2.0g of a monobasic acid was made up to 250 cmᣔ3 with distilled water. 25.00 cmᣔ3 of this solution required 20.00 cmᣔ3 of 0.1 M NaOH solution for complete neutralization. The molar mass of the acid is

2.0g of a monobasic acid was made up to 250 cmᣔ3 with distilled water. 25.00 cmᣔ3 of this solution required 20.00 cmᣔ3 of 0.1 M NaOH solution for complete neutralization. The molar mass of the acid is A. 200g 

B. 160g 

C. 100g 

D. 50g

The correct answer is C. 100g

Let’s solve it clearly step by step.

Given:

• Mass of monobasic acid = 2.0 g

• Total volume of solution = 250 cm³

• Volume of acid used = 25.00 cm³

• Volume of NaOH used = 20.00 cm³

• Concentration of NaOH = 0.1 M

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1. Moles of NaOH used

Moles of NaOH = C *V = 0.1 *20.00/1000
= 0.002  mol

2. Moles of acid in 25.00 cm³

The acid is monobasic, so it reacts with NaOH in a 1 : 1 ratio.

Moles of acid = 0.002  mol

3. Moles of acid in 250 cm³

250 cm^3 = 10 *25  cm^3

Total moles of acid = 0.002 *10 = 0.02 mol

4. Molar mass of the acid

Molar mass = Mass/Moles = 2.0/0.02 = 100  g mol^-1
✅ Correct Answer

C. 100 g

QUESTION NUMBER 19