How many moles are there in 3.0 mL of concentrated 18M sulfuric acid?
The correct answer and explanation is:
Correct Answer:
There are 0.054 moles of sulfuric acid (H₂SO₄) in 3.0 mL of 18 M sulfuric acid.
Explanation (Approx. 300 words):
To determine the number of moles in a given volume of a solution, you can use the formula: Moles=Molarity (M)×Volume (L)\text{Moles} = \text{Molarity (M)} \times \text{Volume (L)}
In this question, the molarity (M) of the sulfuric acid solution is 18 M, which means 18 moles of H₂SO₄ per liter of solution.
The volume given is 3.0 mL, but in the formula, volume must be in liters (L). To convert milliliters to liters: 3.0 mL=3.01000=0.003 L3.0\ \text{mL} = \frac{3.0}{1000} = 0.003\ \text{L}
Now substitute the values into the formula: Moles=18 mol/L×0.003 L=0.054 mol\text{Moles} = 18\ \text{mol/L} \times 0.003\ \text{L} = 0.054\ \text{mol}
So, there are 0.054 moles of H₂SO₄ in 3.0 mL of 18 M sulfuric acid.
Why This Matters:
Understanding how to calculate moles from volume and molarity is fundamental in chemistry. This skill is critical when preparing solutions, performing titrations, or predicting the amount of reactants and products in chemical reactions.
Sulfuric acid (H₂SO₄) is a diprotic strong acid, meaning it can donate two protons (H⁺) per molecule in aqueous solutions. While this affects reactions involving acid-base chemistry, for mole calculations, you simply focus on the formula and unit conversions.
In industrial and lab settings, 18 M sulfuric acid is considered highly concentrated and corrosive. Even small amounts, like 3.0 mL, contain a significant number of moles due to the high molarity. Always handle such solutions with proper protective equipment and safety protocols.
By mastering molarity and mole calculations, you build a foundation for understanding solution chemistry, stoichiometry, and quantitative analysis in science.