question about amount of water in a certain molarity of HCl?

Question

I need to find the concentration of water in 1M HCl. I measured the density of 1MHCl as .9886g/mL
Can someone help me out here?
I'm drawing a blank.

Answer 1

I think papastol... above me is wrong, he forgot to factor in the weight of the HCl.

The solution has a density of .9886 g/mL, which = 988.6 g/L

Now find the weight of the HCl in solution. You know there is 1 mol and can figure out the molecular weight of HCl is ~36.5g/mol. So there is 36.5 g of HCl in the solution. So subtract that from the total weight of 988.6 g and you get 952.1 g out of the 1 liter is weight of water.

Then divide by the molecular weight of water, which is 18 and you get 52.9 mol/L, the concentration of the water.

Answer 2

1 M HCl is 1 mole HCl per liter of SOLUTION not 1 mole of HCl per liter of WATER as Roger has stated.

1M HCl weighs 36.5 g

your 1 L weighs 988.6 g from your density

so your 1 liter contains 952.1 g water.

molarity = moles / L = (wt/mw) / L = (952.1g/18g/mole) / 1 L = 52.9 M

Kainkin is correct.


*******

I'm not a chemist. I'm a chemical engineer......

Answer 3

It's 100% water by volume and 98% water by weight, but read on .....

1 molar HCl contains 1 mole of HCl per liter of water. A "mole" is actually a number, and this many molecules of HCl has a characteristic weight. This weight is also the sum of the weights of the atoms which the molecule is made of. HCl has 1 Hydrogen atom and a Chlorine atom and a "mole" of both weigh 36.5 grams. Therefore, a 1 molar solution of HCl would contain 36.5 grams of HCl. Water happens to weigh exactly 1 kilogram per liter, so achedemically speaking, there ought to be 1000 grams - 36.5 grams of water in a 1 molar solution of HCl.

////////////////////// HOWEVER

If one wanted to split hairs, it could be mentioned the density of HCl isn't exactly 1 gram per milliliter. It ought to also be mentioned HCl itself is actually a water soluable gas, not a liquid. It really ought to be mentioned this gas is not infinitly soluable in water, either. "Concentrated HCl" is actually a 22% solution of this gas. The "1 molar" solution was probably made by adding 36.5 ml of acid to a flask and bringing it up to the 1 liter mark with water. It's 100% water by volume for the same reason a cup of coffee with a tablespoon of sugar in it is still exactly 1 cup. The volume of the sugar is literally absorbed by the water. The sugar molecules fit neatly between the water molecules, and there is no change in volume. In terms of weight, well that 36.5 ml of concentrated HCl weighed 36.5 grams, but only 22% of it was HCl. This means there was only about 8 actual grams of HCl gas. Therefore in terms of weight, a 1 molar solution of HCl is 98.2% water and 0.8% HCl by weight.

Answer 4

Kainkin is right. What matters is the density and composition of your solution, so the density of pure water is not actually relevant.