Question

quiz : balancing chemical reactions
cao(s) + h₂o (l) → ca(oh)₂(s)
in this reaction, there are ____ oxygen atom(s) in ca(oh)₂
○ 3
○ 4
○ 1
○ 2

Explanation:

Step1: Analyze the formula \(Ca(OH)_2\)

In the formula \(Ca(OH)_2\), the sub - script outside the parentheses (\(2\)) applies to each element inside the parentheses.

Step2: Calculate the number of oxygen atoms

For oxygen (\(O\)): there is \(1\) oxygen atom in the \(OH\) group, and since there are \(2\) \(OH\) groups (because of the sub - script \(2\) outside the parentheses), the number of oxygen atoms is \(1\times2 = 2\).

Answer:

\(2\) (the fourth option)