Question

The limiting reactant in a reaction: a. has the lowest coefficient in a balanced equation. b. is the reactant for which you have the fewest number of moles c. has the lowest ratio: moles available/coefficient in the balanced equation. d. has the lowest ratio: coefficient in the balanced equation/moles available. d. None of the above. For choices you did not pick, explain what you feel is wrong with them, and justify the choice you did pick.

Short answer

The correct choice is (c): "The limiting reactant in a reaction has the lowest ratio of moles available to the coefficient in the balanced equation." This accurately describes the limiting reactant as the one that determines the maximum amount of product that can be formed in the chemical reaction. Choices (a), (b), and (d) are incorrect as they do not correctly relate the limiting reactant to the ratio of moles available and the stoichiometric coefficients in the balanced reaction.

Step-by-step solution

A limiting reactant is the reactant in a chemical reaction that is completely consumed and which determines the maximum amount of product that can be formed. It "limits" the reaction from proceeding once it is used up. To identify the limiting reactant, we compare the mole ratios of the reactants to the stoichiometric ratios in the balanced equation. #Step 2: Evaluating each choice#

We will now go through each choice and evaluate if it is the correct definition or description for the limiting reactant. a. has the lowest coefficient in a balanced equation.

This statement is incorrect because the limiting reactant is not determined by the lowest coefficient in the balanced equation. It depends on the ratio of moles of reactants to the stoichiometric coefficients. b. is the reactant for which you have the fewest number of moles.

This statement is also incorrect because having the fewest number of moles does not necessarily mean that the reactant will be limiting. It depends on the ratio of moles of reactants to the stoichiometric coefficients. c. has the lowest ratio: moles available/coefficient in the balanced equation.

This statement is correct. The limiting reactant can be determined by comparing the ratio of moles available to the stoichiometric coefficients in the balanced reaction. The reactant with the lowest ratio will be the limiting reactant, since it will be consumed first according to the balanced reaction. d. has the lowest ratio: coefficient in the balanced equation/moles available.

This statement is incorrect because it is essentially the inverse of the correct choice (c). This ratio, coefficient in the balanced equation/moles available, would not give us the correct limiting reactant. e. None of the above.

Since we have determined that choice (c) is correct, this statement is incorrect. #Step 3: Conclusion#

The correct choice is (c): "The limiting reactant in a reaction has the lowest ratio of moles available to the coefficient in the balanced equation." This correctly identifies the limiting reactant, which determines the maximum amount of product that can be formed in the chemical reaction.

Key concepts

Stoichiometry

Stoichiometry is a branch of chemistry that deals with the quantitative relationship between reactants and products in a chemical reaction. Understanding stoichiometry helps us predict the amounts of substances consumed and produced in a reaction. It involves calculations based on the balanced chemical equation of a reaction.

When working with stoichiometry, it's essential to have a clear understanding of the mole concept. A mole is simply a specific number of particles, roughly equivalent to Avogadro's number (\( 6.022 \times 10^{23} \) particles). In context, stoichiometry allows us to convert moles of one substance in a reaction to moles of another, using the mole ratio derived from the balanced chemical equation.

Let's take a common example to solidify our understanding. Consider the reaction between hydrogen gas and oxygen gas to form water:

Simplified Reaction: 2 H₂ + O₂ → 2 H₂O

This equation tells us that 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water. Stoichiometry would allow us to calculate how many moles of water are produced if we start with a specific amount of hydrogen and oxygen, or vice versa.

Mole Ratio

The mole ratio is a critical component in stoichiometry, providing the direct link between the reactants and products in a chemical equation. It is derived from the coefficients of the substances in a balanced chemical equation and used as a conversion factor.

For every reaction, the balanced equation indicates the fixed ratio in which reactants combine and products form. If we take the simple reaction of hydrogen and oxygen forming water, the mole ratio of hydrogen to oxygen is 2:1, and the mole ratio of hydrogen to water is 1:1. This means that for every 2 moles of hydrogen, there is 1 mole of oxygen reacting, and each mole of hydrogen can form one mole of water.

It's important to use the mole ratio accurately to predict the correct amounts of reactants needed and the potential yield of the product. Any mistake in using the mole ratio can lead to an incorrect determination of the limiting reactant, resulting in an inaccurate depiction of the reaction's outcome.

Balanced Chemical Equation

A balanced chemical equation provides a symbolic representation of a chemical reaction, with reactants on the left side and products on the right side. The balancing act involves making sure that the same number of atoms for each element is present on both sides of the equation. It's a law of conservation of matter that states matter cannot be created or destroyed in a chemical reaction.

The balanced equation serves as a blueprint for conducting stoichiometric calculations. It tells us the exact proportions in which substances react and the amounts of products formed. For example, in a combustion reaction of methane:

Simplified Reaction: CH₄ + 2 O₂ → CO₂ + 2 H₂O

This shows that one molecule (or mole) of methane reacts with two molecules (or moles) of oxygen to produce one molecule of carbon dioxide and two molecules of water. Without a balanced equation, we cannot accurately employ the principles of stoichiometry nor calculate the mole ratio, which is essential in determining the limiting reactant in a reaction.