An alkaline earth metal with a mass of 5 g was oxidized by atmospheric oxygen. the resulting oxide reacted

An alkaline earth metal with a mass of 5 g was oxidized by atmospheric oxygen. the resulting oxide reacted with water resulting in the formation of a metal hydroxide weighing 9.25 g. What alkaline earth metal was taken?

To solve this problem, you need to know that alkali metals are only four chemical elements:

calcium;
strontium;
barium;
radium.

We discard radium due to radioactivity – conducting experiments with it is simply life-threatening.

In laboratories, from this list, you can always find only calcium. Let’s try to make calculations for it:

1) 2Ca + O2 -> 2CaO;

x = 5 * (56 * 2): (40 * 2) = 7 (g) – the mass of oxidized calcium.

2) Calculate the mass of CaO for calcium hydroxide:

CaO + H2O -> Ca (OH) 2;

x = 56 * 9.25: 74 = 7 (g).

The first and second actions gave the same result, which means that the required element is calcium. (However, if the answers did not coincide, we would have to substitute, as the first action, the data for barium, and then for strontium in the calculations.)