If you react 0.1 M sodium hydroxide (NaOH) with a 0.2 M sulfuric acid (H2SO4), what volume combinations do you expect to see the largest change in temperature? 15 mL sodium hydroxide and 60 mL sulfuric acid 40 mL sodium hydroxide and 20 mL sulfuric acid 30 mL sodium hydroxide and 30 mL sulfuric acid 60 mL sodium hydroxide and 15 mL sulfuric acid 20 mL sodium hydroxide and 40 mL sulfuric acid
The Correct Answer and Explanation is:
The combination that is expected to produce the largest temperature change is 60 mL sodium hydroxide and 15 mL sulfuric acid.
Here’s the reasoning:
The neutralization reaction between sodium hydroxide (NaOH) and sulfuric acid (H₂SO₄) follows this balanced chemical equation:
H₂SO₄+2NaOH→Na₂SO₄+2H₂O\text{H₂SO₄} + 2\text{NaOH} \rightarrow \text{Na₂SO₄} + 2\text{H₂O}
This means that 1 mole of sulfuric acid reacts with 2 moles of sodium hydroxide. We need to find the combination that produces the maximum amount of water, since the temperature change in an exothermic neutralization reaction depends on the amount of heat released. That heat is directly proportional to the number of moles of water formed.
Now, calculating the number of moles for each combination:
Option: 60 mL NaOH and 15 mL H₂SO₄ NaOH: 0.060 L×0.1 mol/L=0.006 mol0.060 \, \text{L} \times 0.1 \, \text{mol/L} = 0.006 \, \text{mol} H₂SO₄: 0.015 L×0.2 mol/L=0.003 mol0.015 \, \text{L} \times 0.2 \, \text{mol/L} = 0.003 \, \text{mol}
This pairing gives a 2:1 mole ratio, which matches the stoichiometry of the balanced equation perfectly. That means complete neutralization, where all of the acid and base react to form the maximum possible moles of water. Other combinations are either limiting in one reagent or have significant excess, which leaves some reactant unused and leads to a smaller energy release.
Furthermore, this combination also uses the largest total volume (75 mL), allowing efficient heat distribution while still preserving the optimal stoichiometry.
Hence, 60 mL NaOH with 15 mL H₂SO₄ results in the most exothermic reaction, producing the largest change in temperature.
