Consider the following half cell reaction:

The reaction was conducted with the ratio .

The pH value at which the EMF of the half cell will become zero is (nearest integer value).

Given: Standard

Question

Consider the following half cell reaction:

The reaction was conducted with the ratio .

The pH value at which the EMF of the half cell will become zero is  (nearest integer value).

Given: Standard half cell reduction potential  V,  V

Canvas Classes · Accepted Answer

🧠 Set Nernst = 0 and Solve for pH

Half-reaction: , , .

The reaction quotient with the given ratio:
.

Set :

.

🗺️ Solve for pH

.

Answer: 10.

⚡ The Smart Move

For "find pH at which E = 0" problems on pH-dependent half-cells, the chain:
1. Set E = 0 in Nernst.
2. Solve for log Q.
3. Substitute the pH-dependent expression and isolate pH.

For dichromate at high pH, the cell loses oxidising power (E drops) until eventually E = 0 (no driving force). This happens around pH 10 with the

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