Question

which of the following is a possible way to describe the ca(oh)₂ component in the reaction below? 2hcl(aq) + ca(oh)₂(aq) → 2h₂o(l) + cacl₂(aq) 40.08 g ca(oh)₂ 2 moles oh 1 formula unit ca(oh)₂ 1 l ca(oh)₂

Explanation:

Step1: Analyze the molar mass of \(Ca(OH)_2\)

The molar mass of \(Ca(OH)_2\) is \(M = 40.08+(16 + 1)\times2=74.08\space g/mol\). So \(40.08\space g\) is not one mole of \(Ca(OH)_2\).

Step2: Analyze the number of \(OH^-\) ions

One formula unit of \(Ca(OH)_2\) contains \(2\) \(OH^-\) ions. But the option says \(2\) moles \(OH\) (should be \(OH^-\)), and it doesn't specify per mole of \(Ca(OH)_2\) clearly in the context of the reaction equation.

Step3: Analyze the formula unit concept

In chemistry, for ionic compounds like \(Ca(OH)_2\), we can refer to formula units. In the reaction, \(Ca(OH)_2\) is an ionic compound in aqueous solution, and \(1\) formula unit \(Ca(OH)_2\) is a valid way to describe a “unit” of \(Ca(OH)_2\) at the particulate level.

Step4: Analyze the volume description

\(1\space L\space Ca(OH)_2\) is an incorrect description. We should describe the amount of a substance in terms of moles, mass, or formula units (for ionic compounds), not just volume for a pure compound (unless it's a gas and using molar volume, but \(Ca(OH)_2\) is not a gas here)

Answer:

1 formula unit \(Ca(OH)_2\)