Normality Problems
1. What is the normality of the following?
a. 0.1381 M NaOH
0.1381 mol/L x (1 eq/1mol) = 0.1381 eq/L = 0.1381 N
b. 0.0521 M H3PO4
0.0521 mol/L x (3 eq/1mol) = 0.156 eq/L = 0.156 N
c. 0.5781 g acid (eq wt = 187.3) in 250.0 mL of solution
0.5781 g x (1 eq/187.3 g) = 0.003086 eq/0.2500L
= 0.01235 N
d. 0.321 g sodium carbonate in 250.0 mL of solution
0.321 g Na2CO3
x (1 mol/105.99 g) x (2 eq/1mol) = 0.01886 eq/0.2500L = 0.0755 N
2. What is the molarity of the following?
a. 0.3181 N HCl
0.3181 eq/L x (1 mol/1 eq) = 0.3181 M
b. 0.1115 N Sr(OH)2
0.1115 eq/L x (1 mol/2 eq) = 0.05575 M
c. 0.4237 g of KHP (eq wt = 204.23) in 100.0 mL of solution
0.4237 g KHP x (1 eq/204.3 g) x (1 mol/1 eq) =
0.002074 mol/0.1000 L = 0.02074 M
3. What is the equivalent weight of the following?
a. C6H5COOH b. Na2CO3 c. H3PO4
a. mw = 122.13 g/mol x (1 mol/1 eq) = 122.13 g/eq
b. mw = 105.99 g/mol x (1 mol/2 eq) = 52.99 g/eq
c. mw = 98.00 g/mol x (1mol/3 eq) = 32.67 g/eq
4. If 25.00 mL of citric acid solution is titrated with 28.12 mL of 0.1718 N KOH, what is the concentration of citric acid? (hint: normality is a concentration unit!)
Na·Va = Nb·Vb
Na(25.00 mL) =
(0.1718N)(28.12 mL) Na
= 0.1932 N
or
28.12 mL KOH x
(0.1718 meq/1 mL) x (1 meq
acid/1 meq base) = 4.831 meq
acid/25.00 mL = 0.1932 N
5. If 31.87 mL of base is required in the standardization of 0.4258 g of KHP (eq wt = 204.23), what is the normality of the base?
0.4258 g KHP x (1 eq/204.23g) x (1 eq base/1eq
acid) = 2.085 x 10-3 eq base/0.03187 L =
0.6542 N
6. What is the normality of an acid if 21.18 mL were needed to titrate 0.1369 g Na2CO3?
0.1369 g Na2CO3
x (1 mol/105.99 g) x (2 eq/1 mol) x (1 eq acid/1 eq base) = 2.583 x 10-3
eq acid/0.02118 L = 0.1212 N
7. What is the equivalent weight of a base is 0.2131 g required 43.71 mL of 0.0132 N acid?
43.71 mL x (1 L/1000
mL) x (0.0132 eq acid/1 L )
x (1 eq base/1 eq acid) =
5.770 x 10-4 eq
eq
wt = 0.2131 g/5.770 x 10-4 eq = 369 g/eq
8. What is the %acid (eq wt = 173.8) if 20.07 mL of 0.1100 N base were required to neutralize 0.7231 g of sample?
20.07 mL x (1 L/1000
mL) x (0.1100 eq base/1 L) x (1 eq
acid/1 eq base) x (173.8 g /1 eq)
= 0.3837 g acid
(0.3837 g acid/0.7231
g sample) x 100 = 53.06%