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Pharmacist mixed a 20 percent solution with a 30 percent solution to obtain 100 liters of a 24 percent solution How much of the 20 percent solution did the pharmacist use in the mixture?
10
A solution containing 30 percent insecticide is to be mixed with a solution containing 50 percent insecticide to make 200 L of a solution containing 42 percent insecticide How much of the 30 percent i?
80 liters
A chemist has one solution that is 60 percent chlorinated and another that is 40 percent chlorinated How much of each solution is needed to make a 100 liter solution that is 50 percent chlorinated?
50 Liters of the 60% solution.
How much water should be added to four liters of 75 percent alcohol to make a mixture of 30 percent alcohol?
There are 3 litres of alcohol in your starting mixture of 4 litres. If you add 6 litres of water you will have 3 litres of alcohol in a total of 10 litres. This is the required strength.
How much pure alcohol must be added to 7 liters of 10 percent alcohol solution to increase the concentration to 30 percent alcohol?
2 litersLet X represent the amount of pure alcohol to be added to the 7 liters of 10% alcohol solution to get a 30% alcohol solution. We want .3(7+x)=.1*7+x [because we need the alcohol in the final solution to equal the amount of alcohol in the original solution plus the amount of alcohol we are adding). Solving for x, we get:.3(7+x)=.1*7+x2.1+.3x=.7+x1.4=.7x2=xThus, 2 liters of pure alcohol needs to be added to the solution.Added noteto deal with the so called 'dilution contraction' of total volumeIf it were % by MASS ( %m/m), it's quite easy to do (based on the 'Mass Conservation Law). You calculate with mass (kg) and mass-% (%m/m) i.s.o. volume (L) and vol% (%v/v).However if the meaning was: % by Volume ( %v/v) then calculation appears to become quite complicated, but not impossible if you know at least the density values of all solutions (original 100%v/v or 10%v/v and final 30%v/v).DO NOT use: (orig. volume) + (added volume) = final volume, as done above, if exact figures are necessary.It's only a rule of thump, an approximation. This is because fluids can contract on mixing at dilution. There is no rule such as: conservation of volume.Your case: 7 L + 2 L (is not equal but) < 9 L final solution.
