The products that represent a rational number are:
- \(5 \times \frac{1}{2}\)
- \(3 \times 4\)
- \(\sqrt{2} \times \frac{1}{\sqrt{2}}\)
- \(\sqrt{16} \times \frac{1}{2}\)
- \(\frac{\pi}{2} \times \frac{2}{\pi}\)
Thus, the final answer is:
\(\boxed{5 \times \frac{1}{2}, 3 \times 4, \sqrt{2} \times \frac{1}{\sqrt{2}}, \sqrt{16} \times \frac{1}{2}, \frac{\pi}{2} \times \frac{2}{\pi}}\)