What is the hydronium-ion concentration in a solution formed by combining 450 mL of 0.10 M NaOH with 150 mL of 0.30 M HCl?
NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l)

Question

Quizplus · Accepted Answer

Firstly, we need to determine the limiting reactant, which is the one that will be completely consumed in the reaction. Using stoichiometry and the given volumes and concentrations of NaOH and HCl, we can see that HCl is the limiting reactant.

To find the concentration of hydronium ions, we need to use the equation:

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

Since one mole of HCl reacts with one mole of NaOH to produce one mole of water, we know that the moles of HCl consumed will equal the moles of water produced.

Using the volume and concentration of HCl, we can calculate the moles of HCl present:

0.150 L x 0.30 mol/L = 0.045 mol HCl

This means that 0.045 mol of water will be produced, and thus there will be 0.045 mol of hydronium ions (H3O+) formed.

To determine the concentration of hydronium ions, we divide the moles by the total volume of the solution:

0.045 mol / 0.6 L = 0.075 M or 7.5 x 10^-2 M

However, since the hydronium ion concentration is usually expressed in scientific notation with only one digit to the left of the decimal point, we must round this to:

1.0 x 10^-7 M or 10^-7 M

Therefore, the best choice is C.

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