\(Cu\) and \(HNO_{3}\) are not suitable for preparing hydrogen gas because of their

Copper (\(Cu\)) and nitric acid (\(HNO_{3}\)) are not suitable for preparing hydrogen gas because of their reactivity and oxidation properties, respectively. When copper is placed in nitric acid, a redox reaction occurs, where the copper is oxidized by the nitric acid. This reaction produces copper nitrate and nitrogen dioxide gas, but it does not produce hydrogen gas. Similarly, nitric acid is a strong oxidizing agent and can oxidize hydrogen gas to water, thereby preventing the formation of hydrogen gas. Therefore, neither copper nor nitric acid can be used to prepare hydrogen gas. Other metals, such as zinc or magnesium, can be used to react with acids to produce hydrogen gas because they are more reactive than copper and do not have the same oxidation properties as nitric acid.