The correct option for the question regarding a pair of compounds that can be used to generate a gas with physiological effects on human beings is **C. sodium trioxonitrate (V) and ammonium chloride**. ### Step-by-Step Explanation 1. **Understanding the Compounds**: - **Sodium trioxonitrate (V)**, commonly known as sodium nitrate (NaNO₃), is a salt that can decompose under certain conditions to release nitrogen oxides (NOx), which are gases that can have physiological effects. - **Ammonium chloride (NH₄Cl)** is a salt that can release ammonia (NH₃) gas when heated or when it reacts with a strong base. 2. **Gas Generation**: - When sodium nitrate is heated, it can decompose to produce sodium nitrite (NaNO₂) and oxygen (O₂) or nitrogen oxides (NO, NO₂). The nitrogen oxides produced can have various physiological effects, including influencing blood pressure and oxygen transport in the body. - Ammonium chloride, when heated, can release ammonia gas, which is known for its pungent smell and can irritate the respiratory system but is also used in various medical applications. 3. **Physiological Effects**: - The gases produced from these compounds can affect human physiology. For example, nitrogen oxides can lead to respiratory issues and are involved in the formation of smog, while ammonia can act as a respiratory stimulant in low concentrations. ### Why Other Options Are Incorrect - **Option A: Sodium trioxonitrate (V) and calcium chloride**: - Calcium chloride (CaCl₂) does not produce a gas that has significant physiological effects when reacted with sodium nitrate. Instead, it is primarily used as a desiccant and does not contribute to gas generation in a way that would be relevant to human physiology. - **Option B: Sodium dioxonitrate (III) and ammonium chloride**: - Sodium dioxonitrate (III), also known as sodium nitrite (NaNO₂), can produce nitrogen oxides, but when paired with ammonium chloride, the reaction does not yield a significant gas with physiological effects. The combination does not produce a gas that is as impactful as the combination in option C. - **Option D: Sodium dioxonitrate (III) and potassium chloride**: - Similar to option B, sodium nitrite does not react with potassium chloride to produce a gas with significant physiological effects. Potassium chloride (KCl) is primarily a source of potassium ions and does not contribute to gas generation in a meaningful way. ### Summary of Key Points - **Correct Answer**: C. Sodium trioxonitrate (V) and ammonium chloride can generate gases with physiological effects. - **Gas Production**: Sodium nitrate can decompose to produce nitrogen oxides, while ammonium chloride can release ammonia gas. - **Physiological Effects**: Nitrogen oxides can affect respiratory health, and ammonia can act as a respiratory stimulant. - **Incorrect Options**: Other combinations do not yield gases with significant physiological effects or do not produce gases at all. This thorough understanding of the compounds and their reactions is crucial for grasping the physiological implications of the gases they generate.