Impedance

Can you please tell me a bit about impedance, and some formulas or calculations that would shed light on the attached.

Operational amplifier, OP-AMP

See attached file for full problem description.

What electric characteristics must an amplifier have for use with pH electrode?

What electrical characteristics must an amplifier have for use with a pH electrode? How would you calibrate such an electrode?

Twin Tee Circuit

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op amp applications derivations

Please see attached scan; this is a review from my electronics course; q1. derivation and circuit for a non-inverted output. q2. derivation of equation q3. derivation for gain showing high pass filter and breakpoint frequency q4. derivation for gain showing highpass filter and the difference between an active filter and a filter in q3. q5. I have the derivation of the twin-t alone, but please help me understand qualitatively how it works in concert with the op amp. please include as many steps as possible. Thank you.