Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Richeyyy on September 05, 2021, 02:25:25 PM

Hello, I'm kind of a newbie in chemistry calculations but I know a lot of basics about chemistry. Anyway, I've got a question. How do I convert grams to mililters, knowing molar mass, density and concentration?
I need 13g of HCl to be converted into ml.
Concentration is 32%
Molar mass is 36.458 g/mol
Density is 1.18 g/ml
Longer more detailed version: I have a 32% concentration HCl solution, I need 13g of HCl, how do I figure out how many mililiters (ml) I'll need to get those 13g of HCl?
If not too difficult, please could you give me the entire formula and how it's supposed to be calculated step by step? I need to do an autocalculator in Microsoft Excel based on those formulas

13g of HCl
13 g of HCl, or 13 g of 32% solution?
In general, m=V*d, where m is mass, V is volume, d is density.

oh so to get mass it's m=V*d, thanks a lot, and sorry I didn't mention that, I'll fix that up in a second. 13g of HCl. I have HCl solution that is 32% concentration, and I need to figure out how many mililiters of the 32% solution I'll need, if I need 13g of HCl. I need the formula as well if possible

Look at the definition of percent concentration, if you know what mass of HCl you need finding mass of a solution that contains it is just a matter of rearranging the formula.

Yeah it may be possible for me to do, is concentration like, HCl 32% conc= 32g of HCl in 100ml of water?

Is it 32/13=2.46. 100/2.46=40ml?

Yeah it may be possible for me to do, is concentration like, HCl 32% conc= 32g of HCl in 100ml of water?
Depends, but generally  no. If you dissolve 32 g of HCl in 100 mL of water you will get 24% solution.
Most often 32% is 32 g of HCl in 100 g of solution.

Sounds insanely complicated tbh

Rip, after all I couldn't figure out what the formula was

Sounds insanely complicated tbh
No, that's quite simple. If you start with the definition (pretty easy to google):
[tex]C_\% = \frac {m_{solute}}{m_{solution}} \times 100\%[/tex]
32% means 32/100 of something, so if you have 100g of SOLUTION it contains 32 g of SOLUTE (HCl in your case).
100 mL of water is quite exactly 100 g of water.
Solution is both SOLUTE and SOLVENT. If you combine 32 g of HCl and 100 g of water you get 132 grams of solution. It contains 32g/132g*100% (just plugging into the definition) or 24% of HCl.

Thanks a bunch! ^^

oh but that's only how to figure out concentration, but still thanks, I'll add that to my excel auto calculator. Idk if I didn't google enough but I couldn't rly find that percentage concentration fact that easily on google

Is it 32/13=2.46. 100/2.46=40ml? Is that correct though?
Because if 32% HCl solution equals to 32g of 100(ml or g I dunno) of that 32% solution.
And I need to have 13g of HCl in my beaker. So calculating based on mass only, 32g divided by 13g would give me the factor which would tell me by how much I'm supposed to divide 100(ml or g?) of that 32% HCl solution to have grams converted to mililiters. Idk any other way to calculate it

Your calculation is partially right, but you are abusing units. You need about 40 g of the solution, not 40 mL. Then the mass of HCl is 32/100*40g = 12.8 g.
Density of the solution is about 1.16 g/mL (taken from the density tables), so the volume is lower than 40 mL.

Niiice thanks, probably the last question, if you're saying I need 40g of solution and not 40ml, can I use a measuring scale ir a kitchen scale to measure out 40g of solution? Like adding the solution into the beaker, 40g of it, would that be correct?

can I use a measuring scale ir a kitchen scale to measure out 40g of solution?
Yes.
Or convert to volume (I gave you density) as it is much easier to measure given volume than given mass.

thanks! Idk though, it really comes down to personal preferences, measuring mass has more of that chemistry vibe than measuring volume, still thanks a whole lot!

Hey btw that concentration formula you've showed me before, it applies to solids only, but there isn't any info about percentage concentration definition if the solute is a gas. HCl is a gas dissolved in something

Hey btw that concentration formula you've showed me before, it applies to solids only
No, it is universal.

Thanks! That solved the issue then:))