1. You have the containers in front of you. How much should you measure out to make 200 mL of a 1% aqueous solution of sucrose?

    One way: 2 gms solid sucrose made up to 200 mL with water.

    Another way: dilute one of the pre-existing sucrose solutions using the CV=CV equation.

     

  2. You have the containers in front of you. You have added 5.844 grams of NaCl crystals to water and made it up to 100 mL. What percent solution have you made?

    5.844%

    Remember: "%" is the amount you add to 100 mL.

     

  3. You have have the containers in front of you. You have taken 100 mL of the 4% lactose solution and added it to 300 mL of water to obtain 400 mL of what percent concentration?

    CV = CV
    100 mL x 4% = 400 mL x ?%
    ?% = (100 x 4%)/400 = 1%

     

  4. You have have the containers in front of you. You need to make two 100 mL solutions: 2% glucose in water, and 2% sucrose in water. Do you weigh out more glucose than sucrose, or the other way round?

    Both take 2 grams.

     

  5. You have 5 mL of a solution that is quite red, but it is so intense that it sends your meter over the top. You decide that were you to dilute it such that the intensity beomes half as much, the meter should then be able read it. How should you go about making a dilution that is half as intense?

    Take some of the deep red solution and add an equal amount of water so that it is now half as red.

     

  6. You are disk-testing the potencies of liquid antibacterial agents. You want to test one in its pure form and then also when it is only 1/1000 as concentrated. How should you do this? (Due to a shortage, you are limited to using no more than 5 mL of water!)

    Make 3 tubes of a 10-fold serial dilution using 0.9 mL of water in each tube.
    the first tube would be 1/10; the second 1/100 and the third would be 1/1000

     

  7. The prescription is that you are to give 300 units of insulin to a patient. Your supervisor makes up an injection for you to administer. From a bottle containing 1,000 units of insulin per mL, she withdraws 0.3 cc and then dilutes it by drawing in enough sterile saline to make 1 full mL. Is this right? Should you give the injection?

    If there were 1,000 units in 1 mL,
    0.3 mL would contain 0.3 x 1,000 = 300 U.
    However much salline you might add to that, there is still 300 U in the syringe.