Making Zinc Chloride

[dubois928]

What would be the proportion/ratio of zinc metal to hydrochloric acid to make a zinc chloride solution, which in in turn would be evaporated to precipitate zinc chloride crystals?

 

Thanks,

Ken

[YT2095]

Zn + 2 HCl → ZnCl2 + H2

 

that should help

[dubois928]

So that would be 1 part Zinc to 2 parts Hydrochloric acid? Sorry if I have it way wrong, I'm kind of new at this.

 

Thanks,

Ken

[insane_alien]

yeah 1mol of zinc will react with 2 mols of hydrochloric acid.

[YT2095]

a mole is 6.02x10^23 atoms of ANY element or molecule, for Zinc 1 mol is 65.4 grams, and H=1 and Cl= 35.5 so when you add them you get 36.5 grams for 1 mole of HCl, but you`ll need 2 moles so ya double it to 73 grams.

 

although you`ll not be able to buy pure HCl as it`s a Gas, so you`ll have to factor in the percentage of it in the acid you`re using.

[dubois928]

Wow thats a lot of zinc. I am having trouble understanding the measurement of moles. Just to make sure I'm have this right, would I take 2ml of 30% HCl and dissolve 1 gram of zinc in it? Or does the amount change because it's 30% and not 100%?

 

Thanks,

Ken

 

Oh, never mind YT explained it. So what would I have to do to get the amount required for 30% HCl?

[YT2095]

it is a lot if you`re planning on making it in whole Molar amounts, but these work right down into nano grams and lower too, it`s just a maths thing.

 

and I`m really crap at maths as anyone (incl myself) will tell you.

 

but your Ratio is 65.4 : 73

 

that`s all I dare say. I`ll ask Insane Alien to do that bit

[insane_alien]

okay, you have 15(ish)mmol of zinc so you'll need 30(ish)mmol of HCl

 

30mmol of HCl is 1.1g

 

so you'll need 3.7g of the 30% solution (assuming it is weight for weight) to disolve it. this would equate to about 3.7ml call it 4ml to make sure you disolve it all.

[dubois928]

So, if I'm doing my math correctly, if I had a 40% solution of HCl instead of 30%, I would need 2.75ml of of it?

 

Thanks,

Ken

[YT2095]

yup, that comes up about right when I fiddle with my calculator a bit

[insane_alien]

i concur. i get 2.75ml as well.

[dubois928]

One more thing:

 

okay, you have 15(ish)mmol of zinc so you'll need 30(ish)mmol of HCl

 

How did you get 15mol Zinc and 30mol HCl?

 

Thanks,

Ken

[insane_alien]

15 mmol. mmol is millimol a thousandth of a normal mol.

 

i don't like working with 0.000XXX numbers so i use the prefixes. it's still SI

 

though i more commonly work with kmols(thosand mols)

[dubois928]

So 1.0g Zn = 15mmol?

 

Ken

[insane_alien]

pretty much. its 1/65.4 to be more exact.

[dubois928]

Finally, here is all of my math, hopefully correct:

 

ZnCl2

1 mol Zn -to- 2 mol HCl

 

 

1 mol Zn = 65.4g

1 mol H = 1.0g

1 mol Cl = 35.5g

 

1 mol HCl = 36.5g

2 mol HCl = 73.0g

 

15mmol Zn -to- 30mmol HCl

 

15mmol Zn = 1.0g

30mmol HCl = 1.1g

 

30% HCl = 0.3

 

1.1/0.3 = 3.666 (3.7)

 

3.7g = 3.7ml

 

ZnCl2 = 1.0g Zn -to- 3.7ml 30% HCl

 

Thanks,

Ken

[insane_alien]

yeah we got there a while ago.

[dubois928]

Great! Thank you Insane_Alien and YT for all of your help! I think I have a better understanding of the math behind chemistry now.

 

Ken