Calcium hydride (CaH2) is an ionic binary hydride of calcium that reacts with water to give calcium hydroxide and hydrogen gas. In Inorganic Chemistry I, it shows up as a reactive main-group hydride, drying agent, and hydrogen source.
Calcium hydride is the ionic hydride of calcium, written CaH2. In Inorganic Chemistry I, you can think of it as a main-group compound made from Ca2+ and H- ions, not as a molecule with shared hydrogen like you would see in an organic compound.
That ionic picture matters because hydride, H-, is a very basic and very reactive species. Calcium gives up its two valence electrons easily, and hydrogen is present as hydride in the solid. This makes CaH2 a binary hydride, meaning it contains only two elements, calcium and hydrogen.
The most famous reaction is with water: CaH2 + 2 H2O -> Ca(OH)2 + 2 H2. The hydride ion pulls protons from water, so hydrogen gas is released quickly. That is why the compound has to be handled away from moisture and why it can be used to generate hydrogen on demand.
You will also see calcium hydride described as a drying agent. It removes traces of water from some solvents or gases because it reacts with the water instead of just holding it weakly. That is different from a desiccant like silica gel, which traps moisture physically.
Structurally, calcium hydride is a gray-white solid with a high melting point, which fits its ionic lattice. The solid is stable when dry, but the surface reacts readily with humid air, so storage conditions matter. In lab settings, that reactivity is the whole story: dry reagent, then controlled reaction when you actually want the hydrogen or the drying effect.
A common misconception is to treat all hydrides the same. Calcium hydride is not like methane or a covalent molecular hydride. In this course, it belongs with the alkaline earth compounds that form simple ionic solids and react predictably based on charge and lattice behavior.
Calcium hydride gives you a clean example of how Group 2 metals form ionic compounds with nonmetals and how those compounds behave in water. In Inorganic Chemistry I, that connects directly to periodic trends, cation formation, and the chemistry of alkaline earth metals.
It also shows the difference between a compound that is stable as a dry solid and one that becomes reactive the moment water is present. That before-and-after change is a big idea in inorganic chemistry, especially when you compare salts, oxides, hydroxides, and hydrides.
If you are studying lab technique, CaH2 is one of the classic examples of a drying reagent used to remove small amounts of water from a sample. That gives you a practical reason to care about hydride chemistry, not just a formula to memorize.
It also ties into hydrogen generation and reduction chemistry. When a question asks why CaH2 releases H2 with water, you are really tracing electron transfer, acid-base behavior, and lattice chemistry all at once.
Keep studying Inorganic Chemistry I Unit 4
Visual cheatsheet
view galleryHydride
Calcium hydride is a specific hydride, so this is the broader category term. In this course, hydrides can behave very differently depending on whether they are ionic, covalent, or metallic. CaH2 is the ionic type, which is why it reacts so strongly with water and can act as a drying agent.
Alkaline Earth Metals
Calcium is a Group 2 metal, so CaH2 reflects the chemistry of the alkaline earth metals. These elements form 2+ cations readily, and that charge helps explain why calcium pairs with two hydride ions in the solid. The compound is a good example of how Group 2 reactivity shows up in real substances.
Calcium Hydroxide
This is the product you get when calcium hydride reacts with water. Seeing Ca(OH)2 in the products helps you track where the calcium ends up after hydride has taken protons from water. If you can write that reaction correctly, you are showing you understand both formula writing and reaction products.
Cation Formation
Calcium hydride only makes sense once calcium has formed Ca2+. That cation formation is the electron-loss step that lets calcium join with hydride ions in a neutral solid. This connection comes up again and again in main-group chemistry whenever you predict formulas for ionic compounds.
A quiz question might ask you to predict the product when CaH2 is added to water, identify the type of hydride, or explain why the solid must be kept dry. On problem sets, you may need to balance the hydrolysis reaction and recognize that hydrogen gas is evolved. If a lab scenario gives you a reagent bottle labeled CaH2, the right move is to connect its moisture sensitivity to drying or hydrogen generation, not to treat it like an inert salt. You may also be asked to classify it as an ionic compound formed from a Group 2 metal, which is where cation formation and periodic trends come together.
Both calcium hydride and calcium chloride are calcium compounds that can appear as white solids, but they behave very differently. Calcium chloride is a common ionic salt used as a drying agent by absorbing water, while calcium hydride actually reacts with water and releases hydrogen gas. If a problem asks which one is a hydride, the answer is CaH2, not CaCl2.
Calcium hydride is the ionic binary hydride CaH2, made from calcium and hydride ions.
Its most useful reaction is hydrolysis, where water produces calcium hydroxide and hydrogen gas.
Because it reacts with moisture, CaH2 has to be kept dry and is handled very differently from ordinary salts.
It is a classic example of alkaline earth metal chemistry in Inorganic Chemistry I.
Its behavior connects formula writing, ionic bonding, acid-base ideas, and lab use as a drying reagent.
Calcium hydride is CaH2, an ionic compound made from calcium and hydride ions. In inorganic chemistry, it is a main-group binary hydride that reacts strongly with water to produce hydrogen gas and calcium hydroxide.
The hydride ion, H-, is very basic, so it takes protons from water. That proton transfer forms H2 gas, while the calcium ends up as calcium hydroxide. This is why CaH2 cannot be exposed to moisture like an ordinary salt.
It is used as a drying agent because it removes water by chemical reaction, not by just trapping moisture. That makes it different from materials like silica gel. In a lab, that distinction matters when you choose how to dry a solvent or gas.
The main products are calcium hydroxide and hydrogen gas. The balanced reaction is CaH2 + 2 H2O -> Ca(OH)2 + 2 H2. If you are solving a problem, make sure the hydrogen comes from the hydride, not from calcium itself.