Final answer:
The compound that would cause the least change in pH when added to distilled water is LiH. LiH is a metal hydride and does not dissociate in water as much as strong acids or bases, which leads to a minimal effect on the pH level of the solution compared to HCl, LiOH, or CsOH.
Step-by-step explanation:
The question pertains to the effect of adding different compounds to distilled water and which would cause the least change in pH. When 1g of LiOH is added to distilled water, it will change the pH significantly since it is a strong base. Similarly, adding 1g of HCl or CsOH, which are strong acid and strong base respectively, would cause a considerable change in pH. However, LiH is a metal hydride, which is not as dissociative in water as the strong acid or bases mentioned. It reacts much less extensively with water, resulting in a smaller production of hydroxide or hydronium ions, and therefore causes the least change in pH when added to distilled water.
Therefore, the correct answer to the student's query is option (A) LiH. This is because LiH is expected to affect the pH of distilled water to a lesser extent compared to the other options provided, which are either strong acids or strong bases that dissociate completely in solution and can dramatically alter the pH.