1. You dissolved 2 grams of NaCl in 100 mL of water. Then you added enough water to make the volume to 200 mL. What is the % concentration?

    Ultimately you have 2 grams in 200 mL; that's 1 gram in 100 mL = 1%

  2. You took 100 mL of what you made in 1, above, and added 200 mL of water. The new concentration is _______ of the original?
    1. the same
    2. 3/4
    3. 1/2
    4. 1/3 ← (C1V1=C2V2; C1 x 100 mL = C2 x 300 mL; C2 = C1 x (100/300))
    5. 1/4

  3. You have some 12% sucrose and you need to make 200 mL of 3%. How much of the 12% should you use?

    CV=CV; 12% x V = 3% x 200 mL
    V = (3% x 200 mL)/12% = 50 mL

  4. You have a "concentration meter." But what you have to measure is too concentrated for the meter. You find that if you put 1 mL of the original into 3 mL of water, the meter shows the concentration to be 12%. What is the % concentration of the original?

    CV=CV; C x 1 mL = 12% x 4 mL
    C = (12% x 4)/1 = 48%

  5. One pill is for 15 kilos of body weight. Your patient weight 75 kilos. How many pills do you give?

    1 is to 15 as X is to 75; X = 75/15 = 5 pills