Do gas particles touch

Calcium hydride (cah2) reacts with water to form hydrogen gas: cah2(s) + 2h2o(l) → ca(oh)2(aq) + 2h2(g) how many grams of cah2 are needed to generate 45.0 l of h2 gas at a pressure of 0.995 atm and a temperature of 32 °c?

This is a characteristic of the elements in the periodic table that shows a pattern. it may increase or decrease across or down the table.

Why is carbon ideal for making different compounds?