Reaction:
The given reaction is a 2b = c, which means that 2 moles of substance A react with 1 mole of substance B to produce 1 mole of substance C.

Given:
- 5 moles of A
- 8 moles of B

Explanation:
To determine the amount of substance C that will be produced, we need to first calculate the limiting reactant. The limiting reactant is the reactant that will be completely consumed and determines the maximum amount of product that can be formed.

Step 1: Calculate the moles of B required:
Since the reaction is a 2:1 ratio between A and B, we need half the moles of A for the reaction. Therefore, 5 moles of A will require (5/2) * 1 = 2.5 moles of B.

Step 2: Determine the limiting reactant:
Comparing the moles of B required (2.5 moles) with the amount of B given (8 moles), we see that B is not the limiting reactant since we have an excess of it.

Step 3: Calculate the moles of C produced:
Since B is in excess, all 8 moles of B will react with 4 moles of A (2 moles of B for every mole of A). This will produce 4 moles of C.

Conclusion:
- The limiting reactant is A.
- 5 moles of A will react with 8 moles of B.
- The reaction will produce 4 moles of C.