Problem 36 - Chemistry: Structure and Properties

Question

Consider the unbalanced equation for the neutralization of acetic acid: HC2H3O2(aq) + Ba(OH)2(aq)-H2O(l ) + Ba(C2H3O2)2(aq) Balance the equation and determine how many moles of Ba(OH)2 are required to completely neutralize 0.461 mole of HC2H3O2.

Step-by-Step Solution

Answer

0.2305 mole of Ba(OH)2 is required to completely neutralize 0.461 mole of HC2H3O2.

Step 1: Balance the chemical equation

Write down the unbalanced equation and balance it by adjusting the coefficients to ensure there are equal numbers of each type of atom on both sides of the equation. The balanced equation is: 2 HC2H3O2(aq) + Ba(OH)2(aq) → 2 H2O(l) + Ba(C2H3O2)2(aq)

Step 2: Determine the molar ratio

From the balanced equation, determine the molar ratio between acetic acid and barium hydroxide. The ratio is 2 moles of HC2H3O2 to 1 mole of Ba(OH)2.

Step 3: Calculate moles of Ba(OH)2 needed

Calculate the moles of Ba(OH)2 needed to neutralize 0.461 mole of HC2H3O2 using the molar ratio. The calculation is based on the ratio from step 2: 0.461 mole HC2H3O2 x (1 mole Ba(OH)2 / 2 moles HC2H3O2) = 0.2305 mole Ba(OH)2.This calculation gives the amount of Ba(OH)2 needed to completely neutralize 0.461 mole of HC2H3O2.

Key Concepts

Chemical Equation Balancing

One of the fundamental skills in chemistry is the ability to balance chemical equations. A balanced chemical equation represents the conservation of matter, indicating that the number of atoms for each element is the same on both the reactants and products side.

For the given neutralization reaction between acetic acid (HC2H3O2) and barium hydroxide (Ba(OH)2), balancing the equation is the first crucial step. You start by listing the number of atoms for each element present in the reactants and products. Then, you adjust the coefficients in front of each compound to match the number of atoms on both sides. As seen in the example, we balanced the equation by having two acetic acid molecules react with one barium hydroxide molecule to produce two water molecules and one molecule of barium acetate (Ba(C2H3O2)2).

It's important not to change the chemical formulas of the reactants or products to achieve balance; instead, you should only adjust the coefficients. A systematic approach may involve balancing elements that appear in fewer compounds first, usually leaving hydrogen and oxygen last.

Stoichiometry

Stoichiometry is the aspect of chemistry that pertains to the quantitative relationships between the substances involved in a chemical reaction. After balancing the chemical equation, stoichiometry allows you to use the molar ratios of reactants and products to calculate how much of a reactant is needed to produce a certain amount of product or vice versa.

In the example, we applied stoichiometry to determine the amount of barium hydroxide needed to neutralize a specific amount of acetic acid. The balanced equation provided the molar ratio of 2:1 between acetic acid and barium hydroxide. Knowing this ratio is essential because it tells you that two moles of acetic acid react with one mole of barium hydroxide. Using this information, you can find the precise amount of one reactant needed to react with a given amount of another reactant.

Mole Concept

The mole concept is a cornerstone of chemistry, allowing for the quantification of matter. One mole is defined as the amount of substance that contains as many entities (atoms, ions, molecules, etc.) as there are atoms in 12 grams of pure carbon-12. This number is known as Avogadro's number and is approximately 6.022 x 10^23 entities.

In stoichiometric calculations, the mole concept helps translate the mass of a substance into an amount of moles using molar mass—the mass of one mole of the substance. When the problem states that you have 0.461 mole of acetic acid, this represents a specific number of acetic acid molecules. Through the mole concept, you can use this quantity to predict how much of another substance, such as barium hydroxide, will be required in the reaction, as shown in the solution where 0.461 mole of acetic acid corresponds to 0.2305 mole of Ba(OH)2.