Calcium reacts with oxygen in air to produce calcium oxide in the reaction 2Ca(s) + O2(8)2CO(5).

How many grams of oxygen gas must react to yield 20.55 g of calcium oxide?

The answer is the first option just took the test

Order of filling levels and sublevels of electrons: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²3f¹⁴5d¹⁰6p⁶for an element with 5 electrons in the 3d energy level: full configuration: 1s²2s²2p⁶3s²3p³.

D. h2o + h2o > h3o + oh- confirmed.

Answerlimiting reactant;