Step 1: Calculate the molar mass of calcium hydroxide [Ca(OH)₂].
The molar masses of Ca, O, and H are 40.08 g, 16.00 g, and 1.008 g, respectively.
[tex]\begin{aligned} \text{molar mass} & = \text{40.08 g + 2(16.00 g) + 2(1.008 g)} \\ & = \text{74.10 g} \end{aligned}[/tex]
Step 2: Calculate the number of moles of calcium hydroxide by using dimensional analysis.
[tex]\begin{aligned} \text{moles of} \: \text{Ca(OH)}_2 & = \text{20 g} \: \text{Ca(OH)}_2 \times \frac{\text{1 mol} \: \text{Ca(OH)}_2}{\text{74.10 g} \: \text{Ca(OH)}_2} \\ & = \boxed{\text{0.27 mol}} \end{aligned}[/tex]
Hence, there are 0.27 mol in 20 g of calcium hydroxide.
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SOLUTION:
Step 1: Calculate the molar mass of calcium hydroxide [Ca(OH)₂].
The molar masses of Ca, O, and H are 40.08 g, 16.00 g, and 1.008 g, respectively.
[tex]\begin{aligned} \text{molar mass} & = \text{40.08 g + 2(16.00 g) + 2(1.008 g)} \\ & = \text{74.10 g} \end{aligned}[/tex]
Step 2: Calculate the number of moles of calcium hydroxide by using dimensional analysis.
[tex]\begin{aligned} \text{moles of} \: \text{Ca(OH)}_2 & = \text{20 g} \: \text{Ca(OH)}_2 \times \frac{\text{1 mol} \: \text{Ca(OH)}_2}{\text{74.10 g} \: \text{Ca(OH)}_2} \\ & = \boxed{\text{0.27 mol}} \end{aligned}[/tex]
Hence, there are 0.27 mol in 20 g of calcium hydroxide.