PROBLEM
SOLVING : Normality, Molarity, Percentages
1. WRITE
DOWN FORMULA 1ST.
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 10 g NaCl solution and dissolve
it in 600 ml of diluent. ( 5 pts. each)
A.
What is the Molarity?
M= 10
58.5
0.6 L
ANSWER= M = 0.28 M NaCl
B.
What is the Normality?
N= M X v or factor
N= 0.28 X 1
ANSWER N = 0.28 N NaCl
C.
What is the percent solution?
% = Weight of solute X
100
Total Volume of solution
% = 10 X 100
600
ANSWER % = 1.67%
2. What
is the Molarity of a 2 N H2SO4 solution? ( 5 pts.)
M= N
v (valence or factor)
M= 2
2
ANSWER M = 1 M H2SO4
3. What
is the dilution if you add 0.25 ml of serum to 5.0 ml of diluent? ( 5 pts.)
0.25 mL = 1 part
5.0 mL = 20 parts
1:21
ANSWER Dilution = 1:21
Or
Parts of diluent = 5/0/25
5
0.25
= 20 parts of diluent
DILUTION FACTOR= parts of solute
+ parts of diluent
Dilution factor = 1 + 20 = 21
ANSWER Dilution = 1:21
4. How
would you prepare 1:6 serum dilution? (
5 pts.)
THERE ARE
VARIOUS WAYS TO PREPARE SERUM DILUTIONS:
THE SIMPLEST
WAY IS TO CONSIDER 1 mL of SERUM AS 1 PART.
ANSWERS:
1mL of serum =
1 part
5 mL of NSS = 5
parts
6 parts
Dilution = 1:6
0.25 mL of
serum = 1 part
0.25 X 5 =
2.25 mL= 5 parts
6 parts
Dilution = 1:6
5. How
would you prepare a 0.85 % NaCl solution? (5 pts.)
W=(%) X
Total volume of solution
100
W= 0.85 X 100
100
ANSWER W= 0.85 g NaCl
diluted to 100 mL of water in a volumetric flask
6. What is the
Normality of a 10% CaCl2 solution?
N= % X 10
EW (MW/v)
N= 10 X 10
111/2
ANSWER N = 1.80 N
CaCl2
7. Convert 40
mEq/L of calcium to mg/dL
40 mEq X 1L X 20
mg (40 atomic weight / valence)
L 10 dL 1 mEq
ANSWER= 80 mg/dL
