A stream of aqueous hydrochloric acid, 57.3 wt% HCl, is mixed with pure water to produce a stream of 16.5% acid. Perform a DFA.

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**Degree of freedom = Number of unknowms – Number of equations**

**Number of unknowns**

**1) acid flowrate**

**2) % water in acid feed**

**3) flow rate of water**

**4) Flow rate of product**

**5) mass % of water in product**

**Number of equations:**

**1) sum of mass % = 100 in feed**

**2) sum of mass % = 100 in product**

**3) mass balance of HCl**

**4) Total mass balance (mass feed + mass water = mass product)**

**Note: mass balance of water is a redundant equation.**

**.: COF = 5 – 4 = 1**

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