[Danial]

Q:
2L of 0.120M HClO4 from the commercial reagent. [60% w/w HClO4, sp gr 1.6]

so what i've done
0.12M x 2L = 0.24mol HClO4.     0.24mol x 68.443(mm of HClO4) = 16.42632g
16.42632g/0.6 = 27.3772
27.3772/68.443 = 0.4mol

then this is the part im not 100% about. Im not realy sure what sp gr means, specific gravimetric?
so
1.6 = mol / kg
kg = 0.4 / 1.6 = 0.25
= 250mL
the book has 25mL
ive been looking over to find what i did wrong, if messed up my units or somthing. but i cant figure it out.
thanks

[opti384]

sp gr stands for specific gravity which is the relative density when we define water as 1g/1ml. So it means the density of the HClO4 will be 1.6g/1ml

[Danial]

sweeeeeeeeet
i got it, thanks

[opti384]

I'm not sure if I got the question. What are you supposed to find?

[Borek]

Seems like Danial needs to calculate volume of stock acid required to prepare 2L of 0.120M solution.

That's what my CASC does in no time

But it also shows that density of 60% w/w solution of perchloric acid is 1.53 g/mL, not 1.6.

[Danial]

I need to get me a CASC
I was just following the 1.6 that was in the question.
My book kind of confused me it showed sp gr with different units, but when i did it this way it fit perfectly with the answer in the book

[Borek]

Please note: if you have a density given in the question it is better to use it, even if it is an incorrect one. Otherwise the answer you will get will be different from the one you prof expects. CASC is great in such situations to check if you are on the right track.

[Danial]

hey could I ask a quick question about significant figures
what do i do when it's
2.000/(1.002 x 12.2)
the book explains it weird, it like takes the inverse of the biggest number and times' it by the answer and some how determines how many figures to use.
Is there a less confusing way to do it?
I thought it was just to use the number with the smallest amount of significant figures

[opti384]

As far as I know, the significant figures in multiplication and division follow the figure which has the least number of significant figures.