Which of the following is NOT true of standard reduction potential?

• A. It is measured under standard conditions: 1 M concentration, 1 atm pressure, and 25°C.
• B. Standard reduction potentials are always negative for all elements.
• C. A more positive standard reduction potential indicates a greater tendency to be reduced.
• D. The standard hydrogen electrode is assigned a potential of 0.00 V.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand what standard reduction potential means. It is the voltage measured when a species gains electrons (is reduced) under standard conditions: 1 M concentration for solutions, 1 atm pressure for gases, and 25°C temperature.
2. Step 2: Recall that standard reduction potentials are measured relative to the standard hydrogen electrode (SHE), which is assigned a potential of 0.00 V by definition.
3. Step 3: Recognize that standard reduction potentials can be either positive or negative depending on the species. A more positive value means a greater tendency to gain electrons (be reduced), while a more negative value means a lesser tendency.
4. Step 4: Evaluate the statement 'Standard reduction potentials are always negative for all elements.' Since many elements have positive standard reduction potentials, this statement is false.
5. Step 5: Conclude that the false statement is the one claiming all standard reduction potentials are negative, while the other statements correctly describe standard reduction potentials.