**Time required for 50% decomposition of H2O2 in the presence of an acid**

To determine the time required for 50% decomposition of hydrogen peroxide (H2O2) in the presence of an acid, we need to understand the concept of reaction order and the rate equation for this reaction.

**Reaction Order and Rate Equation:**
The rate of a chemical reaction is generally determined by the concentration of the reactants. In the case of the decomposition of H2O2, the reaction is usually assumed to be first-order with respect to H2O2 concentration. This means that the rate of the reaction is directly proportional to the concentration of H2O2.

The rate equation for the decomposition of H2O2 can be written as follows:
Rate = k [H2O2]^n

Where:
- Rate is the rate of the reaction
- k is the rate constant
- [H2O2] is the concentration of H2O2
- n is the order of the reaction with respect to H2O2 concentration

**Relationship between Reaction Order and Half-life:**
The half-life of a reaction is the time it takes for the concentration of a reactant to decrease by half. In a first-order reaction, the half-life is constant and independent of the initial concentration. The relationship between the half-life (t1/2) and the rate constant (k) for a first-order reaction is given by the following equation:

t1/2 = 0.693 / k

**Determining the Time for 50% Decomposition:**
Since the reaction is assumed to be first-order with respect to H2O2, we can calculate the time required for 50% decomposition using the half-life equation.

Given that the time required for 20% decomposition is 5 minutes, we can calculate the rate constant (k) using the half-life equation:

t1/2 = 0.693 / k
5 min = 0.693 / k

Solving for k:
k = 0.693 / 5 min

Now, we can calculate the time required for 50% decomposition:

t1/2 = 0.693 / k
t1/2 = 0.693 / (0.693 / 5 min)
t1/2 = 5 min

Therefore, the time required for 50% decomposition of H2O2 in the presence of an acid is 5 minutes.