How much do you already know?
Applications in Science

Try the six problems below to see what you already know. Problems 1 and 2 are taken from the stoichiometry section, 3 and 6 are from the concentrations of solutions review, 4 is from the section on statistics, and 5 is from the pH section. How you do on these should help you decide which parts of Session 3 you need to work through.

Be honest with yourself! You will need to know this stuff for chemistry. Remember: You only get one chance to take the quizzes and final, so be prepared!

1. How many moles are there in 38.6 grams of H₂O, or water? Hydrogen has a weight of 1 gram and oxygen has a weight of 16 grams.

   (A)  694.8 moles        (B) 2.14 moles  
   
   (C)  656.2 moles       (D) 2.27 moles  
   
   

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2. How many ATOMS are there in 45.6 grams of NaOH? Sodium (Na) has a weight of 23 grams, oxygen is 16, and hydrogen is 1.

   (A)  1.10 x 1027        (B) 3.03 x 10-21  
   
   (C)  6.87 x 1023       (D) 1.89 x 10-24  
   
   

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3. I have a 15.0 M solution of HCl (hydrogen is 1 gram, Cl is 35.5 grams). How many grams of HCl are dissolved in one liter of solution?

   (A) 547.5 grams        (B) 0.41 grams  
   
   (C)  36.5 grams       (D) 18.4 grams  
   
   

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4. A student in the lab measures the pH of a substance as 5.7. The theoretical value for this measurement is 6.1. What is the percent error for the students's value?

   (A)  -6.6%        (B) 6.6%
   
   (C)  4.38%       (D) None  
   
   

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5. The pCO₂ value in the patient's blood is 13.6. What is the concentration of pCO₂ in the blood?

   (A)  1.13              (B) 3.98 x 1013
   
   (C)  2.51 x 1014       (D) 2.51 x 10-14  
   
   

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6. I need to prepare 250.0 mL of a 6-M solution of NaOH. How many grams of NaOH are needed?

   (A)  1042 grams              (B) 60 grams
   
   (C)  1.67 grams      (D) 0.038 grams  
   
   

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The answers are:

(1) B     (2) C     (3) A     (4) B     (5) D     (6) B

How did you do? If any of these were difficult, or you got them wrong, we recommend that you go through Session 3 prior to taking the final exam!