Recycling back of outlet stream to the reactor from an ideal CSTR carrying out a first order liquid phase reaction will result in __________ in conversion.

The correct answer is:
B. Increase

🔍 Explanation:
In an ideal Continuous Stirred Tank Reactor (CSTR) conducting a first-order liquid-phase reaction, recycling a portion of the reactor outlet back to the inlet will:

Increase the reactant residence time in the system.

Expose unconverted reactants to the catalyst/reactive zone multiple times, effectively enhancing conversion.

Make the system behave more like a plug flow reactor (PFR) as the recycle ratio increases — and a PFR gives higher conversion than a CSTR for first-order reactions at the same space time.

💡 Why conversion increases:
In a single CSTR, due to perfect mixing, reactants are immediately diluted with products — leading to lower conversion.

With recycle, the fresh feed is diluted with unconverted reactants, which improves conversion efficiency across the system.

✅ Final Answer:
B. Increase