Friday, March 18, 2011

Answers to Normality, Molarity Problem Solving Review Questions in Clinical Chemistry

PROBLEM SOLVING :

1. WRITE DOWN FORMULA.
2. SHOW COMPUTATIONS.
3. ENCLOSE ANSWERS IN BOXES.

ATOMIC WEIGHTS:

Na = 23 H = 1 S = 32
Cl= 35.5 O = 16

1. If you weigh 5 g NaCl solution and dissolve it in 1000 ml of diluent. ( 5 pts. each)

A. What is the Molarity?

M= Gram molecular weight per liter of solution, hence: M= 5 /58.5/1 liter

M = 0.085 M

B. What is the Normality?

Since Normality (N) = M x valence(factor)

M = 0.085 x 1 (valence)

M = 0.085 N

N.B. WHEN THE VALENCE OR FACTOR IS ONE THE NORMALITY IS EQUIVALENT TO THE MOLARITY.

C. What is the percent solution?

% = Weight/total volume x 100

% = (5/1,000 mL) X 100

% = 0.5%

ANSWERS TO THE REMAINING QUESTIONS WILL BE GIVEN NEXT POST.

2. What is the Molarity of a 0.5 N H2SO4 solution? (5 pts.)
3. What is the dilution if you add 0.75 ml of serum to 3.0 ml of diluent? ( 5 pts.)
4. How would you prepare 1:20 serum dilution? (5 pts.)
5. How would you prepare a 0.5 % NaCl solution? (5 pts.)
6. You are asked to prepare 200 ml of the following standard concentrations from a 20 mg/dL standard stock solution: Tabulate volume of solute and solvent and also dilution. ( 5 pts. each)

A. 2 mg/dL C. 8 mg/dL
B. 4 mg/dL D. 10 mg/dL
E. 15 mg/dL



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