Final answer:
Among the compounds listed, CaH₂ reacts with water to produce calcium hydroxide and hydrogen gas, whereas the others are soluble but do not react in the same manner.
Step-by-step explanation:
The student's question asks which one of the listed compounds reacts with water, given that the other compounds are soluble or sparingly soluble in water. Among the options provided (CaH₂, Ca(NO₃)₂, Ca(OH)₂, CaBr₂), CaH₂ (calcium hydride) reacts with water to produce calcium hydroxide and hydrogen gas:
- CaH₂ + 2 H₂O → Ca(OH)₂ + 2 H₂
Ca(NO₃)₂ (calcium nitrate), Ca(OH)₂ (calcium hydroxide), and CaBr₂ (calcium bromide) are all soluble in water, but they do not react in the same way as calcium hydride does.