Classify the following numbers as rational or irrational: (i) \( 2 - \sqrt{5} \) (ii) \( (3 + \sqrt{23}) - \sqrt{23} \) (iii) \( \frac{2\sqrt{7}}{\sqrt{7}} \) (iv) \( \frac{1}{\sqrt{2}} \) (v) \( 2\pi \)