Making solutions of a known molarity

So I left my notebook at home but if I recall, the formula is:

molecular mass (of compound) x molarity (desired) x volume = amount (in grams) of a solid I need to dissolve

So to produce 1.00 kI(aq) it would be:

166 x 1.00 x 0.1(l) = 16 grams of kI ?

It has been a long long time since I needed to do this (before March!)

Many thanks :)
 
So to produce 1.00 kI(aq) it would be:

Not sure I understand this part of the question, but 16.6g KI (you shouldn't really be rounding to whole grams when you're making up solutions; and anyway 16.6 would round up not down) would give 1L at 0.1M , or 100ml at 1M. I hope one of those is what you were aiming for !
 
Not sure I understand this part of the question, but 16.6g KI (you shouldn't really be rounding to whole grams when you're making up solutions; and anyway 16.6 would round up not down) would give 1L at 0.1M , or 100ml at 1M. I hope one of those is what you were aiming for !

The rounding up was a typo. 100mls at 1M is what I am aiming for :)
 

ajmc98

Don't lick, smell or touch it and you won't die.
Your equation is right.
I always work in two stages, backwards from the desired volume and concentration.

Vol (in litres) x Conc. = moles
mass / Mr = moles

rearrange as needed.
 
Ah I forgot I am using Sodium Thiosulphate-5-water, as opposed to Sodium Thiosulphate. I can imagine I simply add the molecular mass of the waters and re-do ones calculations? Many thanks :)
 

ajmc98

Don't lick, smell or touch it and you won't die.
Ah I forgot I am using Sodium Thiosulphate-5-water, as opposed to Sodium Thiosulphate. I can imagine I simply add the molecular mass of the waters and re-do ones calculations? Many thanks :)
Yeah, the majority of the time it will tell you the molecular weight on the storage container, saves doing even more maths ;)
 
Cleapps recipe cards tell you all this. very useful and also stop you being caught out with thing like Iron II solutions made up in acid.
 
For those times when you start to doubt yourself I find the page at the link below useful. Especially helpful on cold Monday mornings when the caffeine hasn't had time to kick in.

and you can get smart phone versions as well - I use 'Solution Calculator Lite' by P_Z for Android it does dilutions as well. Since I have my phone with me at all times, I never get caught out.
 
Top