Question

Some sulfuric acid is spilled on a lab bench. You can neutralize the acid by sprinkling sodium bicarbonate on it and then mopping up the resultant solution. The sodium bicarbonate reacts with sulfuric acid according to: $$ \begin{aligned} 2 \mathrm{NaHCO}_{3}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow & \mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+\\\ & 2 \mathrm{H}_{2} \mathrm{O}(l)+2 \mathrm{CO}_{2}(g) \end{aligned} $$ Sodium bicarbonate is added until the fizzing due to the formation of \(\mathrm{CO}_{2}(g)\) stops. If \(27 \mathrm{~mL}\) of \(6.0 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}\) was spilled, what is the minimum mass of \(\mathrm{NaHCO}_{3}\) that must be added to the spill to neutralize the acid?

Short answer

The minimum mass of NaHCO3 required to neutralize the spilled H2SO4 is approximately \(27.22\: g\).

Step-by-step solution

Calculate the moles of H2SO4

To find the moles of H2SO4, we will use the given volume and the concentration of the solution: moles of H2SO4 = volume × concentration \[moles\: of\:H_2SO_4 = 27 \times 10^{-3} L \times 6.0\: moles/L\] \[moles\: of\:H_2SO_4 = 0.162\: moles\]

Determine the moles of NaHCO3 required

Using the stoichiometry of the balanced equation, we see that 2 moles of NaHCO3 are required to neutralize 1 mole of H2SO4. Therefore, we can calculate the moles of NaHCO3 needed: moles of NaHCO3 = 2 × moles of H2SO4 \[moles\: of\:NaHCO_3 = 2 \times 0.162\: moles\] \[moles\: of\:NaHCO_3 = 0.324\: moles\]

Convert moles of NaHCO3 to mass

Now we need to convert the number of moles of NaHCO3 to mass using the molar mass of NaHCO3. The molar mass is calculated as follows: Molar mass of NaHCO3 = 1(22.99 g/mol) + 1(1.01 g/mol) + 1(12.01 g/mol) + 3(16.00 g/mol) Molar mass of NaHCO3 = 84.01 g/mol Now, we convert moles to mass using the molar mass: mass of NaHCO3 = moles of NaHCO3 × molar mass of NaHCO3 \[mass\: of\:NaHCO_3 = 0.324\: moles \times 84.01\: g/mol\] \[mass\: of\:NaHCO_3 \approx 27.22\: g\] Hence, the minimum mass of NaHCO3 required to neutralize the spilled H2SO4 is 27.22 g.

Key concepts

Stoichiometry

Understanding stoichiometry is crucial when dealing with chemical reactions. Stoichiometry can be thought of as the 'recipe' for a chemical reaction, detailing the proportions of reactants and products. In the context of neutralizing a sulfuric acid spill with sodium bicarbonate, stoichiometry tells us how much sodium bicarbonate (NaHCO₃) is required to completely react with a given amount of sulfuric acid (H₂SO₄).

The balanced chemical equation provided in the exercise is the foundation for stoichiometric calculations. It shows a 2-to-1 ratio, meaning two moles of sodium bicarbonate are needed for every mole of sulfuric acid to achieve neutralization. This ratio is essential when calculating the quantity of the neutralizing agent needed. By flipping the perspective, students must understand that for every mole of H₂SO₄ spilled, twice the amount of NaHCO₃ in moles is required.

Molar Mass Calculation

The concept of molar mass is a gateway to translating between the microscopic world of atoms and molecules and the macroscopic world we observe. The molar mass is the weight of one mole of a substance and is typically expressed in grams per mole (g/mol).

In this exercise, calculating the molar mass of sodium bicarbonate is pivotal in converting moles to mass, which is a more practical measure for handling chemicals. To calculate molar mass, we sum the atomic masses of each element in the compound, multiplied by the number of atoms of each element. Sodium (Na), hydrogen (H), carbon (C), and oxygen (O) are the elements present in NaHCO₃. Using the periodic table, students combine these atomic masses accordingly, which then allows them to find out how much NaHCO₃ in grams is needed to neutralize the sulfuric acid.

Chemical Reaction Equation

The chemical reaction equation is a concise notation that describes the transformation of reactants into products. It must be balanced to obey the Law of Conservation of Mass, which states that matter cannot be created or destroyed in an ordinary chemical reaction. The coefficients in the balanced equation represent the ratio of moles of each substance involved.

In our example, the equation details the reaction between sodium bicarbonate and sulfuric acid, resulting in the formation of sodium sulfate, water, and carbon dioxide. The balanced equation gives a clear picture of the process and is the cornerstone for stoichiometry. Understanding this equation enables students to predict the outcome of the reaction and to calculate the amounts of reactants needed for a complete reaction.

Acid-Base Neutralization

Acid-base neutralization is a type of chemical reaction where an acid and a base react to form water and a salt. Classically, acids are compounds that can donate a proton (H⁺ ions) while bases can accept a proton or release hydroxide ions (OH⁻).

Safety and Practical Application

In practical terms, acid spills like the one involving sulfuric acid are neutralized to prevent damage to surfaces or harm to individuals. Sodium bicarbonate is commonly used as it is a mild base, which when reacting with a strong acid like sulfuric acid, creates a neutral solution safe for disposal.

The fizzing of carbon dioxide noted in the exercise is a good indicator that the reaction is occurring. Once the fizzing ceases, it suggests that the acid has been neutralized and provides a real-world cue to the end of a neutralization reaction. This practical application of acid-base reaction concepts is an excellent illustration of chemistry in action and brings theory into the real world.