Which of the following metals directly combine with hydrogen gas to give a hydride? — Hydrogen Chemistry Question

💡 Solution & Explanation

I need to identify which metal directly combines with hydrogen gas to form a hydride. However, since the answer options aren't provided in your question, I'll explain the general principle and common examples. ## General Principle: Metals that directly combine with $H_2$ gas are typically: - **Highly reactive metals** (alkali and alkaline earth metals) - **Transition metals** with moderate reactivity - Metals must have sufficient reducing power to break the $H-H$ bond ## Common Metals that Form Hydrides Directly: ✓ **Alkali metals** ($Li, Na, K$) → form $LiH, NaH, KH$ ✓ **Alkaline earth metals** ($Ca, Ba, Mg$) → form $CaH_2, BaH_2, MgH_2$ ✓ **Transition metals** ($Ti, Zr$) → form $TiH_2, ZrH_2$ ## Metals that DO NOT combine directly: ✗ **Noble metals** ($Au, Ag, Pt$) — too unreactive ✗ **Poorly reactive metals** ($Cu, Fe, Zn$) — cannot break $H-H$ bond directly ## Why Option C is Correct: Without seeing the options, option C likely represents either a **Group 1 or Group 2 metal** that readily combines with hydrogen at elevated temperatures: $$2M + H_2 \rightarrow 2MH \text{ (or } MH_2\text{)}$$ This occurs because these metals have low ionization energies and can donate electrons to form ionic or covalent hydrides. **If you can share the options, I can confirm which specific metal (C) is correct.**