What is the hydronium-ion concentration in a solution formed by combining 750 mL of 0.10 M NaOH with 250 mL of 0.30 M HCl? NaOH(aq)+ HCl(aq)→ NaCl(aq)+ H₂O(l) A) 0.075 M B) 1.7 × 10^-13 M C) 1.0 × 10^-7 M D) 0.30 M E) 0.10 M

Question

Quizplus · Accepted Answer

First, we need to find out which reactant is limiting:

NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Using the balanced equation, we can see that the reaction consumes 1 mole of NaOH for every 1 mole of HCl, so we need to convert the volumes of each solution to moles:

(750 mL)(1 L/1000 mL)(0.10 mol/L) = 0.075 mol NaOH
(250 mL)(1 L/1000 mL)(0.30 mol/L) = 0.075 mol HCl

Since both reactants have the same number of moles, neither is in excess or limiting. Therefore, we need to use the stoichiometry of the balanced equation to find the concentration of hydronium ions (H3O+):

1 mol HCl produces 1 mol H3O+
0.075 mol HCl produces 0.075 mol H3O+
So, the concentration of H3O+ is:

[H3O+] = (0.075 mol)/(0.750 L + 0.250 L) = 0.0675 M

Since this is in scientific notation, we can write it as 6.75 × 10^-2 M or 1.0 × 10^-7 M after rounding to the appropriate number of significant figures. The answer choice closest to this is C, which is the correct answer.

What Is the Hydronium-Ion Concentration in a Solution Formed by Combining