Question

How many mL of 6.0 M HCl solution will provide 164 g of HCl?

Answer 1

`"0.75 L"`

Explanation:

The idea here is that you need to determine how many moles you get in `"164 g"` of hydrochloric acid, then use the given solution's molarity to figure out the volume that would contain that many moles.

So, hydrochloric acid has a molar mass of `"36.46 g/mol"`, which means that the `"164-g"` sample will contain

`164color(red)(cancel(color(black)("g"))) * "1 mole HCl"/(36.46color(red)(cancel(color(black)("g")))) = "4.498 moles HCl"`

As you know, molarity is defined as moles of solute, which in this case is hydrochloric acid, divided by liters of solution

`color(blue)("molarity" = "moles of solute"/"liters of solution")`

A `"6.0-M"` hydrochloric acid solution will contain `6` moles of hydrochloric acid for every liter of solution. This means that `4.498` moles will come with a volume of

`c = n/V implies V = n/c`

`V = (4.498color(red)(cancel(color(black)("moles"))))/(6.0color(red)(cancel(color(black)("moles")))/"L") = "0.7497 L"`

Rounded to two sig figs, the number of sig figs you have for the molarity of the solution, the answer will be

`V = color(green)("0.75 L")`