**Answer:**

**Molarity of Unknown Acid = 0.1332 M**

**Explanation:**

**Data for solving problem: **

Molarity of base in buret (M₁)= **0.1517 M**

volume of the acid in Erlenmeyer flask (V₂)= **25.0 mL**

Volume of the base in the buret (V₁) = **final volume of buret - initial volume in buret**

final volume of buret = **22.5 mL**

initial volume in buret = **0.55 mL**

So

Volume of the base in the buret (V₁) = **22.5 mL -0.55 mL = 21.95 mL**

Volume of the base in the buret (V₁) = **21.95 mL**

Molarity of Unknown acid in the Erlenmeyer flask (M₂) = **To be find**

**Explanation:**

It is acid base titration and formula for this titration is as follows:

**Molarity of base x Volume of base = Molarity of acid x volume of acid**

it can be written as

**M₁V₁ = M₂V₂ -------------------- equation (1)**

we have to find **M₂ **

so by rearrangment the equation **(1)**

**M₁V₁ / V₂ = M₂ ------------------ equation (2)**

put the values in equation in **equation (2)**

**M₂ = 0.1517 M x 21.95 mL / 25.0 mL **

**M₂ = 3.3298 /25.0 **

**M₂ = 0.1332 M**

**so the Molarity of Unknown acid is **<u>**0.1332 M**</u>