Do acids and bases have the same coefficients if they neutralize one another? The questions states: Ammonia has the formula $\ce{NH3}$. Household ammonia is a dilute aqueous solution of $\ce{NH3}$. Aqueous ammonia is a base that can neutralize acids.
If 18.2 mL of 0.800 M $\ce{HCl}$ solution are needed to neutralize 5.00 mL of a household ammonia solution, what is the molar concentration of the ammonia?
Express your answer with the appropriate units.
I used the values I was given; converted the $\ce{HCl}$ to moles; divided the moles of $\ce{HCl}$ by the liters of ammonia solution. However, I do not understand why this is correct.
$\ce{HCl}$ is an acid and $\ce{NH3}$ is a base. How does finding the molar mass of $\ce{HCl}$ help one calculate the molarity of $\ce{NH3}$?
Look at the chemical equation. One mole of $\ce{HCl}$ will neutralize one mole of $\ce{NH3}$. $\ce{HCl}$ is an acid so it loses a hydrogen ion and ammonia is a base so it gains a hydrogen ion.

$\ce{HCl + NH3 -&gt; NH4Cl}$

So, you found the number of moles $\ce{HCl}$ added, and this equals the number of moles in the 5.00 mL sample of $\ce{NH3}$. Divide that by the volume and you get concentration, which is moles per liter. You don't need to find the molar mass of $\ce{HCl}$ and you didn't find it as described in your calculations above.