Calculate the number of mL of HCl reagent (36.0%, specific gravity = 1.18) that are needed to prepare one liter of 0.1M HCl solution. .


Thanks advance. .

The atomic weight of H is 1 and Cl 35, thus 1 mole of HCl would weigh 36g. A molar solution is 1mole (weight) per liter of water. A .1Mole strength solution will have one tenth of the original amount per liter. So a 1 mole solution has 36g or HCl, a .1 mole solution would have only 3.6g per liter. Specific gravity should let us calculate the volume of HCl is in the reagent.

We need to find how to make one liter of solution with 3.6g of HCl in it.

One liter of water has 1000g. Because the reagent has a specific gravity of 1.8 one liter of it would weigh 1800g. Thus 36% of its weight is HCl: 684g. That also means that .648g of HCl will be present in every mL of regeant. We need to have a total of 3.6. How many times does .648 go into 3.6? About 5.6 times. You will need 5.6mL of 36% HCl to produce 1 liter of .1M HCl.

Thanks a lot , but how u get 5.6 times " what do u mean 648 go into 3.6?".. I didn't understand this point. .

There sure are many typos in the post #2...

By the way Asoom, try not to write in text language, please.

I'm not used to deal with the specific gravity of a substance, and I don't understand the 36%.

If I take what InfoJunkie4Life said, a specific gravity of 1.18 means that the weight of 1 litre of the HCl solution will weight 1180 g. Since 1000 g is water, wouldn't 180 g be the HCl in the solution?

By the way Asoom, try not to write in text language, please.

I will do it next time , sorry . .

I'm not used to deal with the specific gravity of a substance, and I don't understand the 36%.

If I take what InfoJunkie4Life said, a specific gravity of 1.18 means that the weight of 1 litre of the HCl solution will weight 1180 g. Since 1000 g is water, wouldn't 180 g be the HCl in the solution?




mmm , I dont know . .

Oops, sorry, my question on that was intended to InfoJunkie :o

But tell me, haven't you learnt about what specific gravity was? Or the notation of putting a percentage?

36% is the concentration of the solution by weight. 36% of the weight of the whole is HCl and the rest is water. Specific gravity is a type of measurement without units. It tells you how much the weight is compared to water. Water has a specific gravity of 1 because 1 cc of water weighs 1 gram. Anything that is more or less dense is comparable via specific gravity. 1L of water weighs 1000g thus a specific gravity of 1.8 is 1.8 times heavier at one liter.

Its kind of like a multiple.

They are giving you two solution units and asking you to dilute the reagent so that its concentration is equal to .1 M.

By using the specific gravity we can calculate the density, and total weight. Of that we can take 36% of its weight and know that that much is HCl.

We found how much (weight) was in each mL by way of conversions. Then we need to add so much reagent so that there will be the 3.6 grams of HCl. This is why we are dividing the .648 into the 3.6. That will tell us how many mL of reagent to add to an empty pot, and then fill the rest with water so that it equals 1L. That will dilute the reagent to .1M.

If you want I can show it to you via mathematics...

Ok, I'm trusting you InfoJunkie, I'll be applying what you are saying.

Spe. Gravity = 1180
Mass of HCl = 36% x 1180 = 424.8 g
No. of moles of HCl per litre = 11.6 mol

You need 0.1 mole of that, so:
11.6 mol -> 1 litre
1 mol -> 1/(11.6) litre
0.1 mol -> (1/11.6)*0.1 = 0.00859 litre = 8.59 mL of conc. HCl

Then add water up to make 1 litre, that is 1000 - 8.59 = 991 mL of water.

What is quite odd though, that number...

You're correct but it could be simpler.

424.8g of HCl are present in the Liter of reagent.

\frac{424.8g}{1L} * \frac{1L}{1000mL} = 0.4248g
Present in each mL of Reagent.

A 0.1 molar solution of HCl has 3.6g of HCl in it and 1000mL of water.

Thus we need to know how many mL of reagent to add to get 3.6g.

\frac{3.6}{0.4248} = 8.5

So it takes 8.5mL of reagent to get 3.6g of HCl.

When we fill the rest with water the remainder is 991.5

You're correct but it could be simpler.

424.8g of HCl are present in the Liter of reagent.

\frac{424.8g}{1L} * \frac{1L}{1000mL} = 0.4248g
Present in each mL of Reagent.

A 0.1 molar solution of HCl has 3.6g of HCl in it and 1000mL of water.

Thus we need to know how many mL of reagent to add to get 3.6g.

\frac{3.6}{0.4248} = 8.5

So it takes 8.5mL of reagent to get 3.6g of HCl.

When we fill the rest with water the remainder is 991.5

Well, I guess every one find his own method 'simpler' to use :rolleyes:

True... as in our parachute guy...