Chemistry question - Normality?

2017-08-18 10:28 pm
What is the normality of an acid solution if 50 mL of the solution requires 48.61 mL of 0.1879 N alkali for neutralization?

(A) 0.4000 N (C) 0.1827 N
(B) 0.2678 N (D) 0.1274 N

The answer key said C, but I have no idea how to arrive to that answer.

What is principle/formulas used in this question?

Please be as thorough as possible--giving the step-by-step procedure to this would really help me.

Thank you in advance!

回答 (3)

2017-08-19 1:21 am
✔ 最佳答案
Basic techniques in normality calculation:
1. No. of equivalents of the acid = No. of equivalents of the alkali (*needless to consider the mole ratio).
2. No. of equivalents = Normality × (Volume in L)

Solution to the question :
No. of equivalents of the alkali = (0.1879 eq/L) × (48.61/1000 mL) = 0.009134 eq
No. of equivalents of the acid = 0.009134 eq
normality of the acid = (0.009134 eq) / (50/1000 L) = 0.1827 eq/L = 0.1827 N

The answer: (C) 0.1827 N
2017-08-19 1:20 am
For a solution, the number of moles of the hydronium ions must be equal to the number of moles of the hydroxide ions. A one normal solution contains one mole of these ions per liter of the solution. To determine the number of moles multiply the volume in liters by the normality.

For the hydroxide ion, n = 0.04861 * 0.1879 = 0.009133819
0.050 * N = 0.009133819
N = 0.009133819 ÷ 0.050
This is approximately 0.1827. C is the correct answer.

V1 * N1 = V2 * N2
If you use the equation above, you will get the same answer.
48.61 * 0.1879 = 50 * N
N = 9.133819 ÷ 50
I hope this is helpful for you.
2017-08-19 12:19 am
(48.61 mL) x (0.1879 N) / (50 mL) = 0.1826 N
[Although four significant digits are not justified when given "50" mL.]


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