (c) does not specifically address the importance of balancing chemical equations and only states that the ratio of reactants affects the formation of products. - Choice (e) is true but is less specific about the importance of balancing chemical equations than option (d).

Key concepts

Law of Conservation of Mass

The Law of Conservation of Mass is a fundamental principle in chemistry that underscores why it's crucial to balance chemical equations. According to this law, matter cannot be created or destroyed during a chemical reaction. This means that the sum of the masses of the reactants must equal the sum of the masses of the products.

To illustrate, if you start with a total mass of reactants weighing 20 grams, the products formed after the chemical reaction must also weigh 20 grams. In practical terms, balancing an equation ensures that the number of atoms for each element involved in the reaction is the same on both sides of the equation.

This process visually and mathematically demonstrates the conservation of matter. It helps in confirming that all atoms are accounted for, showcasing the perfect transition from reactants to products without any loss or gain in matter.

Chemical Reactions

In chemistry, chemical reactions are processes where reactants transform into products. These reactions happen when molecules, atoms, or ions interact and rearrange their bonds. Understanding chemical reactions is central to balancing chemical equations.

When writing chemical reactions, the substances you start with are called reactants, and the new substances formed are called products. This change involves breaking old bonds and forming new bonds as atoms rearrange.

For instance, in the reaction of hydrogen and oxygen to form water, the reactant molecules (hydrogen and oxygen) rearrange to create the product water.

• Reactants: Hydrogen (H₂) and Oxygen (O₂)
• Product: Water (H₂O)

Balancing these reactions is crucial because it reflects the true conversion of reactants to products as dictated by the Law of Conservation of Mass.

Reactant and Product Ratios

Understanding reactant and product ratios is key when balancing chemical equations. These ratios stem from the mole concept, a basic measure in chemistry that helps quantify atoms, molecules, or ions.

The balanced chemical equation provides the necessary mole-to-mole ratios of reactants and products. For example, in the reaction between hydrogen and oxygen to produce water, the balanced equation is:
\[2H_2 + O_2 \rightarrow 2H_2O\]

This equation shows the reactants and products in a precise 2:1:2 molar relationship. It means that two moles of hydrogen react with one mole of oxygen to yield two moles of water.

• The ratio helps determine how much of each reactant is needed.
• It also predicts the amount of products that can be formed.

Accurately understanding these ratios is crucial for predicting experimental outcomes and ensuring that chemical reactions proceed efficiently and effectively.