A chemical agent is kept in bottles having 50 percent concentration

Question

A chemical agent is kept in bottles having 50 percent concentration of a particular chemical. A part of the chemical agent was kept aside and equal quantity of water was added to the remaining chemical agent. The chemical now forms what percentage concentration in the final mixture?

(1) Each bottle of the chemical agent contains 60 ml of the mixture.
(2) 60 percent part of the chemical agent in the bottle was kept aside and equal quantity of water was added to the remaining chemical agent.

chetan2u · Accepted Answer

gvvsnraju@12 ,

concentrate means % of the chemical, so 50% concentrate means 50% water and 50% chemical..
chemical mixture means a mix of chemical, water etc

now..
we know whatever we remove 50% of it will be the chemical and other 50% will be water...
so if we are looking for  percentage concentration in the final mixture , the % of mix taken out will be ok as only that % is getting added as water..

say 10% is removed. this 10% has 5% of water and 5% chemical, BUT now we add this entire 10% as water
so water increases by 5% and chemical reduces by 5% and the concentrate becomes 50-5=45%.

(1) Each bottle of the chemical agent contains 60 ml of the mixture.
we can say 30ml is water and 30ml is chemical
insuff

(2) 60 percent part of the chemical agent in the bottle was kept aside and equal quantity of water was added to the remaining chemical agent.
so 40% of initial quantity is remaining, which will have 20% of initial quantity as water and 20% of initial quantity as chemical..
we add 60% water back to it.. so chemical remains 20% of initial quantity and 20%+60=80% of initial quantity as water
suff

B

pushpitkc · Answer

The chemical agent(kept in bottles) had 50% concentration.
A part of this solution was kept aside(had to be diluted with water)
Adding the chemical agent(in bottles) with the chemical agent(once diluted) will give a mixture.
We need to find out how much percentage concentration is present in that final mixture.

(1) Each bottle of the chemical agent contains 60 ml of the mixture.
 Knowing how much chemical agent, without the number of bottles present and the 
quantity of the agent kept aside, we can't give the final concentration(Not sufficient)

(2) 60 percent part of the chemical agent in the bottle was kept aside 
and equal quantity of water was added to the remaining chemical agent.
 It has been given that the quantity kept aside was 60% of the total chemical solution
and was diluted in the same proportion, we can clearly tell that the chemical is 50% of the final mixture(Sufficient) (Option B)

lichting · Answer

Not totally clear about the question and solution. Can any one please show me detail solution on this?

chandra004 · Answer

My approach:-
The chemical concentration is 50%, given in the question stem. After some part of chemical is removed then we're asked to find the final concentration of the chemical left.

i) Here it's given that chemical is 60 ml and hence total solution volume = 120 ml.
This much info isn't enough to deduce the chemical concentration left after remove a part of chemical.
Hence A is insufficient.

ii) Here it's given that 60% of the chemical was removed.
Now suppose total volume was 100 ml. Hence the chemical content initially = 50% of 100 ml = 50 ml
Now after 60% is removed from 50 ml. Left chemical = 40% of 50 = 20 ml
Hence chemical concentration = (20/100)*100
Hence B is sufficient.

gvvsnraju@12 · Answer

hi  chetan2u

I m unable to assimilate the info provided in the question !

Stem says a chemical agent is kept  in bottles , where as option B says  the bottle . so i thought more info is needed in addition to option B .
But OA is B.
Kindly let me know "where i was wrong?"

amanvermagmat · Answer

Hello

I think it just means that this chemical agent is always kept in particular bottles of equal size and equal concentration of the chemical agent. This is just given so that we can treat all bottles of this agent alike.

And then statement 2 just talks about one of the bottles out of the many.

gvvsnraju@12 · Answer

Hi  amanvermagmat

Thanks for your reply.

Even i thought the same what you said.

But Option A made my head rotated by citing "Each bottle of the chemical agent contains 60 ml of the mixture".

kindly advise me how can i avoid such confusions hereafter.

amanvermagmat · Answer

Hello Well, the question stem says that each bottle is 50% concentrated (which means whatever be the total quantity of solution in it, 50% of it will be chemical agent and rest 50% will be water). Statement 1 gives additional info by saying that actual quantity of solution (or mixture) is 60 ml. So now combining it with question stem we can conclude that out of this 60 ml, 50% or 30 ml is the chemical agent and rest 30 ml is water. Well, such confusions can be resolved by understanding, and understanding will come by resolving our doubts like this - as you are doing right now

Thats what I believe.

krish76 · Answer

I got the answer right but can someone confirm if this method of equating amount is correct in this case.

So, after 60% chemical agent (of say v volume) is taken out, the chemical conc. is still 50% but the amount will be 50%*30% of soln =15%
once it is replaced by same amount of water the amount of chemical doesnt change. so, the final volume is back to v again

so. can i say (50%)(30% of v)=(final concentration)*(v)

so, final concentration = 15 %

LordStark · Answer

krish76 we dont't need to calculate the answer

weighted average method can be used here let the percentage of the chemical in the final solution be x% quantity of remaining chemical agent = P quantity of water added = Q therefore \frac{P}{Q} = \frac{(0-x)}{(x-50)} \frac{P}{Q} = \frac{x}{(x-50)} therefore to get the percentage of chemical in the final solution we need to have the ratio of the remaining chemical and water statement 1 : gives only total quantity of original chemical agent. No suff. statement 2: provides ratio of remaining chemical and water. sufficient

Sejal16 · Answer

Vi * Ci = Vf * Cf

40 * 50% / 100 = Cf
Cf = 20%

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A chemical agent is kept in bottles having 50 percent concentration

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