Hey guys,
Just going back to atrickplay's study guide:
[FONT="]1) [/FONT]How much pure acid must be added to 12 ounces of a 40% acid solution in order to produce a 60% acid solution?
I thought the guide's method was confusing. The following made more sense to me (from my chemistry notes):
M1V1 + M2V2 = M3(V1+V2) ; where M = concentration and V = volume
(ideally those numbers are supposed to be subscripts but i don't know how to do that in a forum post)
Therefore,
(0.40)(12oz) + (1.00)(V2) = (0.60)(12+V2)
solve for V2 = 6oz
-------------------------------------
one more question:
[FONT="]1) [/FONT]A tank that holds 450 gallons of water can be filled by 1 pipe in 15 minutes, and emptied by another in 30 min. How long would it take to fill the tank if both pipes are open?
I'm not sure if my method is correct (I was going strictly by unit analysis) but I was hoping it was an easier/faster way than how atrickplay solved this problem. Basically,
net rate = fill rate - empty rate
Therefore, net rate = (450gal/15min) - (450gal/30min) = 450gal/30min
So if you look at the net rate, you see that 450gal pairs to 30min so 30 min is the answer. (Is this a valid logic/approach to solving this problem?)
------------------------------
Also, were there any other discrepancies/mistakes in atrickplay's study guide? The only one I caught so far is:
[FONT="]1) [/FONT]A businesswoman spends 1/5 of her income for rent, and 3/8 of the remainder goes towards salary. How much does she have remaining?
The answer is supposed to be 1/2 (I hope).
I wish you all 50+++ on your upcoming ASTB exams! :icon_tong
------------------------------
atrickplay, if you're still active on this forum, i just want to thank you for passing on your knowledge and gouge for others to use.