# What is the molar concentration of the solution after adding 1 mL of 6.00 mol/L "HCl" to 499 mL of water?

Aug 14, 2016

#### Answer:

The molar concentration of the dilute $\text{HCl}$ solution is 0.0120 mol/L.

#### Explanation:

The critical thing to remember is that

$\text{moles of HCl before dilution = moles of HCl after dilution}$

The formula for molar concentration $c$ is

color(blue)(bar(ul(|color(white)(a/a)c = "moles"/"litres"color(white)(a/a)|)))" " or $\textcolor{b l u e}{\overline{\underline{| \textcolor{w h i t e}{\frac{a}{a}} c = \frac{n}{V} \textcolor{w h i t e}{\frac{a}{a}} |}}} \text{ }$

Moles of $\text{HCl}$ in 1 mL

$n = \text{0.001 00" color(red)(cancel(color(black)("L HCl"))) × "6.00 mol HCl"/(1 color(red)(cancel(color(black)("L HCl")))) = "0.006 00 mol HCl}$

Molar concentration of the dilute $\text{HCl}$

There will still be 0.006 00 mol of $\text{HCl}$ after you have added 499 mL of water.

$c = \frac{n}{V} = \text{0.006 00 mol"/"0.500 L" = "0.0120 mol/L}$