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Having a problem with word problems. example A chemist mixes a 10% acid solution with a 50% acid solution to form 400mL of a 40% solution. How much of each solution should be used. Need to identify the variables. Thank you
 

 

Hi,

You have two solutions, a weak solution (10%) and a strong solution (50%). You need to mix some of the weak solution and some of the strong solution and end up with 400 ml of a mild solution. Suppose that you take x ml of the weak solution then you know that you will need (400 - x) ml of the strong solution since the the total amount must be 400 ml.

You also know that the final solution is 40% acid, so in the final solution the amount of acid is 40% of 400 ml, that is

40% of 400 = 40/100  400 = 160 ml of acid.

10% of the weak solution is acid, that is 10% of x ml is acid, so the amount of acid that comes from the weak solution is

10% of x = 10/100  x = x/10 ml of acid.

50% of the weak solution is acid, that is 50% of (400 - x) ml is acid, so the amount of acid that comes from the weak solution is

50% of (400 - x) = 50/100  (400 - x) = (400 - x)/2 ml of acid.

Since the total amount of acid is 160 ml you have

x/10 + (400 - x)/2 = 160.

Solve for x.

Cheers,
Penny

 
 

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