A teacher showed demonstration of action of acids on the metals in the laboratory. After the activity was over, one naughty student took an alluminium rod. He dipped it in a bottle containing concentrated nitric acid. Later, he dipped it in a beaker containing dilute `H_(2)SO_(4)` But, he did not find any bubbles coming out. He was surprised because he was able to see bubbles coming out when a metal rod is dipped in sulphuric acid when teacher did the experiment. He then approached the teacher and asked what is wrong with his activity. Predict the answer given by the teacher.

Explanation

### Step-by-Step Solution:

1. **Understanding the Experiment**:
The student dipped an aluminum rod in concentrated nitric acid (HNO3) and then in dilute sulfuric acid (H2SO4). The teacher had previously demonstrated the reaction of metals with sulfuric acid, which produced bubbles.

2. **Reaction with Concentrated Nitric Acid**:
When aluminum is exposed to concentrated nitric acid, it reacts to form a passive oxide layer on its surface. This layer is a protective barrier that prevents further reactions between the aluminum and other substances.

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