# Question #a6138

##### 1 Answer

The answer is

A solution's percent concentration by mass is defined as the mass of the solute, in your case hydrochloric acid, divided by the total mass of the solution, and multiplied by 100.

You know that the stock solution has a concentration of **37%**, which means that you get **37 g** of hydrochloric acid for every **100 g** of solution.

Now, let's assume we have a **1-L** bottle of this solution (you can assume any volume for the bottle, the answer is the same - 1L just made the calculations easier). Its density is

You can use the solution's density to determine the mass of the 1-L solution

Now, you know that for every **100 g** of solution you have **37 g** of hydrochoric acid. This means that you get

Now use hydrochloric acid's molar mass to determine how many moles you get in that much solution

The stock solution's molarity will thus be

Use the dilution concentration formula, to get the volume of the stock solution needed to make your target solution

Rounded to two sig figs, the number of sig figs you gave for the volume of the target solution, the answer will be