Aqueous solutions of sodium thiosulfate, Na₂S₂O₃, are used as an antidote to some snakebites. How many moles of sodium ions are found in 10.0 mL of a 0.15 M solution of Na₂S₂O₃?

• A. 0.0015 mol
• B. 0.15 mol
• C. 1.5 mol
• D. 0.030 mol
• E. 0.0030 mol

Answer: (E)

Verified step by step guidance

1. First, understand that the molarity (M) of a solution is defined as the number of moles of solute per liter of solution. Here, the molarity of Na2S2O3 is given as 0.15 M.
2. Next, calculate the number of moles of Na2S2O3 in the given volume of solution. Use the formula: \( \text{moles of Na2S2O3} = \text{Molarity} \times \text{Volume in liters} \). Convert 10.0 mL to liters by dividing by 1000.
3. Now, determine the number of sodium ions produced from the dissociation of Na2S2O3. Each formula unit of Na2S2O3 dissociates into 2 Na\(^+\) ions and 1 S2O3\(^{2-}\) ion in solution.
4. Calculate the total moles of sodium ions by multiplying the moles of Na2S2O3 by 2, since each mole of Na2S2O3 produces 2 moles of Na\(^+\) ions.
5. Finally, verify your calculation by ensuring the units are consistent and the stoichiometry of the dissociation is correctly applied. This will give you the total moles of sodium ions in the solution.